[calmbeep]

Hi, i have some questions on N-S Equations on 2D Lid Driven Cavity.

Edited Question:
Re = UL / v (U=velocity of lid, L=length of lid, v=kinematic viscosity)

As far I know, I have to vary the Reynolds number to get different results. but which of the variable on the RHS I have to change? For example, I want to get the results on Re=100 and Re=200, so do i change the L/V/v?

[FMDenaro]

I suggest to study better the basics of fluid dynamic before go into the CFD study... It exists only one system of equations, they can be made non-dimensional but the solution obeys the same system and the mathematical character of the PDE is the same.
The discretization is the same for dimensional or non-dimensional form.

[LUQILIN]

Originally Posted by calmbeep

Hi, i have some questions on N-S Equations.

1)There are two types of N-S Equations, one which is with (1/Re) and another one with (miu) with them being dimensionless and dimensional respectively. is this correct?

2) I was given lid driven cavity problem, using SIMPLE algorithm to solve NS equations. Firstly I need to do discretization on the momentum equation. May I know do i discretize the one with (1/Re) or (miu)?

Read a test book and you may find what you need. Dimensionless or not does not really matter. You should know the fact that they stand for the identical physics.

Test book 1. Computational Fluid Mechanics and Heat Transfer, Richard H.P. , Chapter 9 Section 3.

Test book 2. Computational Fluid Dynamics - The Basics with Applications. John D. Anderson., Chapter 2.

[davidwilcox]

The discritization does not matter. Your boundary inputs does. by normalizing the navier stokes, your solver now becomes "Reynolds-number dependent". your velocity at the inlet is normally 1. For example, if you are doing a flow over an airfoil and the Reynolds number is 500 (based on chord and freestream velocity), the right hand side of the eqn( the viscous term) is now divided by 500. This suggests that you need to have an option for the user to input the desired Reynolds number. Again velocity at the inlet is unity.

[calmbeep]

okay thanks DENARO and Luqilin for the heads up. I will look on the textbook first.

david : ah i see. thank u for the help edited: so u mean Re=vL/(viscousity). For the coding, which variable am i changing? As in if I am varying Reynolds number, which terms on RHS I should be changing?