Laminar-turbulent transition in Taylor-Dean flow

An experimental study is reported of flows produced in a moderate Taylor-Couette system, Gamma approximate to 15, closed or azimuthally opened. In the last case, the flow is bounded by theta = 0 and (2 pi - theta(1)) where theta(1) = 30 degrees represents the region cut-off by a diaphragm. The basic flow is a combination of a flow caused by the rotation of the inner cylinder and a flow provided azimuthally in the gap by external pumping. Our observations of the laminar-turbulent transition for a wide range of tau, the ratio of pumping and rotation flow rates, reveals competition between the Taylor-Dean flow due to rotation and the Dean flow due to pumping leading to new flow regimes which have not counterpart in the closed Taylor-Couette flow.