# Real Gas table generation

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 April 29, 2014, 01:50 Real Gas table generation #1 Member   omid Join Date: Apr 2011 Posts: 98 Rep Power: 6 Hi all i have usual problem when i simulate real gas flow, peng-robinson or RK model. this problem is " temperature and absolute pressure table range". for some absolute and pressure range solver diverged and return errors like: Newtons method failed to converge in 100 iterations. This | | occurred while computing the following variable: | | | | Variable Name : Total Temperature | | Location Name : NOZZLE | | Mesh location : VERTICES | | Mesh entity : | | Last 3 Changes : 1.73755E+01 1.71344E+01 1.70618E+01 | | Tolerance : 1.0000E-02 | | | | The Newton iteration was either slowly converging or has stalled. | | The solver will continue with the variable set as it was on the | | final iteration. If this situation continues you might try | | increasing the number of iterations allowed for Newtons method. | | This can be changed by setting one of the parameters: | | | | Temperature : "Constitutive Relation Iteration Limit" | | Pressure : "Newton Pressure Iteration Limit" | | | | for your mixture using the definition file editor. | +--------------------------------------------------------------------+ i generate this range by try and error! is there any relation for set this ranges? Best regards

 April 29, 2014, 03:38 #2 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 11,053 Rep Power: 86 These sort of errors are common with complex equations of state. You need to improve your simulation's numerical stability. You can do this by: * Better mesh quality * Better initial conditions * double precision numerics * smaller time steps * lower order differencing in space and/or time (this one will reduce the accuracy of your simulation)

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