High Order Numerical Simulation Of Complex Compressible Flows Based On GPU Heterogeneous Computing

Speed and accuracy are the most important things in computational fluid dynamics(CFD).In this work,considering the development tendency of high performance computer(HPC),high efficient techniques and methods are developed to accelerate CFD solver for compressible flow on modern GPU platform.A new kind of high order numerical scheme is proposed for simulating compressible flow.Based on GPU accelerated implicit large eddy simulation,the effects of bevelled nozzles in planar jets on flow structure and noise are investigated.The details and conclusions of this work as follows:(1)Based on the development tendency of high performance computer,and the characteristics of modern heterogeneous computing platform of GPU,a number of new techniques and methods are developed and optimized to accelerate high order compress-ible flow solver in general curvilinear coordinate system with GPU.The corresponding solver is developed based on these techniques.Considering the complex topologies of architecture in modern GPU computing platform,we developed a hardware-aware technology,which can optimize hardware distribution based on computation workload,including optimization of memory distribution in CPU,data transfer between CPU and GPU,communication between CPU processes,communication between GPU processes.The atomic operation and kernel decomposition technology,accompanied by high efficient memory utilization strategy,are developed to accelerate solving compressible Navier-Stokes equations.Performance tests show a maximum speedup of nearly 2000 over a single CPU core.Practical simulations prove the validity and high efficiency of present solver.(2)A new kind of high order finite difference method named AFTENO is proposed for hyperbolic conservation laws by introducing the idea of classical TENO into alternative formulation of weighted essentially non-oscillatory scheme(AFWENO).The new scheme inherits the advantages of both classical TENO and AFWENO,including interpolation of primitive variables,conservative variables,etc.,and choosing any monotone flux to construct numerical flux.AFTENO can be extended to any order that is not lower than third order,thus it is free from the constraint of WENO that has only odd orders.AFTENO can solve the problems that AFWENO may fail due to existence of multiple discontinuities in the global stencil which leads to non-smoothness in all substencils.Classical test cases demonstrate that the new scheme is capable of capturing shocks and small-scale structures better than AFWENO-type schemes.(3)The effects of bevelled nozzles in planar jets on flow structure and noise emission are investigated with high order implicit large eddy simulation.Jets with the ratios of planar difference and height L/h=0.5 and 1.0 is investigated and compared with their symmetric counterpart.Results show that the asymmetric nozzle can suppress the shock screech intensity,and a maximum drop of 7.9dB is found.Dynamic mode decomposition(DMD)analysis shows that,the frequency of the most energetic mode matches with frequency of the fundamental shock screech.The bevelled nozzles suppress the longitudinal oscillation of shock-cell structure.In the symmetric nozzle case,shock-leakage phenomenon is clearly observed,which provides evidence for shock-leakage theory to explain the source of screech generation.Moreover,shock-cell structures and shear layers in asymmetric jets are more stable than their symmetric counterpart,which can weaken the interactions between shocks and shear layers,and thus suppress the source of screech.