Proceedings PaperWavelets, turbulence, and boundary value problems for partial differential equations
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In this paper the qualitative properties of an inviscid, incompressible two-dimensional fluid are examined by numerical methods based on the compactly supported wavelets (the wavelet- Galerkin method). In particular, we examine the behavior of the spatial gradients of the vorticity. The growth of these gradients is related to the transfer of enstrophy (integral of squared vorticity) to the small-scales of the fluid motion. Implicit time differencing and wavelet-Galerkin space discretization allow a direct investigation of the long time behavior of the inviscid fluid. The effects of hyperviscosity on the long time limit are examined. To solve boundary problems we developed a new numerical method for the solution of partial differential equations in nonseparable domains. The method uses a wavelet-Galerkin solver with a nontrivial adaptation of the standard capacitance matrix method. The numerical solutions exhibit spectral convergence with regard to the order of the compactly supported, Daubechies wavelet basis. Furthermore, the rate of convergence is found to be independent of the geometry. We solve the Helmholtz equation since, for the indefinite case, the solutions have qualitative properties that well illustrate the applications of our method.