弹箭设计、弹道计算和稳定性研究都需要准确预测旋转弹箭的马格努斯力和力矩,国内针对旋转弹箭气动特性的数值模拟工作集中在旋成体上,对带翼外形进行完全时间相关的非定常研究鲜有见到;国外虽然有对带翼外形开展研究,但以验证方法为主...弹箭设计、弹道计算和稳定性研究都需要准确预测旋转弹箭的马格努斯力和力矩,国内针对旋转弹箭气动特性的数值模拟工作集中在旋成体上,对带翼外形进行完全时间相关的非定常研究鲜有见到;国外虽然有对带翼外形开展研究,但以验证方法为主,对湍流模型在复杂外形弹箭旋转中的研究未曾见到.采用完全时间相关的非定常N-S方程,对带翼弹箭开展计算,对比了一方程SA(Spalart-Allmaras)湍流模型和两方程k-ωSST(shear-stress-transport)湍流模型对马格努斯效应产生的影响,并分析了旋转导致的边界层和涡非对称畸变,以及周向压力分布和剪切应力分布非对称畸变.结果表明:旋转引起的物面流场参数变化主要体现在弹体中后部,SA和SST湍流模型预测的全弹马格努斯特性与阿诺德工程发展中心(Arnold Engineering Development Center,AEDC)实验及陆军研究实验室(Army Research Laboratory,ARL)的计算结果一致性很好,对动导数而言两湍流模型计算精度相当.两湍流模型计算的弹体左侧流场参数差异比右侧大,分析认为正向旋转使左侧壁面速度方向与来流速度相反,相互阻碍使气流脉动效应更强.壁面附近湍流黏性系数SA结果大于SST结果,y=0截面物面压力SA结果小于SST结果、最大相差6%,摩阻系数SA结果大于SST结果、最大相差35%.SA对旋转产生的分离抑制作用强于SST.展开更多
In this paper, a novel study on performance of closed loop pulsating heat pipe（CLPHP）using ammonia as working fluid is experimented. The tested CLPHP, consisting of six turns, is fully made of quartz glass tubes wit...In this paper, a novel study on performance of closed loop pulsating heat pipe（CLPHP）using ammonia as working fluid is experimented. The tested CLPHP, consisting of six turns, is fully made of quartz glass tubes with 6 mm outer diameter and 2 mm inner diameter. The filling ratio is50%. The visualization investigation is conducted to observe the oscillation and circulation flow in the CLPHP. In order to investigate the effects of inclination angles to thermal performance in the ammonia CLPHP, four case tests are studied. The trends of temperature fluctuation and thermal resistance as the input power increases at different inclination angles are highlighted. The results show that it is very easy to start up and circulate for the ammonia CLPHP at an inclining angle.The thermal resistance is low to 0.02 K/W, presenting that heat fluxes can be transferred from heating section to cooling section very quickly. It is found that the thermal resistance decreases as the inclination angle increases. At the horizontal operation, the ammonia CLPHP can be easy to start up at low input power, but hard to circulate. In this case, once the input power is high,the capillary tube in heating section will be burnt out, leading to worse thermal performance with high thermal resistance.展开更多
Experimental study was conducted for boundarylayers on a sharp 5° half-angle cone of 400mm length at angles of attack. The model was tested in the T-326 hypersonic wind tunnel （ITAM） at freestream Mach number M...Experimental study was conducted for boundarylayers on a sharp 5° half-angle cone of 400mm length at angles of attack. The model was tested in the T-326 hypersonic wind tunnel （ITAM） at freestream Mach number M = 5.95. Mean and fluctuation wall characteristics of the boundary layer are measured at 0°, 2°, 3° and 4° angles of attack for different stagnation pressures. Pulsation measurements are carried out by means of ALTP sensor. Pressure and temperature distributions along the model are obtained, and transition beginning and end locations have been found. Boundary layer stabilization with the increase of angle of attack and the decrease of stagnation pressure is observed. High frequency pulsations inherent to hypersonic boundary layer （second mode） have been detected.展开更多
The inner flow environment of turbomachinery presents strong three-dimensional, rotational, and unsteady characteristics. Consequently, a deep understanding of these flow phenomena will be the prerequisite to establis...The inner flow environment of turbomachinery presents strong three-dimensional, rotational, and unsteady characteristics. Consequently, a deep understanding of these flow phenomena will be the prerequisite to establish a state-of-the-art design system of turbomachinery. Currently the development of more accurate turbulence models and CFD tools is in urgent need for a high-quality database for validation, especially the advanced CFD tools, such as large eddy simulation（LES）. Under this