# Testing model yachts for drag.

1. Jan 31, 2010

### meb09JW

1. The problem statement, all variables and given/known data

A yacht is of length 5m and travels at 10m/s. A scale model of length 0.5m is tested in a tank in order to predict drag on the yacht. Assuming that the fluid density and viscosity are the same for the yacht and model, can we obtain similarity?
What is our best value for viscosity in the tank?
What is the predicted drag ratio for drag on yacht to drag on model?

2. Relevant equations

Reynolds number, Froude number.

3. The attempt at a solution

Not sure where to start with this one. Am i right in saying that both numbers need to be the same for both the yacht and model to obtain similarity?

Cheers.

Last edited: Jan 31, 2010
2. Jan 31, 2010

### FredGarvin

3. Jan 31, 2010

### meb09JW

ok, so similarity can be obtained if the flow speed in the tank is increased by 10x?