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The vortical property in a three dimensional cavity of micro-channel flow, which is very important, was investigated numerically. The results show that the rotation direction of vortex in the cavity depends on the dimension and shape of the cavity as well as the viscosity of the fluid. With the dimension and shape of the cavity fixed, there exists a critical inlet velocity. When the inlet velocity is less than the critical value, the rotation direction of vortex in the cavity will change. The critical velocity is directly proportional to the viscosity of the fluid, and inversely proportional to square of the thickness, length and depth of cavity. For the ratio of length and depth of cavity equals to one, there is a critical dimensionless parameter Re_ cr ~′, when Re~′ is less than Re_ cr ~′, the rotation direction of vortex will change too. Re_ cr ~′ is equal to 11.8 approximately.
The vortical property in a three dimensional cavity of micro-channel flow, which is very important, was investigated numerically. The results show that the rotation direction of vortex in the cavity depends on the dimension and shape of the cavity as well as the viscosity of the fluid. With the dimension and shape of the cavity fixed, there exists a critical inlet velocity. When the inlet velocity is less than the critical value, the rotation direction of vortex in the cavity will change. The critical velocity is directly proportional to the viscosity of the fluid, and inversely proportional to square of the thickness, length and depth of cavity. For the ratio of length and depth of cavity equals to one, there is a critical dimensionless parameter Re_cr ~ ’, when Re ~’ is less than Re_cr ~ ’, the rotation direction of vortex will change too. Re_cr ~’ is equal to 11.8 approximately.