Varieties of research on turbulent-induced noise are conducted with combinations of acoustic analogy methods and computational fluid dynamic methods to analyse efficiently and accurately. Application of FW-H acoustic ...Varieties of research on turbulent-induced noise are conducted with combinations of acoustic analogy methods and computational fluid dynamic methods to analyse efficiently and accurately. Application of FW-H acoustic analogy without turbulent noise is the most popular method due to its calculation cost. In this paper, turbulent-induced noise is predicted using RANS turbulence model and permeable FW-H method. For simplicity, noise from 2D cylinder is examined using three different methods: direct method of RANS, FW-H method without turbulent noise and permeable FW-H method which can take into account of turbulent-induced noise. Turbulent noise was well predicted using permeable FW-H method with same computational cost of original FW-H method. Also, ability of permeable FW-H method to predict highly accurate turbulent-induced noise by applying adequate permeable surface is presented. The procedure to predict turbulent- induced noise using permeable FW-H is established and its usability is shown.展开更多
In the present work, the improved version of the meshless singular boundary method(ISBM) is developed for analyzing the performance of bottom standing submerged permeable breakwaters in regular normally incident waves...In the present work, the improved version of the meshless singular boundary method(ISBM) is developed for analyzing the performance of bottom standing submerged permeable breakwaters in regular normally incident waves and in the proximity of a vertical wall. Both single and dual prismatic breakwaters of rectangular and trapezoidal forms are examined. The physical problem is cast in terms of the Laplace equation governing an irrotational flow and incompressible fluid motion with appropriate mixed type boundary conditions, and solved numerically using the ISBM. To model the permeability of the breakwaters fully absorbing boundary conditions are assumed. Numerical results are presented in terms of hydrodynamic quantities of the reflection coefficients. These are firstly validated against the results of a multi-domain boundary element method(BEM) developed independently for a previous study. The agreement between the results of the two methods is excellent. The coefficients of reflection are then computed and discussed for a variety of structural conditions including the breakwaters height, width, spacing, and absorbing permeability. Effects of the proximity of the vertical plane wall are also investigated. The breakwater's width is found to have only marginal effects compared with its height. Permeability tends to decrease the minimum reflections. These coefficients show periodic variations with the spacing relative to the wavelength. Trapezoidal breakwaters are found to be more cost-effective than the rectangular breakwaters. Dual breakwater systems are confirmed to perform much better than single structures.展开更多
Interstitial flows in breakwater cores and seabeds are a key consideration in coastal and marine engineering designs and have a direct impact on their structural safety.In this paper,a unified fully coupled model for ...Interstitial flows in breakwater cores and seabeds are a key consideration in coastal and marine engineering designs and have a direct impact on their structural safety.In this paper,a unified fully coupled model for wave−permeable breakwater−porous seabed interactions is built based on an improved N−S equation.A numerical wave flume is constructed,and numerical studies are carried out by applying the finite difference method.In combination with a physical model test,the accuracy of the numerical simulation results is verified by comparing the calculated and measured values of wave height at measurement points and the seepage pressure within the breakwater and seabed.On this basis,the characteristics of the surrounding wave field and the internal flow field of the pore structure,as well as the evolution process of the fluctuating pore water pressure inside the breakwater and seabed,are further analyzed.The spatial distribution of the maximum fluctuating pore water pressure in the breakwater is compared between two cases by considering whether the seabed is permeable,and then the effect of seabed permeability on the dynamic pore water pressure in the breakwater is clarified.This study attempts to provide a reference for breakwater design and the protection of nearby seabeds.展开更多
This article investigates an unbiased analysis for the unsteady two-dimensional laminar flow of an incompressible, electrically and thermally conducting fluid across the space separated by two infinite rotating permea...This article investigates an unbiased analysis for the unsteady two-dimensional laminar flow of an incompressible, electrically and thermally conducting fluid across the space separated by two infinite rotating permeable walls.The influence of entropy generation, Hall and slip effects are considered within the flow analysis. The problem is modeled based on valid physical arguments and the unsteady system of dimensionless PDEs (partial differential equations) are solved with the help of Finite Difference Scheme. In the presence of pertinent parameters, the precise movement of the flow in terms of velocity, temperature, entropy generation rate, and Bejan numbers are presented graphically, which are parabolic in nature. Streamline profiles are also presented, which exemplify the accurate movement of the flow. The current study is one of the infrequent contributions to the existing literature as previous studies have not attempted to solve the system of high order non-linear PDEs for the unsteady flow with entropy generation and Hall effects in a permeable rotating channel. It is expected that the current analysis would provide a platform for solving the system of nonlinear PDEs of the other unexplored models that are associated to the two-dimensional unsteady flow in a rotating channel.展开更多
