Large Eddy Simulation of Turbulent Flow Over a Sphere Using an Immersed Boundary Method
SEOUL NATIONAL UNIV (KOREA) SCHOOL OF MECHANICAL AND AEROSPACE ENGINEERING
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Large eddy simulation of turbulent flow over a sphere is conducted at two different Reynolds numbers Re 3700 and 10exp 4 based on the free-stream velocity and the sphere diameter, in order to investigate the flow characteristics over the sphere. The present numerical method is based on a newly developed immersed boundary method in a cylindrical coordinate Kim et al. 2001. Also, a hybrid numerical method of eliminating 2-delta waves in laminar accelerating flow region and also avoiding numerical dissipation in turbulent flow region is newly proposed for large eddy simlation of turbulent flow over a bluff body. At Re3700, the shear layer is elongated in the streamwise direction to form a cylindrical vortex sheet and its instability begins to appear at x approximately equal 2d. Also, the flow behind the sphere is nearly laminar at x d and contains few vortices. On the other hand, at Re 10exp 4, the shear layer instability occurs right behind the sphere in the form of vortex tube and the flow becomes turbulent in the near wake. Therefore, at Re 10exp 4 the size of the recirculation region is smaller and the wake recovers more quickly than at Re 3700.
- Fluid Mechanics