Numerical calculation of the flow field over the upwelling producing structure in an oscillatory flow is conducted using the k- ε turbulence model. Particular emphasis is on the flow field with or without stratification. The characteristic phenomenon such as the vortex formation was simulated. Irrespective of the value of Ri, the density interface will be destroyed when the height of the upwelling producing structure is higher than that of the density interface. Also with decreasing KC number, the separated vortex with intense vorticity is formed and a fast residual flow is seen near the upwelling producing structure through the experiment.
An upwelling flow has the major effect on creating fishing grounds, for it carries the water mass which contains the nutrition from the lower layer to the upper layer. Therefore, it is important to study the development of an upwelling producing structure. The previous research, however, has been focused on the flow field without stratification, and there are only a few approaches for the stratified flow field. The direction of the upwelling flow may change from vertical direction to horizontal direction near the density interface due to the stratified layer, and the destruction of the density interface does not happen easily. So it is necessary to study the flow field with stratification. In this paper the flow field over the upwelling producing structure settled at the sea bottom is examined experimentally and theoretically. The experiment was conducted in a two dimensional water tank where several kinds of upwelling producing structure are settled and the velocity profile is measured by using an electromagnetic current meter. The numerical simulation is also carried out by using the k-ε turbulence model under an oscillatory flow with or without stratification.
