Ice crystal icing is an important cause of accidents in aircraft engines.Ice formation in aircraft engines can cause internal blades to freeze,affecting the quality of the air flow field and blocking the flow path.On ...Ice crystal icing is an important cause of accidents in aircraft engines.Ice formation in aircraft engines can cause internal blades to freeze,affecting the quality of the air flow field and blocking the flow path.On the other hand,the entry of ice crystal particles into the combustion chamber can cause a decrease in temperature or even flameout,leading to engine surge or shutdown.Therefore,it is necessary to conduct multiphase flow tests on ice crystals for aircraft components such as aircraft engines.Conducting ice crystal multiphase flow tests on aircraft is an effective research method,but it requires the construction of an ice crystal multiphase flow test platform that meets relevant technical requirements.The paper focuses on the relevant experimental requirements and combines wind tunnel test structures to conduct multiphase flow numerical simulations on various forms of jet pipelines,obtaining particle motion distribution results.After comparison,the optimal form of jet structure is obtained,providing the best selection scheme for the design of relevant wind tunnel structures.展开更多
Sand/dust storms are some of the main hazards in arid and semi-arid zones. These storms also influence global environmental changes. By field observations, empirical statistics, and numerical simulations, pioneer rese...Sand/dust storms are some of the main hazards in arid and semi-arid zones. These storms also influence global environmental changes. By field observations, empirical statistics, and numerical simulations, pioneer researchers on these natural events have concluded the existence of a positive relationship between thermodynamic effects and sand/dust storms. Thermodynamic effects induce an unsteady stratified atmosphere to influence the process of these storms. However, studies on the relationship of thermodynamic effects with particles (i.e., sand and dust) are limited. In this article, wind tunnel with heating was used to simulate the quantitative relationship between thermodynamic effects and particle movement on different surfaces. Compared with the cold state, the threshold wind velocity of particles is found to be significantly decrease under the hot state. The largest decrease percentage exceedes 9% on fine and coarse sand surfaces. The wind velocity also has a three-power function in the sand transport rate under the hot state with increased sand transport. Thermodynamic effects are stronger on loose surfaces and fine particles, but weaker on compacted surfaces and coarse particles.展开更多
The western coast of Hainan Island exhibits a savanna landscape. Many types of sand dunes, including transverse dune ridges, longitudinal dune ridges, elliptical dunes, coppice dunes, and climbing dunes, are widely di...The western coast of Hainan Island exhibits a savanna landscape. Many types of sand dunes, including transverse dune ridges, longitudinal dune ridges, elliptical dunes, coppice dunes, and climbing dunes, are widely distributed in the coastal zone. In winter, high-frequency and high-energy NE winds （dominant winds） are prevalent, with a resultant drift direction （RDD） of S35.6°W. In spring, low-frequency and low-energy SW secondary winds prevail, with a RDD of N25.1°E. Wind tunnel simulations revealed that the airflow over the dune surface is the main factor controlling the erosion and deposition patterns of dune surfaces and the morphological development of dunes. In the region＇s bidirectional wind environment, with two seasonally distinct energy levels, the airflow over the surface of elliptical dunes, barchan dunes, and transverse dune ridges will exhibit a transverse pattern, whereas the airflow over longitudinal dunes ridges exhibits a lateral pattern and that over climbing dunes exhibits a climbing-circumfluent pattern. These patterns represent different dynamic processes. The coastal dunes on the western coast of Hainan Island are influenced by factors such as onshore winds, sand sources, coastal slopes, rivers, and forest shelter belts. The source of the sand that supplements these dunes particularly influences the development pattern： when there is more sand, the pattern shows positive equilibrium deposition between dune ridges and dunes; otherwise, it shows negative equilibrium deposition. The presence or absence of forest shelter belts also influences deposition and dune development patterns and transformation of dune forms. Coastal dunes and inland desert dunes experience similar dynamic processes, but the former have more diversified shapes and more complex formation mechanisms.展开更多
Based on numerical simulations,this study highlights the sedimentation and erosion problems around a sand barrier through the relationship between the shear stress of the surface around the sand barrier and the critic...Based on numerical simulations,this study highlights the sedimentation and erosion problems around a sand barrier through the relationship between the shear stress of the surface around the sand barrier and the critical shear stress of sand grains.The numerical simulation results were verified using data measured by the wind tunnel test.The results showed that when the porosity was the same,the size and position of the vortex on the leeward side of the sand barrier were related to the inlet wind speed.As the wind speed increased,the vortex volume increased and the positions of the separation and reattachment points moved toward the leeward side.When the porosity of the sand barrier was 30%,the strength of the acceleration zone above the sand barrier was the highest,and the strength of the acceleration zone was negatively correlated with the porosity.Sand erosion and sedimentation distance were related to wind speed.With an increase in wind speed,the sand grain forward erosion or reverse erosion areas on the leeward side of the sand barrier gradually replaced the sedimentation area.With an increase in porosity,the sand sedimentation distance on the leeward side of the sand barrier gradually shortened,and the sand erosion area gradually disappeared.The sand sedimentation distance on the leeward side of the sand barrier with 30%porosity was the longest.The numerical simulation results were in good agreement with the wind tunnel test results.Based on the sand erosion and sedimentation results of the numerical simulation and wind tunnel test,when the porosity was 30%,the protection effect of the High Density Polyethylene(HDPE)board sand barrier was best.展开更多
Intense freezing and thawing actions occur in the Qinghai-Tibet Plateau because of its high elevation and cold temperature. The plateau＇s unique environment makes it easy to generate wind erosion under dry, windy wea...Intense freezing and thawing actions occur in the Qinghai-Tibet Plateau because of its high elevation and cold temperature. The plateau＇s unique environment makes it easy to generate wind erosion under dry, windy weather conditions, resulting in the emergence ofdesertification. As a major form of freeze-thaw erosion, freeze-thaw and wind erosion is displayed prominently on the Qinghai-Tibet Plateau. Therefore, in this study, soil samples were collected from the surface of the plateau to undergo freeze-thaw and wind erosion simulation experiments. Results show that wind erosion strength increases with an increasing number of freeze-thaw cycles, water content in the freezing-thawing process, and the difference in freeze-thaw temperatures. Therefore, in the conditions of water participation, the main reason for the freeze-thaw and wind erosion in the Qinghai-Tibet Plateau is the damage to the soil structure by repeated, fierce freeze-thaw actions, and the sand-bearing wind is the main driving force for this process. The research results have theoretical significance for exploring the formation mechanism of freeze-thaw and wind erosion in the Qinghai-Tibet Plateau, and provide a scientific basis for freeze-thaw desertification control in the plateau.展开更多
