melangeur.py

# MigFlow - Copyright (C) <2010-2018>
# <Universite catholique de Louvain (UCL), Belgium
#  Universite de Montpellier, France>
# 	
# List of the contributors to the development of MigFlow: see AUTHORS file.
# Description and complete License: see LICENSE file.
# 	
# This program (MigFlow) is free software: 
# you can redistribute it and/or modify it under the terms of the GNU Lesser General 
# Public License as published by the Free Software Foundation, either version
# 3 of the License, or (at your option) any later version.
# 
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU Lesser General Public License for more details.
# 
# You should have received a copy of the GNU Lesser General Public License
# along with this program (see COPYING and COPYING.LESSER files).  If not, 
# see <http://www.gnu.org/licenses/>.

#!/usr/bin/env python
'''
Grains in circular shear flow.
This example shows how to set boundary conditions as a function of some parametres.
A boolean parametre give the possibility to use lmgc90 to solve contacts or not.
'''
from migflow import fluid as fluid
from migflow import scontact2

import numpy as np
import os
import time
import shutil
import random

#Define output directory
outputdir = "output"
if not os.path.isdir(outputdir) :
    os.makedirs(outputdir)

'''
genInitialPosition is a function that sets all the grains centre positions and create the grains objects to add in the computing structure
Args:    -filename    : name of the output file
         -r           : max radius of the grains
         -rout        : outer radius of the drum
         -rhop        : grains density        
'''
def genInitialPosition(filename, r, rout, rin, rhop) :
    #Grains structure builder
    p     = scontact2.ParticleProblem()
    #Load mesh.msh file specifying physical boundaries names
    p.load_msh_boundaries("mesh.msh", ["Outer", "Inner"])
    
    #Definition of the points where the grains are located
    x     = np.arange(rout, -rout, 2 * -r)
    x, y  = np.meshgrid(x, x)
    R2    = x**2 + y**2
    #condition to be inside the outer boundary
    keep  = R2 < (rout - r)**2
    x     = x[keep]
    y     = y[keep]
    R2    = x**2 + y**2
    #condition to be outside the inner boundary
    keep  = R2 > (rin + r)**2
    x     = x[keep]
    y     = y[keep]
    #Add a grain at each centre position
    for i in range(x.shape[0]) :
        if y[i]<0:
            rhop1 = random.choice([rhop*.9,1.1*rhop,rhop])
            p.add_particle((x[i], y[i]), r, r**2 * np.pi * rhop1)
    p.write_vtk(filename,0,0)

 
#physical parameters
g         =  0                                        # gravity
rho       =  1.253e3                                  # fluid density
rhop      =  1000                                     # grains density
nu        =  1e-4                                     # kinematic viscosity

#numerical parameters
dt        =  1e-2                                     # time step
tEnd      =  50                                       # final time

#geometry parameters
outf      =  5                                        # number of iterations between output files
rout      =  0.0254                                   # outer radius
rin       =  0.0064                                   # inner radius
r         =  397e-6/2                                 # grains radius

#Object particles creation
genInitialPosition(outputdir, r, rout, rin, rhop)
p         =  scontact2.ParticleProblem()
p.read_vtk(outputdir,0)

#Initial time and iteration
t         =  0
ii        =  0

'''
fluid_problem is the function builder of the fluid class
Args:     -g             : gravity
          -viscosity     : list of fluid phases viscosities
          -density       : list of fluid phases densities
'''
fluid = fluid.fluid_problem(g,[nu*rho],[rho])
#Set the mesh geometry for the fluid computation
fluid.load_msh("mesh.msh")
'''
set_strong_boundary is the function setting the strong boundaries (=constraints) for the fluid problem
Args:     -Tag           : physical tag (set in the mesh.geo file) of the boundary on which you want to add a constraint
          -Field         : O: x-velocity; 1: y-velocity; 2: pressure
          -Value         : value assigned to the specified field on the specified boundary
'''
fluid.set_strong_boundary("Outer",0,lambda x : -x[:, 1])
fluid.set_strong_boundary("Outer",1,lambda x : x[:, 0])
fluid.set_strong_boundary("Inner",0,0)
fluid.set_strong_boundary("Inner",1,0)
fluid.set_strong_boundary("PtFix",2,0)
'''
set_weak_boundary is the function setting the weak boundaries (=normal fluxes) for the fluid problem
Args:     -Tag           : physical tag (set in the mesh.geo file) of the boundary on which you want to add a constraint
          -Bnd Type      : boundaries can be of type: wall, inflow, outflow
'''
fluid.set_weak_boundary("Inner","Wall")
fluid.set_weak_boundary("Outer","Wall")

#Set location of the grains in the mesh and compute the porosity in each computation cell
fluid.set_particles(p.mass(), p.volume(), p.position(), p.velocity())
fluid.export_vtk(outputdir,0,0)

tic = time.time()
#Computation loop
fluid.set_particles(p.mass(), p.volume(), p.position(), p.velocity())
while t < tEnd :
    #Fluid solver
    fluid.implicit_euler(dt)

    #Computation of the new velocities
    forces      = fluid.compute_node_force(dt)
    vn          = p.velocity() + forces * dt / p.mass()
    vmax        = np.max(np.hypot(vn[:, 0], vn[:, 1]))
    #number of contact sub time step
    nsub        = max(1, int(np.ceil((vmax * dt * 4)/min(p.r()))))
    print("NSUB", nsub,"VMAX",vmax, "VMAX * dt", vmax * dt, "r", min(p.r()))
    #Contact solver
    for i in range(nsub) :
        tol     = 1e-6                                #numerical tolerance for grains intersection
        p.iterate(dt/nsub, forces, tol)

    #Localisation of the grains in the fluid
    fluid.set_particles(p.mass(), p.volume(), p.position(), p.velocity())
    t          += dt

    #Output files writting
    if ii %outf == 0 :
        ioutput = int(ii/outf) + 1
        p.write_vtk(outputdir, ioutput, t)
        fluid.export_vtk(outputdir, t, ioutput)
    ii         += 1
    print("%i : %.2g/%.2g (cpu %.6g)" % (ii, t, tEnd, time.time() - tic))