Nested polyhedra model of turbulence
Abstract
A discretization of the wavenumber space is proposed, using nested polyhedra, in the form of alternating dodecahedra and icosahedra that are selfsimilarly scaled. This particular choice allows the possibility of forming triangles using only discretized wave vectors when the scaling between two consecutive dodecahedra is equal to the golden ratio and the icosahedron between the two dodecahedra is the dual of the inner dodecahedron. Alternatively, the same discretization can be described as a logarithmically spaced (with a scaling equal to the golden ratio), nested dodecahedronicosahedron compounds. A wave vector which points from the origin to a vertex of such a mesh, can always find two other discretized wave vectors that are also on the vertices of the mesh (which is not true for an arbitrary mesh). Thus, the nested polyhedra grid can be thought of as a reduction (or decimation) of the Fourier space using a particular set of selfsimilar triads arranged approximately in a spherical form. For each vertex (i.e., discretized wave vector) in this space, there are either 9 or 15 pairs of vertices (i.e., wave vectors) with which the initial vertex can interact to form a triangle. This allows the reduction of the convolution integral in the NavierStokes equation to a sum over 9 or 15 interaction pairs, transforming the equation in Fourier space to a network of "interacting" nodes that can be constructed as a numerical model, which evolves each component of the velocity vector on each node of the network. This model gives the usual Kolmogorov spectrum of k^{5 /3}. Since the scaling is logarithmic, and the number of nodes for each scale is constant, a very large inertial range (i.e., a very high Reynolds number) with a much lower number of degrees of freedom can be considered. Incidentally, by assuming isotropy and a certain relation between the phases, the model can be used to systematically derive shell models.
 Publication:

Physical Review E
 Pub Date:
 June 2017
 DOI:
 10.1103/PhysRevE.95.063102
 arXiv:
 arXiv:1603.01503
 Bibcode:
 2017PhRvE..95f3102G
 Keywords:

 Physics  Fluid Dynamics;
 Mathematics  Numerical Analysis;
 Nonlinear Sciences  Cellular Automata and Lattice Gases
 EPrint:
 Phys. Rev. E 95, 063102 (2017)