The research of different kinds of permeable non-Newtonian fluid flow is increasing day by day owing to the development of science,technology and production modes.It is most common to use power rate equation to descri...The research of different kinds of permeable non-Newtonian fluid flow is increasing day by day owing to the development of science,technology and production modes.It is most common to use power rate equation to describe such flows.However,this equation is nonlinear and very difficult to derive explicit exact analytical solutions.Generally,people can only derive approximate solutions with numerical methods.Recently,an advanced separating variables method which can derive exact analytical solutions easier is developed by Academician CAI Ruixian(the method of separating variables with addition).It is assumed that the unknown variable may be indicated as the sum of one-dimensional functions rather than the product in the common method of separating variables.Such method is used to solve the radial permeable power rate flow unsteady nonlinear equations on account of making the process simple.Four concise(no special functions and infinite series)exact analytical solutions is derived with the new method about this flow to develop the theory of non-Newtonian permeable fluid,which are exponential solution,two-dimensional function with time and radius,logarithmic solution,and double logarithmic solution,respectively.In addition,the method of separating variables with addition is developed and applied instead of the conventional multiplication one.It is proven to be promising and encouraging by the deducing.The solutions yielded will be valuable to the theory of the permeable power rate flow and can be used as standard solutions to check numerical methods and their differencing schemes,grid generation ways,etc.They also can be used to verify the accuracy,convergency and stability of the numerical solutions and to develop the numerical computational approaches.展开更多
Permeability is a key parameter to describe fluid transport properties of porous medium; however, the permeability measurement is extremely difficult for tight porous medium, e.g. fine-grained rock or dense soil. In t...Permeability is a key parameter to describe fluid transport properties of porous medium; however, the permeability measurement is extremely difficult for tight porous medium, e.g. fine-grained rock or dense soil. In this paper, three methods for gas permeability measurement, i.e. steady state method, pulse decay method(PDM) and pressure oscillation method(POM), are first reviewed and then their advantages and drawbacks are discussed. Both analytical and numerical solutions of gas permeability are presented for the tight porous medium. The results show that the analytical method is relatively simple but only valid under certain conditions, whilst the numerical method is more robust and generic, which can take into account several factors such as porosity, saturation, gas leakage, and unconventional boundary conditions. The influence of the effective porosity on the permeability determination is further analyzed using the proposed numerical method. In this study, new pressure data interpretation procedures for PDM and POM are proposed, and the obtained results can serve as a guidance to define a proper method for permeability measurement of the tight porous medium.展开更多
An improved design method of pervious concrete was proposed to lower the deviation between the designed and actual porosity and maintain both mechanical property and permeability of pervious concrete. The improved des...An improved design method of pervious concrete was proposed to lower the deviation between the designed and actual porosity and maintain both mechanical property and permeability of pervious concrete. The improved design method is mainly based on the optimal volume ratio of paste to aggregate(VRPA), which was determined by testing the average thickness of cement paste coating aggregate. The performances of pervious concrete designed by the traditional method and the improved one were compared. The results show that with the increase of designed porosity, the reduction of compressive strength and flexural strength of pervious concrete designed by the improved method is significantly smaller than those designed by the traditional one. The maximum deviation between the designed and actual porosity of the pervious concrete by the improved method is only 1.54%, which is far less than 8.7% obtained by the traditional one. Micro-structural analysis shows that the porous distribution of pervious concrete designed by improved method exhibits better uniformity.展开更多
Owing to the fact that the conventional deterministic back analysis of the permeability coefficient cannot reflect the uncertainties of parameters, including the hydraulic head at the boundary, the permeability coeffi...Owing to the fact that the conventional deterministic back analysis of the permeability coefficient cannot reflect the uncertainties of parameters, including the hydraulic head at the boundary, the permeability coefficient and measured hydraulic head, a stochastic back analysis taking consideration of uncertainties of parameters was performed using the generalized Bayesian method. Based on the stochastic finite element method （SFEM） for a seepage field, the variable metric algorithm and the generalized Bayesian method, formulas for stochastic back analysis of the permeability coefficient were derived. A case study of seepage analysis of a sluice foundation was performed to illustrate the proposed method. The results indicate that, with the generalized Bayesian method that considers the uncertainties of measured hydraulic head, the permeability coefficient and the hydraulic head at the boundary, both the mean and standard deviation of the permeability coefficient can be obtained and the standard deviation is less than that obtained by the conventional Bayesian method. Therefore, the present method is valid and applicable.展开更多
文摘Varieties of research on turbulent-induced noise are conducted with combinations of acoustic analogy methods and computational fluid dynamic methods to analyse efficiently and accurately. Application of FW-H acoustic analogy without turbulent noise is the most popular method due to its calculation cost. In this paper, turbulent-induced noise is predicted using RANS turbulence model and permeable FW-H method. For simplicity, noise from 2D cylinder is examined using three different methods: direct method of RANS, FW-H method without turbulent noise and permeable FW-H method which can take into account of turbulent-induced noise. Turbulent noise was well predicted using permeable FW-H method with same computational cost of original FW-H method. Also, ability of permeable FW-H method to predict highly accurate turbulent-induced noise by applying adequate permeable surface is presented. The procedure to predict turbulent- induced noise using permeable FW-H is established and its usability is shown.
