|
[Sponsors] |
![]() |
![]() |
#1 |
New Member
Join Date: Dec 2017
Posts: 2
Rep Power: 0 ![]() |
Hi, I've found two different versions of NS equations and I would enjoy some explanations.
The doubts are related to the diffusive term. I've found both: \nu * \nabla^2 u ; 1/Re * \nabla ^2 u ; I tend to think that the 1st one is more correct, even though some academic notes refer to the 2nd one and I can't figure out why. Can you please give me some help? |
|
![]() |
![]() |
![]() |
![]() |
#2 |
Senior Member
Michael Prinkey
Join Date: Mar 2009
Location: Pittsburgh PA
Posts: 363
Rep Power: 25 ![]() |
The first is assuming dimensional quantities for velocity, length, and time. The second is the dimensionless form that assumes dimensionless velocity, length, etc. based on some characteristic length and time scales. Dimensional analysis is usually taught in first semester fluids, heat transfer, and thermodynamics texts. It is central to flow characterization, especially for experimental work and for tabulation of practical engineering data and model creation. It is not a difficult thing to master.
|
|
![]() |
![]() |
![]() |
![]() |
#3 |
New Member
Join Date: Dec 2017
Posts: 2
Rep Power: 0 ![]() |
Thank you for such a fast and precise reply.
Now I've got it. May be I've done quite a superficial analysis of the problem, also mislead by the fact that neither any nondimensional hypothesis was stated nor a coherent mathematical notation was used in the notes. |
|
![]() |
![]() |
![]() |
![]() |
#4 | |
Senior Member
Lucky
Join Date: Apr 2011
Location: Orlando, FL USA
Posts: 5,728
Rep Power: 66 ![]() ![]() ![]() |
Quote:
You did not say what nu nabla u or nabla^2 or Re is. They could mean anything. You were just as misleading yet it somehow still made sense to someone. |
||
![]() |
![]() |
![]() |
Tags |
navier, reynolds number, stokes, viscosity |
|
|
![]() |
||||
Thread | Thread Starter | Forum | Replies | Last Post |
Periodic boundary conditions for solving Navier Stokes Equations on a Staggered Grid | tanmayagrawal7 | Main CFD Forum | 17 | June 15, 2021 10:05 |
Solving Navier Stokes equations by projection method and predictor-corrector method. | Saideep | Main CFD Forum | 10 | February 13, 2017 10:29 |
how to solver perturbation equations of navier stokes equations ? | mechy | OpenFOAM Programming & Development | 1 | June 8, 2014 17:04 |
Implicit method for Navier Stokes equations | Vasiliy | Main CFD Forum | 9 | December 3, 2012 13:07 |
LBM Vs navier stokes equations in turbulent fluid flow modeling. | sharad_shevate | Main CFD Forum | 0 | August 3, 2009 01:25 |