SPIN-UP IN A RECTANGULAR TANK WITH LOW ANGULAR VELOCITY

A comparison is made between numerical and experimental results for sp in-up from rest in a rectangular container. The numerical results were obtained by using a three-dimensional finite volume method on a super computer. The experiments were performed with water, using tracer part icles floating at the free surface in order to visualize the flow fiel d. The numerical and experimental results are in good agreement. They show the formation of a stable three-cell pattern. In contrast to simi lar experiments performed at higher angular velocities, the center cel l of this pattern appears to be anticyclonic. Initially, the relation between vorticity omega and streamfunction psi of this organized flow is linear, but it is seen to evolve slowly into a relation with partia l derivative(2) omega/partial derivative psi(2) <0.