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	tset default density and add temporal functionality - granular - granular dynam…
	git clone git://src.adamsgaard.dk/granular
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	---
	commit b56ddb27d47ed549245aedb47bbed51949c8c36e
	parent b5116979a34a77b651a34b8e51665749e20dd2f0
	Author: Anders Damsgaard <[email protected]>
	Date: Thu, 22 Apr 2021 13:48:09 +0200

	set default density and add temporal functionality

	Diffstat:
	M grain.c \| 27 +++++++++++++++++++++++++++
	M grain.h \| 4 ++++
	M granular.c \| 1 +
	M simulation.c \| 50 +++++++++++++++++++++++++++++…
	M simulation.h \| 4 +++-

	5 files changed, 83 insertions(+), 3 deletions(-)
	---
	diff --git a/grain.c b/grain.c
	t@@ -40,6 +40,7 @@ grain_defaults(struct grain *g)
	g->gridpos[i]
	= g->acc_lock[i] = 0;
	}
	+ g->density = 2.5e3;
	g->fixed = 0;
	g->rotating = 1;
	g->enabled = 1;
	t@@ -375,3 +376,29 @@ grain_register_contact(struct grain *g, size_t i, size_t …
	}
	}
	}
	+
	+double
	+grain_stiffness_normal(const struct grain *g)
	+{
	+ return 2.0 / 3.0 * g->youngs_modulus / (1.0 - pow(g->poissons_ratio, 2…
	+}
	+
	+double
	+grain_stiffness_tangential(const struct grain *g)
	+{
	+ return 2.0 * g->youngs_modulus
	+ / ((1.0 + g->poissons_ratio) * (2.0 - g->poissons_ratio));
	+}
	+
	+double
	+grain_collision_time(const struct grain *g)
	+{
	+ double m;
	+
	+ m = grain_mass(g);
	+
	+ return fmin(PI * pow(2.0 * grain_stiffness_normal(g) / m
	+ - pow(g->damping_n, 2.0) / 4.0, -0.5),
	+ PI * pow(2.0 * grain_stiffness_tangential(g) /…
	+ - pow(g->damping_t, 2.0) / 4.0, -0.5)…
	+}
	diff --git a/grain.h b/grain.h
	t@@ -60,4 +60,8 @@ void grain_temporal_integration(struct grain *g, double dt);
	void grain_register_contact(struct grain *g, size_t i, size_t j,
	double centerdist[3], double overlap);

	+double grain_stiffness_normal(const struct grain *g);
	+double grain_stiffness_tangential(const struct grain *g);
	+double grain_collision_time(const struct grain *g);
	+
	#endif
	diff --git a/granular.c b/granular.c
	t@@ -63,6 +63,7 @@ main(int argc, char *argv[])
	usage();

	sim_read_grains(&sim, stdin);
	+ sim_set_timestep(&sim);
	if (sim.t < sim.t_end)
	sim_run_time_loop(&sim);
	sim_print_grains(stdout, &sim);
	diff --git a/simulation.c b/simulation.c
	t@@ -6,6 +6,7 @@
	#include <stdlib.h>
	#include <err.h>
	#include <string.h>
	+#include <math.h>
	#include "grain.h"
	#include "grains.h"
	#include "simulation.h"
	t@@ -23,9 +24,11 @@ sim_new(void)
	void
	sim_defaults(struct simulation *sim)
	{
	- int i;
	+ int i, ret;

	- snprintf(sim->name, sizeof(sim->name), DEFAULT_SIMULATION_NAME);
	+ ret = snprintf(sim->name, sizeof(sim->name), DEFAULT_SIMULATION_NAME);
	+ if (ret < 0 \|\| (size_t)ret >= sizeof(sim->name))
	+ errx(1, "%s: could not write simulation name", __func__);
	sim->ng = 0;
	for (i = 0; i < 3; i++) {
	sim->constacc[i] = 0.0;
	t@@ -89,6 +92,24 @@ sim_print_grains_vtk(FILE *stream, const struct simulation …
	grains_print_vtk(stream, sim->grains, sim->ng);
	}

	+void
	+sim_write_output_files(struct simulation *sim)
	+{
	+ int ret;
	+ char outfile[256];
	+ FILE *fp;
	+
	+ ret = snprintf(outfile, sizeof(outfile), "%s.grains.%05zu.tsv",
	+ sim->name, sim->n_file++);
	+ if (ret < 0 \|\| (size_t)ret >= sizeof(outfile))
	+ errx(1, "%s: could not write grains filename", __func__);
	+ if ((fp = fopen(outfile, "w")) != NULL) {
	+ sim_print_grains(fp, sim);
	+ fclose(fp);
	+ } else
	+ err(1, "%s: fopen: %s", __func__, outfile);
	+}
	+
	double
	sim_grain_pair_overlap(struct simulation *sim, size_t i, size_t j)
	{
	t@@ -123,6 +144,24 @@ sim_check_add_contact(struct simulation *sim, size_t i, s…
	grain_register_contact(&sim->grains[i], j, i, centerdist, over…
	}

	+/* Silbert et al. 2001 */
	+void
	+sim_set_timestep(struct simulation *sim)
	+{
	+ int ret = 0;
	+ size_t i;
	+ double t_col, t_col_min = INFINITY;
	+
	+ for (i = 0; i < sim->ng; i++) {
	+ t_col = grain_collision_time(&sim->grains[i]);
	+ if (t_col_min > t_col)
	+ t_col_min = t_col;
	+ }
	+
	+ check_float("t_col_min", t_col_min, &ret);
	+ sim->dt = t_col_min / 50.0;
	+}
	+
	/* TODO: add grid sorting */
	void
	sim_detect_contacts(struct simulation *sim)
	t@@ -162,6 +201,13 @@ sim_step_time(struct simulation *sim)
	for (i = 0; i < sim->ng; i++)
	grain_temporal_integration(&sim->grains[i], sim->dt);

	+ if ((sim->t_file >= sim->dt_file \|\| sim->iter == 0) &&
	+ strncmp(sim->name, DEFAULT_SIMULATION_NAME,
	+ sizeof(sim->name)) != 0) {
	+ sim_write_output_files(sim);
	+ sim->t_file = 0.0;
	+ }
	+
	sim->t += sim->dt;
	sim->t_file += sim->dt;
	sim->iter++;
	diff --git a/simulation.h b/simulation.h
	t@@ -1,7 +1,7 @@
	#ifndef GRANULAR_SIMULATION_
	#define GRANULAR_SIMULATION_

	-#define DEFAULT_SIMULATION_NAME "unnamed_simulation"
	+#define DEFAULT_SIMULATION_NAME "unnamed"

	#include <stdio.h>
	#include "grain.h"
	t@@ -43,7 +43,9 @@ void sim_read_grains(struct simulation sim, FILE stream);

	void sim_print_grains(FILE stream, const struct simulation sim);
	void sim_print_grains_vtk(FILE stream, const struct simulation sim);
	+void sim_write_output_files(struct simulation *sim);

	+void sim_set_timestep(struct simulation *sim);
	void sim_detect_contacts(struct simulation *sim);
	void sim_step_time(struct simulation *sim);
	void sim_run_time_loop(struct simulation *sim);