Turbulent structure beneath air-water interface during natural convection

Results from an experimental study investigating the turbulent structure beneath the air-water interface during natural convection are reported. The two-dimensional velocity field beneath the surface in a plane perpendicular to the surface was measured using digital particle image velocimetry. The results show that the waterside flow field undergoes three-dimensional flow interactions forming complex flow patterns, which appear to be random. The magnitude of the turbulent velocities and turbulent kinetic energy increases with the heat flux. The profiles of the turbulent velocities are self-similar and appropriately scaled by the parameters proposed for the natural convection above a heated wall. The wave number and frequency spectra exhibit −3 slopes providing the evidence that during natural convection the buoyancy subrange exists within the inertial subrange where the energy loss is due to the work against buoyancy.