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I'm looking at a preprint of a paper by Davis, Stone and Pessah, 2009, wherein they state that their viscous forces in the momentum equation (including compressible effects) is the divergence of (rho)*(nu)*(divj + djvi - (2/3)*I*(div v)). This is certainly a compressible effect (With the appearance of a div v) and it is clear that they have taken this new mu as equal to the viscous mu - but what is this form that they quote? Should it be included in this article? 131.111.17.143 (talk) 14:16, 23 October 2009 (UTC)[reply]

This form of the viscous stress tensor is given in the article on viscosity, near the end. The term left out is the part which is proportional to the volume viscosity. Yes, in my opinion, this should be included here (that's what I was looking for), but I don't know how to create the equation or copy the picture. Robert Hiller (talk) 07:47, 5 November 2009 (UTC)[reply]

I quickly looked up articles in Google scholar on volume viscosity, and it seems that progress in understanding volume viscosity has been made recently. See http://blanche.polytechnique.fr/preprint/repository/611.pdf http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=PHFLE6000021000003033105000001&idtype=cvips&gifs=yes (doi:10.1063/1.3085814) -- Patrick 98.207.63.126 (talk) 07:14, 11 November 2009 (UTC)[reply]

130.83.54.163 (talk) 09:07, 6 January 2016 (UTC)[reply]

I'm wondering why bulk viscosity and second viscosity are seemingly the same in this article.

In the Navier-Stokes equations it is stated clearly that the second viscosity is:

   \zeta \equiv \lambda + \tfrac23 \mu 

where \lambda is the bulk and \mu the dynamic viscosity. 130.83.54.163 (talk) 09:02, 6 January 2016 (UTC)[reply]