# Problem using ANSYS Fluent 15.07

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 July 11, 2015, 01:08 Problem using ANSYS Fluent 15.07 #1 New Member   Saikat Das Join Date: Jul 2014 Location: Cincinnati, Ohio, USA Posts: 8 Rep Power: 11 I am using ANSYS Fluent 15.07 for my simulation work. I am currently working on 1D shock tube problem. Shock tubes as you all know is a long tube, have a membrane type of thing in the middle. The membrane separates the two sides which have different pressures and densities. Actually one side of the tube has a high pressure and the other side has a low pressure. Flow is initiated by the rupture of the membrane due to the pressure difference. My particular problem is that, I am unable to give different densities for the two portions of the shock tube using Fluent. How can I give two different densities for the two sections of the shock tube using Fluent ? I have found out that whenever I am giving a specific density to one particular side, the other side of the tube is also taking that same density by default.

 July 11, 2015, 21:17 #2 Senior Member   Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,686 Rep Power: 66 You can use a custom field function to specify a dummy field variable (but it's actually pressure) and then initialize your solution using the dummy field variable. Finally, density is a material property and should be determined from the equation of state, I think you should only need to specify the pressure and temperatures.

 July 13, 2015, 05:10 #3 New Member   Join Date: Jun 2015 Posts: 11 Rep Power: 10 Hi, You can use VoF model with two phases : same gaz (or liquid) for both but with different density. after that, you need to adapt regions et then you can patch the different zones where you want to put one or an other phase. solution initialization -> initialize Adapt -> region -> enter x, y, z values solution initialization -> patch -> select the phase (not mixture) -> volume fraction -> put 0 or 1 as you want.

 Tags different densities, fluent 15.07