Outlet Limit: water depth and flow rate

1. To help prevent downstream flooding, the City of Portland may require draining stormwater into a stream at a controlled rate.

The city of Portland's hydraulic design handbook describes how to properly size a small outlet to limit flow to a specific flow rate: A=(0.9)*((QH)/(sqrt(64.4H^(3/2))))

• Write a MATLAB program (an M-file) called outlet_areathat finds the area of this outlet, and accepts water depth (H) and flow rate (Q) as input arguments, in that order.

For example, your program might operate as such:

>> outlet_area(1.4,3.27)

ans = 0.39891

• Engineers using your program told you that most of the outlets are round, and so another program that calculated the diameter would be more useful.

Write another M-file called outlet_diameter that accepts water depth (H) and flow rate (Q) as input. It will work much the same way as your outlet_areaprogram but will output diameter instead of area.

A=(piD^2)/(4)

[James Tursa]

What have you done so far? What specific problems are you having with your code?

[Asuna Rayleigh]

i am having trouble with the second part where it is asking for the diameter instead of area.

i got this for the first part:

function outlet_area(H, Q)

A=0.9

B=(Q*H)/(sqrt(64.4*H^(3/2)))

C=A*B

endfunction

with the answer being 0.39891 for the area

Answer 1

[James Tursa]

You are being asked to write a function that takes H and Q as inputs, and outputs the diameter D. So the function outline would be:

function D = outlet_diameter(H, Q)
D = _____;
end

You need to fill in the D part above. You could start by calling your output_area function:

A = outlet_area(H,Q);

Or you could just hard code the same area expression that you used in your outlet_area function to determine A.

Then for the D part, just solve this expression A=(piD^2)/(4) for D and code that up and you are done.