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Wave drag during an unsteady motion
The average wave drag in unsteady motion is studied experimentally with force measurements. Towing hulls of size $L$ at sinusoidal speed, the mean drag is measured for different amplitudes and frequencies of the fluctuating velocity, as well as different Froude numbers $\mathcal {F}_0$ associated wi...
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Published in: | Journal of fluid mechanics 2022-11, Vol.951, Article A15 |
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Main Authors: | , , , , |
Format: | Article |
Language: | English |
Subjects: | |
Citations: | Items that this one cites Items that cite this one |
Online Access: | Get full text |
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Summary: | The average wave drag in unsteady motion is studied experimentally with force measurements. Towing hulls of size $L$ at sinusoidal speed, the mean drag is measured for different amplitudes and frequencies of the fluctuating velocity, as well as different Froude numbers $\mathcal {F}_0$ associated with the mean velocity $V_0$ ($\mathcal {F}_0 = V_0/\sqrt {gL}$). The wave drag is reported to be either increased or decreased by velocity fluctuations depending on $\mathcal {F}_0$. For small fluctuation amplitudes, this drag change is proportional to the square of the amplitude. The effect is maximized for a resonance frequency identified as the Wehausen frequency, which scales as $\sqrt {g/L}$ times the inverse of the Froude number. All these results are rationalized by developing an extension to Havelock's theory. |
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ISSN: | 0022-1120 1469-7645 |
DOI: | 10.1017/jfm.2022.592 |