Preliminary experimental study on the influence of the local wind field on forces from breaking waves on a circular cylinder

Kristoffersen, Julie Caroee and Bredmose, Henrik and Georgakis, Christos Thomas and Tao, Longbin; (2019) Preliminary experimental study on the influence of the local wind field on forces from breaking waves on a circular cylinder. In: ASME 2019 38th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers (ASME), GBR. ISBN 9780791858851 (https://doi.org/10.1115/OMAE2019-95179)

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Abstract

The spatial localized influence of wind on wave induced load on a flexible cylinder has been assessed throughout a test series conducted in a wave-wind-current flume at Newcastle University. The tests are motivated from other experimental and numerical investigations showing air flow separation on the leeward side of steep waves that can lead to added wind energy transfer, which could suggest an increase in the impulsive wave loading. The waves are generated as focused waves, resulting in a plunging breaker, leading to an impulsive wave load. The test model was equipped with a load cell measuring the connection load. Due to the flexibility of the cylinder, the measured force response shows oscillations and dynamic amplification of the load. The maxima of the force responses are compared for the tests with and without wind. Another measure for comparison is the local and short-lived impulse, which is responsible for the amplification. This impulsive load is estimated from the load cell and acceleration measurements. For the tests in this study, the introduction of wind over the breaking waves does for some cases lead to a slight increase in the peak of the impulsive load and thereby the load response, although large scattering is present. Further investigations are needed to verify this effect. Some differences in the time series of the free surface elevation are observed when wind is present, but the maximum of the surface elevation does not change notably, and the slope is only minimally changed, meaning that this should not give basis for the differences in the loads.

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