For a complex flow about multi-element airfoils a mixed grid method is set up. C-type grids are produced on each element′s body and in their wakes at first, O-type grids are given in the outmost area, and H-type grid...For a complex flow about multi-element airfoils a mixed grid method is set up. C-type grids are produced on each element′s body and in their wakes at first, O-type grids are given in the outmost area, and H-type grids are used in middle additional areas. An algebra method is used to produce the initial grids in each area. And the girds are optimized by elliptical differential equation method. Then C-O-H zonal patched grids around multi-element airfoils are produced automatically and efficiently. A time accurate finite-volume integration method is used to solve the compressible laminar and turbulent Navier-Stokes (N-S) equations on the grids. Computational results prove the method to be effective.展开更多
The paper is to integrate aerodynamic and aero-acoustic optimizatiom design of high lift devices,especially for two-element airfoils with slat.Aerodynamic analysis on flow field utilizes a high-order,high-resolution s...The paper is to integrate aerodynamic and aero-acoustic optimizatiom design of high lift devices,especially for two-element airfoils with slat.Aerodynamic analysis on flow field utilizes a high-order,high-resolution spatial differential method for large eddy simulation(LES),which can guarantee accuracy and efficiency.The aeroacoustic analysis for noise level is calculated with Ffowcs Williams-Hawkings(FW-H)integration formula.Fidelity of calculation is verified by standard models.Method of streamline-based Euler simulation(MSES)is used to obtain the aerodynamic characters.Based on the confirmation of numerical methods,detailed research has been conducted for the leading edge slat on multi-element airfoils.Various slot parameter influences on noise are analyzed.The results of the slot optimization parameters can be used in multi-element airfoil design.展开更多
A hybrid Cartesian grid/gridless method is developed for calculating viscous flows over multi-element airfoils.The method adopts an unstructured Cartesian grid to cover most areas of the computational domain and leave...A hybrid Cartesian grid/gridless method is developed for calculating viscous flows over multi-element airfoils.The method adopts an unstructured Cartesian grid to cover most areas of the computational domain and leaves only small region adjacent to the aerodynamic bodies to be filled with the cloud of points used in the gridless methods,which results in a better combination of the computational efficiency of the Cartesian grid and the flexibility of the gridless method in handling complex geometries.The clouds of points in the local gridless region are implemented in an anisotropic way according to the features of the thin boundary layer of the viscous flows over the airfoils,and the clouds of points at the vicinity of the interface between the grid and the gridless regions are also controlled by using an adaptive refinement technique during the generation of the unstructured Cartesian grid.An implementation of the resulting hybrid method is presented for solving two-dimensional compressible Navier-Stokes(NS)equations.The simulations of the viscous flows over a RAE2822airfoil or a two-element airfoil are successfully carried out,and the obtained results agree well with the available experimental data.展开更多
Under complex flight conditions,such as obstacle avoidance and extreme sea state,wing-in-ground(WIG)effect aircraft need to ascend to higher altitudes,resulting in the disappearance of the ground effect.A design of hi...Under complex flight conditions,such as obstacle avoidance and extreme sea state,wing-in-ground(WIG)effect aircraft need to ascend to higher altitudes,resulting in the disappearance of the ground effect.A design of high-speed WIG airfoil considering non-ground effect is carried out by a novel two-step inverse airfoil design method that combines conditional generative adversarial network(CGAN)and artificial neural network(ANN).The CGAN model is employed to generate a variety of airfoil designs that satisfy the desired lift-drag ratios in both ground effect and non-ground effect conditions.Subsequently,the ANN model is utilized to forecast aerodynamic parameters of the generated airfoils.The results indicate that the CGAN model contributes to a high accuracy rate for airfoil design and enables the creation of novel airfoil designs.Furthermore,it demonstrates high accuracy in predicting aerodynamic parameters of these airfoils due to the ANN model.This method eliminates the necessity for numerical simulations and experimental testing through the design procedure,showcasing notable efficiency.The analysis of airfoils generated by the CGAN model shows that airfoils exhibiting high lift-drag ratios under both flight conditions typically have cambers of among[0.08c,0.105c],with the positions of maximum camber occurring among[0.35c,0.5c]of the chord length,and the leading-edge radiuses of these airfoils primarily cluster among[0.008c,0.025c]展开更多
To study the effects of the gamma reflection of multi-element materials,gamma ray transport models of single-element materials,such as iron and lead,and multielement materials,such as polyethylene and ordinary concret...To study the effects of the gamma reflection of multi-element materials,gamma ray transport models of single-element materials,such as iron and lead,and multielement materials,such as polyethylene and ordinary concrete,were established in this study.Relationships among the albedo factors of the gamma photons and energies and average energy of the reflected gamma rays by material type,material thickness,incident gamma energy,and incidence angle of gamma rays were obtained by Monte Carlo simulation.The results show that the albedo factors of single-element and multi-element materials increase rapidly with an increase in the material thickness.When the thickness of the material increases to a certain value,the albedo factors do not increase further but rather tend to the saturation value.The saturation values for the albedo factors of the gamma photons,and energies and the reflection thickness are related not only to the type of material but also to the incident gamma energy and incidence angle of the gamma rays.At a given incident gamma energy,which is between 0.2 and 2.5 MeV,the smaller the effective atomic number of the multi-element material is,the higher the saturation values of the albedo factors are.The larger the incidence angle of the gamma ray is,the greater the saturation value of the gamma albedo factor,saturation reflection thickness,and average saturation energy of the reflected gamma photons are.展开更多
