An experimental investigation of the near surface flow over air-water and air-solid interfaces

Results from an experimental study, investigating the similarities and dissimilarities of the airflow structure over water and solid surfaces for smooth and wavy conditions, are reported, The experiments were conducted at the same location, under identical flow conditions, The two-dimensional velocity fields were measured using particle image velocimetry technique over a wind speed range from 1.5 to 4.4 m s(-1). The mean velocity profiles for all surface configurations showed the logarithmic behavior. The profiles of different turbulent properties followed similar trend over water and solid surfaces, however, their magnitudes varied over different surface types. The results show that the level of enhancement of normalized Reynolds stress, rates of energy production, and dissipation from the free-stream region toward the surface is higher over the water surface especially in the presence of waves as compared to that over the solid surface. It is also observed that the normalized magnitudes of turbulent properties are largest above the water surface and smallest above the wavy solid wall. It is concluded that, at a given free stream condition, the flow behavior over the solid surface is not necessarily similar to that over the water surface. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3313929]