Stream gauging by combined use of surface PTV and CFD techniques in channel flows

A video imagery technique for free surface velocity measuring is presented and used to calculate discharge for uniform open channel flows numerically. When the surface velocities are measured and used as boundary conditions on the water surface, velocity field can then be solved numerically to satisfy the surface boundary conditions. This approach can provide a precise tool for velocity field, discharge and boundary shear distribution calculation. PTV or particle tracking velocimetry is implemented over the free surface to provide the boundary condition for numerical solution. Present paper describes the limitations and capabilities of conducting PTV measurements for a variety of flow conditions. Sensitivity of the PTV measurements is investigated for different lighting conditions, time interval between successive frames, location of the tracking particle, size and material of the particle with respect to changing free surface velocity. Finally, the measured surface velocity are compared to the computed ones.