The wind tunnel simulations of wind loading on a solid structure of revolution with one smooth and five rough surfaces were conducted using wind tunnel tests. Timemean and fluctuating pressure distributions on the sur...The wind tunnel simulations of wind loading on a solid structure of revolution with one smooth and five rough surfaces were conducted using wind tunnel tests. Timemean and fluctuating pressure distributions on the surface were obtained, and the relationships between the roughness Reynolds number and pressure distributions were analyzed and discussed. The results show that increasing the surface roughness can significantly affect the pressure distribution, and the roughness Reynolds numbers play an important role in the change of flow patterns. The three flow patterns of subcritical, critical and supercritical flows can be classified based on the changing patterns of both the mean and the fluctuating pressure distributions. The present study suggests that the wind tunnel results obtained in the supercritical pattern reflect more closely those of full-scale solid structure of revolution at the designed wind speed.展开更多
Airflow in open spaces can significantly affect spatial quality. Therefore, according to the type of building structures, the airflow also has different forms. Studies have been conducted on the relation between airfl...Airflow in open spaces can significantly affect spatial quality. Therefore, according to the type of building structures, the airflow also has different forms. Studies have been conducted on the relation between airflow and pedestrian comfort; however, only few of them have focused on comprehensive urban planning that considers different weather conditions and people＇s ability to adapt. This research focuses on the differences in wind conditions caused by different spatial forms in different seasons. On the basis of a field survey in both summer and winter in a public open space, evaluation standards developed from environmental meteorological data and public feedback were used to evaluate simulation results. Next, several assumptions about canyon orientation and building types were proposed. Wind tunnel and CFD （computational fluid dynamics） simulations were conducted to evaluate the assumptions. The results showed that the canyon orientation significantly affected overall wind conditions and different building structures affected airflow. This research also provides a method to evaluate urban areas that have complicated wind environments.展开更多
Regional climatic conditions should be considered while designing urban development plans, with special attention to the impact of snowfall on public spaces in cities with harsh winters. The Kitami-city-hall-renewal p...Regional climatic conditions should be considered while designing urban development plans, with special attention to the impact of snowfall on public spaces in cities with harsh winters. The Kitami-city-hall-renewal project in Hokkaido, Japan was studied as an environmental assessment of snow drifting. Assessments of the two site plans proposed during the architectural planning process （A-type and B-type） were conducted in terms of the following three items： （1） The two site plans indicate snow-drifting problems around the main entrance; （2） More number of local snowdrifts on the main-street sidewalks were suggested in the B-type design; （3） Less number of snowdrifts in the parking area beside the railroad were indicated in the A-type design. These results were reflected in the architectural planning process. On the basis of this study, a desirable design process incorporating environmental assessments has been identified for cities with harsh winters.展开更多
Combining the computational fluid dynamics-based numerical simulation with the forced vibration technique for extraction of aerodynamic derivatives, an approach for calculating the aerodynamic derivatives and the crit...Combining the computational fluid dynamics-based numerical simulation with the forced vibration technique for extraction of aerodynamic derivatives, an approach for calculating the aerodynamic derivatives and the critical flutter wind speed for long-span bridges is presented in this paper. The RNG k-ε turbulent model is introduced to establish the governing equations, including the continuity equation and the Navier-Stokes equations, for solving the wind flow field around a two-dimensional bridge section. To illustrate the effectiveness and accuracy of the proposed approach, a simple application to the Hume Bridge in China is provided, and the numerical results show that the aerodynamic derivatives and the critical flutter wind speed obtained agree well with the wind tunnel test results.展开更多
For wind tunnels,it is essential to conduct temperature and flow field calibration on their test section,which is an important indicator for evaluating the quality of wind tunnel flow fields.In the paper,a truss compo...For wind tunnels,it is essential to conduct temperature and flow field calibration on their test section,which is an important indicator for evaluating the quality of wind tunnel flow fields.In the paper,a truss composed of temperature sensors was used to calibrate the temperature field of a completed wind tunnel section.By adjusting the distance between the temperature measurement truss and the nozzle,as well as the wind speed,the temperature field distribution data at different positions could be obtained.Analyze these data to identify important factors that affect the distribution of temperature field.Simultaneously,the temperature field of the wind tunnel was simulated accordingly.The purpose is to further analyze the fluid heat transfer between air and wind tunnel walls through numerical simulation.Through the above analysis methods,the quality of the temperature field in the wind tunnel has been further verified,providing reference for future wind tunnel tests of relevant models.展开更多
This paper briefs the background and process of setting-up andupdating of Environmental Wind Tunnel Laboratory of State Power Corporation,details the environmental wind tunnel, completed measuring instruments andequip...This paper briefs the background and process of setting-up andupdating of Environmental Wind Tunnel Laboratory of State Power Corporation,details the environmental wind tunnel, completed measuring instruments andequipment of the laboratory, and also describes the experimental projects thePower Environmental Protection Research Institute has completed, theexperiences gained and the services the Institute can provide in the future.[展开更多