A set of serf-developed apparatus for foundation physical model were utilized to conduct model tests of the multi-element composite foundation with a steel pipe pile and several gravel piles. Some load-bearing charact...A set of serf-developed apparatus for foundation physical model were utilized to conduct model tests of the multi-element composite foundation with a steel pipe pile and several gravel piles. Some load-bearing characteristics of the multi-element Composite foundation, including the curves of foundation settlement, stresses of piles, pile-soil stress ratio, and load-sharing ratio of piles and soil, were obtained to study its working performances in silty sand soil. The experimental results revealed that the multi-element composite foundation with steel pipe pile and gravel pile contributed more than the gravel pile composite foundation in improving the bearing capacity of the silty fine sand.展开更多
To improve the cruise flight performance of aircraft, two new configurations of plasma actuators(grid-type and super-dense array) were investigated to reduce the turbulent skin friction drag of a low-speed airfoil. Th...To improve the cruise flight performance of aircraft, two new configurations of plasma actuators(grid-type and super-dense array) were investigated to reduce the turbulent skin friction drag of a low-speed airfoil. The induced jet characteristics of the two actuators in quiescent air were diagnosed with high-speed particle image velocimetry(PIV), and their drag reduction efficiencies were examined under different operating conditions in a wind tunnel. The results showed that the grid-type plasma actuator was capable of producing a wall-normal jet array(peak magnitude: 1.07 m/s) similar to that generated in a micro-blowing technique, while the superdense array plasma actuator created a wavy wall-parallel jet(magnitude: 0.94 m/s) due to the discrete spanwise electrostatic forces. Under a comparable electrical power consumption level,the super-dense array plasma actuator array significantly outperformed the grid-type configuration,reducing the total airfoil friction drag by approximately 22% at a free-stream velocity of 20 m/s.The magnitude of drag reduction was proportional to the dimensionless jet velocity ratio(r), and a threshold r = 0.014 existed under which little impact on airfoil drag could be discerned.展开更多
To avoid the aerodynamic performance loss of airfoil at non-design state which often appears in single point design optimization, and to improve the adaptability to the uncertain factors in actual flight environment, ...To avoid the aerodynamic performance loss of airfoil at non-design state which often appears in single point design optimization, and to improve the adaptability to the uncertain factors in actual flight environment, a two-dimensional stochastic airfoil optimization design method based on neural networks is presented. To provide highly efficient and credible analysis, four BP neural networks are built as surrogate models to predict the airfoil aerodynamic coefficients and geometry parameter. These networks are combined with the probability density function obeying normal distribution and the genetic algorithm, thus forming an optimization design method. Using the method, for GA（W）-2 airfoil, a stochastic optimization is implemented in a two-dimensional flight area about Mach number and angle of attack. Compared with original airfoil and single point optimization design airfoil, results show that the two-dimensional stochastic method can improve the performance in a specific flight area, and increase the airfoil adaptability to the stochastic changes of multiple flight parameters.展开更多
The flow around airfoil NACA0012 enwrapped by the body-fitted grid is simulated by a coupled doubledistribution-function （DDF） lattice Boltzmann method （LBM） for the compressible Navier-Stokes equations. Firstly, ...The flow around airfoil NACA0012 enwrapped by the body-fitted grid is simulated by a coupled doubledistribution-function （DDF） lattice Boltzmann method （LBM） for the compressible Navier-Stokes equations. Firstly, the method is tested by simulating the low Reynolds number flow at Ma =0. 5,a=0. 0, Re=5 000. Then the simulation of flow around the airfoil is carried out at Ma：0. 5, 0. 85, 1.2; a=-0.05, 1.0, 0.0, respectively. And a better result is obtained by using a local refined grid. It reduces the error produced by the grid at Ma=0. 85. Though the inviscid boundary condition is used to avoid the problem of flow transition to turbulence at high Reynolds numbers, the pressure distribution obtained by the simulation agrees well with that of the experimental results. Thus, it proves the reliability of the method and shows its potential for the compressible flow simulation. The suecessful application to the flow around airfoil lays a foundation of the numerical simulation of turbulence.展开更多
文摘For a complex flow about multi-element airfoils a mixed grid method is set up. C-type grids are produced on each element′s body and in their wakes at first, O-type grids are given in the outmost area, and H-type grids are used in middle additional areas. An algebra method is used to produce the initial grids in each area. And the girds are optimized by elliptical differential equation method. Then C-O-H zonal patched grids around multi-element airfoils are produced automatically and efficiently. A time accurate finite-volume integration method is used to solve the compressible laminar and turbulent Navier-Stokes (N-S) equations on the grids. Computational results prove the method to be effective.
