CFD Online Discussion Forums (https://www.cfd-online.com/Forums/)
-   CFX (https://www.cfd-online.com/Forums/cfx/)
-   -   "Newtons method failed in Atomization Problem (https://www.cfd-online.com/Forums/cfx/104742-newtons-method-failed-atomization-problem.html)

 a_cucen July 14, 2012 12:00

"Newtons method failed in Atomization Problem

I m simulating spray of heptane. Liquid heptane sprays from an injector. but after injection began, I got this error. Because of specific heat depends on temperature, I m using Nasa polynomials. If I take a specific value for specific heat, the error doesn' t happen. How can I solve this problem?

****** Notice ****** |
| Newtons method failed to converge in 100 iterations. This |
| occurred while computing the following variable: |
| |
| Variable Name : Temperature |
| Location Name : Flow Domain 1 |
| Mesh location : VERTICES |
| Mesh entity : |
| Last 3 Changes : 6.25499E-02 4.23251E-02 4.36934E-02 |
| Tolerance : 1.0000E-02 |
| |
| The Newton iteration was diverging. The solver will continue |
| with the variable field as it was on the final iteration. If |
| this situation continues you might try decreasing the Newton |
| iteration under relaxation factor. This can be changed by |
| setting one of the following parameters: |
| |
| Temperature : "Constitutive Relation Under Relaxation" |
| Pressure : "Newton Pressure Under Relaxation" |
| |
| for your mixture using the definition file editor. |
+--------------------------------------------------------------------+

 a_cucen July 15, 2012 05:14

I solved the problem. But now I have another problem :S It gave this failure after 10 iterations from spray began. How can I solve this problem?

Parallel run: Received message from slave
-----------------------------------------
Slave partition : 4
Slave routine : get_TWFTFC
Master location : End of Continuity Loop
Message label : 009100015
Message follows below - :
+--------------------------------------------------------------------+
| ****** Notice ****** |
| The non-dimensional near wall temperature (T+) has been clipped |
| for calculation of Wall Heat Transfer Coefficient. |
| |
| Boundary Condition : piston |
| T+ clip value = 1.0000E-10 |
| |
| If this situation persists and you are using the High Speed Model, |
| consider enabling Mach number based blending between low speed and |
| high speed wall functions. You can do so by specifying a Mach |
| number threshold as follows: |
| |
| EXPERT PARAMETERS: |
| highspeed wf mach threshold = 0.1 # default=0.0 (off) |
| END |
+--------------------------------------------------------------------+

 ghorrocks July 15, 2012 08:28

If you are modelling multiphase spraying with NASA polynomial fluids then you should expect a numerically unstable simulation. You need to get each bit of this model working one at a time before doing the entire simulation.

 a_cucen July 15, 2012 20:04

I have fixed this error too. But there is something I can not explain. The liquid heptane particles are vapourised meanwhile it enters the domain. It must enter the domain in liquid form and break up to small particles in normal conditions. Where do I make mistake?

 ning April 14, 2013 21:48

Newtons method failed to converge in 100 iterations.

Dear a_cucen,
I have also countered this problem"Newtons method failed to converge in 100 iterations ",and have not find a way to deal with it.Could you tell me the reasons that cause this problem.Is it a BC problem or a grid problem?And how can I solve it?
Thank you very much!I hope to hear from you soon.

 ghorrocks April 15, 2013 18:50

The Newtons method failed to converge message means some material properties could not converge. To debug this you should simplify your problem one thing at a time to isolate what is causing it.

 ning April 16, 2013 21:57

Quote:
 Originally Posted by ghorrocks (Post 420781) The Newtons method failed to converge message means some material properties could not converge. To debug this you should simplify your problem one thing at a time to isolate what is causing it.