Author(s): Alireza Keshavarzi; James Ball
Linked Author(s): James Ball
Keywords: Bursting Process; Vector angles; Statistical analysis; Turbulent flow
Abstract: Entrainment of sediment particles is stochastic in nature due to the instantaneous fluctuation of velocity fluctuations and turbulent shear stress. The temporal variations of turbulent flow are a very important characteristic for sediment entrainment particularly at low shear stress. To characterise the temporal variation, the velocity vector angles in two dimensions are investigated in this experimental study. Data for this study was obtained from three dimensional flow velocities measured in an experimental flume using an Acoustic Doppler Velocimeter (Micro-ADV). This data was analysed to calculate the instantaneous vector angles of the turbulent velocities. The changes in vector angles ( (35) θ) at sequential time steps were calculated also. A statistical analysis of the values of (35) θobtained from the different experimental tests was undertaken. The resultant statistical characteristics were found to be a good representation of the characteristics of movement between quadrants of the turbulence. Also the results indicated that standard deviation of vector angles changed with flow depth from the bed to the free surface.