CFD Online Logo CFD Online URL
Home > Forums > Main CFD Forum

Is my equation stiff????

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

LinkBack Thread Tools Display Modes
Old   June 16, 2008, 05:49
Default Is my equation stiff????
Mehdi Asghari
Posts: n/a
Hi all;

I want to solve following problem by a numerical method.

In a one-dimentional problem, particle velocity equation for particulated flows is given as follows:

D(Up)/Dt=Fd(Up-U);U =10+x;Up=dx/dt;

That Fd=18mu/ (dp*dp*ro_p*Cc) Cc=1+2l/dp*(1.257+0.4exp-(1.1dp/(2l)) Dp(particle diameter) is equal to 10 (micro meter) and 0.01(micro meter), respectively. Also, mu=0.001003,l=3e-10,ro_p=3900.

I used forth-order Runge-kutta method for solution. dt was suitable for dp=10(micro meter), but required dt for stability in dp=0.01(micro meter) was very small. This dt was so small that solution became impossible. Is his equation stiff? Is there a logical numerical method instead of forth-order runge-kutta method to be solved this problem?

Thanx in advance for any suggestion.
  Reply With Quote


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
Calculation of the Governing Equations Mihail CFX 7 September 7, 2014 06:27
Constant velocity of the material Sas CFX 15 July 13, 2010 08:56
Viscosity and the Energy Equation Rich Main CFD Forum 0 December 16, 2009 15:01
mass flow in is not equal to mass flow out saii CFX 2 September 18, 2009 08:07
continuity equation Rafal Main CFD Forum 4 November 29, 2006 10:27

All times are GMT -4. The time now is 03:34.