GfsDefine

From Gerris

Define is used to define text macros in parameter files, similar to the macros of the C preprocessor (and still more similar to those of m4).

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). Note also that the -m or -D options should not be used when restarting a simulation from a (binary) simulation file (e.g. created using GfsOutputSimulation).

Macros may be used but not defined in external files included via GfsInclude.

The builtins from m4 are also available, prefixed with m4_; thus for example to defer deciding till run-time whether a uniform mesh refinement were in order, one could write

Refine m4_ifelse(UNIFORM, 1, 6, (x>0 ? 6 : 5))

and call gerris with either -DUNIFORM=1 or -DUNIFORM=0.

Examples

• Collapse of a column of grains

Define D 0.04623

Define RHOF 0.001

Define RHO(T) (T + RHOF*(1. - T))

Define MUF 0.0001

Define LDOMAIN 32.

Define H0 6.26

Define R0 1.

Define LEVEL 10

• Starting vortex of a NACA 2414 aerofoil

Define FRAMEPERIOD 0.02

• Savart--Plateau--Rayleigh instability of a water column

Define RHO_L            998.

Define RHO_G            1.2

Define MU_L             1.003e-3

Define MU_G             1.8e-5

Define RADIUS 0.2

Define EPSILON 0.02

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

Define RHO(T)           VAR(T, RHO_G/RHO_L, 1.)

Define MUR(T)           VAR(T, MU_G/MU_L, 1.)

• Forced isotropic turbulence in a triply-periodic box

Define MU 0.01

Define VOLUME (8.*M_PI*M_PI*M_PI)

Define Ubar (SU/VOLUME)

Define Vbar (SV/VOLUME)

Define Wbar (SW/VOLUME)

Define Unbar (Un/VOLUME)

• Wingtip vortices behind a rectangular NACA 2414 wing

Define FRAMEPERIOD 0.02

• 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))

• Tsunami runup onto a complex three-dimensional beach

Define DRY 1e-4

• The 2004 Indian Ocean tsunami

Define RADIUS 6371220.

Define LENGTH 6000e3

Define LONGITUDE 94.

Define LATITUDE 8.

Define DRY 0.01

Define MAXLEVEL 12

Define LEVEL (fabs (rx) < 0.46 && fabs (ry) < 0.46 ? MAXLEVEL : 5)

• Time-reversed advection of a VOF concentration

Define CIRCLE (ellipse (0, -.236338, 0.2, 0.2))

Define GAUSSIAN (exp(-100.*((x + 0.2)*(x + 0.2) + (y + .236338)*(y + .236338))))

• Comparison between explicit and implicit diffusion schemes on concentration tracer

Define R sqrt(x*x+y*y)

Define R0 0.25

Define GAUSSIAN (exp(-250.*((R-R0)*(R-R0))))

• Viscous flow past a sphere

Define A0 0.5

Define U0 1.

• Bagnold flow of a granular material

Define ALPHA 0.43

Define D 0.04

Define U0 (sqrt(cos(ALPHA))*(-0.114 + 0.3*tan(ALPHA))/(D*(0.64 - tan(ALPHA))))

Define UB(x) ((1. - pow(1. - x, 1.5))*2./3.*U0)

• Coriolis formulation in 3-D

Define U0 2

Define V0 3

Define Vsol0 (-A0*sin(Phi)*sin(2*Omega*t) + B0*sin(Phi)*cos(2*Omega*t) + C0)

Define Wsol0 (A0*cos(Phi)*sin(2*Omega*t) - B0*cos(Phi)*cos(2*Omega*t) + D0)

Define W0 1

Define Phi (M_PI/4.)

Define Omega 7.292e-5

Define A0 U0

Define B0 (sin(Phi)*V0-cos(Phi)*W0)

Define C0 (cos(Phi)*(cos(Phi)*V0+sin(Phi)*W0))

Define D0 (sin(Phi)*(cos(Phi)*V0+sin(Phi)*W0))

Define Usol0 (A0*cos(2*Omega*t)+B0*sin(2*Omega*t))

• Wind-driven stratified lake

Define ALPHA 1e-4

Define ALPHAT 1e-3

• 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 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))))

• Oscillations in a parabolic container

Define h0 10.

Define a 3000.

Define tau 1e-3

Define B 5

Define G 9.81

• Parabolic container with embedded solid

Define h0 10.

Define a 3000.

Define tau 1e-3

Define B 5

Define G 9.81

Define SLOPE (0.3/pow(2., LEVEL))

Define ANGLE (atan(SLOPE))

Define R(x,y) ((x)*cos(ANGLE) + (y)*sin(ANGLE))

• Tsunami runup onto a plane beach

Define MINLEVEL 7

Define DRY 1e-3

• Circular dam break on a sphere

Define LENGTH (150./180.*M_PI)

• Circular dam break on a rotating sphere

Define LENGTH (150./180.*M_PI)

• Circular dam break on a ``cubed sphere''

Define LENGTH (150./180.*M_PI)

• Advection of a cosine bell around the sphere

Define U0 (2.*M_PI)

• Creeping Couette flow between eccentric cylinders

Define R1 (1./sinh(1.5))

Define R2 (1./sinh(1.))

Define X1 (1./tanh(1.5))

Define X2 (1./tanh(1.))

Define ECC (X2 - X1)

• Flow between eccentric cylinders on a stretched grid

Define R1 (1./sinh(1.5))

Define R2 (1./sinh(1.))

Define X1 (1./tanh(1.5))

Define X2 (1./tanh(1.))

Define ECC (X2 - X1)

• Groundwater flow with piecewise constant permeability

Define THETA atan2(y,x)