CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > CFX

How do I increase Newton Pressure Iteration Limit when used with CFX-RIF?

Register Blogs Members List Search Today's Posts Mark Forums Read

Reply
 
LinkBack Thread Tools Display Modes
Old   May 28, 2012, 17:48
Default How do I increase Newton Pressure Iteration Limit when used with CFX-RIF?
  #1
New Member
 
Join Date: May 2012
Posts: 22
Rep Power: 5
alpha754293 is on a distinguished road
I ran into the same error that some other folks here have been getting with the "Newton Pressure Iteration Limit" error message and I've tried to see/find where I can add the extra expert control parameter for that.

Through the reading that I've done upto this point, someone pointed to the CFXPreRules.ccl and there I was able to find that it's a valid option for OBJECT: MATERIAL, under CONTEXT: {Homogenous binary mixture, Fixed Composition Mixture, ...}.

I am trying to simulate a spark ignition engine (one of the cylinders from a V8 engine). I've already created the chemical reaction using CFX-RIF (gasoline, as modeled by n-heptane and isooctane). (I'm using 0.13 n-heptane, 0.87 isooctane (by mass fraction).)

Oxidizer is 0.767 N2, 0.233 O2. No EGR. I've used the default values for the size of the table.

Whenever I try to add the fuel injection as a boundary condition (where the fuel injector port is) into my model - this is when I get the same error:
Code:
 
+--------------------------------------------------------------------+
 |                     ****** Notice ******                           |
 | Newtons method failed to converge in  100 iterations.  This        |
 | occurred while computing the following variable:                   |
 |                                                                    |
 | Variable Name  : Total Temperature                                 |
 | Location Name  : inj                                               |
 | Mesh location  : BELG57                                            |
 | Mesh entity    : VERTEX                                            |
 | Last 3 Changes :  2.42255E+01  2.42255E+01  2.42255E+01            |
 | Tolerance      :  1.0000E-02                                       |
 |                                                                    |
 | The Newton iteration was either slowly converging or has stalled.  |
 | The solver will continue with the variable set as it was on the    |
 | final iteration.  If this situation continues you might try        |
 | increasing the number of iterations allowed for Newtons method.    |
 | This can be changed by setting one of the parameters:              |
 |                                                                    |
 | Temperature : "Constitutive Relation Iteration Limit"              |
 | Pressure    : "Newton Pressure Iteration Limit"                    |
 |                                                                    |
 | for your mixture using the definition file editor.                 |
 +--------------------------------------------------------------------+
From what people were saying, I'm supposed to add the expert control parameter into the MATERIAL object, but "Newton Pressure Iteration Limit" is not a valid option for pure substances, which are the materials that result from the CFX-RIF computation.

So, how do I go about increasing the Newton Pressure Iteration Limit?

I'm using total energy throughout for the heat transfer, and I've tried setting the Total/Static Temperature at 300 [K] and that didn't work. I even tried setting it to 500 [K] (because I thought that there might be a divide by subtraction in there somewhere as my fuel and oxidizer are also at 300 [K]) and that didn't work either.

The CEL that governs my injection sequence (as a pressure) is given by the following:
Code:
step((t-160*dt)/1[s])*20e6 [Pa] + step((170*dt-t)/1[s])*20e6 [Pa]
where dt is an expression (variable) that I define earlier.

It also doesn't seem like it matters whether I have it as that expression or as just straight constant 20e6 [Pa].

Any help would be greatly appreciated.

If you need additional information about how the model/simulation is set up, please do not hesitate to ask. Thanks.
alpha754293 is offline   Reply With Quote

Old   November 28, 2012, 09:28
Default How do I increase Newton Pressure Iteration Limit when used with CFX-RIF?
  #2
New Member
 
Usman
Join Date: Jul 2012
Posts: 14
Rep Power: 4
dk_damo is on a distinguished road
HI,Mate.
did you manage to fix this problem you posted i am having the same error but cant find where to change this parameter.Thanks
dk_damo is offline   Reply With Quote

Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Pulsatile pressure inlet with pressure outlet a.lynchy FLUENT 3 March 23, 2012 14:45
Pressure Outlet Guage pressure Mohsin FLUENT 34 January 12, 2012 06:45
Pressure outside of upper limit Martin CFX 0 August 6, 2004 07:04
Hydrostatic pressure in 2-phase flow modeling (CFX4.2) HB &DS CFX 0 January 9, 2000 14:19
Hydrostatic pressure in 2-phase flow modeling (long) DS & HB Main CFD Forum 0 January 8, 2000 16:00


All times are GMT -4. The time now is 20:39.