Electric discharge phenomenon is often observed during the passage of sandstorms over desert regions and sometimes does great damage to human beings. Based on previous researches on the electrification of sandstorms b...Electric discharge phenomenon is often observed during the passage of sandstorms over desert regions and sometimes does great damage to human beings. Based on previous researches on the electrification of sandstorms by the scholars both at home and aboard,the authors conducted the simulation experiments on the electric fields of sandstorm-triggered creeping-saltating sand, suspending sand and watered suspending sand in the large-scale wind tunnel. According to the experimental results the electric field structure and its formation mechanism were analysed and discussed, the quantity of electric charges and electric field strengthwere measured and calculated, and finally several conclusions were drawn.展开更多
The ejector-powered engine simulator(EPES)system is an important piece of equipment in conducting an influence test of the intake and jet flow in low-speed wind tunnels.In this work,through the analysis of the structu...The ejector-powered engine simulator(EPES)system is an important piece of equipment in conducting an influence test of the intake and jet flow in low-speed wind tunnels.In this work,through the analysis of the structure and principle of EPES,three parts of the internal flow force were obtained,namely,the additional resistance before the inlet,the internal flow force in the inlet and the thrust produced by the ejector.On the assumption of one-dimensional isentropic adiabatic flow,the theoretical formulae for calculating the forces were derived according to the measured total pressure,static pressure and total temperature of the internal flow section.Subsequently,a calibration tank was used to calibrate the EPES system.On the basis of the characteristics of the EPES system,the process and method of its calibration were designed in detail,and the model installation interface of the calibration tank was reformed.By applying this method,the repeatability accuracy of the inlet flow rate calibration coefficient was less than0.05%,whereas that of the exhaust flow rate and velocity was less than 0.1%.Upon the application of the calibration coefficients to the correction of the wind tunnel experiment data,the results showed good agreement with the numerical simulation results in terms of regularity and magnitude before stall,which validates the reasonableness and feasibility of the calibration method.Analysis of the calibration data also demonstrated the consistency in the variation law and trend between the theoretical calculation and actual measurement of internal flow force,further reflecting the rationality and feasibility of the theoretical calculation.Nevertheless,the numerical difference was large and further widened with a higher ejection flow rate mainly because of the accuracy of flow measurement and the inhomogeneity of internal flow.The thrust deflection angle of EPES is an important factor in correcting this issue.In particular,the thrust deflection angle becomes larger with small ejection flow and becomes smaller with an increase in flow rate,essentially exhibiting a general change of less than 10°.展开更多
The current research of tire aerodynamics mainly focus on the isolated and simplified tread tire.Compared with the real complex pattern tire,the tread pattern structure and deformed profile of a loaded tire has a grea...The current research of tire aerodynamics mainly focus on the isolated and simplified tread tire.Compared with the real complex pattern tire,the tread pattern structure and deformed profile of a loaded tire has a greatly influence on tire aerodynamic drag.However,the mechanisms of the isolated loaded tires with different tread patterns effects on the aerodynamic drag are subjects worthy of discussion.The purpose of this study is to experimentally and compu-tationally investigate the aerodynamic characteristics of three tires 185/65 R14 with different patterns under loaded.A wind tunnel test model was first established using three-dimensional(3D)printing with a ratio of 1:1,and the pres-sure coefficients C_(p) of the three tires with different patterns are measured.The paper then conducted computational fluid dynamics(CFD)simulations for analyzing the pressure and flow characteristics.The accuracy of CFD simulation is verified by comparing the simulation results with the test results of pressure coefficients C_(p),and they are of good consistency.While,the general analysis of pressure coefficients C_(p) results of the three tires indicates high-pressure area on the windward surface,and occurrence of low-pressure area on the leeward surface,the pressure coefficients C_(p) of all three tires decreased firstly and then increased along in the air flow direction.The authors finally analyzed the effect of tread patterns on the flow field around the tire and revealed the differences between flow characteristics and aerodynamic drag.The results show that,angle of tire lateral groove has great effect on the flow field characteristics such that;the more the angle of lateral groove agrees with the air flow direction,the less the flow separation and flow vortices,and a minimum observable aerodynamic drag.The research provides a guidance for the design of low aerodynamic drag tires,and helps to illustrate the impact of tire aerodynamics on the car body in the future.展开更多
Fluid-structure interaction is an important issue for non-rigid airships with inflated envelopes. In this study, a wind tunnel test is conducted, and a loosely coupled procedure is correspondingly established for nume...Fluid-structure interaction is an important issue for non-rigid airships with inflated envelopes. In this study, a wind tunnel test is conducted, and a loosely coupled procedure is correspondingly established for numerical simulation based on computational fluid dynamics and nonlinear finite element analysis methods. The typical results of the numerical simulation and wind tunnel experiment, including the overall lift and deformation, are in good agreement with each other. The results obtained indicate that the effect of fluid-structure interaction is noticeable and should be considered for non-rigid airships. Flow- induced deformation can further intensify the upward lift force and pitching moment, which can lead to a large deformation. Under a wind speed of 15 m/s, the lift force of the non-rigid model is increased to approximatelv 60% compared with that of the rigid model under a high angle of attack.展开更多
In wind tunnel experiments,support devices inevitably disturb the surrounding flow field,thereby degrading the accuracy of measured aerodynamic data.A new subsonic and transonic wind tunnel has recently been construct...In wind tunnel experiments,support devices inevitably disturb the surrounding flow field,thereby degrading the accuracy of measured aerodynamic data.A new subsonic and transonic wind tunnel has recently been constructed,and the support system for dynamic six degree of freedom experiments is currently under conceptual design.A key challenge is to optimize the support configuration while satisfying stringent flow quality requirements.In this study,the influence of different support configurations on the flow field is investigated numerically by analyzing velocity and pressure distributions.The results show that the optimized six degree of freedom support significantly reduces disturbances in both pressure and velocity fields,with the improvement becoming more pronounced as the Mach number increases.The main optimization measures include the addition of a tail fairing,reduction of the thickness of the connecting bases between the support rods and the sting,and downsizing of the anchor feet.In contrast,the effect of the tail support poles is found to be negligible.It is shown that,overall,the extent of upstream flow disturbance is governed primarily by the separation region and associated momentum loss induced by the support sting,the connecting bases and the anchor feet.Flow separation originates from spiral points or separation lines on the model surface,resulting from viscous effects combined with shock waves generated by the support system.展开更多
