URGENT: External SS and HS Flow Modelling

August 12, 2002, 14:34

Hi !

I am new to Fluent, I am using 5.5. To model Supersonic or Hypersonic External Aerodynamic flow while definig materials: How should I specify Density, Thermal Conductivity, Viscosity and Specific Heat? What should I do: specify them a constant? ideal gas law? polynomial, sutherland etc etc there are many options?

August 12, 2002, 16:58

For this problem, you probably work with air. It's certain that they have noumerous choice to fix it. For your first approximation, you chould fix your density with ideal gas law. It's a good and simple way to work in compressible flows. In this first guess, you can let Thermal conductivity and specific heat to default values. But, in futur operations, you should use polynomial fonctions for these parameters. For the viscosity, try default constant or Sutherland model with three constants.

For the kind of work you seem to do, you should work in the coupled code. The segregated code is mostly for incompressible calculations. To choose between implicit and explicit, a validation calculation could be interresting.

Good luck and patience

August 18, 2002, 11:51

Hi Mr. Antoine !

(a) I have tried the default values for Thermal Cond. and Specific Heat. I have also used Ideal Gas Law for Density and Sutherlands law with 3 Coeff. for viscosity. I have been able to get the results. But no matter what I do the residuals are not decreasing below 0.008.

I have monitored Cm, Cd and Cl also and they also get to one point and show no more change.

After that I have tried changing the under Relaxation factors as well, but the results are no more changing.

Have I got the converged results??

By seeing the soln, things appeared to be alright.

(b) Where can I find the polynomial functions for Specific Heat & Thermal Cond. in case of Air. I have tried but unable to find these properties of Air (Sp Heat & Therm. Cond.). Can you guide me wher to find these values w.r.t Temperature for Air. Definitely I need the values at high Tepmerature if I am modelling the flow at high Supersonic and Hypersonic regimes.

Thanx really for your previous help.

Cheers

August 12, 2002, 14:34	URGENT: External SS and HS Flow Modelling	#1
faq Guest Posts: n/a	Hi ! I am new to Fluent, I am using 5.5. To model Supersonic or Hypersonic External Aerodynamic flow while definig materials: How should I specify Density, Thermal Conductivity, Viscosity and Specific Heat? What should I do: specify them a constant? ideal gas law? polynomial, sutherland etc etc there are many options?

August 12, 2002, 16:58	Re: URGENT: External SS and HS Flow Modelling	#2
Pierre-Antoine Rainville Guest Posts: n/a	For this problem, you probably work with air. It's certain that they have noumerous choice to fix it. For your first approximation, you chould fix your density with ideal gas law. It's a good and simple way to work in compressible flows. In this first guess, you can let Thermal conductivity and specific heat to default values. But, in futur operations, you should use polynomial fonctions for these parameters. For the viscosity, try default constant or Sutherland model with three constants. For the kind of work you seem to do, you should work in the coupled code. The segregated code is mostly for incompressible calculations. To choose between implicit and explicit, a validation calculation could be interresting. Good luck and patience

August 18, 2002, 11:51	Re: URGENT: External SS and HS Flow Modelling	#3
faq Guest Posts: n/a	Hi Mr. Antoine ! (a) I have tried the default values for Thermal Cond. and Specific Heat. I have also used Ideal Gas Law for Density and Sutherlands law with 3 Coeff. for viscosity. I have been able to get the results. But no matter what I do the residuals are not decreasing below 0.008. I have monitored Cm, Cd and Cl also and they also get to one point and show no more change. After that I have tried changing the under Relaxation factors as well, but the results are no more changing. Have I got the converged results?? By seeing the soln, things appeared to be alright. (b) Where can I find the polynomial functions for Specific Heat & Thermal Cond. in case of Air. I have tried but unable to find these properties of Air (Sp Heat & Therm. Cond.). Can you guide me wher to find these values w.r.t Temperature for Air. Definitely I need the values at high Tepmerature if I am modelling the flow at high Supersonic and Hypersonic regimes. Thanx really for your previous help. Cheers