论文标题

具有光谱样分辨率的声波和冲击波捕获紧凑的高阶高阶气动方案

An acoustic and shock wave capturing compact high-order gas-kinetic scheme with spectral-like resolution

论文作者

Zhao, Fengxiang, Ji, Xing, Shyy, Wei, Xu, Kun

论文摘要

在本文中,将介绍具有光谱分辨率的紧凑型高阶气动方案(GKS),并将其用于模拟声波和冲击波。为了进行准确的模拟,需要数值方案具有出色的耗散分散属性,而波浪模式,传播特性和数值解的波速应保持尽可能近的距离。对于可压缩的流量模拟,数值方案必须配备适当的数值耗散,以在冲击层中进行脆皮过渡。基于高阶气体演化模型,GKS在细胞界面上提供了时间精确的溶液,可以从中获得准确的通量函数和时间不断发展的流量变量。 GKS通过沿控制体积的边界应用高斯理论,明确更新了细胞平均的保守流量变量和细胞平均梯度。基于细胞平均流量变量和细胞平均梯度,可以获得带有紧凑的模板的重建。使用二阶方案的相同模具,可以构建最高8阶的空间精度的重建,其中包括非平衡和平衡状态的非线性和线性重建。 GKS通过从非平衡状态到平衡的细胞界面处的时间演化过程统一了非线性和线性重建。在这两个限制之间的区域中,非线性和线性重建的贡献取决于$ \ exp(-ΔT /τ)$和$(1- \ exp(-ΔT /τ))$的权重函数,其中$Δt$是时间步,$τ$是粒子碰撞的时间,在冲击区域中增强了粒子碰撞。结果,可以在GK中准确捕获冲击和声波。

In this paper, a compact high-order gas-kinetic scheme (GKS) with spectral resolution will be presented and used in the simulation of acoustic and shock waves. For accurate simulation, the numerical scheme is required to have excellent dissipation-dispersion preserving property, while the wave modes, propagation characteristics, and wave speed of the numerical solution should be kept as close as possible to the exact solution of governing equations. For compressible flow simulation with shocks, the numerical scheme has to be equipped with proper numerical dissipation to make a crispy transition in the shock layer. Based on the high-order gas evolution model, the GKS provides a time accurate solution at a cell interface, from which both time accurate flux function and the time evolving flow variables can be obtained. The GKS updates explicitly both cell-averaged conservative flow variables and the cell-averaged gradients by applying Gauss-theorem along the boundary of the control volume. Based on the cell-averaged flow variables and cell-averaged gradients, a reconstruction with compact stencil can be obtained. With the same stencil of a second-order scheme, a reconstruction up to 8th-order spacial accuracy can be constructed, which include the nonlinear and linear reconstruction for the non-equilibrium and equilibrium states respectively. The GKS unifies the nonlinear and linear reconstruction through a time evolution process at a cell interface from the non-equilibrium state to an equilibrium one. In the region between these two limits, the contribution from nonlinear and linear reconstructions depends on the weighting functions of $\exp(-Δt/τ)$ and $(1-\exp(-Δt /τ))$, where $Δt$ is the time step and $τ$ is the particle collision time, which is enhanced in the shock region. As a result, both shock and acoustic wave can be captured accurately in GKS.

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