JSME international journal. Ser. 2, Fluids engineering, heat transfer, power, combustion, thermophysical properties
Print ISSN : 0914-8817
Diffusion of Fluid Particles by the Combined Model of Random Fourier Modes and Random Flight
Yasuhiko SAKAIJulian C. R. HUNTJimmy C. H. FUNG
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1992 Volume 35 Issue 4 Pages 497-506


To investigate the motion of fluid particles around a cylinder in turbulent flows, we developed a new model for simulating the trajectory of particles : the combined model of kinematic simulation (KS) and random flight (RF). The large-scale turbulence is simulated by a sum of random Fourier modes varying in space and time, and the small-scale turbulent fluctuation is simply modelled by an ITO type of stochastic differential equation with a memory time comparable to the Lagrangian integral time scale TLS of small-scale motion. The Lagrangian properties of fluid particles in homogeneous isotropic turbulence with uniform mean flow have been examined. Some new results have been obtained using this new model : (a) the cross-correlation of the displacements due to the large- and small-scale motions is negligibly small ; (b) random small-scale motion causes decorrelation of the large-scale velocity ; (c) the value of TLS used in RF can be reasonably estimated from pure KS.

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