Pressure Based Model (Scaled Residuals Convergence)

hellsblade.91 · January 19, 2018, 13:04

Is it a golden thumb rule in Ansys Fluent ehat while using a pressure based model the residuals should awlays converge to 10^-6 ?

I am trying to simulate a flow of air at high pressures . I am using pressure based model my residuals dont converge upto the range of 10^-6 as mentioned in the fluent manual do i need to further dampen my resisuals . I am also getting reversed flow at my inlets and outlets

rewol · January 23, 2018, 10:45

What is the operating pressure ?

Usually, for pressures more than 5 Mpa or temperatures lower than 200K fluid behaves non-ideally and you may want to use a real-gas model. If you are not solving energy equation, you can write UDF for density to achieve that.

Also, order of 1e-6 for residuals is just a rule of thumb and not the one and only criteria for convergence. You may want to check the mass flow entering and leaving your domain to see if they are sufficiently close.

As for your reverse flow, warnings should be removed as the iterations continue unless your mesh and initializations are proper for your case. I was able to get rid of reverse flow warnings when i provided a better mesh to my problem many times. (better does not necessarily mean "denser")

Try to initialize your flow field a bit better, close to final solution if possible.

Best of luck.

January 19, 2018, 13:04	Pressure Based Model (Scaled Residuals Convergence)	#1
hellsblade.91 Member Hells Blade Join Date: Nov 2017 Posts: 61 Rep Power: 8	Is it a golden thumb rule in Ansys Fluent ehat while using a pressure based model the residuals should awlays converge to 10^-6 ? I am trying to simulate a flow of air at high pressures . I am using pressure based model my residuals dont converge upto the range of 10^-6 as mentioned in the fluent manual do i need to further dampen my resisuals . I am also getting reversed flow at my inlets and outlets

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January 23, 2018, 10:45		#2
rewol Member Refik Join Date: Dec 2014 Location: Turkey Posts: 53 Rep Power: 11	What is the operating pressure ? Usually, for pressures more than 5 Mpa or temperatures lower than 200K fluid behaves non-ideally and you may want to use a real-gas model. If you are not solving energy equation, you can write UDF for density to achieve that. Also, order of 1e-6 for residuals is just a rule of thumb and not the one and only criteria for convergence. You may want to check the mass flow entering and leaving your domain to see if they are sufficiently close. As for your reverse flow, warnings should be removed as the iterations continue unless your mesh and initializations are proper for your case. I was able to get rid of reverse flow warnings when i provided a better mesh to my problem many times. (better does not necessarily mean "denser") Try to initialize your flow field a bit better, close to final solution if possible. Best of luck.