# Modelling Impeller and validate

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March 20, 2019, 05:09
Modelling Impeller and validate
#1
New Member

Iljar Dickhof
Join Date: Mar 2019
Posts: 8
Rep Power: 7
Hallo experts,

I'm modelling an impeller which exhaust in radial direction and validate it with the given operating point. My model can be seen in image 1 in which two stationary domains and 1 rotating domain (middle and rotating with 2400 rpm) has been set up. The domains have a transient rotor stator interface. My mesh can be seen in image 2.

The given operating point is 4159 m^3/h with a pressure build up of 603 Pa. The Air density is 1,20 kg/m^3. In my model I've given the outlet a mass flow of 1,39 kg/s and the inlet a pressure of 0 Pa.

My results after simulating gave me a pressure build up of 993 Pa. This is a big difference in comparison with the real point (603 Pa). Does someone know where my fault is? Do I need to make a finer mesh (current: 500.000 elements)? I'm limited to the academic version through.

I also checked y+ on the walls (image 3). My assumption is a safe marge of 0-500 which my model is.

I would like to hear from you. Thank in advance.

Greetings,
Iljar
Attached Images
 Model.PNG (112.6 KB, 15 views) Mesh result.jpg (95.0 KB, 12 views) y plus result.PNG (189.4 KB, 15 views)

 March 20, 2019, 07:30 #2 Senior Member   urosgrivc Join Date: Dec 2015 Location: Slovenija Posts: 365 Rep Power: 11 Maybe your boundary conditions are too close to the rotor and have some effect on the result

 March 20, 2019, 16:33 #3 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,727 Rep Power: 143 FAQ: https://www.cfd-online.com/Wiki/Ansy..._inaccurate.3F The big three things to check when you want accurate simulations are mesh size, convergence criteria and boundary proximity. You should do sensitivity analyses in all three of these factors to ensure accuracy. __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

 Tags impeller, modelling, validations