2D higly underexpanded jet

Gianmario28 · April 17, 2019, 11:46

Hi, I work for my master thesis and I must study an higly underexpanded jet due to an accidental release of methane from a pressurized pipe.
I try to work with a 2D geometry but I have different results from 3D to 2D geometry and I don't understand why.
In 3d I have a result in according with the theory, meanwhile in 2D I'm not able to reach it.
I use Fluent 18.2
I use a convergent nozzle, with a pressure inlet

LuckyTran · April 17, 2019, 12:11

What are we looking for?

The nozzle contours are different.

Even if the contours are the same, you are doing a 2D slot versus (we can't see it but presumably) a 3D axissymmetric nozzle.

Maybe an apples to apples comparison rather than an apples to elephant comparison would be more helpful?

Gianmario28 · April 17, 2019, 12:31

Tank you for the answer LuckyTran. I already fix the contours of the nozzle and now are the same, but my problem is the same. I have my 3D problem, but because I have a radial simmetry I decide to study the problem in 2D, and according with the theory the result must be the same that I have reached in 3D. So the theory says that I can study my problem in 2D and the velocity field must be similar to 3D image. But I'm not able to do this.
Do you think that I must study also my 2D problem like axissymetric?

Gianmario28 · April 17, 2019, 12:57

LuckyTran, I understand and solve my problem, thank you so much.

akashgupta · April 28, 2019, 06:18

Hello

I am working on CD Nozzle (2D Model) simulation in ANSYS Fluent- (real time project). The Inlet conditions are: Pressure =0.6mpa and Temperature = 588.6 k. Expected outlet Temperature is around 350 k.
As I am trying to simulate in Fluent, after few iterations, I am getting a reverse flow on pressure inlet and pressure outlet and there is also a reduce in time step due to excess temperature change.
How can I resolve these kind of errors that will help me to in the simulation.
can you help me
plz

April 17, 2019, 12:11		#2
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,761 Rep Power: 66	What are we looking for? The nozzle contours are different. Even if the contours are the same, you are doing a 2D slot versus (we can't see it but presumably) a 3D axissymmetric nozzle. Maybe an apples to apples comparison rather than an apples to elephant comparison would be more helpful? Gianmario28 likes this.

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April 17, 2019, 12:31		#3
Gianmario28 New Member Gianmario Ledda Join Date: Oct 2018 Posts: 6 Rep Power: 8	Tank you for the answer LuckyTran. I already fix the contours of the nozzle and now are the same, but my problem is the same. I have my 3D problem, but because I have a radial simmetry I decide to study the problem in 2D, and according with the theory the result must be the same that I have reached in 3D. So the theory says that I can study my problem in 2D and the velocity field must be similar to 3D image. But I'm not able to do this. Do you think that I must study also my 2D problem like axissymetric?

April 17, 2019, 12:57		#4
Gianmario28 New Member Gianmario Ledda Join Date: Oct 2018 Posts: 6 Rep Power: 8	LuckyTran, I understand and solve my problem, thank you so much.

April 28, 2019, 06:18		#5
akashgupta New Member akash gupta Join Date: Apr 2019 Posts: 2 Rep Power: 0	Hello I am working on CD Nozzle (2D Model) simulation in ANSYS Fluent- (real time project). The Inlet conditions are: Pressure =0.6mpa and Temperature = 588.6 k. Expected outlet Temperature is around 350 k. As I am trying to simulate in Fluent, after few iterations, I am getting a reverse flow on pressure inlet and pressure outlet and there is also a reduce in time step due to excess temperature change. How can I resolve these kind of errors that will help me to in the simulation. can you help me plz