The effects of wind speed and turbulence model on wave formation in open systems

Abstract

Open systems, that include both water and air fractions, and whose behavior is highly dominated by the interaction between these two phases are particularly important and interesting for many industrial applications (e.g. energy production, maritime and aerial transport, food resources). Since the physics governing these flows is highly complex and incorporates many unexplained phenomena, novel physical models, as well as measurement techniques, are still being developed and tested in accordance with the particular problem that is being analyzed. Although real engineering cases often involve wind-wave interactions, stochastic waves, geometrically irregular boundaries, turbulence, wave interference etc, the main interests of this work are the effects of oncoming wind speed as well as adopted turbulence model on the initially still water surface and consequential wave formation. These aspects have to be considered in the development of amphibian aircrafts or ekranoplans since they take off from water surfaces while later aircrafts operate in the vicinity of water during the entire flight. Wave formation is also extremely important for off-shore wind turbines. For the sake of simplicity, the conducted numerical simulations are planar. The fluids (air and water) are considered incompressible, while the flow is unsteady and turbulent. The unsteady Reynolds averaged Navier-Stokes equations are closed by one of the two two-equation turbulence models based on the Boussinesq hypothesis: realizable k-ε or k-ω SST model. The investigated wind speeds are 30 m/s, 50 m/s and 80 m/s, while the results are presented in the shape of water volume fractions. As expected, the increase in wind speed induces higher amplitude waves, when the effects of turbulence models also become important.