H1. A Surface PIV Approach for the Remote Monitoring of Mean and Turbulent Flow: Properties in an Open Channel
Johnson, Erika D; Cowen, Edwin A.
In an effort to develop a reliable, continuous and efficient method of remotely monitoring mean velocities, water column turbulence levels and bathymetry, a surface PIV (particle image velocimetry) experiment is conducted in a wide open channel (B/h >12) for a range of flow conditions. Mean and turbulent velocities, longitudinal power spectra and the longitudinal integral length scale have been calculated at the free-surface from the PIV data. The results reveal the presence of secondary flow within the channel, which leads to heterogeneous turbulence metrics on the surface; for example, the streamwise turbulent velocities and the Reynolds stress vary strongly as a result of the secondary motion. The results also indicate two methods by which the flow depth can be determined: 1.) the longitudinal integral length scale which varies predictably with the flow depth (L22,1 ≈ 0.3h) and 2.) the normalized longitudinal spatial spectra which exhibit a slight bump at the wave number corresponding to the flow depth. These results suggest that it is possible to determine volumetric flow rate solely from measurements of the free- surface water flow. These findings have important implications for developing new technologies for stream gauging, near-shore and estuarine monitoring.
Internet-First University Press