This paper investigates the influence of numerical methods and mesh resolution on the prediction accuracy of the aerodynamic behaviors of a 1/20 scaled generic high-speed train(HST)model.A thorough comparison is made ...This paper investigates the influence of numerical methods and mesh resolution on the prediction accuracy of the aerodynamic behaviors of a 1/20 scaled generic high-speed train(HST)model.A thorough comparison is made between partially averaged Navier-Stokes(PANS),large eddy simulation(LES),and wind tunnel experiments,covering aerodynamic forces,surface pressure,velocity distribution,and Reynolds stress and turbulent kinetic energy in the wake region.The Reynolds number for both simulations and experiments is set to 4.75×10^(5).The results show that the PANS approach accurately predicts flow characteristics observed in experiments and fine LES calculations,even with a low resolution grid.PANS exhibits a distinct advantage over LES when grid resolutions are insufficient for resolving near wall flow structures around the HST,both in open-air conditions and crosswind environments.Additionally,grid refinement improves the predictive accuracy of the HST's aerodynamic performance,particularly in the presence of small yaw angle.展开更多
The liquid nitrogen(LN2)supplying system,one of the four key systems of the cryogenic wind tunnel(CWT),is an essential guarantee for the precise control,fast and safe regulation of the wind tunnel’s total temperature...The liquid nitrogen(LN2)supplying system,one of the four key systems of the cryogenic wind tunnel(CWT),is an essential guarantee for the precise control,fast and safe regulation of the wind tunnel’s total temperature.Firstly,the technical schemes,advantages and disadvantages of different LN2 supplying systems are discussed and analyzed based on the operation conditions and test requirements of different CWTs.Then,together with the development of the pilot cryogenic transonic wind tunnel(PCTW),the key technologies of the system,including the supplying mode,rapid and accurate regulation of injection pressure,development of large scale cryogenic centrifugal pump,and matching technology between pumps and pipe network,have been summarized and the solutions to the existing issues are given.Finally,a supplying process suitable for large-scale CWT is proposed,which has the ability of independent commissioning,rapid regulation,accurate control of injection pressure and transient response to the wind tunnel’s wide range of working conditions.The breakthrough in LN2 supplying system enables China to construct a CWT for the future competitive high Reynolds number aircraft.展开更多
In wind tunnel tests of tall building models comprised of rounded or streamlined surfaces, Reynolds Number Effects (RNE) may be remarkable. In most researches and projects, owing to the presence of sharp edged corners...In wind tunnel tests of tall building models comprised of rounded or streamlined surfaces, Reynolds Number Effects (RNE) may be remarkable. In most researches and projects, owing to the presence of sharp edged corners at model, RNE was often treated as negligible, and data colleCted in subcritical flow regime were applied directly to designs which were sure to be supercritical without any modification. But it was proved necessary to take RNE into consideration when a model had predominant rounded smooth surface(s). Some research activities were devoted to the mentioned condition and two experimental techniques accompanied by two wind tunnel model tests were introduced in the article. The authors also presented some amusing phenomenon such as extremely low pressure coefficients caused by the separating bubbles when now past sharp edged corners, unsymmetrical pressure coefficient distributions commenced by biased gap f'low (seen Figs. 3, 4) while models were placed symmetrically in the approaching flow.展开更多
In recent years,train-tail swaying of 160 km/h electric multiple units(EMUs)inside single-line tunnels has been heavily researched,because the issue needs to be solved urgently.In this paper,a co-simulation model of v...In recent years,train-tail swaying of 160 km/h electric multiple units(EMUs)inside single-line tunnels has been heavily researched,because the issue needs to be solved urgently.In this paper,a co-simulation model of vortex-induced vibration(VIV)of the tail car body is established,and the aerodynamics of train-tail swaying is studied.The simulation results were confirmed through a field test of operating EMUs.Furthermore,the influence mechanism of train-tail swaying on the wake flow field is studied in detail through a wind-tunnel experiment and a simulation of a reduced-scaled train model.The results demonstrate that the aerodynamic force frequency(i.e.,vortex-induced frequency)of the train tail increases linearly with train speed.When the train runs at 130 km/h,with a small amplitude of train-tail swaying(within 10 mm),the vortex-induced frequency is 1.7 Hz,which primarily depends on the nose shape of the train tail.After the tail car body nose is extended,the vortex-induced frequency is decreased.As the swaying amplitude of the train tail increases(exceeding 25 mm),the separation point of the high-intensity vortex in the train wake shifts downstream to the nose tip,and the vortex-induced frequency shifts from 1.7 Hz to the nearby car body hunting(i.e.,the primary hunting)frequency of 1.3 Hz,which leads to the frequency-locking phenomenon of VIV,and the resonance intensifies train-tail swaying.For the motor vehicle of the train tail,optimization of the yaw damper to improve its primary hunting stability can effectively alleviate train-tail swaying inside single-line tunnels.Optimization of the tail car body nose shape reduces the amplitude of the vortex-induced force,thereby weakening the aerodynamic effect and solving the problem of train-tail swaying inside the single-line tunnels.展开更多
文摘Ice crystal icing is an important cause of accidents in aircraft engines.Ice formation in aircraft engines can cause internal blades to freeze,affecting the quality of the air flow field and blocking the flow path.On the other hand,the entry of ice crystal particles into the combustion chamber can cause a decrease in temperature or even flameout,leading to engine surge or shutdown.Therefore,it is necessary to conduct multiphase flow tests on ice crystals for aircraft components such as aircraft engines.Conducting ice crystal multiphase flow tests on aircraft is an effective research method,but it requires the construction of an ice crystal multiphase flow test platform that meets relevant technical requirements.The paper focuses on the relevant experimental requirements and combines wind tunnel test structures to conduct multiphase flow numerical simulations on various forms of jet pipelines,obtaining particle motion distribution results.After comparison,the optimal form of jet structure is obtained,providing the best selection scheme for the design of relevant wind tunnel structures.