基金financially supported by the Direction Général des Enseignements et de la Formation Supérieure of Algeria(Grant CNEPRU No.G0301920140029)
文摘In the present work, the improved version of the meshless singular boundary method(ISBM) is developed for analyzing the performance of bottom standing submerged permeable breakwaters in regular normally incident waves and in the proximity of a vertical wall. Both single and dual prismatic breakwaters of rectangular and trapezoidal forms are examined. The physical problem is cast in terms of the Laplace equation governing an irrotational flow and incompressible fluid motion with appropriate mixed type boundary conditions, and solved numerically using the ISBM. To model the permeability of the breakwaters fully absorbing boundary conditions are assumed. Numerical results are presented in terms of hydrodynamic quantities of the reflection coefficients. These are firstly validated against the results of a multi-domain boundary element method(BEM) developed independently for a previous study. The agreement between the results of the two methods is excellent. The coefficients of reflection are then computed and discussed for a variety of structural conditions including the breakwaters height, width, spacing, and absorbing permeability. Effects of the proximity of the vertical plane wall are also investigated. The breakwater's width is found to have only marginal effects compared with its height. Permeability tends to decrease the minimum reflections. These coefficients show periodic variations with the spacing relative to the wavelength. Trapezoidal breakwaters are found to be more cost-effective than the rectangular breakwaters. Dual breakwater systems are confirmed to perform much better than single structures.
基金supported by the National Key R&D Program of China(Grant No.2019YFB1600702)the Scientific Research Project of Yangtze-to-Huaihe Water Diversion Project(Grant No.YJJH-YJJC-ZX-20191106220)+1 种基金the Nanjing Hydraulic Research Institute Special Fund for Basic Scientific Research of Central Public Research Institutes(Grant Nos.Y220002 and Y220013)the Water Conservancy Science and Technology Project of Jiangsu Province(Grant No.2019009).
文摘Interstitial flows in breakwater cores and seabeds are a key consideration in coastal and marine engineering designs and have a direct impact on their structural safety.In this paper,a unified fully coupled model for wave−permeable breakwater−porous seabed interactions is built based on an improved N−S equation.A numerical wave flume is constructed,and numerical studies are carried out by applying the finite difference method.In combination with a physical model test,the accuracy of the numerical simulation results is verified by comparing the calculated and measured values of wave height at measurement points and the seepage pressure within the breakwater and seabed.On this basis,the characteristics of the surrounding wave field and the internal flow field of the pore structure,as well as the evolution process of the fluctuating pore water pressure inside the breakwater and seabed,are further analyzed.The spatial distribution of the maximum fluctuating pore water pressure in the breakwater is compared between two cases by considering whether the seabed is permeable,and then the effect of seabed permeability on the dynamic pore water pressure in the breakwater is clarified.This study attempts to provide a reference for breakwater design and the protection of nearby seabeds.
基金Support of the National Natural Science Foundation of China under Grant Nos.51709191 and 51706149Key Laboratory of Advanced Reactor Engineering and Safety,Ministry of Education under Grant No.ARES-2018-10
文摘This article investigates an unbiased analysis for the unsteady two-dimensional laminar flow of an incompressible, electrically and thermally conducting fluid across the space separated by two infinite rotating permeable walls.The influence of entropy generation, Hall and slip effects are considered within the flow analysis. The problem is modeled based on valid physical arguments and the unsteady system of dimensionless PDEs (partial differential equations) are solved with the help of Finite Difference Scheme. In the presence of pertinent parameters, the precise movement of the flow in terms of velocity, temperature, entropy generation rate, and Bejan numbers are presented graphically, which are parabolic in nature. Streamline profiles are also presented, which exemplify the accurate movement of the flow. The current study is one of the infrequent contributions to the existing literature as previous studies have not attempted to solve the system of high order non-linear PDEs for the unsteady flow with entropy generation and Hall effects in a permeable rotating channel. It is expected that the current analysis would provide a platform for solving the system of nonlinear PDEs of the other unexplored models that are associated to the two-dimensional unsteady flow in a rotating channel.
