Cascade kernels for models of the turbulent fluid cascade

Abstract

This paper presents calculations of the Castaing (Physica D, 46, 177, 1990) cascade kernels for five well-known models of the turbulent cascade and demonstrates that these kernels provide conceptually simple and direct descriptions of turbulence models equivalent to their multifractal spectra. The problem with a log-normal model seems to be that its Castaing kernel predicts a small but non-zero probability that finite-amplitude turbulence will decay to arbitrarily large turbulent amplitudes at smaller scales. Kernels for log-Poisson models do not have this pathology. It is shown how kernels evolve when the cascade model itself varies with scale. Future studies of other kernels compatible with and even dictated by detailed fluid physics may assist understanding of the turbulent cascade.