基金Under the auspices of National Natural Science Foundation of China(No.40930741,41071009,41001005)Knowledge Innovation Programs of Chinese Academy of Sciences(No.KZCX2-YW-329)
文摘Sand/dust storms are some of the main hazards in arid and semi-arid zones. These storms also influence global environmental changes. By field observations, empirical statistics, and numerical simulations, pioneer researchers on these natural events have concluded the existence of a positive relationship between thermodynamic effects and sand/dust storms. Thermodynamic effects induce an unsteady stratified atmosphere to influence the process of these storms. However, studies on the relationship of thermodynamic effects with particles (i.e., sand and dust) are limited. In this article, wind tunnel with heating was used to simulate the quantitative relationship between thermodynamic effects and particle movement on different surfaces. Compared with the cold state, the threshold wind velocity of particles is found to be significantly decrease under the hot state. The largest decrease percentage exceedes 9% on fine and coarse sand surfaces. The wind velocity also has a three-power function in the sand transport rate under the hot state with increased sand transport. Thermodynamic effects are stronger on loose surfaces and fine particles, but weaker on compacted surfaces and coarse particles.
基金National Natural Science Foundation of China, No.40671186 No.40271012
文摘The western coast of Hainan Island exhibits a savanna landscape. Many types of sand dunes, including transverse dune ridges, longitudinal dune ridges, elliptical dunes, coppice dunes, and climbing dunes, are widely distributed in the coastal zone. In winter, high-frequency and high-energy NE winds （dominant winds） are prevalent, with a resultant drift direction （RDD） of S35.6°W. In spring, low-frequency and low-energy SW secondary winds prevail, with a RDD of N25.1°E. Wind tunnel simulations revealed that the airflow over the dune surface is the main factor controlling the erosion and deposition patterns of dune surfaces and the morphological development of dunes. In the region＇s bidirectional wind environment, with two seasonally distinct energy levels, the airflow over the surface of elliptical dunes, barchan dunes, and transverse dune ridges will exhibit a transverse pattern, whereas the airflow over longitudinal dunes ridges exhibits a lateral pattern and that over climbing dunes exhibits a climbing-circumfluent pattern. These patterns represent different dynamic processes. The coastal dunes on the western coast of Hainan Island are influenced by factors such as onshore winds, sand sources, coastal slopes, rivers, and forest shelter belts. The source of the sand that supplements these dunes particularly influences the development pattern： when there is more sand, the pattern shows positive equilibrium deposition between dune ridges and dunes; otherwise, it shows negative equilibrium deposition. The presence or absence of forest shelter belts also influences deposition and dune development patterns and transformation of dune forms. Coastal dunes and inland desert dunes experience similar dynamic processes, but the former have more diversified shapes and more complex formation mechanisms.
基金financially supported by the fellowship of the China Postdoctoral Science Foundation(2021M703466)the Natural Science Foundation of Gansu Province,China(20JR10RA231)+1 种基金the Basic Research Innovation Group Project of Gansu Province,China(21JR7RA347)an Special Funds for Guiding Local Scientific and Technological Development by the Central Government(22ZY1QA005)。
文摘Based on numerical simulations,this study highlights the sedimentation and erosion problems around a sand barrier through the relationship between the shear stress of the surface around the sand barrier and the critical shear stress of sand grains.The numerical simulation results were verified using data measured by the wind tunnel test.The results showed that when the porosity was the same,the size and position of the vortex on the leeward side of the sand barrier were related to the inlet wind speed.As the wind speed increased,the vortex volume increased and the positions of the separation and reattachment points moved toward the leeward side.When the porosity of the sand barrier was 30%,the strength of the acceleration zone above the sand barrier was the highest,and the strength of the acceleration zone was negatively correlated with the porosity.Sand erosion and sedimentation distance were related to wind speed.With an increase in wind speed,the sand grain forward erosion or reverse erosion areas on the leeward side of the sand barrier gradually replaced the sedimentation area.With an increase in porosity,the sand sedimentation distance on the leeward side of the sand barrier gradually shortened,and the sand erosion area gradually disappeared.The sand sedimentation distance on the leeward side of the sand barrier with 30%porosity was the longest.The numerical simulation results were in good agreement with the wind tunnel test results.Based on the sand erosion and sedimentation results of the numerical simulation and wind tunnel test,when the porosity was 30%,the protection effect of the High Density Polyethylene(HDPE)board sand barrier was best.
