sonicFoam forwardstep negative temperature problem.

ecad · January 8, 2018, 09:14

Hello, im trying to solve forwardstep tutorial by using sonicFoam solver with mach numbers of 0.8 and 2 and Gauss linear divSchemes. I tried finer meshes and lower deltaT values but i get the FOAM FATAL ERROR: Negative initial temperature T0 everytime im trying to solve this. Seems like this is due to changes in divSchemes but its required for the problem so i can't change it. Is there any other way to get around this ?

Taataa · January 8, 2018, 18:28

Assuming that you've setup boundary and initial conditions correctly, negative T means that the solution is unbounded. You have to change schemes e.g. using limiters and/or tighten tolerances. Usually limitedLinear 1 is a good option in unbounded cases. If it worked you can loosen the limiter by lowering the coefficient e.g. limitedLinear 0.2.

ecad · January 8, 2018, 18:31

Quote:

Originally Posted by Taataa

Assuming that you've setup boundary and initial conditions correctly, negative T means that the solution is unbounded. You have to change schemes e.g. using limiters and/or tighten tolerances. Usually limitedLinear 1 is a good option in unbounded cases. If it worked you can loosen the limiter by lowering the coefficient e.g. limitedLinear 0.2.

Thank you. I solved it before reading this and i have done the same thing. Im gonna try lower than 1.

January 8, 2018, 09:14	sonicFoam forwardstep negative temperature problem.	#1
ecad New Member Join Date: Jan 2018 Posts: 2 Rep Power: 0	Hello, im trying to solve forwardstep tutorial by using sonicFoam solver with mach numbers of 0.8 and 2 and Gauss linear divSchemes. I tried finer meshes and lower deltaT values but i get the FOAM FATAL ERROR: Negative initial temperature T0 everytime im trying to solve this. Seems like this is due to changes in divSchemes but its required for the problem so i can't change it. Is there any other way to get around this ?

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January 8, 2018, 18:28		#2
Taataa Senior Member Taher Chegini Join Date: Nov 2014 Location: Houston, Texas Posts: 125 Rep Power: 12	Assuming that you've setup boundary and initial conditions correctly, negative T means that the solution is unbounded. You have to change schemes e.g. using limiters and/or tighten tolerances. Usually limitedLinear 1 is a good option in unbounded cases. If it worked you can loosen the limiter by lowering the coefficient e.g. limitedLinear 0.2.