# energy loss of flow

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 April 30, 2012, 22:24 energy loss of flow #1 New Member   suong Join Date: Apr 2012 Posts: 7 Rep Power: 6 Hello, I want to calculate the energy loss of flow through some obstacle (cylinders, ..). In my opinion, I think the velocity magnitude at outlet boundary will smaller than input. But the result is both velocity magnitude (u,v,w), are same at inlet and outlet I setup inlet_velocity and outflow for boundaries. (model 3D,_LES, transient) Any one can help me, give me advices. thank you!

 May 1, 2012, 07:50 #2 Senior Member   xrs333 Join Date: Aug 2010 Posts: 125 Rep Power: 9 Hi, Suong, i think i can explain it. i guess you are modeling incompressible flow, that is density is constant. So, according to mass conservation law, mass flows are the same for inlet and outlet in steady flow. Furthermore, if the area is same for the inlet and outlet, the velocity magnitude will be same. Energy loss for in flow should be evaluated with total pressure, which is the mechanical energy of the fluid.

May 5, 2012, 10:06
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suong
Join Date: Apr 2012
Posts: 7
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Quote:
 Originally Posted by xrs333 Hi, Suong, i think i can explain it. i guess you are modeling incompressible flow, that is density is constant. So, according to mass conservation law, mass flows are the same for inlet and outlet in steady flow. Furthermore, if the area is same for the inlet and outlet, the velocity magnitude will be same. Energy loss for in flow should be evaluated with total pressure, which is the mechanical energy of the fluid.