基金funded by the National Natural Science Foundation of China(Grant No.41401611)the China Postdoctoral Science Foundation(Grant Nos.2014M560817 and 2015T81069)+1 种基金one of Special Fund for Forest Scientific Research in the Public Welfare(201504401)the Science and Technology Program of Gansu Province(Grant No.145RJZA118)
文摘Intense freezing and thawing actions occur in the Qinghai-Tibet Plateau because of its high elevation and cold temperature. The plateau＇s unique environment makes it easy to generate wind erosion under dry, windy weather conditions, resulting in the emergence ofdesertification. As a major form of freeze-thaw erosion, freeze-thaw and wind erosion is displayed prominently on the Qinghai-Tibet Plateau. Therefore, in this study, soil samples were collected from the surface of the plateau to undergo freeze-thaw and wind erosion simulation experiments. Results show that wind erosion strength increases with an increasing number of freeze-thaw cycles, water content in the freezing-thawing process, and the difference in freeze-thaw temperatures. Therefore, in the conditions of water participation, the main reason for the freeze-thaw and wind erosion in the Qinghai-Tibet Plateau is the damage to the soil structure by repeated, fierce freeze-thaw actions, and the sand-bearing wind is the main driving force for this process. The research results have theoretical significance for exploring the formation mechanism of freeze-thaw and wind erosion in the Qinghai-Tibet Plateau, and provide a scientific basis for freeze-thaw desertification control in the plateau.
文摘The wind tunnel simulations of wind loading on a solid structure of revolution with one smooth and five rough surfaces were conducted using wind tunnel tests. Timemean and fluctuating pressure distributions on the surface were obtained, and the relationships between the roughness Reynolds number and pressure distributions were analyzed and discussed. The results show that increasing the surface roughness can significantly affect the pressure distribution, and the roughness Reynolds numbers play an important role in the change of flow patterns. The three flow patterns of subcritical, critical and supercritical flows can be classified based on the changing patterns of both the mean and the fluctuating pressure distributions. The present study suggests that the wind tunnel results obtained in the supercritical pattern reflect more closely those of full-scale solid structure of revolution at the designed wind speed.
文摘Airflow in open spaces can significantly affect spatial quality. Therefore, according to the type of building structures, the airflow also has different forms. Studies have been conducted on the relation between airflow and pedestrian comfort; however, only few of them have focused on comprehensive urban planning that considers different weather conditions and people＇s ability to adapt. This research focuses on the differences in wind conditions caused by different spatial forms in different seasons. On the basis of a field survey in both summer and winter in a public open space, evaluation standards developed from environmental meteorological data and public feedback were used to evaluate simulation results. Next, several assumptions about canyon orientation and building types were proposed. Wind tunnel and CFD （computational fluid dynamics） simulations were conducted to evaluate the assumptions. The results showed that the canyon orientation significantly affected overall wind conditions and different building structures affected airflow. This research also provides a method to evaluate urban areas that have complicated wind environments.
文摘Regional climatic conditions should be considered while designing urban development plans, with special attention to the impact of snowfall on public spaces in cities with harsh winters. The Kitami-city-hall-renewal project in Hokkaido, Japan was studied as an environmental assessment of snow drifting. Assessments of the two site plans proposed during the architectural planning process （A-type and B-type） were conducted in terms of the following three items： （1） The two site plans indicate snow-drifting problems around the main entrance; （2） More number of local snowdrifts on the main-street sidewalks were suggested in the B-type design; （3） Less number of snowdrifts in the parking area beside the railroad were indicated in the A-type design. These results were reflected in the architectural planning process. On the basis of this study, a desirable design process incorporating environmental assessments has been identified for cities with harsh winters.
基金National Natural Science Foundation of China Under Grant No. 50278029
文摘Combining the computational fluid dynamics-based numerical simulation with the forced vibration technique for extraction of aerodynamic derivatives, an approach for calculating the aerodynamic derivatives and the critical flutter wind speed for long-span bridges is presented in this paper. The RNG k-ε turbulent model is introduced to establish the governing equations, including the continuity equation and the Navier-Stokes equations, for solving the wind flow field around a two-dimensional bridge section. To illustrate the effectiveness and accuracy of the proposed approach, a simple application to the Hume Bridge in China is provided, and the numerical results show that the aerodynamic derivatives and the critical flutter wind speed obtained agree well with the wind tunnel test results.
文摘For wind tunnels,it is essential to conduct temperature and flow field calibration on their test section,which is an important indicator for evaluating the quality of wind tunnel flow fields.In the paper,a truss composed of temperature sensors was used to calibrate the temperature field of a completed wind tunnel section.By adjusting the distance between the temperature measurement truss and the nozzle,as well as the wind speed,the temperature field distribution data at different positions could be obtained.Analyze these data to identify important factors that affect the distribution of temperature field.Simultaneously,the temperature field of the wind tunnel was simulated accordingly.The purpose is to further analyze the fluid heat transfer between air and wind tunnel walls through numerical simulation.Through the above analysis methods,the quality of the temperature field in the wind tunnel has been further verified,providing reference for future wind tunnel tests of relevant models.
文摘This paper briefs the background and process of setting-up andupdating of Environmental Wind Tunnel Laboratory of State Power Corporation,details the environmental wind tunnel, completed measuring instruments andequipment of the laboratory, and also describes the experimental projects thePower Environmental Protection Research Institute has completed, theexperiences gained and the services the Institute can provide in the future.[
基金This project was supported by the InnovationProject of the Chinese Academy of Sciences (Grant No. 210027) the Knowledge Innovation Project of Chinese Academy of Sciences (GrantNo. KZCX2-304)+1 种基金the National Natural Science Foundation of China(Grant No.39971013) the State Key Basic Research Development Planning (Grnat No.20000487).
