Science of Wakes: Low Pressure Region Explained

[kundukoustav]

we all know wakes are very much undesirable. Also, wakes are of generally very low pressure region. Why is is so? Discussions are welcome

 

[Bobbywhy]

kundukoustav, we all do not know wakes are very much undesirable. Will you please say why they are?

I see plenty of ship wakes while exploring on Google Earth. (Try in the Suez Canal, for example...there are some great ship wake examples to see.) I can't understand why you say they are "of generally very low pressure region". How can that be? Will you please explain that for me also? Thank you.
Bobbywhy

 

[kundukoustav]

Consider a car moving! check the drag force (pressure drag) of air on the car! You will get the idea!

 

[Bobbywhy]

The wake behind a moving ship is more than hydrodynamic drag. That's not a sufficient description of the wake-forming mechanism.

 

[ZapperZ]

we all know wakes are very much undesirable. Also, wakes are of generally very low pressure region. Why is is so? Discussions are welcome

This is not always true. Wakes generated in a plasma are now being used to generate high gradients as part of a research for the next generation of particle accelerators.

http://physicsworld.com/cws/article...a-wakefield-turbocharges-particle-accelerator

Other groups are using wakefields generated in metallic and dielectric structures.

Zz.

 

[sophiecentaur]

A wake (from a boat and probably from any other source too) is surely a wave. The energy in it takes a long time to dispel because, once it has settled down, it has a straight wave front. Until it comes to a discontinuity (shallow water) it hardly disperses at all. It represents a huge proportion of the ship's engine output, I think.

 

[Bobbywhy]

kundukoustav, You must have noticed by now there are several kinds of wakes. The wakefield accelerator has great promise. From your mistaken comparison with aerodynamic drag on a car I am assuming you are referring to boat or ship wakes.

"Wake pattern of a boat:
Waterfowls and boats moving across the surface of water produce a wake pattern, first explained mathematically by Lord Kelvin and known today as the Kelvin wake pattern. This pattern consists of two wake lines that form the arms of a V, with the source of the wake at the point. Each wake line is offset from the path of the wake source by around 19° and is made up with feathery wavelets that are angled at roughly 53° to the path. The interior of the V is filled with transverse curved waves, each of which is an arc of a circle centered at a point lying on the path at a distance twice that of the arc to the wake source."
http://en.wikipedia.org/wiki/Wake

For a more detailed analysis of steel ship wakes see:
http://www.steelnavy.com/WavePatterns.htm