|
[Sponsors] |
It is reasonable to suppose that viscosity is locally constant in compressible NS? |
|
LinkBack | Thread Tools | Search this Thread | Display Modes |
July 4, 2017, 16:47 |
It is reasonable to suppose that viscosity is locally constant in compressible NS?
|
#1 |
New Member
Antonio
Join Date: Mar 2017
Posts: 8
Rep Power: 9 |
Well, I opened a thread about my project months ago and I am starting again from scratch.
It's a flat plate model of a solar collector for water heating. I want to study the movement of the air (ideal gas approximation) inside by solving the full set of compressible navier stokes. Now I want to do things well because last time I had convergence problems (I had to put too much relaxation between iterations with a time step so little that it was impossible to get to the steady solution). I'm going with an implicit method and hybrid differentiation (switching between upwind and central difference depending on the peclet number). I am using a staggered grid (not necessary because odd-even decoupling shouldn't appear in compressible flows as i have the ideal gas law, but I think it feels better the pressure). My question now is... can I suppose that the viscosity is locally constant? I mean, I am using a correlation for viscosity but I want to neglect every single term where viscosity derivatives appear. It would simplify things, and it means a shorter code, faster,... Just think as a rectangle where the upper side is cold and the lower side is hot so you have free convection. Thanks in advance. |
|
July 4, 2017, 17:21 |
|
#2 |
Senior Member
Filippo Maria Denaro
Join Date: Jul 2010
Posts: 6,773
Rep Power: 71 |
viscosity is generally assumed to be a function of the temperature https://en.wikipedia.org/wiki/Temper...quid_viscosity
...for small variation you could assume it constant |
|
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
viscosity for compressible fleos (rhosimplecfoam) | mihaipruna | OpenFOAM Running, Solving & CFD | 0 | June 28, 2012 20:50 |
Trans. SST Intermittency Factor and Viscosity Ratio | eishinsnsayshin | FLUENT | 3 | May 23, 2012 03:02 |
Artificial Viscosity | Luiz Eduardo Bittencourt Sampaio | Main CFD Forum | 12 | November 13, 2011 10:21 |
kinematic viscosity at diff temperatures,pressures | Mecobio | Main CFD Forum | 0 | November 7, 2005 12:55 |
Problem of Turbulent Viscosity Ratio Limited | David Yang | FLUENT | 3 | June 3, 2002 06:13 |