circumstance, this paper presents a detailed experimental investigation on the 3D unsteady flow field inside a laboratory-scale isolated-rotor with multiple advanced measurement techniques, including traditional aerodynamic probes, hotwire probes, unsteady endwall static pressure measurement, and stereo particle image velocimetry（SPIV）. The inlet boundary layer profile is measured with both hotwire probe and aerodynamic probe. The steady and unsteady flow fields at the outlet of the rotor are measured with a mini five-hole probe and a single-slanted hotwire probe. The instantaneous flow field in the rotor tip region inside the passage is captured with SPIV,and then a statistical analysis of the spatial distribution of the instantaneous tip leakage vortex/flow is performed to understand its dynamic characteristics. Besides these, the uncertainty analysis of each measurement technique is described. This database is quite sufficient to validate the advanced numerical simulation with LES. The identification process of the tip leakage vortex core in the instantaneous frames obtained from SPIV is performed deliberately. It is concluded that the ensemble-averaged flow field could not represent the tip leakage vortex strength and the trajectory trace. The development of the tip leakage vortex could be clearly cataloged into three phasesaccording to their statistical spatial distribution. The streamwise velocity loss induced by the tip leakage flow increases until the splitting process is weak and the turbulent mixing phase is dominant.展开更多
An experimental study was conducted on the interactions of shock wave/turbulence or laminar boundary layer caused by fin-type protuberance, as the lack of detailed understanding of fluctuating pressure loads inside an...An experimental study was conducted on the interactions of shock wave/turbulence or laminar boundary layer caused by fin-type protuberance, as the lack of detailed understanding of fluctuating pressure loads inside and outside the laminar or turbulence boundary layer separation region in hypersonic flow. The changes of fluctuating pressure in separation region were focused on in this paper. The study shows that the existence of fin changes flowfiled on the plate significantly. The laminar boundary layer separation occurs earlier and the separation region is more extensive. Similar flow is observed between a couple of measurement points outside the laminar separation region. However, there are significant differences between the flow inside and outside the separation region. The level of fluctuating pressure of laminar boundary layer is smaller than that in turbulent case. Even so, in laminar case, the peak fluctuating pressure still reaches a high level. Therefore, the structural influence （damage and/or early fatigue） of fluctuating pressure loads caused by the laminar boundary layer separation should not be ignored.展开更多
The interaction flowfield of gaseous jets ejecting from three different orifice configurations into a Mach 5 turbulent crossflow over a flat plate was investigated experimentally. These jet configurations have equal e...The interaction flowfield of gaseous jets ejecting from three different orifice configurations into a Mach 5 turbulent crossflow over a flat plate was investigated experimentally. These jet configurations have equal equivalent throat diameter of 6 mm and nominal exit Mach number of 3. Schlieren photography was used to visualize the spatial flow structures;meanwhile surface oil flow patterns were employed to identify the separation and reattachment regions on the flat plate. Results show the influence of the jet-to-freestream static pressure ratio and jet configurations on flow interaction characteristics.展开更多
