# Title: Momentum conservation for large density ratios
#
# Description:
#
# A dense droplet moves through a lighter background fluid. The
# kinetic energy decreases due to viscous dissipation (Figure
# \ref{k}). For these density and viscosity ratios of 1000, the
# calculation is stable only if a "mollified" volume fraction is used
# to compute the average density and viscosity.
#
# \begin{figure}[htbp]
# \caption{\label{k}Evolution of the kinetic energy.}
# \begin{center}
# \includegraphics[width=0.8\hsize]{k.eps}
# \end{center}
# \end{figure}
#
# Author: St\'ephane Popinet
# Command: gerris2D kinetic.gfs
# Version: 1.1.0
# Required files: kinetic.gfs
# Generated files: k.eps
1 0 GfsSimulation GfsBox GfsGEdge {} {
    Time { end = 0.5 }

    Global {
        #define var(T,min,max) (CLAMP(T,0,1)*(max - min) + min)
        #define rho(T) var(T, 0.001, 1.)
        #define mu(T)  var(T, 1e-6, 1e-3)
        #define level 7
        #define radius 0.05
    }

    Refine level

    ProjectionParams { tolerance = 1e-6 }
    ApproxProjectionParams { tolerance = 1e-6 }

    VariableTracerVOF T
    VariableFiltered T1 T 1
    InitFraction T (- ellipse(-0.3,0,radius,radius))
    Init {} { U = T }

    PhysicalParams { alpha = 1./rho(T1) }
    SourceViscosity mu(T1)

    AdaptVorticity { istep = 1 } { cmax = 0.3 maxlevel = level }
    AdaptGradient { istep = 1 } { cmax = 1e-3 maxlevel = level } T

    OutputScalarSum { istep = 1 } k { v = Velocity2*rho(T1) }
    OutputScalarSum { istep = 1 } t { v = T }

    EventScript { start = end } {
        gnuplot <<EOF
            set term postscript eps color lw 3 solid 20
            set output 'k.eps'
            set xlabel 'Time'
            set ylabel 'Kinetic energy'
            set grid
            plot 'k' u 3:5 w l t ''
EOF
        if awk '{if ($5 > 7.2e-3) exit (1);}' < k ; then
            return 0;
        else
            return $GFS_STOP;
        fi
    } 
}
GfsBox {}