# Navier-Stokes equations - Parameters ?

## Recommended Posts

AgentChaos    109
I need some help [img]http://public.gamedev.net//public/style_emoticons/default/wink.png[/img]
The pdf file: is Real-Time Fluid Dynamics for Games (Jos Stam) GDC 03 ..
and at page 3 of the pdf they make
6 arrays :
static u[size], v[size], u_prev[size], v_p rev[size];
static dens[size], dens_prev[size];

Dens = Density
So V=Velocity? or U? I'm dont understand what is U and V..
My English is not the best so its harder for me [img]http://public.gamedev.net//public/style_emoticons/default/unsure.png[/img]

So I need to understand what is u and v and another question...
In another pdf i see that the equations have a P (Pressure) parameter so
why he didnt worte it?

Thanks [img]http://public.gamedev.net//public/style_emoticons/default/biggrin.png[/img]

##### Share on other sites
FLeBlanc    3141
Velocity is a vector (2D, in this case), so it is probable that he is using the arrays u and v to store the X and Y components of the velocity vector, and u_prev/v_prev are probably storing the velocity of the previous iteration.

##### Share on other sites
AgentChaos    109
[quote name='FLeBlanc' timestamp='1348515318' post='4983327']
Velocity is a vector (2D, in this case), so it is probable that he is using the arrays u and v to store the X and Y components of the velocity vector, and u_prev/v_prev are probably storing the velocity of the previous iteration.
[/quote]

Thanks man [img]http://public.gamedev.net//public/style_emoticons/default/smile.png[/img]
Are you sure its the x,y components and not a different variables?

##### Share on other sites
FLeBlanc    3141
Well, just xy by common convention. Some people do use uv for 2 dimensional vectors (witness uv coordinates in 3D graphics, to differentiate from xyz). It's all just personal preference.

##### Share on other sites
AgentChaos    109
[quote name='FLeBlanc' timestamp='1348516543' post='4983334']
Well, just xy by common convention. Some people do use uv for 2 dimensional vectors (witness uv coordinates in 3D graphics, to differentiate from xyz). It's all just personal preference.
[/quote]

Ok thanks [img]http://public.gamedev.net//public/style_emoticons/default/biggrin.png[/img]
Do you know about the missing pressure parameter?