GfsDefine

From Gerris

Define is used to define text macros in parameter files, similar to the macros of the C preprocessor.

Examples of valid macros are:

Define PI 3.14159265359

Define SQUARE(x) (x*x)

Define REYNOLDS(U,L,nu) (U*L/nu)

Note that Define macros are more general than the C macros which can be defined using GfsGlobal. They apply to the parameter file as a whole rather than just to the GfsFunctions. For example, this parameter file:

...
Define LEVEL 7
...
Refine LEVEL
...
OutputSimulation { start = end } sim-LEVEL.gfs
...

will result in Gerris generating a simulation file called sim-7.gfs.

Note that macro support needs to be turned on explicitly (using the -m or -D options when starting gerris).

Examples

• Lunar tides in Cook Strait, New Zealand

Define M2F (2.*M_PI/44700.)

Define M2(t) (A_amp*cos (M2F*t)+B_amp*sin (M2F*t))

• Viscous flow past a sphere

Define A0 0.5

Define U0 1.

• Circular droplet in equilibrium

Define CIRCLE (ellipse (-0.5,0.5,0.4,0.4))

Define MU sqrt(0.8/LAPLACE)

• Axisymmetric spherical droplet in equilibrium

Define CIRCLE (ellipse (-0.5,0.,0.4,0.4))

Define MU sqrt(0.8/LAPLACE)

• Shape oscillation of an inviscid droplet

Define DIAMETER 0.2

Define EPSILON 0.05

Define VAR(T,min,max)   (min + CLAMP(T,0,1)*(max - min))

Define RHO(T)            VAR(T, 1., 1e-3)

Define RADIUS(x,y)      (DIAMETER/2.*(1. + EPSILON*cos (2.*atan2 (y, x))))