Effect of Roughness Geometry on Characteristics of Density Currents Head

Abstract

Density currents occur when fluid of one density propagates along a horizontal boundary into fluid of a different density. The front part of a density current is deeper than the following steady fluid and this raised section of the flow is referred to as the head of the density current. In the present paper, the influence of roughness geometry on the head concentration, velocity and height are investigated experimentally. A total number of 21 experiments were performed using six rough beds as well as a smooth bed. The roughness elements were in cylindrical and conic shape. It was found that the head is influenced by height and project area of roughness elements. In a particular shape of roughness elements, the observed trend is that as the surface roughness increases the head concentration and velocity decrease while the head height increases. It was also found that the aforementioned trends occur at higher rates as the beds get rougher. In a given height of roughness elements, the head velocity and concentration decreases and head height rises when the project area of roughness elements increases.