Nonlinear evolution analysis of T-S disturbance wave at finite amplitude in nonparallel boundary layers

ＩｎｔｒｏｄｕｃｔｉｏｎＮｏｎｌｉｎｅａｒｓｔａｂｉｌｉｔｙｐｒｏｂｌｅｍｉｎｎｏｎｐａｒａｌｌｅｌｂｏｕｎｄａｒｙｌａｙｅｒｓｎｅｅｄｓｍａｉｎｌｙｃｏｎｓｉｄｅｒｔｈｅｅｖｏｌｕｔｉｏｎｏｆｕｎｓｔａｂｉｌｉｔｙＴ＿Ｓｗａｖｅａｎｄｉｎｔｅｒａｃｔｉｏｎｂｅｔｗｅｅｎｗａｖｅｓｏｆｄｉｆｆｅｒｅｎｔｆｒｅｑｕｅｎｃｉｅｓ.Ｉｔｉｓｖｅｒｙｉｍｐｏｒｔａｎｔｔｏｓｉｍｕｌａｔｅａｃｃｕｒａｔｅｌｙｓｐａｔｉａｌｅｖｏｌｕｔｉｏｎｒｏｌｅｏｆｄｉｓｔｕｒｂａｎｃｅｉｎｂｏｕｎｄａｒｙｌａｙｅｒｓ,…     

三维扰动波的非平行边界层稳定性研究

导出了三维扰动波的原始变量形式的抛物化稳定性方程（PSE）,研究了三维空间模态TS波的非平行边界层稳定性问题.采用了法向四阶紧致格式,以提高计算精度.通过给出不会导致奇性的坐标变换、修改外边界条件以及克服平行流初始值的瞬态影响和推进步长的限制,保证了计算的数值稳定.用补全元素带状矩阵法求解块三对角矩阵,大大提高了速度.计算结果清楚地显示了三维扰动波的演化过程和非平行性对边界层稳定性的影响,特别是,观察到非平行性对三维扰动波的影响,有时会使其稳定性出现逆转的现象.还研究了逆压梯度的作用.算例的结果与其他结果符合良好.     

Self-consistent parabolized stability equation (PSE) method for compressible boundary layer

The parabolized stability equation (PSE) method has been proven to be a useful and convenient tool for the investigation of the stability and transition problems of boundary layers. However, in its original formulation, for nonlinear problems, the complex wave number of each Fourier mode is determined by the so-called phase-locked rule, which results in non-self-consistency in the wave numbers. In this paper, a modification is proposed to make it self-consistent. The main idea is that, instead of allowing wave numbers to be complex, all wave numbers are kept real, and the growth or decay of each mode is simply manifested in the growth or decay of the modulus of its shape function. The validity of the new formulation is illustrated by comparing the results with those from the corresponding direct numerical simulation (DNS) as applied to a problem of compressible boundary layer with Mach number 6.     

Improvement for expansion of parabolized stability equation method in boundary layer stability analysis

An improved expansion of the parabolized stability equation(iEPSE) method is proposed for the accurate linear instability prediction in boundary layers. It is a local eigenvalue problem, and the streamwise wavenumber α and its streamwise gradient dα/dx are unknown variables. This eigenvalue problem is solved for the eigenvalue dα/dx with an initial α, and the correction of α is performed with the conservation relation used in the PSE. The i EPSE is validated in several compressible and incompressible boundary layers. The computational results show that the prediction accuracy of the i EPSE is significantly higher than that of the ESPE, and it is in excellent agreement with the PSE which is regarded as the baseline for comparison. In addition, the unphysical multiple eigenmode problem in the EPSE is solved by using the i EPSE. As a local non-parallel stability analysis tool, the i EPSE has great potential application in the eNtransition prediction in general three-dimensional boundary layers.     

一种分析具有局部非线性的多自由度动力系统动力特性的方法

对于具有局部非线性的多自由度动力系统,提出一种有效方法,该方法将线性自由度转换到模态空间中,并对其进行缩减,而将非一自由度仍保留在物理空间中,避免了在数值分析中求非线性因素时的坐标转换。     

Difference scheme for an initial-boundary value problem for linear coefficient-varied parabolic differential equation with a nonsmooth boundary layer function

In this paper, using nonumiform mesh and exponentially fitted difference method,a uniformly convergent difference scheme .for an initial-boundary value problem of linear parabolic differential equation with the nonsmooth boundary layer function with respect to small parameter ε is given, and error estimate and numerical result are also given.     

A compact finite difference method for solving Burgers' equation

In this paper, a high‐order accurate compact finite difference method using the Hopf–Cole transformation is introduced for solving one‐dimensional Burgers' equation numerically. The stability and convergence analyses for the proposed method are given, and this method is shown to be unconditionally stable. To demonstrate efficiency, numerical results obtained by the proposed scheme are compared with the exact solutions and the results obtained by some other methods. The proposed method is second‐ and fourth‐order accurate in time and space, respectively. Copyright © 2009 John Wiley & Sons, Ltd.     

色散方程的高稳定性两层四点显格式的单点精细积分法

基于单点精细积分的思想,对色散方程Ｕｔ＝ａＵｘｘｘ构造了一类高稳定性的两层四点显式差分格式,其局部截断误差为Ｏ（τ＋ｈ）稳定性条件为│Ｒ│＝│ａτ／ｈ＾３│≤ｆ（β）,对任意正实数β为单调递增函数,它们不仅显著地改善了同类格式的稳定性条件│Ｒ│≤０．２５而且也优于众多三层多点（５点或５点以上）显格式的稳定性条件。     

色散方程的高稳定性三层五点显格式的广义单点精细积分法

基于文（１）中的单点精细积分方法,对色散方程Ｕｔ＝ａＵｘｘｘ提出了一种构造高稳定性三层五点（蛙跳）显格式的广义单点精细积分法,文中格式的局部截断误差为Ｏ（ｘ＾２＋ｈ＾２）,而稳定性条件为｜Ｒ｜≤ｇ（β）（其中ｇ对任意正实数是单调递增函数）,同时类格式中最好的。     

A numerical method based on boundary integral equations and radial basis functions for plane anisotropic thermoelastostatic equations with general variable coefficients

A boundary integral method with radial basis function approximation is proposed for numerically solving an important class of boundary value problems governed by a system of thermoelastostatic equations with variable coefficients. The equations describe the thermoelastic behaviors of nonhomogeneous anisotropic materials with properties that vary smoothly from point to point in space. No restriction is imposed on the spatial variations of the thermoelastic coefficients as long as all the requirements of the laws of physics are satisfied. To check the validity and accuracy of the proposed numerical method, some specific test problems with known solutions are solved.     

An efficient numerical solution for linear stability of circular jet: A combination of Petrov–Galerkin spectral method and exponential coordinate transformation based on Fornberg's treatment

This paper presents the linear stability analysis of a round jet in a radially unbounded domain using a spectral Petrov–Galerkin scheme coped with exponential coordinate transformation based on Fornberg's treatment. A Fourier–Chebyshev Petrov–Galerkin spectral method is described for the computation of the linear stability equations based on half a Gauss–Lobatto mesh. Complex basis functions presented here are exponentially mapped as Chebyshev functions, which satisfy the pole condition exactly at the origin, and can be used to expand vector functions efficiently by using the solenoidal condition. The mathematical formulation is presented in detail focusing on the solenoidal vector field used for the approximation of the flow. The scheme provides spectral accuracy in the present cases and the numerical results are in agreement with former works. Copyright © 2008 John Wiley & Sons, Ltd.