بررسي تاثير آرايش بلوك هاي مستغرق بر ضريب اختلاط عرضي در يك فلوم آزمايشگاهي

Investigation of different local bottom roughness arrangements on transverse mixing coefficient in an open rectangular flume

Transverse mixing coefficient is one of the hydraulic parameters of flow by which the amount of self-refinement and dilatation of rivers can be estimated. In this research, the effect of different roughness arrangements on transverse mixing coefficient has been studied. Experimental studies were carried out in a rectangular straight open channel with 7m length and 0.32m width and 0.35m height. Water was circulated in the flume with the rate of 16.4 lit/s. The flow was uniform and the depth of water was 11.4 cm which was controlled with a gate way. Tracer was continuously injected with a constant head in to the open channel flow at the center of the flume. The dye concentrations at 4 different downstream distances from the injection point in 27 points were measured and dimensionless transverse mixing coefficient has been determined for different bl^ck arrangements. The results show that the block arrangement with three row of increasing height from 1.5 cm to 3 cm in the flow direction gives the best efficiency.