Post date: Oct 05, 2015 4:14:24 PM
This week I wanted to really look at the measurement techniques for figuring out how much energy is produced by a wake. The two major aspects of a wake are its energy and amplitude. Height is a rather straight forward measurement, whether it's in the ocean or the height a wake hits a wall at. What is difficult to measure is the wake energy. Wakes are produced when there is turbulent flow followed by a solid body moving through a fluid. In order for there to be turbulent flow, the Reynolds number of the fluid must first be calculated. It is a fairly straight forwards equation and it dependent upon the viscosity of the fluid, the diameter of the place water is being ejected from, the density of the fluid and the average velocity that it is moving at. If this value is 2000 or less, then it is considered laminar flow. Laminar flow is when the moving particles are in straight parallel lines, and therefore no wakes are being produced. If the value exceeds 4000, then that is considered turbulent flow which means wakes will be produced.
The energy itself is next to impossible to calculate because of several factors. It is moving at a high velocity and is constantly fluctuating and changing directions. These changes are very hard to detect and must be measured with lasers. Because of this, most analyses of wakes are done in experimental settings. It is especially difficult within the canals because the wakes bounce off of the canals and reverberate back and forth. This means that the wake you are trying to measure may not necessarily by coming from the boat that you thought it came from.
-Jacqueline