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高超声速粗糙元诱导转捩的数值模拟及机理分析
粗糙元 直接数值模拟 高超声速 转捩机理
2018/12/28
采用直接数值模拟方法细致刻画了钻石型粗糙元诱导的高超声速边界层从层流到湍流的转捩过程,从拓扑结构稳定性和边界层流动稳定性两个角度分析了钻石型粗糙元诱导转捩的机理. 流动结构的拓扑分析表明,钻石型粗糙元头部区域和底部区域分别存在不稳定的鞍点-鞍点(SS) 型轨线和鞍点-结点-鞍点(SNS) 型轨线,在扰动的作用下其会形成非定常、非对称的振荡结构. 边界层流动失稳过程计算分析表明,钻石型粗糙元会产生高...
OCS4格式的数值边界格式及其渐近稳定性
Taylor展开 数值边界格式 渐近稳定性 整体精度
2014/4/8
根据多项式拟合数值边界格式(SFEBS)和Taylor展开数值边界格式(TEBS)相结合的思想,构造了与优化3对角4阶跳点紧致差分格式(OCS4)及其插值格式(OCI4)相匹配的具有4阶精度的数值边界格式(SF-TEBS4).通过计算格式特征值的理论分析表明,OCS4、OCI4格式在与数值边界格式SF-TEBS4格式相结合时,数值格式在整体上能够满足渐进稳定性的要求.一阶导数数值试验表明,OCS4...
A posteriori error analysis for a continuous space-time finite element method for a hyperbolic integro-differential equation
integro-differential equation continuous Galerkin finite element method convolution kernel stability a posteriori estimate
2012/5/9
An integro-differential equation of hyperbolic type, with mixed boundary conditions, is considered. A continuous space-time finite element method of degree one is formulated. A posteriori error repres...
Nonlinear dynamo in a short Taylor-Couette setup
Finite elements Magnetohydrodynamics Taylor-Couette dynamo action
2012/4/18
It is numerically demonstrated by means of a magnetohydrodynamics code that a short Taylor-Couette setup with a body force can sustain dynamo action. The magnetic threshold is comparable to what is us...
Embedded Zassenhaus Expansion to Operator Splitting Schemes: Theory and Application in Fluid Dynamics
Operator splitting method Iterative splitting Zassenhaus product Parabolic differential equations Convection-Diffusion-Reaction Equations
2012/4/18
In this paper, we contribute operator-splitting methods improved by the Zassenhaus product for the numerical solution of linear partial differential equations. We address iterative splitting methods, ...
Two-subspace Projection Method for Coherent Overdetermined Systems (Technical Report)
Two-subspace Projection Method Coherent Overdetermined Systems Technical Report Numerical Analysis
2012/4/17
In this technical report we present a Projection onto Convex Sets (POCS) type algorithm for solving systems of linear equations. POCS methods have found many applications ranging from computer tomogra...
Two-subspace Projection Method for Coherent Overdetermined Systems
Two-subspace Projection Method Coherent Overdetermined Systems Numerical Analysis Probability
2012/4/17
We present a Projection onto Convex Sets (POCS) type algorithm for solving systems of linear equations. POCS methods have found many applications ranging from computer tomography to digital signal and...
A viscoplasticity model with an enhanced control of the yield surface distortion
viscoplasticity yield function kinematic hardening distortional hardening rheology
2012/4/17
A new model of metal viscoplasticity, which takes combined isotropic, kinematic, and distortional hardening into account, is presented. The basic modeling assumptions are illustrated using a new two-d...
A cooperative conjugate gradient method for linear systems permitting multithread implementation of low complexity
cooperative conjugate gradient method linear systems multithread implementation low complexity Numerical Analysis
2012/4/17
This paper proposes a generalization of the conjugate gradient (CG) method used to solve the equation $Ax=b$ for a symmetric positive definite matrix $A$ of large size $n$. The generalization consists...
An algorithm for autonomously plotting solution sets in the presence of turning points
turning point implicit function cusp bifurcation curv
2011/8/23
Abstract: Plotting solution sets for particular equations may be complicated by the existence of turning points. Here we describe an algorithm which not only overcomes such problematic points, but doe...
Congruences for central binomial sums and finite polylogarithms
Congruences central binomial sums finite polylogarithms
2011/1/19
(This is still a preliminary draft: the proofs are complete, but the exposition will be improved in the next version.) We prove congruences, modulo a power of a prime p, for certain finite sums involv...
Time domain numerical modeling of wave propagation in 2D heterogeneous porous media
porous media elastic waves Biot’s model time splitting
2011/3/2
This paper deals with the numerical modeling of wave propagation in porous media described by Biot’s theory. The viscous efforts between the fluid and the elastic skeleton are assumed to be a linear f...
Robin inequality for $7-$free integers
Dedekind function Robin inequality Riemann Hypothesis Primorial numbers
2011/1/17
Recall that an integer is t−free iff it is not divisible by pt for some prime p. We give a method to check Robin inequality (n) < e n log log n, for t−free integers n and apply it for t =...
Numerical modeling of transient two-dimensional viscoelastic waves
wave propagation Zener model memory variables ADER schemes
2011/3/2
This paper deals with the numerical modeling of transient mechanical waves in linear viscoelastic solids. Dissipation mechanisms are described using the Zener model.
A Pseudo Random Numbers Generator Based on Chaotic Iterations. Application to Watermarking
Internet Security Chaotic Sequences Statistical Tests
2010/12/28
In this paper, a new chaotic pseudo-random number gen-erator (PRNG) is proposed. It combines the well-known ISAAC and XORshift generators with chaotic iterations. This PRNG possesses im-
portant prop...