How fast will an inflated cube with a lift force of 220lbs rise in water if submerged at 30ft

Question

a cube with a measured lift force of 220lb is at 30ft depth in a water tower with tap water. how fast will it rise to the top when it is released?

any formula for underwater rise speed?

10x

Answer 1

formula for bluff body drag is

drag = A x Cd x (1/2 rho v^2)

220 lbs = 980 Newtons

Coefficient of drag, Cd for a cube is approx 1.0

density, rho for water is 1000 kg/m^3

980N = 1m^2 x 1.0 x (1/2 1000 kg/m^3 x v^2)

v^2 = 1.96

v= 1.4 m/s

Answer 2

A few unknowns. if this is in a tower, that will restrict the flow of water around the cube if it is narrow. Or course you also need the size of the cube and the shape (if it's not actually a cube) and how the surface is formed (smooth, rough, etc).

Get all those numbers, you then get into fluid dynamics, which can be complicated.

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