Spin-up in a rectangular tank with low angular velocity

A comparison is made between numerical and experimental results for spin-up from rest in a rectangular container. The numerical results were obtained by using a three-dimensional finite volume method on a supercomputer. The experiments were performed with water, using tracer particles floating at the free surface in order to visualize the flow field. The numerical and experimental results are in good agreement. They show the formation of a stable three-cell pattern. In contrast to similar experiments performed at higher angular velocities, the center cell of this pattern appears to be anticyclonic. Initially, the relation between vorticity ω and streamfunction ψ of this organized flow is linear, but it is seen to evolve slowly into a relation with ∂²ω/∂ψ² < 0.