Abstract：Vortex breakdown of swirl flow in an enclosed conical chamber with a rotating bottom wall was studied by numerical simulation, and the influences of Reynolds number and geometric parameters on the development mechanism of vortex breakdown phenomenon were analyzed. The flow was go-verned by the unsteady three-dimensional incompressible Navier-Stokes equations. The finite volume method was used to discretize the governing equations and the Semi-Implicit Method for Pressure Linked Equation(SIMPLE)algorithm was employed to couple the solutions of the system. The unstructured grid is applied to divide the computational domain. The development characteristics of vortex breakdown in the conical chamber derived from the simulation results are as follows: the low pressure region of vortex breakdown with local fluid recirculation would appear near the axis in the conical chamber when the Reynolds number reaches a critical value. As the Reynolds number increases further, the size of the vortex breakdown bubble increases first and then decreases until it disappears and it moves away from the driving surface within the parameter range studied. However, the position where the vortex breakdown first appears and disappears doesn′t change with the variation of the geometry for the conical chamber with the same aspect ratio. From the values of the critical Reynolds number when the vortex breakdown bubble appears, conical chamber suppresses the generation of vortex breakdown compared with cylindrical chambers and the conical chamber(H1/H=0)with the maximum diameter of the top surface has the best suppress effect.
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