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Here in this image, you can see the water flow onto the beach to a certain distance. After a while, the water retracts back. If I put a V-shaped collector (like a vertical standing open book) facing the ocean, would I be able to accumulate water in the center of the v shape? I was thinking that instead of the water reaching and spreading out to a certain distance onto the beach, that flow would stop and accumulate vertically upwards. However, I'm not sure if this is correct or partially correct. Would the water retain the same height and just go around the collector? What if the v-shape expands 1/2 mile into the ocean. Would that reduce seepage and cause the water to accumulate vertically in the center?

Any insight would greatly help!

  • 1
    $\begingroup$ The only thing that will keep that water higher than the surrounding water is the inertia of the water crashing into the wall. Once that's gone it is going to level out again. $\endgroup$
    – DKNguyen
    Sep 14, 2022 at 3:54
  • $\begingroup$ Related "Can the crest of an ocean wave be increased by directing ocean waves to a center of a curved column?" $\endgroup$
    – AJN
    Sep 14, 2022 at 12:21

2 Answers 2


Yes water will go higher than the average height of the wave.

Imagine an infintisimally small droplet hit the wall with an angle $\theta$. it reflects with an angle $2\theta$ with respect to the main wave keeping coming straight. so it will spill water over the center flow and raise its height.

The same phenomenon happens to the side of the bow of a boat or ship. there is the great noise of parting of the water and sending it climbing up the sides of the bow and later falling in a white foamy cascade.

  • $\begingroup$ Thank you for your thorough response. Can you please elaborate on your analogy of the waves parting as a ship passes by? I thought it was just the waves hitting the bow which causes the water to spray up (not any changes to flow width or wave height). $\endgroup$
    – ARJ
    Sep 16, 2022 at 1:40
  • 1
    $\begingroup$ @ARJ, it's the preservation of momentum. m1v1=m2v2. m=the mass of fluid per second, and v is the vector of velocity. you can try it by holding a hose of water spraying at different angles to a concrete wall and studying its deflection and splash. on a ship's bow, the water hitting the haul has to dislodge the ocean water or go up the bow which is easier. it does both. $\endgroup$
    – kamran
    Sep 16, 2022 at 7:02
  • $\begingroup$ Also, another question if you don't mind. Instead of the water height increasing with decreasing cross-sectional width in my example, can't the velocity increase? My end goal is just to maximize force in the center of a funnel. In other words, the same amount of force hitting a 10 feet long wall condensed to hit a small 1 inch V center. $\endgroup$
    – ARJ
    Sep 17, 2022 at 22:13
  • $\begingroup$ The velocity of the deflected water is $V=V(initl)* cos(\theta)$. So it is less than the V of unobstructed flow. $\endgroup$
    – kamran
    Sep 17, 2022 at 23:07

You can't fill above water level using waves like this. Water in a V (assuming you put a base in it to keep the water from just running through the sand) would go to the water level of the wave and that's it. Maye a little higher converting the kinetic energy of the wave moving back to the sea into potential energy.

There are devices using check valves that use kinetic energy to raise water level, and even "pump" water. A vee on the beach won't do this.

  • $\begingroup$ wrong. Go look at Thunder Hole in Acadia Nat'l Park. $\endgroup$ Sep 14, 2022 at 12:34
  • $\begingroup$ @CarlWitthoft have they installed a check valve in it yet? $\endgroup$
    – Tiger Guy
    Sep 14, 2022 at 14:29
  • $\begingroup$ @CarlWitthoft How does the Thunder Hole work? From what I can see in recorded videos, the water speeds up as the the cliff narrows. $\endgroup$
    – ARJ
    Sep 16, 2022 at 1:34

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