Airside velocity measurements over the wind-sheared water surface using particle image velocimetry |
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| Authors: | Nasiruddin Shaikh Kamran Siddiqui |
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| Institution: | (1) Department of Mechanical and Industrial Engineering, Concordia University, H3G 1M8 Montreal, QC, Canada |
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| Abstract: | An experimental investigation of the airflow structure in the near surface region over the wind-sheared air–water interface
is reported. The two-dimensional velocity fields in a plane perpendicular to the water surface were measured using particle
image velocimetry (PIV) technique over a wind speed range from 1.5 to 4.4 m s−1. The results show a reduction in the mean velocity magnitudes and the tangential stresses when gravity waves appear on the
surface. An enhanced vorticity layer was observed immediately above the water surface that extended to a height of approximately
2 cm. The vorticity was enhanced by an order of magnitude, and the energy dissipation rate was enhanced by a factor of 7 in
this layer at all wind speeds. The vertical profiles of Reynolds stress, energy production, and dissipation indicate the contribution
of surface waves in the enhanced transfer of momentum and energy between the two fluids. The results in this study show that
the flow dynamics in a layer immediately adjacent to the water surface whose thickness is of the order of the significant
wave height is significantly different from that at greater heights. Thus, it is concluded that the quantitative investigation
of the flow in the immediate vicinity of the interface is vital for an improved understanding of the heat, mass, and momentum
exchange between air and water. The present study demonstrates that PIV is an effective technique to accurately measure the
velocity fields in this region. |
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| Keywords: | Air– water interface Airflow separation Surface waves PIV measurements |
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