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HEC-RAS : i want to calculate headloss coming from a direction change

HEC-RAS : i want to calculate headloss coming from a direction change

HEC-RAS : i want to calculate headloss coming from a direction change

(OP)
Hello,

I need to integrate a head loss created by a 90° direction change in a unsteady flow model.

I don't see any solution ...

I have think to put a head loss coefficient on a cross section but i can't in unsteady flow. (Headloss = k(v2/2g))

Any body can help me ??

RE: HEC-RAS : i want to calculate headloss coming from a direction change

increase the n-value for the reach

RE: HEC-RAS : i want to calculate headloss coming from a direction change

(OP)
Thank you for your reply !!!

But how much i have to increase n-value ???

Do you know any relation to estimate de headloss if I know the angle ??

RE: HEC-RAS : i want to calculate headloss coming from a direction change

I don't know of a relation.  Depends on the length of the reach also.  You will need to do some calcs to determine a suitable value and then try it to see if it approximates the headloss you are looking for.

RE: HEC-RAS : i want to calculate headloss coming from a direction change

(OP)
My problem is very simple, it is a rectangular channel with a 90° change direction like this :

----------|
 <----    |
-----|  ^ |
     |  | |
     |  | |


The channel's width is 2 meters.

May be somebody know how too calculate the headloss ???

My first idea is to use a headloss coefficient of 1,5 like in pipe ... But i don't now if it is correct ....

RE: HEC-RAS : i want to calculate headloss coming from a direction change

Instead of a pipe try a k value for a similarly sized rectangular duct with a 90d elbow bearing in mind medium adjustement.

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