Quote:
Originally Posted by Northy
I'm no expert, but I think you guys are looking a little deep into it.
I'll see what I can come up with.
G
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Sorry, Northy. From your previous post I was under the impression you were holding out on us!
Quote:
Originally Posted by rich_cree
Could it have something to do with the distance over which the velocity gradient spans and the non proportional nature of which area of a circle varies with radius?
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I think you're right, Richard. That is certainly what I was trying to imply. A linear velocity gradient is defined as a change in velocity over a given distance. Therefore if your velocity difference remains unchanged, but the distance over which it occurs increases, you will see a decreased gradient.
I'm not sure how the area of a circle varying disproportionately to its radius will affect things. That's getting quite deep!
I was simplifying things quite a bit by quoting a flat plate theory where the velocity gradient is constant between two plates (one moving and the other stationary). In this situation both 'plates', i.e. the hole edges, are effectively stationary. In addition you may see boundary layer effects, recirculation and no doubt a myriad of other phenomena playing their part. I hadn't thought of it before, but I think recirculation of the fluid behind the holes is significant (as it causes drag), and hence another reason why more holes would result in increased pack.
Quote:
Originally Posted by usagi
Bloody hell Dunc.....do you have a degree in fluid dynamics?...it's beyond me  |
Indeed I do. Plenty more to learn though.....