On velocity estimations in highly aerated flows with dual-tip phase-detection probes - closure

Air‐Water Mixing in Vegetated Supercritical Flow: Effects of Vegetation Roughness and Water Temperature on Flow Self‐Aeration

“…The turbulence interfacial velocity u rms was calculated for the remaining signal segments as: $$${u}_{\text{rms}}=\sqrt{\frac{\sum {\left({u}_{i}-V\right)}^{2}{w}_{i}}{\sum {w}_{i}}}$$$ where u i is the velocity of the i th window, w i is the window duration weighting, and V is the average of the remaining velocities u i weighted by w i . The AWCC processing usually requires a greater bubble population than the traditional full‐signal‐correlation approach due to the high data rejection rate in the less aerated region (the data rejection rate will be presented with the turbulent velocity results) (Chanson, 2020; Kramer et al., 2021)…”

“…where u i is the velocity of the ith window, w i is the window duration weighting, and V is the average of the remaining velocities u i weighted by w i . The AWCC processing usually requires a greater bubble population than the traditional full-signal-correlation approach due to the high data rejection rate in the less aerated region (the data rejection rate will be presented with the turbulent velocity results) (Chanson, 2020;Kramer et al, 2021) The phase-detection probe was scanned at different normal cross-sections on the chute centerline. The translation of the probe in the normal direction was monitored with a mechanical vernier caliper on the probe supporting frame, with a practical accuracy about 0.2 mm.…”

“…For instance, the turbulence intensity measured at y / y 90 = 0.4 was about 6% in the smooth concrete channel, while it reached around 16% at similar elevation in the vegetated chute in the fully developed aerated flow. Valid Tu data were missing for y / y 90 < 0.4 in Figure 11 because of the high data rejection rate by the filtering criterion Equation during the AWCC processing in the less aerated bubbly flow region, where the signal segmentation required a greater number of bubble detection for a given duration (Chanson, 2020; Kramer et al., 2021). The percentage of rejected velocity data at different depths is shown in Figure 11 by the shadow area.…”

A Review on Methods for Measurement of Free Water Surface

“…A special wave probe variant is a phase detection probe used in multiphase (e.g., aerated) flows to detect whether there is water or air in the measurement zone [ 23 , 24 ]. Dual-tip phase-detection probes are also capable of measuring flow velocity in aerated water flows [ 25 , 26 ]. Nevertheless, it is optimal that wave probes are installed in regions with low velocity whenever possible since higher velocities lead to the formation of stagnation points at the probe (hence, overestimated depth due to local pressure increase), downstream wake (underestimated depth), vortex shedding, probe-wetting issues, variations in conductivity due to the presence of bubbles, etc.…”

Self‐Aeration of Supercritical Water Flow Rushing Down Artificial Vegetated Stepped Chutes

“…The data of Amador et al (2006) are plotted in Figure 9c for the smooth step configuration, showing satisfactory agreement between their nonintrusive imaging-based measurement and the present intrusive phase-detection-based turbulence estimation, although the former was in nonaerated flow and the latter in air-water flow. It has been argued that the adaptive-window cross-correlation processing of the phase-detection signal led to reduction of the number of valid samples in the less aerated flow region, e.g., for y/y 90 < 0.3 in Figure 9, which would result in a rise in the uncertainty of velocity turbulence estimation in the boundary layer thus requiring possibly much longer sampling duration (Chanson, 2020;Kramer et al, 2021).…”