Experimental Study of Flow Hydrodynamics in Meandering Compound Channels with Parallel Floodplain Wall

Predicting the flow behavior in the arch of meandering compound channels has a great importance in coastal protection programs (sediment transport and deposit pattern), pollution propagation and flood control. Therefore; the hydrodynamics of the flow in the composite-meander channel with a constant sinuosity factor 1.3, and at two relative depths 0.3 and 0.55 were investigated using a laboratory model. Due to the three-dimensional structure of the flow in the channel bend, the data were analyzed in seven cross sections with angles of zero, 30 and 60 degrees to the vertices of the bending apex using an ADV velocity-meter in lattice plates with dimensions 3*3 cm2 and perpendicular to the flow. The results showed that the gradient of three components of velocity at relative depths 0.3 are greater than 0.55 which shows more vortex power and intensity of turbulence in less amount of relative depth. average velocity ratio on the outer beach of the floodplain to the average velocity of the whole section, similar to the inner beach, has been a function of the relative depth of the flow, and is less and more than one, respectively. For this reason, the flow in the outer floodplain, unlike the inner floodplain, has a reducing effect on the flow velocity in the main channel. Also, as the relative depth increases from 0.3 to 0.55, the ratio of the average flow velocity in the main channel to the total average velocity decreases and approaches one. Reynolds stress () had maximum and positive values near the main channel bed, and by moving away from the bed, it has reached a negative value and it shows its minimum amount near the flow surface. The value of this local parameter also increases at the edge of floodplains.