OpenFOAM computational fluid dynamics studies on the ocean-atmosphere

Computational fluid dynamics (CFD) is the use of applied mathematics, physics, and computational software to visualize how a fluid flows around objects. CFD is based on the Navier-Stokes equations, which describe how the velocity, pressure, temperature, and density of a moving fluid are related. Here CFD is used to simulate the errors in wind speed measurements caused by flow distortion on two research vessels: the R/V Celtic Explorer and the R/V Knorr. The numerical measurements were obtained from the finite volume CFD code OpenFOAM, which was used to simulate the required velocity fields. From the simulations, the following were determined: (i) the ideal anemometer location for wind speed measurements on these vessels (ii) the effect of varying vessel pitch angles on measurement data (iii) the optimum experimental design by testing two mast designs with three instrumentation setups (iv) the flow distortion effects for wind speed measurements of ±60º to the bow for 5-20 m s-1. A new parameter in flow distortion error wind speed dependence was defined. Furthermore, a correction function for the in-situ wind speed measurements at anemometer measurement locations using the theoretical CFD model was derived. The Reynolds-averaged Navier-Stokes (RANS) and large eddy simulation (LES) simulation models accuracy at predicting air-flow distortion error was compared, and the latter was found to be superior. The wind vector pitch and yaw in wind speed measurements due to air-flow distortion was quantified, and a definition of the underlying cause of the aforementioned wind speed dependence was provided. A correction function and methodology was provided that will lead to a mean accuracy of 3% and define a correction for wave induced flow distortion errors both experimentally and numerically. Finally a variety of CFD studies are presented that have been conducted involving the Air-Sea Interaction Profiler (ASIP), the flow distortion correction of wind speed parameterized air-sea fluxes, and the flow distortion effects associated with the logarithmic wind speed profiles application to off-shore renewable energies.

Funder

Irish Research Council for Science, Engineering and Technology

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Attribution-NonCommercial-NoDerivs 3.0 Ireland

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University of Galway Theses (PhD Theses)