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


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

LinkBack Thread Tools Display Modes
Old   November 12, 2001, 08:43
A Student
Posts: n/a
I am learning about fourier analysis of turbulence, which eventually i will be analysing in an LES approach.

I have read in many book now the idea of convolution, and of its importance especially in LES.

I do not understand convolution!!! nor do i readly understand its importance.

Can anyone give me a brief statement of the importance of convolution, and refer me to a book i could look at.

  Reply With Quote

Old   November 12, 2001, 14:27
Jongdae Kim
Posts: n/a
Large Eddy Simulation = Simulation only large eddies and model small eddies.

How to define large and small eddies --> filtering.

Filtering is a kind of convolution.

In LES, velocity fields are filtered and only grid scales (or filtered scales) are calculated and subgrid scales are modeled (such as dynamic model, etc) using grid scale information.

If the velocity fields are stationary, you can use fourier convolution scheme. Actually convolution is integration and not easy to calculate. But if the velocity fields are transformed to wave number(or frequency) space, the convolution could be transformed to simple algebraic equations. Using FFT, the calculation is very fast.

Reference material of the convolution : Chapter 12 Large eddy simulations, 12.2 Filtering of " Fluid Flow Phenomena", A numerical Toolkit, by P. Orlandi.
  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
Fast Fourier Transform alastormoody11 STAR-CCM+ 0 January 20, 2011 23:49
Poisson equation fourier transform before discretization yohey44 Main CFD Forum 0 November 9, 2010 13:00
Biot and fourier numbers selim Main CFD Forum 2 August 2, 2007 17:00
fourier series prapanj Main CFD Forum 2 December 10, 2006 13:33
neumann analysis using fourier series student Main CFD Forum 1 October 24, 2002 08:55

All times are GMT -4. The time now is 17:23.