In this work,we extend the characteristic-featured shock wave indicator based on artificial neuron training to 3D high-speed flow simulation on unstructured meshes.The extension is achieved through dimension splitting...In this work,we extend the characteristic-featured shock wave indicator based on artificial neuron training to 3D high-speed flow simulation on unstructured meshes.The extension is achieved through dimension splitting.This leads to that the proposed indicator is capable of identifying regions of flow compression in any direction.With this capability,the indicator is further developed to combine with h-adaptivity of mesh refinement to improve resolution with less computational costs.The present indicator provides an attractive alternative for constructing high-resolution,high-efficiency shock-processing methods to simulate high-speed inviscid flows.展开更多
In this work,a direct discontinuous Galerkin(DDG)method with artificial viscosity is developed to solve the compressible Navier-Stokes equations for simulating the transonic or supersonic flow,where the DDG approach i...In this work,a direct discontinuous Galerkin(DDG)method with artificial viscosity is developed to solve the compressible Navier-Stokes equations for simulating the transonic or supersonic flow,where the DDG approach is used to discretize viscous and heat fluxes.A strong residual-based artificial viscosity(AV)technique is proposed to be applied in the DDG framework to handle shock waves and layer structures appearing in transonic or supersonic flow,which promotes convergence and robustness.Moreover,the AV term is added to classical BR2 methods for comparison.A number of 2-D and 3-D benchmarks such as airfoils,wings,and a full aircraft are presented to assess the performance of the DDG framework with the strong residualbased AV term for solving the two dimensional and three dimensional Navier-Stokes equations.The proposed framework provides an alternative robust and efficient approach for numerically simulating the multi-dimensional compressible Navier-Stokes equations for transonic or supersonic flow.展开更多
A comprehensive, universally valid, elegant and yet simple method to design slender axisymmetric body of minimum wave drag in transonic and supersonic flows is developed. Computational aerodynamics is also used as a t...A comprehensive, universally valid, elegant and yet simple method to design slender axisymmetric body of minimum wave drag in transonic and supersonic flows is developed. Computational aerodynamics is also used as a tool for numerical experiments in gaining physical understanding of the drag mechanism due to the geometry of the aftbody, such as the correlation between wave drag and wave distribution of the aftbody geometry. The method utilizes MFD （modified feasible direction） based optimization program, along with the linear slender body aerodynamics, for its elegance and generic optimization convenience. The efforts are focused on inviscid flow. A practical method of reducing the wave drag of a given body is developed for both bodies with pointed end and with base area, using shock wave generator at a particular location on the aftbody. The results show that the MFD optimization program can be effectively utilized in an aerodynamic optimization problem.展开更多
The achievement of laminar flow in the boundary layer at high-speed cruise conditions may further, in addition to shock-wave control, reduce the drag and extend the range of military fighter aircraft. To this end, a f...The achievement of laminar flow in the boundary layer at high-speed cruise conditions may further, in addition to shock-wave control, reduce the drag and extend the range of military fighter aircraft. To this end, a further investigation on transitional boundary-layer flow of fighter wings is needed due to different configurations from the wings used on conventional transport aircraft. In this paper, wind tunnel experiments and numerical simulations were conducted on three-dimensional transition of thin diamond-shaped wings used on advanced fighter aircraft at tran/supersonic design points. A newly proposed correlation of crossflow transition which includes the effect of surface roughness was introduced into the c-Rehttransition model. Predicted results were in good agreement with flow visualizations. Results showed that the strength of the crossflow component grew rapidly around the leading edge because of the severe flow acceleration, just as the same as wings with a large aspect ratio. However, there seemed no regular pattern of instabilitydominance variation in span-wise for a diamond configuration. The dominance of different instability mechanisms strongly depended on the local pressure distribution. Hereby, the research recommended a ‘‘roof-like" shape of pressure distribution to suppress both crossflow and Tollmien-Schlichting(T-S) instabilities. Besides, a sharp suction peak with a serious pressure rise should be cut off to avoid stronger instabilities. Further discussions also revealed an independence of the unit Reynolds number when transition was triggered by T-S instabilities. Aerodynamic force comparisons indicated that further benefit on drag reduction could be expected by including the three-dimensional transition effect into a wing design process.展开更多
基金supported by the National Numerical Wind Tunnel Project,the National Natural Science Foundation of China(No.12001031)the Academic Excellence Foundation of BUAA for PhD Students,China Postdoctoral Science Foundation(No.2020M680284).
