Print Email Facebook Twitter Experimental investigation of wave tip variability of impacting waves Title Experimental investigation of wave tip variability of impacting waves Author van Meerkerk, M. (TU Delft Multi Phase Systems) Poelma, C. (TU Delft Multi Phase Systems) Hofland, Bas (TU Delft Hydraulic Structures and Flood Risk) Westerweel, J. (TU Delft Fluid Mechanics) Date 2020 Abstract We present an experimental study on the variation in wave impact location and present a mechanism for the development of free surface instabilities on the wave crest for repeatable plunging wave impacts on a vertical wall. The existence of free surface instabilities on an impacting wave is well known, but their characteristics and formation mechanism are relatively unknown. The development of the global wave shape is measured using a visualization camera, whereas the local wave shape is measured with an accurate stereo-planar laser-induced fluorescence technique. A repeatable wave is generated with negligible system variability. The global wave behavior resembles that of a plunging breaker, with a gas pocket cross-sectional area defined by an ellipse of constant aspect ratio. The variability of the local wave profile increases significantly as it approaches the wall. The impact location varies by ∼0.5% of the wave height or more than a typical pressure sensor diameter. Additionally, the wave tip accelerates to a velocity of 1.5√gh0 compared to the global wave velocity of 1.2√gh0. The difference in impact location and velocity can result in a pressure variation of ∼25%. A mechanism for instability development is observed as the wave tip becomes thinner and elongates when it approaches the wall. A flapping liquid sheet develops that accelerates the wave tip locally and this triggers a spanwise Rayleigh–Taylor instability. Subject surface wavesflow instabilitiesFlow visualizationfluid mechanicsWave impact To reference this document use: http://resolver.tudelft.nl/uuid:39bd37f6-a6fd-4070-aaa8-a78fe9f32120 DOI https://doi.org/10.1063/5.0016467 Embargo date 2021-02-20 ISSN 1070-6631 Source Physics of Fluids, 32 (8) Bibliographical note Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public. Part of collection Institutional Repository Document type journal article Rights © 2020 M. van Meerkerk, C. Poelma, Bas Hofland, J. Westerweel Files PDF 5.0016467.pdf 6 MB Close viewer /islandora/object/uuid:39bd37f6-a6fd-4070-aaa8-a78fe9f32120/datastream/OBJ/view