Obtaining negative temperature sonicFoam

chelucupar · May 22, 2019, 06:47

Hello!
I am trying to simulate a Naca0012 profile, using the sonicFoam solver.
My trouble is that I am obtaining a negative temperature and the solver crashes. Also, if I plot the residuals, the continuity equation shows negative values. Anyone has any ideas? I saw some posts with similar problems, but no result was found what so ever.
I am also having troubles with setting my boundaries conditions. I am new in openFoam. My trouble is, what kind of boundary conditions should I set if I want to have a farfield like in Fluent?

wkernkamp · May 24, 2019, 00:53

I usually start from a tutorial case. For sonicFoam look in compressible.

hemanthgrylls · July 17, 2019, 14:58

https://www.cfd-online.com/Forums/op....html#poststop

check this out

Increase in courant number maybe the reason for blowup

A same time step through out the simulation is not suitable

During some iterations the demand for time step is very less due to flow characteristics in the domain and non robustness of the solver.

so try to enable "adjustabletimestep" in controldict which can control time step and controls the steady increase in courant number

add this lines in your controldict code:

HTML Code:

adjustTimeStep  yes;

maxCo               0.7;

maxDeltaT          0.01;

You can also limit the degree of temperature value update after every iteration using relaxation factor for you energy equation.

HTML Code:

relaxationFactors 
  { 
      fields
      { 
          p                           0.3; 
          T 			       0.3;
      } 
      equations 
      { 
         U                            0.4; 
        "(rho|k|nuTilda|e).*" 0.4; 
      } 
  }

hemanthgrylls · July 17, 2019, 15:04

https://www.openfoam.com/documentati...conditions.php

http://www.nextfoam.co.kr/lib/downlo...bb43ccfe025b25

Please go through these links and these might help you as a reference when you while you are stuck in defining boundary conditions.

May 22, 2019, 06:47	Obtaining negative temperature sonicFoam	#1
chelucupar New Member adrian chelaru Join Date: Mar 2015 Posts: 4 Rep Power: 11	Hello! I am trying to simulate a Naca0012 profile, using the sonicFoam solver. My trouble is that I am obtaining a negative temperature and the solver crashes. Also, if I plot the residuals, the continuity equation shows negative values. Anyone has any ideas? I saw some posts with similar problems, but no result was found what so ever. I am also having troubles with setting my boundaries conditions. I am new in openFoam. My trouble is, what kind of boundary conditions should I set if I want to have a farfield like in Fluent?

May 24, 2019, 00:53	tutorial case?	#2
wkernkamp Senior Member Will Kernkamp Join Date: Jun 2014 Posts: 316 Rep Power: 12	I usually start from a tutorial case. For sonicFoam look in compressible.

July 17, 2019, 14:58	Try and control cfl number using adjustable time step feature in OF	#3
hemanthgrylls New Member Dumbledore Join Date: Jun 2019 Posts: 10 Rep Power: 6	https://www.cfd-online.com/Forums/op....html#poststop check this out Increase in courant number maybe the reason for blowup A same time step through out the simulation is not suitable During some iterations the demand for time step is very less due to flow characteristics in the domain and non robustness of the solver. so try to enable "adjustabletimestep" in controldict which can control time step and controls the steady increase in courant number add this lines in your controldict code: HTML Code: adjustTimeStep yes; maxCo 0.7; maxDeltaT 0.01; You can also limit the degree of temperature value update after every iteration using relaxation factor for you energy equation. HTML Code: relaxationFactors { fields { p 0.3; T 0.3; } equations { U 0.4; "(rho\|k\|nuTilda\|e).*" 0.4; } }

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July 17, 2019, 15:04		#4
hemanthgrylls New Member Dumbledore Join Date: Jun 2019 Posts: 10 Rep Power: 6	https://www.openfoam.com/documentati...conditions.php http://www.nextfoam.co.kr/lib/downlo...bb43ccfe025b25 Please go through these links and these might help you as a reference when you while you are stuck in defining boundary conditions.