文摘In this work,we extend the characteristic-featured shock wave indicator based on artificial neuron training to 3D high-speed flow simulation on unstructured meshes.The extension is achieved through dimension splitting.This leads to that the proposed indicator is capable of identifying regions of flow compression in any direction.With this capability,the indicator is further developed to combine with h-adaptivity of mesh refinement to improve resolution with less computational costs.The present indicator provides an attractive alternative for constructing high-resolution,high-efficiency shock-processing methods to simulate high-speed inviscid flows.
基金support of National Natural Science Foundation of China(No.12001031)China Postdoctoral Science Foundation(No.2020M680284)National Numerical Wind Tunnel Project.
文摘In this work,a direct discontinuous Galerkin(DDG)method with artificial viscosity is developed to solve the compressible Navier-Stokes equations for simulating the transonic or supersonic flow,where the DDG approach is used to discretize viscous and heat fluxes.A strong residual-based artificial viscosity(AV)technique is proposed to be applied in the DDG framework to handle shock waves and layer structures appearing in transonic or supersonic flow,which promotes convergence and robustness.Moreover,the AV term is added to classical BR2 methods for comparison.A number of 2-D and 3-D benchmarks such as airfoils,wings,and a full aircraft are presented to assess the performance of the DDG framework with the strong residualbased AV term for solving the two dimensional and three dimensional Navier-Stokes equations.The proposed framework provides an alternative robust and efficient approach for numerically simulating the multi-dimensional compressible Navier-Stokes equations for transonic or supersonic flow.
文摘A comprehensive, universally valid, elegant and yet simple method to design slender axisymmetric body of minimum wave drag in transonic and supersonic flows is developed. Computational aerodynamics is also used as a tool for numerical experiments in gaining physical understanding of the drag mechanism due to the geometry of the aftbody, such as the correlation between wave drag and wave distribution of the aftbody geometry. The method utilizes MFD （modified feasible direction） based optimization program, along with the linear slender body aerodynamics, for its elegance and generic optimization convenience. The efforts are focused on inviscid flow. A practical method of reducing the wave drag of a given body is developed for both bodies with pointed end and with base area, using shock wave generator at a particular location on the aftbody. The results show that the MFD optimization program can be effectively utilized in an aerodynamic optimization problem.
基金supported by the National Natural Science Foundation of China (No.11372254)
文摘The achievement of laminar flow in the boundary layer at high-speed cruise conditions may further, in addition to shock-wave control, reduce the drag and extend the range of military fighter aircraft. To this end, a further investigation on transitional boundary-layer flow of fighter wings is needed due to different configurations from the wings used on conventional transport aircraft. In this paper, wind tunnel experiments and numerical simulations were conducted on three-dimensional transition of thin diamond-shaped wings used on advanced fighter aircraft at tran/supersonic design points. A newly proposed correlation of crossflow transition which includes the effect of surface roughness was introduced into the c-Rehttransition model. Predicted results were in good agreement with flow visualizations. Results showed that the strength of the crossflow component grew rapidly around the leading edge because of the severe flow acceleration, just as the same as wings with a large aspect ratio. However, there seemed no regular pattern of instabilitydominance variation in span-wise for a diamond configuration. The dominance of different instability mechanisms strongly depended on the local pressure distribution. Hereby, the research recommended a ‘‘roof-like" shape of pressure distribution to suppress both crossflow and Tollmien-Schlichting(T-S) instabilities. Besides, a sharp suction peak with a serious pressure rise should be cut off to avoid stronger instabilities. Further discussions also revealed an independence of the unit Reynolds number when transition was triggered by T-S instabilities. Aerodynamic force comparisons indicated that further benefit on drag reduction could be expected by including the three-dimensional transition effect into a wing design process.
