The drag on a submarine moving below from free surface (surface wave are not important) is to be determined by a test on a 1/15 scale model in a water tunnel. The velocity of the prototype is sea water (ρ = 1015 kg/m³, ν = 1.4×10^-6 m²/s) is 2 m/s. The test is done in pure water at 20°C.

Determine the speed of the water in the water channel for dynamic similitude and the ratio of the drag force on the model to the drag force on the prototype.

The maximum wave force on a 1/36 model sea wall was found to be 80 N. For a corresponding wave in the full-scale wall, what full-scale force would you expect? Assume fresh water is used in the model study. Assume T = 10°C for both model and prototype water.