Study on the Discrete Vortex Method for Modelling Turbulent Flows

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The study on the development of the Discrete Vortex Method as a modelling of turbulence structures has been carried out, and the following results were obtained.1. Taking account of the viscous diffusion effects on its vorticity strength, the vortex model of the blob technique was modified for a simpler procedure of calculation. From a series of test calculations of interaction between two vortex rings, it was confirmed that not only the connecting proscess of the two vortex rings at an early stage of the interaction but also the splitting process at the following stage were reasonably simulated by the modified blob technique.2. The modified blob technique was applied to simulation of a flow around a sphere, and it was obtained that the boundary layer separation from the sphere surface, the formation of large scale vortex structures and the appearance of three dimensional characteristics in the wake flow were reasonably simulated as far as the starting flow calculation was concerned.3. For the estimation of pressure fluctuations, a simple method was proposed to solve the pressure Poisson equation with use of the Boundary Element Method from an instantaneous velocity field calculated by the Discrete Vortex Method, and its usefulness was confirmed from its applications for unsteady flows around a circular cylinder and a sphere.4. The modified vortex technique was applied for the more reliable simulation of flows either around a circular cylinder and various rectangular cylinders, or over a backwards-facing step, and sutisfactorily reasonable results were obtained.From the results obtained the present study, it is expected that the modified Discrete Vortex Method presented here will be applied to analyze turbulent flows in various engineering fields as one of convenient but reliable calculation methods.