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Time-dependent generalized polynomial chaos

机译:时间相关的广义多项式混沌

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Generalized polynomial chaos (gPC) has non-uniform convergence and tends to break down for long-time integration. The reason is that the probability density distribution (PDF) of the solution evolves as a function of time. The set of orthogonal polynomials associated with the initial distribution will therefore not be optimal at later times, thus causing the reduced efficiency of the method for long-time integration. Adaptation of the set of orthogonal polynomials with respect to the changing PDF removes the error with respect to long-time integration. In this method new stochastic variables and orthogonal polynomials are constructed as time progresses. In the new stochastic variable the solution can be represented exactly by linear functions. This allows the method to use only low order polynomial approximations with high accuracy. The method is illustrated with a simple decay model for which an analytic solution is available and subsequently applied to the three mode Kraichnan-Orszag problem with favorable results.
机译:广义多项式混沌(gPC)具有不均匀的收敛性,并且倾向于分解以进行长时间积分。原因是解决方案的概率密度分布(PDF)随时间变化。因此,与初始分布相关的正交多项式的集合在以后的时间将不是最佳的,从而导致用于长时间积分的方法的效率降低。相对于变化的PDF调整正交多项式的集合消除了关于长时间积分的误差。在这种方法中,随着时间的推移,构造了新的随机变量和正交多项式。在新的随机变量中,解决方案可以由线性函数精确表示。这允许该方法仅使用高精度的低阶多项式逼近。用一个简单的衰减模型说明了该方法,可以使用该模型的解析解,然后将其应用于三模Kraichnan-Orszag问题,并获得满意的结果。

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