Fluent - reference values

Aedun · October 18, 2014, 06:03

Hello ..... i m bit struggling with setting reference values .... i m modeling airflow around an car .... the only way i get correct results is when i set:
1) reference area as frontal area of car
2)density left to 1.225
3) enthalpy 0
4)lenght 1
5) pressure 101325
6) tempreture 288K
7) velocity to 60m/s
8) viscosity 1.7e-5
9) RSH 1.4
And then i use lift and drag coeficient that fluent provides when residuals and my monitors are converged and put them into formula F = density * velocity^2 * C (drag or lift - metters what i m calculating ) * A ( front area or top area depends if i m calculating lift or drag) * 0,5 ........ I m asking cause i m not sure if areas are set correctly ..... results are real but are my calculations 100% correct ? ( i m sure about convergence i have met all conditions i read on this forum and manual i need to satisfy ) Thanks

Kokemoor · October 20, 2014, 10:21

If you're looking for forces instead of coefficients, you can get them directly from Reports (Fluent User's Guide Section 32.4). The coefficients are calculated from the forces using your reference values, so you should always get the same force, even if you back-calculate with different reference values.

October 18, 2014, 06:03	Fluent - reference values	#1
Aedun New Member Ondrej Novak Join Date: Apr 2014 Posts: 10 Rep Power: 12	Hello ..... i m bit struggling with setting reference values .... i m modeling airflow around an car .... the only way i get correct results is when i set: 1) reference area as frontal area of car 2)density left to 1.225 3) enthalpy 0 4)lenght 1 5) pressure 101325 6) tempreture 288K 7) velocity to 60m/s 8) viscosity 1.7e-5 9) RSH 1.4 And then i use lift and drag coeficient that fluent provides when residuals and my monitors are converged and put them into formula F = density * velocity^2 * C (drag or lift - metters what i m calculating ) * A ( front area or top area depends if i m calculating lift or drag) * 0,5 ........ I m asking cause i m not sure if areas are set correctly ..... results are real but are my calculations 100% correct ? ( i m sure about convergence i have met all conditions i read on this forum and manual i need to satisfy ) Thanks

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October 20, 2014, 10:21		#2
Kokemoor Senior Member Andrew Kokemoor Join Date: Aug 2013 Posts: 122 Rep Power: 13	If you're looking for forces instead of coefficients, you can get them directly from Reports (Fluent User's Guide Section 32.4). The coefficients are calculated from the forces using your reference values, so you should always get the same force, even if you back-calculate with different reference values.