Enthalpy calculation

WilliamH · September 3, 2020, 05:14

Hi everyone,
I have successfully found a solution for my Mach 5 scramjet inlet and displayed the results in ParaView. I have values for temperature, density and pressure. I would like to calculate the enthalpy.
Is there an easy way to do so in ParaView using the calculator?
If not, can SU2 calculate the enthalpy?
Thanks!

aero_amit · September 3, 2020, 09:46

You can use calculator in ParaView to do so.
Make use of pressure, density. Get velocity components by dividing momentum with density and use the enthalpy formula..

WilliamH · September 4, 2020, 04:39

Thanks for the help! Would you mind detailing the steps? What formula for entropy are you using?

aero_amit · September 6, 2020, 08:08

Hi William,

Your first post mentioned Enthalpy so I am assuming that as a variable to be computed.

In ParView, press Calculator and compute a variable with any name you like (let us say Vel_vec) and in formula - Momentum/Density

Again highlight this Calculator1 and compute Total specific enthalpy (Hs or whatever name you like) with (let's say 2D case) formula -
Pressure*3.5/Density+0.5*(Vel_vec_X*Vel_vec_X+Vel_vec_Y*Vel_vec _Y)
(here 3.5 is for gamma/(gamma-1)).

Best
Amit

WilliamH · March 31, 2021, 05:31

Hi, sorry for only replying now.
Your method worked well but could you explain how you derived this formula? I've been trying to find similar formula on the Internet but I cannot seem to find it.
I also tried to check the units but they didnt seem to add up. Should the total specific enthalpy be in J/kg?
Thanks
William

aero_amit · April 1, 2021, 07:04

Hi WilliamH, You can find it in most of the text books (Gas Dynamics, CFD).

Basically H=h+V^2/2

here - h= CpT = g*RT/(g-1) = 3.5*P/Rho for g=1.4 & V^2=u^2+v^2+w^2 in 3D.

Yes it is total specific enthalpy and unit is J/kg or m^2 sec^-2.

Here my primary intention was to convey the procedure of calculating a variable of interest in ParaView from available dataset.

Best
Amit

September 3, 2020, 05:14	Enthalpy calculation	#1
WilliamH New Member William Haigh Join Date: Aug 2020 Posts: 20 Rep Power: 5	Hi everyone, I have successfully found a solution for my Mach 5 scramjet inlet and displayed the results in ParaView. I have values for temperature, density and pressure. I would like to calculate the enthalpy. Is there an easy way to do so in ParaView using the calculator? If not, can SU2 calculate the enthalpy? Thanks!

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September 3, 2020, 09:46		#2
aero_amit Member Amit Join Date: May 2013 Posts: 85 Rep Power: 12	You can use calculator in ParaView to do so. Make use of pressure, density. Get velocity components by dividing momentum with density and use the enthalpy formula..

September 4, 2020, 04:39		#3
WilliamH New Member William Haigh Join Date: Aug 2020 Posts: 20 Rep Power: 5	Thanks for the help! Would you mind detailing the steps? What formula for entropy are you using?

September 6, 2020, 08:08		#4
aero_amit Member Amit Join Date: May 2013 Posts: 85 Rep Power: 12	Hi William, Your first post mentioned Enthalpy so I am assuming that as a variable to be computed. In ParView, press Calculator and compute a variable with any name you like (let us say Vel_vec) and in formula - Momentum/Density Again highlight this Calculator1 and compute Total specific enthalpy (Hs or whatever name you like) with (let's say 2D case) formula - Pressure3.5/Density+0.5(Vel_vec_XVel_vec_X+Vel_vec_YVel_vec _Y) (here 3.5 is for gamma/(gamma-1)). Best Amit

March 31, 2021, 05:31		#5
WilliamH New Member William Haigh Join Date: Aug 2020 Posts: 20 Rep Power: 5	Hi, sorry for only replying now. Your method worked well but could you explain how you derived this formula? I've been trying to find similar formula on the Internet but I cannot seem to find it. I also tried to check the units but they didnt seem to add up. Should the total specific enthalpy be in J/kg? Thanks William

April 1, 2021, 07:04		#6
aero_amit Member Amit Join Date: May 2013 Posts: 85 Rep Power: 12	Hi WilliamH, You can find it in most of the text books (Gas Dynamics, CFD). Basically H=h+V^2/2 here - h= CpT = gRT/(g-1) = 3.5P/Rho for g=1.4 & V^2=u^2+v^2+w^2 in 3D. Yes it is total specific enthalpy and unit is J/kg or m^2 sec^-2. Here my primary intention was to convey the procedure of calculating a variable of interest in ParaView from available dataset. Best Amit