Pressure boundary conditions

amin.z · August 6, 2014, 04:02

Quote:

Originally Posted by 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 (0.0 Pa), 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. If i want to give the value of dynamic pressure at the inlet then how can i calculate this value as i know the flowrate.
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 have attached the pictures of model and mesh kindly take a look and also let me know whether my geometry is correct or not

I would be very grateful if you people help me out

Hey!
If your angular velcity is great it can make difficult to convergence for solver!
In this conditon, starting with a low velocity could help you for convergence!

techtradezone · July 22, 2015, 03:59

Hi guys, I first of all appreciate everyone here, I am new in here and new to CFD. i am working on inpipe turbine. I used 1.4 m/s inlet and unknown outlet in autodesk cfd, with 3Xdia upstream and down stream. I initially ramp up the rotatin region to 2400rpm as an ideal RPM, then later change the rotating region to free spinning then further time step till another steady state RPM was gottn. but i dicover that my unknown volume flow rate is higher than inlet after the simulation. also, when i plot the inlet point and outlet point i discover that my result inlet velocity is higher than the what i initially specified. pls guys i need ur help

hashim · July 27, 2015, 02:38

hi, which approach are you using means MRF or any other
second, what does unknown outlet means, are you using pressure outlet and also is your mesh is fine enough?
kindly clear these things i will try to help you out

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July 22, 2015, 03:59		#22
techtradezone New Member Temidayo Join Date: Feb 2015 Posts: 7 Rep Power: 11	Hi guys, I first of all appreciate everyone here, I am new in here and new to CFD. i am working on inpipe turbine. I used 1.4 m/s inlet and unknown outlet in autodesk cfd, with 3Xdia upstream and down stream. I initially ramp up the rotatin region to 2400rpm as an ideal RPM, then later change the rotating region to free spinning then further time step till another steady state RPM was gottn. but i dicover that my unknown volume flow rate is higher than inlet after the simulation. also, when i plot the inlet point and outlet point i discover that my result inlet velocity is higher than the what i initially specified. pls guys i need ur help

July 27, 2015, 02:38		#23
hashim New Member hashim Join Date: Jun 2014 Posts: 2 Rep Power: 0	hi, which approach are you using means MRF or any other second, what does unknown outlet means, are you using pressure outlet and also is your mesh is fine enough? kindly clear these things i will try to help you out