Another Fluid Mechanics problem

[fire]

I'm having problem understanding this one, can clarify and help answer?

A material region is defined as one where the surface velocity W is everywhere equal to the fluid velocity V. Such a region always contains the same fluid. Is it possible to define W in a less restrictive way and still have a region always containing the same material?

Thanks

 

[Astronuc]

If the material region (sounds like 'control volume') is defined as that volume of fluid bounded by the surface and the material is fixed, then it stands that the surface velocity must be the same as the fluid velocity.

See this problem. - www.colorado.edu/ASEN/asen5227/hwk8extra.pdf[/URL]

[PLAIN]http://www.colorado.edu/ASEN/asen5227/ - notes

 

[piercas]

for your question. It is possible to define W in a less restrictive way and still have a region always containing the same material. One way to do this is by using the concept of a material line, which is a line that is always made up of the same fluid particles. This means that the velocity of the fluid particles along the line will always be equal to the surface velocity W. Therefore, by defining W as the velocity along a material line, we can have a less restrictive definition while still maintaining a region containing the same material. I hope this helps clarify the concept for you. Let me know if you have any further questions.