Numerical study of the effect of trapezoidal obstacle in the mixing of muddy flow

muddy flows are gravitational flows, which are the difference in density or difference in weight of unit volume between two fluids due to suspended sediments. Due to the abundance of these streams in nature knowing and studying the characteristics and factors affective it is imperative and unavoidable. The creation of obstacle in the flow path can affect on the muddy flow character such as flow mixing rate and flow density. In this paper by the Flow 3D software the effect of trapezoidal obstacle in the characteristics of the muddy flow especially its mixing rate has been studied. : In order to Verification, results of the this numerical model Were compared with the results of laboratory work Naji Abhari et al. The results showed that the presence of the obstacle caused the kinetic energy of turbulence to increase by almost 1000% more than Without obstacle. the depth-density variation diagram for two channels showed that the current density in channel With obstacle was less than obstacle-free type. also by increasing 1% the height of obstacle, an average of 2% would be added to the turbulence energy and one-percent increase in the angle of entrance prevented an increase of 1.366 % of the energy of turbulence. Simulation for obstacle with different velocities indicates that with increasing the velocity of the pure water, the amount of maximum energy of turbulence and as a result of flow mixing increases.