In the past two decades,the world’s unmanned aerial vehicle(UAV)industry has developed rapidly.Various kinds of UAVs have been used in military and civilian fields.Based on the characteristics of UAVs and the develop...In the past two decades,the world’s unmanned aerial vehicle(UAV)industry has developed rapidly.Various kinds of UAVs have been used in military and civilian fields.Based on the characteristics of UAVs and the development of aerodynamics,this article analyzes the development of aerodynamic optimization design and dynamic numerical simulation technology,then lists engineering applications.Both aerodynamic optimization design and dynamic numerical simulation have greatly shortened the UAV design period and reduced the research and design cost.These two methods gradually replace traditional methods such as wind tunnel test.展开更多
In this paper,a novel study on full visualization and startup performances of pulsating heat pipe using ammonia as working fluid are experimented.The tested pulsating heat pipe,consisting of 6 turns,is fully made of q...In this paper,a novel study on full visualization and startup performances of pulsating heat pipe using ammonia as working fluid are experimented.The tested pulsating heat pipe,consisting of 6 turns,is fully made of quartz glass tubes with 6 mm outer diameter and 2 mm inner diameter.The filling ratio is 70%.Wall temperature fluctuations of several key positions are recorded under a series charge of heat inputs.The visualization investigation is conducted to observe the oscillations and circulation flows with the advantage of high quality digital video camera,by which the unique thermodynamic behaviors are able to recognize and analyze more easily.The experimental results show that the startup power required by the ammonia Pulsating Heat Pipe(PHP)is very small,owing to particular identities of ammonia.It is observed that there are also some unevenly distributions in slug-train during initial and operating state.Phenomena such as circulation flows and local oscillations coupling breaking up of bubbles and formation of slugs are observed.展开更多
In order to investigate the effects of probe support on the stall characteristics of micro compressors, an experiment was carried out on a large-scale low-speed research compressor according to the principle of geomet...In order to investigate the effects of probe support on the stall characteristics of micro compressors, an experiment was carried out on a large-scale low-speed research compressor according to the principle of geometric similarity. A cylindrical probe support intruding to 50% blade span was mounted at 50% chord upstream from the rotor blade leading edge. The static pressure rise characteristic of the compressor is measured, with and without the probe support respectively. The dynamic compressor behavior from pre-stall to full stall was also measured. The results indicate that the stability margin of the compressor is lowered after installing the probe support. The stall inception is aroused by modal wave disturbances. The disturbances developed into two stall cells smoothly before installing the probe support, while the disturbances first developed into a single stall cell then splitting into two stall cells after installing the probe support. The presence of probe support lowers the initial intensity of the rotating stall of the compressor, while it doesn't alter the intensity of the rotation stall after the compressor enters into full stall.展开更多
文摘弹箭设计、弹道计算和稳定性研究都需要准确预测旋转弹箭的马格努斯力和力矩,国内针对旋转弹箭气动特性的数值模拟工作集中在旋成体上,对带翼外形进行完全时间相关的非定常研究鲜有见到;国外虽然有对带翼外形开展研究,但以验证方法为主,对湍流模型在复杂外形弹箭旋转中的研究未曾见到.采用完全时间相关的非定常N-S方程,对带翼弹箭开展计算,对比了一方程SA(Spalart-Allmaras)湍流模型和两方程k-ωSST(shear-stress-transport)湍流模型对马格努斯效应产生的影响,并分析了旋转导致的边界层和涡非对称畸变,以及周向压力分布和剪切应力分布非对称畸变.结果表明:旋转引起的物面流场参数变化主要体现在弹体中后部,SA和SST湍流模型预测的全弹马格努斯特性与阿诺德工程发展中心(Arnold Engineering Development Center,AEDC)实验及陆军研究实验室(Army Research Laboratory,ARL)的计算结果一致性很好,对动导数而言两湍流模型计算精度相当.两湍流模型计算的弹体左侧流场参数差异比右侧大,分析认为正向旋转使左侧壁面速度方向与来流速度相反,相互阻碍使气流脉动效应更强.壁面附近湍流黏性系数SA结果大于SST结果,y=0截面物面压力SA结果小于SST结果、最大相差6%,摩阻系数SA结果大于SST结果、最大相差35%.SA对旋转产生的分离抑制作用强于SST.
