TURBULENCE MODEL FOR WATER-FLOW OVER 2-DIMENSIONAL BED FORMS

A boundary-fitted numerical model adopting the general conservation of mass and momentum equation is applied to free surface water flow over a two-dimensional topography. A three-layer near-wall k-epsilon turbu lence model is used to partly account for the effect of the separated- reattaching region in front of each sand wave. A modification of the s treamline curvature is introduced to achieve a proper response to the degree of anisotropy between the normal stresses. The geometric shape of the train of sand waves is simulated by introducing a general curvi linear coordinate system. The numerical results were compared with the available experimental data reported by Raudkivi in 1963 and 1966, an d more recently by Van Mierlo and De Ruiter, in 1988, and overall agre ement has been satisfactory. Detailed calculations indicate that the t wo-equation k-epsilon model with careful modifications can yield good predictions for the sand-wave problem. The present model provides a ba sis for the extended study of bed-load transport: and resistance to fl ow arising from the movement of sediment bedforms.