# Mass Imbalance in orifice with cavitation-model

 Register Blogs Members List Search Today's Posts Mark Forums Read

 April 12, 2013, 06:08 Mass Imbalance in orifice with cavitation-model #1 New Member   Burkard Spiegel Join Date: Apr 2013 Posts: 2 Rep Power: 0 Hello, I am doing my master thesis on studying cavitation in small orifices. The diameter of the inlet and the outlet are 2 mm and the sharp-edged orifice has a diameter of 0.2 mm. The length of my outlet is about 50 mm. I run my calculation as steady with k-e-rng-model on. My BC are pressure-inlet (100 bar) and pressure outlet (atm). For a one-phase flow I have a mass imbalance for inlet to outlet less 1 %. But if I run the simulation with mixture model (water-liquid and water-vapour) and default cavitation model (schnerr-sauer), I get a difference of the order of around 10. inlet: 12.53 kg/h outlet: - 335 kg/h My residuals fall to 1e-04 and don't change over 5000 iterations. The problem seems to be the condensation of the vapour to the liquid in the outlet. Direct after the orifice the volume fraction of vapour is close to 1. Around 15 mm after the orifice the vapour condensates. (This aspect I also see in pictures I recieve from experiments). Before the condensation I have the same mass flow as at the inlet, after the condensation I have the much higher values of the outlet. Do you have any ideas about this? I'd appreciate any help. Thank you, Burkard

 April 12, 2013, 09:17 #2 Senior Member     Philipp Join Date: Jun 2011 Location: Germany Posts: 1,297 Rep Power: 20 Is this 2d? Can you afford to refine the mesh strongly? What do you use for meshing? __________________ The skeleton ran out of shampoo in the shower.

 April 12, 2013, 13:11 #3 New Member   Burkard Spiegel Join Date: Apr 2013 Posts: 2 Rep Power: 0 Hello Rodriguez, sorry I totally forgot to write s.th. about this. Yes, it's 2D and axisymmetric. I used the mesh generator from the ansys workbench. I have around 800 k cells and the mesh is finer around the orifice. I'll try to refine the grid at the outlet. Burkard

 Thread Tools Display Modes Linear Mode

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is OffTrackbacks are On Pingbacks are On Refbacks are On Forum Rules

 Similar Threads Thread Thread Starter Forum Replies Last Post volo87 CFX 5 June 14, 2013 17:44 Reyhaneh Sadat Ghazanfari FLUENT 0 September 30, 2012 06:36 saii CFX 2 September 18, 2009 08:07 ahourri FLUENT 8 October 26, 2004 23:14 Andy Main CFD Forum 0 March 11, 2004 15:05

All times are GMT -4. The time now is 07:56.