Transient Sim
 

Hi all,

I am doing a 2D transient simulation with pulsatile flow through a pipe. After CFX-solver had produced the results, I noticed that there is only backflow through the pipe. Any ideas on where I've gone wrong? (Note: the outlet was set as "opening", I wasn't able to choose "outlet" because CFX give me an error saying part of the wall is in the outlet, preventing fluid from flowing out...)

Thanks, CC.

Re: Transient Sim
 

Hi CC,

Specifically, how did you define your inlet and outlet and the pulse? Was it a varying static pressure, total pressure, velocity, mass flow rate, ...?

Regards, Robin

Re: Transient Sim
 

Hi Robin,

The inlet cart. velocity was specified with U=0, V=0, W=C1+sin(2*pi*t/Tp) [m*s^-1] where C1 is 4.3[m*s^-1] and Tp is 0.345[s].

The boundary type for outlet is specified as "opening" with "opening pressure and direction" and 4140pa for "relative pressure". Flow direction set as "normal to boundary condition".

I specified 4140pa for relative pressure in the domain and global initialisation. I also tried the simulation with 0pa pressure everywhere, it still fluid flowing in the wrong direction...

Thanks, CC.

Re: Transient Sim
 

Hi CC,

The boundary condition pressure is specified relative to the domain pressure, thus you have an opening pressure of 8280 Pa at your outlet. Leave the domain pressure as it is, but change your opening pressure to 0 Pa.

Regards, Robin