文摘The paper is to integrate aerodynamic and aero-acoustic optimizatiom design of high lift devices,especially for two-element airfoils with slat.Aerodynamic analysis on flow field utilizes a high-order,high-resolution spatial differential method for large eddy simulation(LES),which can guarantee accuracy and efficiency.The aeroacoustic analysis for noise level is calculated with Ffowcs Williams-Hawkings(FW-H)integration formula.Fidelity of calculation is verified by standard models.Method of streamline-based Euler simulation(MSES)is used to obtain the aerodynamic characters.Based on the confirmation of numerical methods,detailed research has been conducted for the leading edge slat on multi-element airfoils.Various slot parameter influences on noise are analyzed.The results of the slot optimization parameters can be used in multi-element airfoil design.
基金Supported by the National Natural Science Foundation of China(11172134)the Funding of Jiangsu Innovation Program for Graduate Education(CXZZ110192)the Priority Academic Program Development of Jiangsu Higher Education Institutions
文摘A hybrid Cartesian grid/gridless method is developed for calculating viscous flows over multi-element airfoils.The method adopts an unstructured Cartesian grid to cover most areas of the computational domain and leaves only small region adjacent to the aerodynamic bodies to be filled with the cloud of points used in the gridless methods,which results in a better combination of the computational efficiency of the Cartesian grid and the flexibility of the gridless method in handling complex geometries.The clouds of points in the local gridless region are implemented in an anisotropic way according to the features of the thin boundary layer of the viscous flows over the airfoils,and the clouds of points at the vicinity of the interface between the grid and the gridless regions are also controlled by using an adaptive refinement technique during the generation of the unstructured Cartesian grid.An implementation of the resulting hybrid method is presented for solving two-dimensional compressible Navier-Stokes(NS)equations.The simulations of the viscous flows over a RAE2822airfoil or a two-element airfoil are successfully carried out,and the obtained results agree well with the available experimental data.
基金supported by the Priority Academic Program Development of Jiangsu Higher Education Institutions,the Fundamental Research Funds for the Central Universities(No.ILA220101A23)CARDC Fundamental and Frontier Technology Research Fund(No.PJD20200210)the Aeronautical Science Foundation of China(No.20200023052002).
文摘Under complex flight conditions,such as obstacle avoidance and extreme sea state,wing-in-ground(WIG)effect aircraft need to ascend to higher altitudes,resulting in the disappearance of the ground effect.A design of high-speed WIG airfoil considering non-ground effect is carried out by a novel two-step inverse airfoil design method that combines conditional generative adversarial network(CGAN)and artificial neural network(ANN).The CGAN model is employed to generate a variety of airfoil designs that satisfy the desired lift-drag ratios in both ground effect and non-ground effect conditions.Subsequently,the ANN model is utilized to forecast aerodynamic parameters of the generated airfoils.The results indicate that the CGAN model contributes to a high accuracy rate for airfoil design and enables the creation of novel airfoil designs.Furthermore,it demonstrates high accuracy in predicting aerodynamic parameters of these airfoils due to the ANN model.This method eliminates the necessity for numerical simulations and experimental testing through the design procedure,showcasing notable efficiency.The analysis of airfoils generated by the CGAN model shows that airfoils exhibiting high lift-drag ratios under both flight conditions typically have cambers of among[0.08c,0.105c],with the positions of maximum camber occurring among[0.35c,0.5c]of the chord length,and the leading-edge radiuses of these airfoils primarily cluster among[0.008c,0.025c]
基金This work was supported by the State Key Lab of Intense Pulsed Radiation Simulation and Effect Basic Research Foundation(No.SKLIPR1504).
