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- Title
The water entry of a sphere in a jet.
- Authors
Speirs, Nathan B.; Belden, Jesse; Pan, Zhao; Holekamp, Sean; Badlissi, George; Jones, Matthew; Truscott, Tadd T.
- Abstract
The forces on an object impacting the water are extreme in the early moments of water entry and can cause structural damage to biological and man-made bodies alike. These early-time forces arise largely from added mass, peaking when the submergence is much less than one body length. We experimentally investigate a means of reducing impact forces on a rigid sphere by placing the sphere inside a jet of water so that the jet strikes the quiescent water surface prior to entry of the sphere into the pool. The water jet accelerates the pool liquid and forms a cavity into which a sphere falls. Through on-board accelerometer measurements and high-speed imaging, we quantify the force reduction compared to the case of a sphere entering a quiescent pool. Finally, we find the emergence of a critical jet volume required to maximize force reduction; the critical volume is rationalized using scaling arguments informed by near-surface particle image velocimetry (PIV) data.
- Subjects
WATER jets; HYDRODEMOLITION; PARTICLE image velocimetry
- Publication
Journal of Fluid Mechanics, 2019, Vol 863, p956
- ISSN
0022-1120
- Publication type
Article
- DOI
10.1017/jfm.2018.931