hi

iam trying to simulate the performance of an axial fan in a wind tunnel.i used the single rotating reference frame model.but iam getting very high static pressure distributions across the domain.also i have reversed flow at the pressure outlet.i have only solved for a couple hundred iterations,but even now the solution seems to diverge.

should i use a mixing plane model so that the domain near the fan rotates and the rest of the domain remains stationary or is the present model sufficient(thats wat the fluent technical support engineer suggested)

thank you

Moving reference frame should do the job very well. What are your boundary conditions? Is the reversed flow physical, or is it nonsens?

Laika, still orbiting

hi laika,

Thanks for your quick response,the boundary conditions are velocity inlet and pressure outlet,with periodic boundaries on either side along the length.the main problem is that iam getting very high static pressure distributions across the domain.Also the velocity vectors at the pressure outlet condition are towards the fan.iam getting reversed flow in almost 6000 faces on the pressure outlet

regards

-switch the periodics to symmetry-boundaries.

-is your case converged?

-check the mass balance.

-is the fan blowing in the right direction?

Laika, still orbiting

hi

no my case has not converged,In the single rotating reference frame model ,there is no mass imbalance.but when i used a mixing plane model,there is very high mass imbalance accross the mixing planes(I have a mixing plane between the tunnel and fan domain,and another between the fan and the atmosphere).

iam guessing that this maybe due to my wrong initial guess.like i have the volume flow rate data from the wind tunnel.now how do i get my inlet velocity to duplicate the volume flow rate in my model.

thanks

[chaudhry_hashim]

Hi I am quite new to CFD i am trying to find out the fan curve. My fan diameter is 71mm and what did uptill now I made inlet duct 15 times of fan dia with pressure inlet (dynamic pressure) calculating from flowrate and fan diameter I have by using the formula (rho x velocity^2 / 2), outlet duct 30 times of fan dia with pressure outlet (0.0 Pa) and I am giving fixed rpm to the rotating region in between. I am measuring pressure in inlet and outlet duct at a position 10 times of fan dia. but Still I didnt find the relevant pressure difference across the fan and also the solution is not converges.

Although I am working in the same way as hiras worked that I am using steady state solution, MRF, pressure-inlet/pressure outlet conditions, k-e standard.

I would be very grateful if you people help me out