Session1: River Engineering and Management
Title: UNDISTURBED FLUID FLOW FOR IMPROVED MACROSCOPIC ESTIMATION OF DRAG FORCES ACTING ON CIRCULAR CYLINDERS
Satoshi Yokojima, Tatsuhiko Uchida, Yusuke Kazehaya, Yoshihisa Kawahara
A drag-force model is essential in practical predictions of flows around vegetation/forest/urban canopies, since it is too prohibitive to resolve details of the canopy elements and associated fluid motions, especially in environmental and geophysical applications. The model, however, has a serious difficulty inherent in its formulation: how one can specify the representative velocity? In ideal situations such as flows past an isolated obstacle, it is the velocity of the inflow and is easily available. In flows past multiple obstacles, on the other hand, a straightforward extension of the idea behind the ideal situations abovementioned leads to introduce undisturbed flow, which is the flow that would exist at an obstacle location in the absence of that obstacle but with all other obstacles present. Clearly, this undisturbed flow is unavailable unless a new system where the target obstacle is removed in actual is introduced. Therefore, most of the past studies used information of the fluid flow disturbed by the obstacle as the representative velocity. To improve the accuracy of this approach, one requires a methodology for estimating the undisturbed flow from the disturbed flow field. Here the undisturbed flow has been evaluated directly in fully resolved computations of a two-dimensional flow past circular cylinders and the fundamental properties of the flow are discussed.