Direct Numerical Simulation of a Wind-Generated Water Wave

The interaction between an airflow and a water surface influences many environmental processes. For example in a rough ocean, entrained droplets from the water surface enhance transport processes above the ocean surface which can lead to the formation of hurricanes. In order to get a better understanding of the fundamental processes we perform direct numerical simulations (DNS) of a wind-generated water wave. To conduct these simulations we use our in-house code Free Surface 3D (FS3D) which is based on the Volume-of-Fluid (VOF) method and uses a Piecewise Linear Interface Calculation (PLIC) method. Two simulations with different grid resolutions are presented. In both cases a gravity-capillary wind-wave develops, starting with a quiescent water surface and solely driven by the turbulent air flow. We evaluate different aspects of the wind-wave characteristics such as topology, phase velocity, and temporal development of the wave energy. Furthermore, we compare the results with linear wave theory and experimental data obtained in the ASIST wave tank of the University of Miami. The comparison shows a very good agreement between experiments and numerical predictions, thus, FS3D is capable of numerically reproducing a gravity-capillary wind-wave with high accuracy. In addition, we continued our work to optimize the performance of FS3D by replacing large pointer arrays in our code with allocatable arrays. The analysis of strong and weak scaling shows an improvement in performance of up to $$48{\%}$$ 48 % .