不同底床粗糙对异重流运动特性的影响.pdf

International Journal of Fluid Dynamics 流体动力学, 2017, 5(4), 141-150 Published Online December 2017 in Hans. /journal/ijfd /10.12677/ijfd.2017.54016 Effects of Bottom Roughness on Gravity Current Motions 1 2 2 Keke Hu , Yu Yang , Yingtien Lin 1 Zhejiang Institute of Hydraulic and Estuary, Hangzhou Zhejiang 2 Ocean College, Zhejiang University, Hangzhou Zhejiang th nd th Received: Dec. 10 , 2017; accepted: Dec. 22 , 2017; published: Dec. 29 , 2017 Abstract In this study, lock-exchange gravity current experiments and numerical models are used to inves- tigate the effect of saline concentration and bottom roughness on gravity current dynamics. The Particle Image Velocimetry (PIV) system and a digital camcorder are employed to obtain the evolution of gravity currents on sediment beds. Spatial-temporal evolutions of the current speed, height and macro-structures of current head are analyzed. The results show that bottom sediments play an important role toward the current kinematics, particularly in decreasing the front velocity and vorticity, and changing the front shape. Using the Re-Normalization Group (RNG) k-ε turbulent model to simulate the gravity current motions can obtain good agreement with the experimental data. The simulated horizontal current velocity can be used to explain the acceleration, constant speed, and deceleration motions. At the interface between the two different fluids, a negative ve- locity can be observed due to the entrainment phenomena. Bed sediments change the horizontal velocity profiles of current, entrainment phenomena and inhibit the occurrence of the negative veloci- ty in the