عنوان مقاله [English]
نویسندگان [English]چکیده [English]
This paper investigates the effects of roughness of the flood plain on hydraulic overbank flow in a compound channel with non-prismatic floodplains. Experiments are done using three depth ratio, three divergence angles and three-roughness size of the floodplain. The flow velocity was measured using a three dimensional Acoustic Doppler Velocimeter (ADV) and directional current meter in a lattice along the divergence channel in three sections of the flume (entrance, middle and end of the divergence) with a different depth ratio. Using the experimental data, the values of the shear stress, depth–averaged velocity, local and zonal roughness coefficients, turbulence parameters and divided discharge between the main channel and floodplain were calculated. The results show that with increasing the floodplain roughness, in non-prismatic section, the ratio of the velocity at floodplain to main channel decreased about 31% and turbulence flow increased about 25%. Also under these conditions, the shear stress at interface zone was increased from 26 to 48%. As well as with increasing depth ratio, the above mentioned values are markedly reduced.