基金supported by National Natural Science Foundation of China(Grant No.50876106)
文摘The research of different kinds of permeable non-Newtonian fluid flow is increasing day by day owing to the development of science,technology and production modes.It is most common to use power rate equation to describe such flows.However,this equation is nonlinear and very difficult to derive explicit exact analytical solutions.Generally,people can only derive approximate solutions with numerical methods.Recently,an advanced separating variables method which can derive exact analytical solutions easier is developed by Academician CAI Ruixian(the method of separating variables with addition).It is assumed that the unknown variable may be indicated as the sum of one-dimensional functions rather than the product in the common method of separating variables.Such method is used to solve the radial permeable power rate flow unsteady nonlinear equations on account of making the process simple.Four concise(no special functions and infinite series)exact analytical solutions is derived with the new method about this flow to develop the theory of non-Newtonian permeable fluid,which are exponential solution,two-dimensional function with time and radius,logarithmic solution,and double logarithmic solution,respectively.In addition,the method of separating variables with addition is developed and applied instead of the conventional multiplication one.It is proven to be promising and encouraging by the deducing.The solutions yielded will be valuable to the theory of the permeable power rate flow and can be used as standard solutions to check numerical methods and their differencing schemes,grid generation ways,etc.They also can be used to verify the accuracy,convergency and stability of the numerical solutions and to develop the numerical computational approaches.
基金financially supported by the National Natural Science Foundation of China (Grant Nos. 41572290, 51479190 and 51879260)the Chinese Fundamental Research (973) Program (Grant No. 2015CB057906)Hubei Provincial Natural Science Foundation of China (Grant No. 2018CFA012)
文摘Permeability is a key parameter to describe fluid transport properties of porous medium; however, the permeability measurement is extremely difficult for tight porous medium, e.g. fine-grained rock or dense soil. In this paper, three methods for gas permeability measurement, i.e. steady state method, pulse decay method(PDM) and pressure oscillation method(POM), are first reviewed and then their advantages and drawbacks are discussed. Both analytical and numerical solutions of gas permeability are presented for the tight porous medium. The results show that the analytical method is relatively simple but only valid under certain conditions, whilst the numerical method is more robust and generic, which can take into account several factors such as porosity, saturation, gas leakage, and unconventional boundary conditions. The influence of the effective porosity on the permeability determination is further analyzed using the proposed numerical method. In this study, new pressure data interpretation procedures for PDM and POM are proposed, and the obtained results can serve as a guidance to define a proper method for permeability measurement of the tight porous medium.
基金Projects(51978346,51778302)supported by the National Natural Science Foundation of ChinaProject(202002N3117)supported by the Ningbo Science and Technology Project,China。
文摘An improved design method of pervious concrete was proposed to lower the deviation between the designed and actual porosity and maintain both mechanical property and permeability of pervious concrete. The improved design method is mainly based on the optimal volume ratio of paste to aggregate(VRPA), which was determined by testing the average thickness of cement paste coating aggregate. The performances of pervious concrete designed by the traditional method and the improved one were compared. The results show that with the increase of designed porosity, the reduction of compressive strength and flexural strength of pervious concrete designed by the improved method is significantly smaller than those designed by the traditional one. The maximum deviation between the designed and actual porosity of the pervious concrete by the improved method is only 1.54%, which is far less than 8.7% obtained by the traditional one. Micro-structural analysis shows that the porous distribution of pervious concrete designed by improved method exhibits better uniformity.
基金supported by the National Natural Science Foundation of China (Grant No. 50579090)the National Basic Research Program of China (973 Program, Grant No. 2007CB714102)National Science and Technology Support Program of China (Program for the Eleventh Five-Year Plan, Grant No. 2006BAB04A06)
文摘Owing to the fact that the conventional deterministic back analysis of the permeability coefficient cannot reflect the uncertainties of parameters, including the hydraulic head at the boundary, the permeability coefficient and measured hydraulic head, a stochastic back analysis taking consideration of uncertainties of parameters was performed using the generalized Bayesian method. Based on the stochastic finite element method （SFEM） for a seepage field, the variable metric algorithm and the generalized Bayesian method, formulas for stochastic back analysis of the permeability coefficient were derived. A case study of seepage analysis of a sluice foundation was performed to illustrate the proposed method. The results indicate that, with the generalized Bayesian method that considers the uncertainties of measured hydraulic head, the permeability coefficient and the hydraulic head at the boundary, both the mean and standard deviation of the permeability coefficient can be obtained and the standard deviation is less than that obtained by the conventional Bayesian method. Therefore, the present method is valid and applicable.