文摘Electric discharge phenomenon is often observed during the passage of sandstorms over desert regions and sometimes does great damage to human beings. Based on previous researches on the electrification of sandstorms by the scholars both at home and aboard,the authors conducted the simulation experiments on the electric fields of sandstorm-triggered creeping-saltating sand, suspending sand and watered suspending sand in the large-scale wind tunnel. According to the experimental results the electric field structure and its formation mechanism were analysed and discussed, the quantity of electric charges and electric field strengthwere measured and calculated, and finally several conclusions were drawn.
基金supported by the funda-mental research the Funds of China Aerodynamics Research and Development Center
文摘The ejector-powered engine simulator(EPES)system is an important piece of equipment in conducting an influence test of the intake and jet flow in low-speed wind tunnels.In this work,through the analysis of the structure and principle of EPES,three parts of the internal flow force were obtained,namely,the additional resistance before the inlet,the internal flow force in the inlet and the thrust produced by the ejector.On the assumption of one-dimensional isentropic adiabatic flow,the theoretical formulae for calculating the forces were derived according to the measured total pressure,static pressure and total temperature of the internal flow section.Subsequently,a calibration tank was used to calibrate the EPES system.On the basis of the characteristics of the EPES system,the process and method of its calibration were designed in detail,and the model installation interface of the calibration tank was reformed.By applying this method,the repeatability accuracy of the inlet flow rate calibration coefficient was less than0.05%,whereas that of the exhaust flow rate and velocity was less than 0.1%.Upon the application of the calibration coefficients to the correction of the wind tunnel experiment data,the results showed good agreement with the numerical simulation results in terms of regularity and magnitude before stall,which validates the reasonableness and feasibility of the calibration method.Analysis of the calibration data also demonstrated the consistency in the variation law and trend between the theoretical calculation and actual measurement of internal flow force,further reflecting the rationality and feasibility of the theoretical calculation.Nevertheless,the numerical difference was large and further widened with a higher ejection flow rate mainly because of the accuracy of flow measurement and the inhomogeneity of internal flow.The thrust deflection angle of EPES is an important factor in correcting this issue.In particular,the thrust deflection angle becomes larger with small ejection flow and becomes smaller with an increase in flow rate,essentially exhibiting a general change of less than 10°.
基金Supported by National Natural Science Foundation of China(Grant Nos.52072156,51675240)Jiangsu Provincial Youth Fund of China(Grant No.KB20160528)+1 种基金Jiangsu Provincial Six Talents Summit Program of China(Grant No.JXQC-011)Jiangsu University Senior Talents Startup Fund(Grant No.1291120046).
文摘The current research of tire aerodynamics mainly focus on the isolated and simplified tread tire.Compared with the real complex pattern tire,the tread pattern structure and deformed profile of a loaded tire has a greatly influence on tire aerodynamic drag.However,the mechanisms of the isolated loaded tires with different tread patterns effects on the aerodynamic drag are subjects worthy of discussion.The purpose of this study is to experimentally and compu-tationally investigate the aerodynamic characteristics of three tires 185/65 R14 with different patterns under loaded.A wind tunnel test model was first established using three-dimensional(3D)printing with a ratio of 1:1,and the pres-sure coefficients C_(p) of the three tires with different patterns are measured.The paper then conducted computational fluid dynamics(CFD)simulations for analyzing the pressure and flow characteristics.The accuracy of CFD simulation is verified by comparing the simulation results with the test results of pressure coefficients C_(p),and they are of good consistency.While,the general analysis of pressure coefficients C_(p) results of the three tires indicates high-pressure area on the windward surface,and occurrence of low-pressure area on the leeward surface,the pressure coefficients C_(p) of all three tires decreased firstly and then increased along in the air flow direction.The authors finally analyzed the effect of tread patterns on the flow field around the tire and revealed the differences between flow characteristics and aerodynamic drag.The results show that,angle of tire lateral groove has great effect on the flow field characteristics such that;the more the angle of lateral groove agrees with the air flow direction,the less the flow separation and flow vortices,and a minimum observable aerodynamic drag.The research provides a guidance for the design of low aerodynamic drag tires,and helps to illustrate the impact of tire aerodynamics on the car body in the future.
基金the National Natural Science Foundation of China (11202215 and 11332011)the Youth Innovation Promotion Association of CAS (2015015)
文摘Fluid-structure interaction is an important issue for non-rigid airships with inflated envelopes. In this study, a wind tunnel test is conducted, and a loosely coupled procedure is correspondingly established for numerical simulation based on computational fluid dynamics and nonlinear finite element analysis methods. The typical results of the numerical simulation and wind tunnel experiment, including the overall lift and deformation, are in good agreement with each other. The results obtained indicate that the effect of fluid-structure interaction is noticeable and should be considered for non-rigid airships. Flow- induced deformation can further intensify the upward lift force and pitching moment, which can lead to a large deformation. Under a wind speed of 15 m/s, the lift force of the non-rigid model is increased to approximatelv 60% compared with that of the rigid model under a high angle of attack.
基金supported by the Guiding Project of Scientific Research Plan of Hubei Education Department of China[Grant No.B2020227].
