5 Replies Latest reply on Apr 26, 2012 11:37 AM by Roland Schwarz

# Determining Energy Loss in flow simulation

Hello, guys.

I'm trying to make a flow simulation in a certain pipe.

I want to define its energy loss generated by my pipe.

as far I know, I have to use the Bernoulli's equation and compare the energy between inlet and outlet. The energy can be defined by find the velocity (v), pressure (p), and height (z).

And here's my problem.

I want to make my pipe a little bit different by change it size into a rectangle one.

My questions is, how do I define v, p, and z?

Should I define the mean pressure of inlet and outlet surface?

or maybe I should define it using "point". Take the pressure value at the center point of the rectangle, and so on?

or there is other method? which one is common?

• ###### Re: Determining Energy Loss in flow simulation

Before finishing uni, I worked as an HVAC balance tech.  We often had to measure flow through ducts.  It was never done with a single point, since flow was almost never uniform.

You need to divide your outlet into sections of equal area, and measure velocity and pressure at each section.

• ###### Re: Determining Energy Loss in flow simulation

Thank you so much, Sir.

may I conclude that I should find the mean pressure of inlet and outlet?

Can I only define 1 surface and find its value in solidworks?

• ###### Re: Determining Energy Loss in flow simulation

No, you ought not conclude that, since it is the opposite of what I said.

Divide inlet an outlet cross-sections into many pieces of equal area, take a mean from each section, and then average.  Pieces should be small enough that each one's mean is representative of that piece.

• ###### Re: Determining Energy Loss in flow simulation

Sorry but I still don't get it.

[Divide inlet an outlet cross-sections into many pieces of equal area, take a mean from each section, and then average.]

my idea:

[Define the pressure at inlet surface]

What is the different between these two?

• ###### Re: Determining Energy Loss in flow simulation

I suppose if you actually define the inlet pressure as constant across the cross-section, then there is no difference.  However, the story would be much different at the outlet.