Modeling flows over gravel beds by a body force method

Abstract

A Reynolds‐averaged Navier‐stokes equations (RANS) model using the body force method (BFM) has been developed to simulate open‐channel flows over gravel beds. The momentum equation is modified by introducing the form drag as an extra body force term to represent the gravel‐bed resistance. By applying the body force within the roughness layer of the flow over small‐scale roughness, it is found that the body force coefficient frk varies inversely with the roughness length scale ks. The method is robust, not sensitive to mesh resolution and is easily extended to deal with large scale roughness.