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# Navier-Stokes equations - Parameters ?

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### #1AgentChaos  Members   -  Reputation: 109

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Posted 24 September 2012 - 12:54 PM

I need some help
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

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

### #2FLeBlanc  Members   -  Reputation: 1851

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Posted 24 September 2012 - 01:35 PM

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.

### #3AgentChaos  Members   -  Reputation: 109

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Posted 24 September 2012 - 01:42 PM

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.

Thanks man
Are you sure its the x,y components and not a different variables?

### #4FLeBlanc  Members   -  Reputation: 1851

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Posted 24 September 2012 - 01:55 PM

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.

### #5AgentChaos  Members   -  Reputation: 109

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Posted 24 September 2012 - 02:19 PM

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.

Ok thanks
Do you know about the missing pressure parameter?

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