文摘In wind tunnel experiments,support devices inevitably disturb the surrounding flow field,thereby degrading the accuracy of measured aerodynamic data.A new subsonic and transonic wind tunnel has recently been constructed,and the support system for dynamic six degree of freedom experiments is currently under conceptual design.A key challenge is to optimize the support configuration while satisfying stringent flow quality requirements.In this study,the influence of different support configurations on the flow field is investigated numerically by analyzing velocity and pressure distributions.The results show that the optimized six degree of freedom support significantly reduces disturbances in both pressure and velocity fields,with the improvement becoming more pronounced as the Mach number increases.The main optimization measures include the addition of a tail fairing,reduction of the thickness of the connecting bases between the support rods and the sting,and downsizing of the anchor feet.In contrast,the effect of the tail support poles is found to be negligible.It is shown that,overall,the extent of upstream flow disturbance is governed primarily by the separation region and associated momentum loss induced by the support sting,the connecting bases and the anchor feet.Flow separation originates from spiral points or separation lines on the model surface,resulting from viscous effects combined with shock waves generated by the support system.
基金Project(2024YFB4303300)supported by the National Key R&D Program of ChinaProject(52202429)supported by the National Natural Science Foundation of ChinaProject(2023JJ40747)supported by the Natural Science Foundation of Hunan Province,China。
文摘This paper investigates the influence of numerical methods and mesh resolution on the prediction accuracy of the aerodynamic behaviors of a 1/20 scaled generic high-speed train(HST)model.A thorough comparison is made between partially averaged Navier-Stokes(PANS),large eddy simulation(LES),and wind tunnel experiments,covering aerodynamic forces,surface pressure,velocity distribution,and Reynolds stress and turbulent kinetic energy in the wake region.The Reynolds number for both simulations and experiments is set to 4.75×10^(5).The results show that the PANS approach accurately predicts flow characteristics observed in experiments and fine LES calculations,even with a low resolution grid.PANS exhibits a distinct advantage over LES when grid resolutions are insufficient for resolving near wall flow structures around the HST,both in open-air conditions and crosswind environments.Additionally,grid refinement improves the predictive accuracy of the HST's aerodynamic performance,particularly in the presence of small yaw angle.
基金supported by the National Natural Science Foundation of China(Grant No.51806234)。
文摘The liquid nitrogen(LN2)supplying system,one of the four key systems of the cryogenic wind tunnel(CWT),is an essential guarantee for the precise control,fast and safe regulation of the wind tunnel’s total temperature.Firstly,the technical schemes,advantages and disadvantages of different LN2 supplying systems are discussed and analyzed based on the operation conditions and test requirements of different CWTs.Then,together with the development of the pilot cryogenic transonic wind tunnel(PCTW),the key technologies of the system,including the supplying mode,rapid and accurate regulation of injection pressure,development of large scale cryogenic centrifugal pump,and matching technology between pumps and pipe network,have been summarized and the solutions to the existing issues are given.Finally,a supplying process suitable for large-scale CWT is proposed,which has the ability of independent commissioning,rapid regulation,accurate control of injection pressure and transient response to the wind tunnel’s wide range of working conditions.The breakthrough in LN2 supplying system enables China to construct a CWT for the future competitive high Reynolds number aircraft.
文摘In wind tunnel tests of tall building models comprised of rounded or streamlined surfaces, Reynolds Number Effects (RNE) may be remarkable. In most researches and projects, owing to the presence of sharp edged corners at model, RNE was often treated as negligible, and data colleCted in subcritical flow regime were applied directly to designs which were sure to be supercritical without any modification. But it was proved necessary to take RNE into consideration when a model had predominant rounded smooth surface(s). Some research activities were devoted to the mentioned condition and two experimental techniques accompanied by two wind tunnel model tests were introduced in the article. The authors also presented some amusing phenomenon such as extremely low pressure coefficients caused by the separating bubbles when now past sharp edged corners, unsymmetrical pressure coefficient distributions commenced by biased gap f'low (seen Figs. 3, 4) while models were placed symmetrically in the approaching flow.
基金supported by the National Natural Science Foundation of China(Nos.52372403 and U2268211)the Natural Science Foundation of Sichuan Province(No.2022NSFSC0034),China+1 种基金the National Railway Group Science and Technology Program(No.2023J071)the Traction Power State Key Laboratory of the Independent Research and Development Projects(No.2022TPL-T02),China.
文摘In recent years,train-tail swaying of 160 km/h electric multiple units(EMUs)inside single-line tunnels has been heavily researched,because the issue needs to be solved urgently.In this paper,a co-simulation model of vortex-induced vibration(VIV)of the tail car body is established,and the aerodynamics of train-tail swaying is studied.The simulation results were confirmed through a field test of operating EMUs.Furthermore,the influence mechanism of train-tail swaying on the wake flow field is studied in detail through a wind-tunnel experiment and a simulation of a reduced-scaled train model.The results demonstrate that the aerodynamic force frequency(i.e.,vortex-induced frequency)of the train tail increases linearly with train speed.When the train runs at 130 km/h,with a small amplitude of train-tail swaying(within 10 mm),the vortex-induced frequency is 1.7 Hz,which primarily depends on the nose shape of the train tail.After the tail car body nose is extended,the vortex-induced frequency is decreased.As the swaying amplitude of the train tail increases(exceeding 25 mm),the separation point of the high-intensity vortex in the train wake shifts downstream to the nose tip,and the vortex-induced frequency shifts from 1.7 Hz to the nearby car body hunting(i.e.,the primary hunting)frequency of 1.3 Hz,which leads to the frequency-locking phenomenon of VIV,and the resonance intensifies train-tail swaying.For the motor vehicle of the train tail,optimization of the yaw damper to improve its primary hunting stability can effectively alleviate train-tail swaying inside single-line tunnels.Optimization of the tail car body nose shape reduces the amplitude of the vortex-induced force,thereby weakening the aerodynamic effect and solving the problem of train-tail swaying inside the single-line tunnels.
