# artificial viscosity

 User Name Remember Me Password
 Register Blogs Members List Search Today's Posts Mark Forums Read

 March 2, 2004, 09:50 artificial viscosity #1 rvndr Guest   Posts: n/a hi when modelling 1D wave eqn. the dissipation error is due to artificial viscosity(For first order schemes).Can anybody explain how this artificial viscosity came into picture as there is no viscosity term either in the model eqn or modified eqn. Model eqn:du_dt=-a du_dx Modified eqn:du_dt=-a du_dx+ [(a*Delta x/2)*(1-c)*(d^2u_dx^2)]. where "a" is speed of sound and "C" is courant number. As per text book the second term in the model eqn that is [(a*Delta x/2)*(1-c)] is called artificial viscosity. How this will become a viscous term ? Any help in this regard is highly appreciated. rvndr

 March 2, 2004, 11:24 Re: artificial viscosity #2 Govinda Guest   Posts: n/a Artificial viscosity (= parabolic diffusive character) is often added to a numerical method to stabilize it and obtain non-oscillating solutions. This is achieved by adding a (negative = diffusive, as opposed to anti-diffusive) second order spatial derivative. To see how this is diffusive: treat the numerical solution as Fourier modes, ~ A_k * exp(i*k . x), and look at the eigenvalues of these operators, d/dx = i*k (purely imaginary, so dispersive) d^2/dx^2 = -k^2 (real and negative, so diffusive) Is this of any help?

 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 Luiz Eduardo Bittencourt Sampaio Main CFD Forum 12 November 13, 2011 11:21 MAB CFX 1 July 30, 2008 22:00 rads CFX 2 July 31, 2006 07:02 Steve Allison Main CFD Forum 1 February 19, 2003 09:50 Girish Bhandari Main CFD Forum 5 January 13, 2001 14:22

All times are GMT -4. The time now is 22:19.

 Contact Us - CFD Online - Top