文摘To study the effects of the gamma reflection of multi-element materials,gamma ray transport models of single-element materials,such as iron and lead,and multielement materials,such as polyethylene and ordinary concrete,were established in this study.Relationships among the albedo factors of the gamma photons and energies and average energy of the reflected gamma rays by material type,material thickness,incident gamma energy,and incidence angle of gamma rays were obtained by Monte Carlo simulation.The results show that the albedo factors of single-element and multi-element materials increase rapidly with an increase in the material thickness.When the thickness of the material increases to a certain value,the albedo factors do not increase further but rather tend to the saturation value.The saturation values for the albedo factors of the gamma photons,and energies and the reflection thickness are related not only to the type of material but also to the incident gamma energy and incidence angle of the gamma rays.At a given incident gamma energy,which is between 0.2 and 2.5 MeV,the smaller the effective atomic number of the multi-element material is,the higher the saturation values of the albedo factors are.The larger the incidence angle of the gamma ray is,the greater the saturation value of the gamma albedo factor,saturation reflection thickness,and average saturation energy of the reflected gamma photons are.
基金The National Natural Science Foundation of China (No.50478090)
文摘A set of serf-developed apparatus for foundation physical model were utilized to conduct model tests of the multi-element composite foundation with a steel pipe pile and several gravel piles. Some load-bearing characteristics of the multi-element Composite foundation, including the curves of foundation settlement, stresses of piles, pile-soil stress ratio, and load-sharing ratio of piles and soil, were obtained to study its working performances in silty sand soil. The experimental results revealed that the multi-element composite foundation with steel pipe pile and gravel pile contributed more than the gravel pile composite foundation in improving the bearing capacity of the silty fine sand.
基金supported by National Natural Science Foundation of China (Nos.12002384, U2341277,and 52025064)Foundation Strengthening Program (No.2021JJ-0786)。
文摘To improve the cruise flight performance of aircraft, two new configurations of plasma actuators(grid-type and super-dense array) were investigated to reduce the turbulent skin friction drag of a low-speed airfoil. The induced jet characteristics of the two actuators in quiescent air were diagnosed with high-speed particle image velocimetry(PIV), and their drag reduction efficiencies were examined under different operating conditions in a wind tunnel. The results showed that the grid-type plasma actuator was capable of producing a wall-normal jet array(peak magnitude: 1.07 m/s) similar to that generated in a micro-blowing technique, while the superdense array plasma actuator created a wavy wall-parallel jet(magnitude: 0.94 m/s) due to the discrete spanwise electrostatic forces. Under a comparable electrical power consumption level,the super-dense array plasma actuator array significantly outperformed the grid-type configuration,reducing the total airfoil friction drag by approximately 22% at a free-stream velocity of 20 m/s.The magnitude of drag reduction was proportional to the dimensionless jet velocity ratio(r), and a threshold r = 0.014 existed under which little impact on airfoil drag could be discerned.
文摘To avoid the aerodynamic performance loss of airfoil at non-design state which often appears in single point design optimization, and to improve the adaptability to the uncertain factors in actual flight environment, a two-dimensional stochastic airfoil optimization design method based on neural networks is presented. To provide highly efficient and credible analysis, four BP neural networks are built as surrogate models to predict the airfoil aerodynamic coefficients and geometry parameter. These networks are combined with the probability density function obeying normal distribution and the genetic algorithm, thus forming an optimization design method. Using the method, for GA（W）-2 airfoil, a stochastic optimization is implemented in a two-dimensional flight area about Mach number and angle of attack. Compared with original airfoil and single point optimization design airfoil, results show that the two-dimensional stochastic method can improve the performance in a specific flight area, and increase the airfoil adaptability to the stochastic changes of multiple flight parameters.
基金Supported by the Aeronautical Science Foundation of China(20061453020)Foundation for Basic Research of Northwestern Polytechnical University(03)~~
文摘The flow around airfoil NACA0012 enwrapped by the body-fitted grid is simulated by a coupled doubledistribution-function （DDF） lattice Boltzmann method （LBM） for the compressible Navier-Stokes equations. Firstly, the method is tested by simulating the low Reynolds number flow at Ma =0. 5,a=0. 0, Re=5 000. Then the simulation of flow around the airfoil is carried out at Ma：0. 5, 0. 85, 1.2; a=-0.05, 1.0, 0.0, respectively. And a better result is obtained by using a local refined grid. It reduces the error produced by the grid at Ma=0. 85. Though the inviscid boundary condition is used to avoid the problem of flow transition to turbulence at high Reynolds numbers, the pressure distribution obtained by the simulation agrees well with that of the experimental results. Thus, it proves the reliability of the method and shows its potential for the compressible flow simulation. The suecessful application to the flow around airfoil lays a foundation of the numerical simulation of turbulence.
