[jpo]

Hello,

would anyone know how to write a UDF that modifies the definition of the gravity vector? Specifically, the magnitude of the gravity with altitude

Thank you

[ComputerGuy]

Interesting problem. You might use a DEFINE_SOURCE macro for the x, y, or z momentum equations and specify whatever functional form of gravity you wanted. You can modify gravity (global) with the M_gravity[ND_ND] function, but it sounds like you want (effectively) cell-by-cell control.

Unchecked!

#include "udf.h"

DEFINE_SOURCE(grav_source,c,t,dS,eqn)
{
real mygrav=9.81; /*constant here, but could be some function of height.*/
real source;
source = mygrav*C_R(c,t); /*rho g */
return source;
}

ComputerGuy

Originally Posted by jpo

Hello,

would anyone know how to write a UDF that modifies the definition of the gravity vector? Specifically, the magnitude of the gravity with altitude

Thank you

[jpo]

Thank you ComputerGuy, I appreciate your answer

[jpo]

One clarification -

when you say "real mygrav=9.81;"
along what axis is this applied?

Thanks