# Calculation of lagrangian integral time scale

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

 June 11, 2003, 23:06 Calculation of lagrangian integral time scale #1 R.Sripriya Guest   Posts: n/a I am trying DPM with KE for one of my simulations. I was going through some literature where it was mentioned that for particles with large stoke's number(defined as the ratio of the particle relaxation time to the turbulent lagrangian integral time), the effect of turbulent fluctuations on the fluid and the particle -particle interaction can be neglected. Here the particle relaxation time is defined as density of the particle*dia of the particle/ 18* viscosity which is known. However the turbulent lagrangian integral time is defined as .2*k/E. We don't know the values of k and E. Any idea as to how this can be calculated

 June 11, 2003, 23:07 Re: Calculation of lagrangian integral time scale #2 R.Sripriya Guest   Posts: n/a

 June 12, 2003, 00:25 Re: Calculation of lagrangian integral time scale #3 Alex Munoz Guest   Posts: n/a Hi careful relaxation time =particle density*particle diameter^2/(18*viscosity) don't forget the square of the diameter! Now the question isnot if you ignore the effect of the turbulent fluctuations, the real question is what is the legth scale for you particle tracking as a results choose a value lower than the relaxation time*velocity. I wonder if the paper that you are reading was written by Chen and Pereira!! Best regards Alex Munoz

 June 12, 2003, 01:55 Re: Calculation of lagrangian integral time scale #4 R.Sripriya Guest   Posts: n/a The length scale is much smaller than the product of the velocity and the relaxation time of the particle.What else is to be done?

 June 12, 2003, 12:49 Re: Calculation of lagrangian integral time scale #5 Alex Munoz Guest   Posts: n/a Hi Your length scale should be smaller than the relaxation time, not much smaller, because this fact demand a longer calculation time. About the fact that your particles doesn't exit the domain, I can not give you a sugguestion. You have to figure out the solution by yourself. Regards Alex Munoz

 Thread Tools Display Modes Linear Mode

 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 OffTrackbacks are On Pingbacks are On Refbacks are On Forum Rules

 Similar Threads Thread Thread Starter Forum Replies Last Post mohammad CFX 1 March 24, 2011 21:31 cyberbrain OpenFOAM 4 March 16, 2011 10:20 m9819348 OpenFOAM Running, Solving & CFD 7 October 27, 2007 00:36 Madhukar FLUENT 1 July 24, 2007 03:51 Matthieu Ubas Main CFD Forum 2 November 5, 1999 15:20

All times are GMT -4. The time now is 00:38.