基金supported by the National Natural Science Foundation of China (No. 51176190)
文摘In this paper, a novel study on performance of closed loop pulsating heat pipe（CLPHP）using ammonia as working fluid is experimented. The tested CLPHP, consisting of six turns, is fully made of quartz glass tubes with 6 mm outer diameter and 2 mm inner diameter. The filling ratio is50%. The visualization investigation is conducted to observe the oscillation and circulation flow in the CLPHP. In order to investigate the effects of inclination angles to thermal performance in the ammonia CLPHP, four case tests are studied. The trends of temperature fluctuation and thermal resistance as the input power increases at different inclination angles are highlighted. The results show that it is very easy to start up and circulate for the ammonia CLPHP at an inclining angle.The thermal resistance is low to 0.02 K/W, presenting that heat fluxes can be transferred from heating section to cooling section very quickly. It is found that the thermal resistance decreases as the inclination angle increases. At the horizontal operation, the ammonia CLPHP can be easy to start up at low input power, but hard to circulate. In this case, once the input power is high,the capillary tube in heating section will be burnt out, leading to worse thermal performance with high thermal resistance.
基金the Russian Foundation for Basic Research (Grant 08-01-91956-NNIO)ADTP RNP 2.1.1/3963Program RAS (project 11/9)
文摘Experimental study was conducted for boundarylayers on a sharp 5° half-angle cone of 400mm length at angles of attack. The model was tested in the T-326 hypersonic wind tunnel （ITAM） at freestream Mach number M = 5.95. Mean and fluctuation wall characteristics of the boundary layer are measured at 0°, 2°, 3° and 4° angles of attack for different stagnation pressures. Pulsation measurements are carried out by means of ALTP sensor. Pressure and temperature distributions along the model are obtained, and transition beginning and end locations have been found. Boundary layer stabilization with the increase of angle of attack and the decrease of stagnation pressure is observed. High frequency pulsations inherent to hypersonic boundary layer （second mode） have been detected.
基金subtask of the Sino-French project Advanced Experiments and Simulations of Complex Flow in Turbomachinesco-supported by the National Natural Science Foundation of China (Nos. 51161130525 and 51136003)+1 种基金the 111 Project (No. B07009)the Innovation Foundation of BUAA for Ph D Graduates (No. YWF-14YJSY-014)
文摘The inner flow environment of turbomachinery presents strong three-dimensional, rotational, and unsteady characteristics. Consequently, a deep understanding of these flow phenomena will be the prerequisite to establish a state-of-the-art design system of turbomachinery. Currently the development of more accurate turbulence models and CFD tools is in urgent need for a high-quality database for validation, especially the advanced CFD tools, such as large eddy simulation（LES）. Under this circumstance, this paper presents a detailed experimental investigation on the 3D unsteady flow field inside a laboratory-scale isolated-rotor with multiple advanced measurement techniques, including traditional aerodynamic probes, hotwire probes, unsteady endwall static pressure measurement, and stereo particle image velocimetry（SPIV）. The inlet boundary layer profile is measured with both hotwire probe and aerodynamic probe. The steady and unsteady flow fields at the outlet of the rotor are measured with a mini five-hole probe and a single-slanted hotwire probe. The instantaneous flow field in the rotor tip region inside the passage is captured with SPIV,and then a statistical analysis of the spatial distribution of the instantaneous tip leakage vortex/flow is performed to understand its dynamic characteristics. Besides these, the uncertainty analysis of each measurement technique is described. This database is quite sufficient to validate the advanced numerical simulation with LES. The identification process of the tip leakage vortex core in the instantaneous frames obtained from SPIV is performed deliberately. It is concluded that the ensemble-averaged flow field could not represent the tip leakage vortex strength and the trajectory trace. The development of the tip leakage vortex could be clearly cataloged into three phasesaccording to their statistical spatial distribution. The streamwise velocity loss induced by the tip leakage flow increases until the splitting process is weak and the turbulent mixing phase is dominant.
