total pressure change in a pipe flow
 

hi everybody. I have been solve pipe flow with orifice. It's very simple problem. The pipe size is L=50m, D=1.0m. It has orifice at L=10m. As everybody knows, the recirculation region occured right after orifice. Because of these recirculating flow, the total pressure dropped suddenly. Now, My problem is that. The average total pressure at around orifice is lower than outlet average total pressure. Is it possible ? As I know, The static pressure at recirculation region is possibly lower than outlet pressure. Decreased static pressure can be increased as dynamic pressure decrease. but the total pressure never can increase without any additional energy. What is wrong? The solution of fluent or my thought that the total pressure never can increased without any addtional energy. If my idea is wrong, please let me know the mechanism of total pressure gain. thanks in advance.

Re: total pressure change in a pipe flow
 

Make sure that you are using the so-called "mass-weighted" averaging.

If not, try it, you should see a decrease in the so-averaged total pressure.

Re: total pressure change in a pipe flow
 

What fluid material are you using?

Re: total pressure change in a pipe flow
 

I tried all kinds of average method. vertex, facet, mass weighted etc... As change averaging method, the magnitude of total pressure changed, but there is no change in the tendency.

Re: total pressure change in a pipe flow
 

I used air. I just change the density and viscosity. density = 0.82kg/m^3, and viscosity = 0.1cp

It looks like due to wake there is a vacuum next to sudden expansion or the orifice, which is causing the total pressure decrease refer below link

http://www-mdp.eng.cam.ac.uk/web/lib...is/node55.html