3 replies to this topic

[Steinweg]

My first task is to sketch an appropriate control volume for the above problem. Would I be correct in drawing my dotted line (to represent the control volume) cutting through the lower surface (there is a solid boundary below the water I've given in the upload) and intersecting the sluice grate close to the free surface downstream? The control volume would cover both downstream and upstream horizontally. 

 

I'm then tasked with applying the momentum equations to derive an expression for the horizontal force per unit width exerted on the gate. (I'm told that atmospheric pressure acts on the water surface both upstream and downstream of the gate, which I'm taking to mean that p2 - p1 = 0, and that I only consider gauge pressure?).

 

Really not sure what equations I should be using here?

 

 

[breizh]

Hi, let you try

www.engineeringtoolbox.com

 

 search "Sluice gate flow measurement "

 

It should help !

 

Breizh

Edited by breizh, 16 November 2013 - 05:07 AM.

[S.AHMAD]

I believe you can use Bernoulli's equation assumung negiligble frictional loss... to be more accurate as per Breizh comments..

Edited by S.AHMAD, 15 November 2013 - 09:32 PM.

[Steinweg]

I believe you can use Bernoulli's equation assumung negiligble frictional loss... to be more accurate as per Breizh comments..

 

I've made an attempt at the problem, and I used continuity rather than Bernoulli's equation. I have assumed the fluid is inviscid. 

 

I was asked to draw a control volume for analysis for the problem above, and attached is what I have at the moment. 

 

This is the way a lot of people have approached this problem in my class, but I have seen someone consider the whole thing as a control volume (including the free surface and floor, but not the sluice gate). They've then drawn it out without anything in it, and drawn the gauge pressure external to it? Is that what I should've done?