基金Acknowledgements The authors acknowledge the support from the Key National Natural Science Foundation of China （No. 91116009 ＆ No. 91216114）. The support provided by the FD-20 wind tunnel staff is greatly appreciated.
文摘An experimental study was conducted on the interactions of shock wave/turbulence or laminar boundary layer caused by fin-type protuberance, as the lack of detailed understanding of fluctuating pressure loads inside and outside the laminar or turbulence boundary layer separation region in hypersonic flow. The changes of fluctuating pressure in separation region were focused on in this paper. The study shows that the existence of fin changes flowfiled on the plate significantly. The laminar boundary layer separation occurs earlier and the separation region is more extensive. Similar flow is observed between a couple of measurement points outside the laminar separation region. However, there are significant differences between the flow inside and outside the separation region. The level of fluctuating pressure of laminar boundary layer is smaller than that in turbulent case. Even so, in laminar case, the peak fluctuating pressure still reaches a high level. Therefore, the structural influence （damage and/or early fatigue） of fluctuating pressure loads caused by the laminar boundary layer separation should not be ignored.
文摘The interaction flowfield of gaseous jets ejecting from three different orifice configurations into a Mach 5 turbulent crossflow over a flat plate was investigated experimentally. These jet configurations have equal equivalent throat diameter of 6 mm and nominal exit Mach number of 3. Schlieren photography was used to visualize the spatial flow structures;meanwhile surface oil flow patterns were employed to identify the separation and reattachment regions on the flat plate. Results show the influence of the jet-to-freestream static pressure ratio and jet configurations on flow interaction characteristics.
文摘In the past two decades,the world’s unmanned aerial vehicle(UAV)industry has developed rapidly.Various kinds of UAVs have been used in military and civilian fields.Based on the characteristics of UAVs and the development of aerodynamics,this article analyzes the development of aerodynamic optimization design and dynamic numerical simulation technology,then lists engineering applications.Both aerodynamic optimization design and dynamic numerical simulation have greatly shortened the UAV design period and reduced the research and design cost.These two methods gradually replace traditional methods such as wind tunnel test.
基金The authors gratefully acknowledge financial support for this work from the National Science Foundation of China(NSFC 51176190).
文摘In this paper,a novel study on full visualization and startup performances of pulsating heat pipe using ammonia as working fluid are experimented.The tested pulsating heat pipe,consisting of 6 turns,is fully made of quartz glass tubes with 6 mm outer diameter and 2 mm inner diameter.The filling ratio is 70%.Wall temperature fluctuations of several key positions are recorded under a series charge of heat inputs.The visualization investigation is conducted to observe the oscillations and circulation flows with the advantage of high quality digital video camera,by which the unique thermodynamic behaviors are able to recognize and analyze more easily.The experimental results show that the startup power required by the ammonia Pulsating Heat Pipe(PHP)is very small,owing to particular identities of ammonia.It is observed that there are also some unevenly distributions in slug-train during initial and operating state.Phenomena such as circulation flows and local oscillations coupling breaking up of bubbles and formation of slugs are observed.
基金funded by the National Natural Science Foundation of China(Grant No.51161130525 and 51136003)the 111 Project,No.B07009
文摘In order to investigate the effects of probe support on the stall characteristics of micro compressors, an experiment was carried out on a large-scale low-speed research compressor according to the principle of geometric similarity. A cylindrical probe support intruding to 50% blade span was mounted at 50% chord upstream from the rotor blade leading edge. The static pressure rise characteristic of the compressor is measured, with and without the probe support respectively. The dynamic compressor behavior from pre-stall to full stall was also measured. The results indicate that the stability margin of the compressor is lowered after installing the probe support. The stall inception is aroused by modal wave disturbances. The disturbances developed into two stall cells smoothly before installing the probe support, while the disturbances first developed into a single stall cell then splitting into two stall cells after installing the probe support. The presence of probe support lowers the initial intensity of the rotating stall of the compressor, while it doesn't alter the intensity of the rotation stall after the compressor enters into full stall.
