Effect of pressure on damping of water waves

[neptunium]

Hi everyone,

 

I have a question for you about the effect of air pressure on damping of water waves. Imagine a container full of water. By dropping sth into the water I create waves and measure the time it takes for these waves to damp out. Now if I repeat the same procedure but this time the container is in a pressure chamber in which air pressure is significantly increased wrt the ambient, would it take the same amount of time for the waves to damp?

 

Looking forward to hearing your opinions. Thanks.

[John Cuthber]

Gas viscosity barely depends on pressure (For an ideal gas the effect of pressure is exactly zero).

Also, the damping will be due to the viscosity of the water, rather than the air.

[Wilmot McCutchen]

The conventional dissipative view is that momentum diffuses from large scale perturbations into tiny eddies, and these eddies diffuse into "viscosity." Hysteresis might be a better term, since it connotes internal energy and is less likely to be confused with behavior of non-Newtonian fluids. Dynamic viscosity is too vague and suffers from the same defect. For collapse, symmetry breaking, and hysteresis in swirling flows, see http://www2.egr.uh.edu/~ifdt/archivalpapers/arfm/ShternHussain1999.pdf. The idea is that organized motion becomes disorganized, and vice versa. Linear momentum becomes angular momentum in the dissipative scenario, and by collapse, angular momentum becomes linear momentum, as in a tornado.

 

The water is in a container, said to be "full." The container is disposed in a pressure chamber and I presume the container has flexible walls because rigid walls would shield the water from the air in the pressure chamber. So there is some interaction between the air in the pressure chamber and the water in the container, via the flexible walls, which will have their own damping effect. But let's assume that the material of the walls has no damping effect and that the waves in the container from the perturbation are directly affected by the air in the pressure chamber.

 

We might do away with the flexible walls by reframing this problem as a bubble in a tank. Could boosting water pressure after perturbing the bubble flatten the bubble surface quicker by providing more energy for undoing dissipation? In the bubble case, it seems that it might. In the inverted case with the infinitely flexible walls and air around the water instead of water around the air, what is the difference? More energy in the material (higher enthalpy) would at least offer the potential for the organizing energy to appear.