sandbox/M1EMN/Exemples/viscous_collapse_ML.c
collapse of a rectangular viscous column,
or collapse of a viscous fluid (double viscous dam break) From the paper: Huppert 82 “The propagation of two-dimensional and axisymmetric viscous gravity currents over a rigid horizontal surface” it is done with only mass equation and lubrication and with shallow watzer
Here we solve it using the Multilayer Shallow Water (Saint Venant Multi Couches) strategy of Audusse Sainte-Marie et al 2011. See De Vita 2020 for details, this example is presented there as a test case.
#include "grid/cartesian1D.h"
#include "saint-venant.h"
int main() {
X0 = 0.;
L0 = 5;
G = 1.;
// N = 512;
one needs details in y
// nl = 256;
N = 128;
nl = 15;
nu = 1.;
run();
}
We impose boundary condition for h and \eta.
h[left] = neumann (0);
eta[left] = neumann (0);
u.n[left] = dirichlet(0);
h[right] = neumann (0);
eta[right] = neumann (0);
Initialization
We set a zero velocity at the inlet and a free outlet.
for (vector u in ul) {
u.n[left] = 0;
u.n[right] = neumann(0.);
}
We initialize h.
foreach()
h[] = (x<1);
}
Output
We print the elevation and the stress.
event output (t += 5; t <= 100) {
vector u0 = ul[0];
foreach()
fprintf (stderr, "%g %g %g %g\n", x, h[], 2.*u0.x[]/((h[]+dry)/nl),t );
fprintf (stderr, "\n");
}
Run
To run
qcc -O2 -o viscous_collapse_ML viscous_collapse_ML.c
./viscous_collapse_ML 2>log
To run
~bash make viscous_collapse_ML.tst make viscous_collapse_ML/plots make viscous_collapse_ML.c.html
source c2html.sh viscous_collapse_ML ~
Results
the selfsimilar collapse over the selfsimilar solution: h(x,t)t^{1/5} plotted as a function of (xt^{-1/5})
set xlabel "x/t^{1/5}"
set ylabel "h(x,t) t^{1/5}"
p [0:1.5]'log' u ($1/($4**.2)):($2*($4**.2)) t'comp.' w l,(9./10*(1.28338-x*x))**(1/3.) t'analytic'
Montpellier 07/17
Links
related examples only mass equation and lubrication and with shallow watzer see as well Navier Stokes solution.
Bibliography
Huppert “The propagation of two-dimensional and axisymmetric viscous gravity currents over a rigid horizontal surface” JFM 82
Francesco De Vita, Pierre-Yves Lagrée, Sergio Chibbaro, Stéphane Popinet Beyond Shallow Water: appraisal of a numerical approach to hydraulic jumps based upon the Boundary Layer Theory. Volume 79, January–February 2020, Pages 233-246 European Journal of Mechanics - B/Fluids https://doi.org/10.1016/j.euromechflu.2019.09.010