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	tImplemented adaptive time step - ns2dfd - 2D finite difference Navier Stokes s…
	git clone git://src.adamsgaard.dk/ns2dfd
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	---
	commit 08a48407f92cd5c0c603c8e5207ab92b8a5df5a5
	parent 712b7d25f92ae5ecd752f39c2d1578a39d973457
	Author: Anders Damsgaard <[email protected]>
	Date: Sun, 2 Mar 2014 20:51:49 +0100

	Implemented adaptive time step

	Diffstat:
	M src/Makefile \| 3 ++-
	M src/main.c \| 23 ++++++++++++++++-------
	M src/utility.c \| 30 ++++++++++++++++++++++++++++++
	M src/utility.h \| 3 +++

	4 files changed, 51 insertions(+), 8 deletions(-)
	---
	diff --git a/src/Makefile b/src/Makefile
	t@@ -1,9 +1,10 @@
	CFLAGS=-Wall -pedantic -g
	+LDLIBS=-lm

	BIN=../ns2dfd

	$(BIN): main.o file_io.o utility.o
	- $(CC) $(CFLAGS) $^ -o $@
	+ $(CC) $(CFLAGS) $(LDLIBS) $^ -o $@

	main.o: file_io.h utility.h
	file_io.o: utility.h
	diff --git a/src/main.c b/src/main.c
	t@@ -18,6 +18,9 @@ int main(int argc, char** argv)
	int nx, ny;
	double P, U, **V;

	+ double dt;
	+ long n = 0;
	+
	int c;
	while ((c = getopt(argc, argv, "hv")) != -1)
	switch (c)
	t@@ -30,7 +33,7 @@ int main(int argc, char** argv)
	return 0;
	break;
	case 'v':
	- printf("%s: Navier Stokes solver in 2D using finite differences, "
	+ printf("%s: A Navier Stokes solver in 2D using finite differences,…
	"version %.1f\n"
	"Written by Anders Damsgaard, "
	"https://github.com/anders-dc/ns2dfd\n", argv[0], VERSION);
	t@@ -57,14 +60,20 @@ int main(int argc, char** argv)
	return 1;
	}

	- printf("omega = %f\n", omega);
	- printf("P[0][0] = %f\n", P[0][0]);
	- printf("V[%d][%d] = %f\n", nx, ny, V[nx][ny]);
	-
	- write_file("unnamed2.dat", &t, &t_end, &tau, &itermax,
	+ /*write_file("unnamed2.dat", &t, &t_end, &tau, &itermax,
	&epsilon, &omega, &gamma,
	&gx, &gy, &re, &w_left, &w_right, &w_top, &w_bottom,
	- &dx, &dy, &nx, &ny, &P, &U, &V);
	+ &dx, &dy, &nx, &ny, &P, &U, &V);*/
	+
	+ /while (t < t_end) {/
	+
	+ dt = select_time_step(tau, re, dx, dy, nx, ny, U, V);
	+ printf("dt = %f\n", dt);
	+
	+
	+ /*t += dt;
	+ n++;
	+ }*/

	free_memory(P, U, V, nx);
	return 0;
	diff --git a/src/utility.c b/src/utility.c
	t@@ -1,5 +1,6 @@
	#include <stdio.h>
	#include <stdlib.h>
	+#include <math.h>

	int allocate_matrix(double ***M, int nx, int ny)
	{
	t@@ -47,3 +48,32 @@ void free_memory(double P, double U, double **V, int nx)
	free_matrix(&U, nx);
	free_matrix(&V, nx);
	}
	+
	+double max_abs_value(double **M, int nx, int ny)
	+{
	+ int i, j;
	+ double tmp;
	+ double max = -1.0e19;
	+ for (j=1; j<=ny; j++) {
	+ for (i=1; i<=nx; i++) {
	+ tmp = fabs(M[i][j]);
	+ if (tmp > max) max = tmp;
	+ }
	+ }
	+ return max;
	+}
	+
	+double select_time_step(double tau, double re, double dx, double dy,
	+ int nx, int ny, double U, double V)
	+{
	+ double t_diff, t_adv_u, t_adv_v;
	+ double u_max, v_max;
	+ u_max = max_abs_value(U, nx, ny);
	+ v_max = max_abs_value(V, nx, ny);
	+
	+ t_diff = re/2.0(1.0/(1.0/(dxdx) + (1.0/(dy*dy))));
	+ t_adv_u = dx/(u_max + 1.0e-12);
	+ t_adv_v = dx/(v_max + 1.0e-12);
	+
	+ return fmin(t_diff, fmin(t_adv_u, t_adv_v));
	+}
	diff --git a/src/utility.h b/src/utility.h
	t@@ -4,4 +4,7 @@
	int allocate_memory(double *P, double U, double **V, int nx, int ny);
	void free_memory(double P, double U, double **V, int nx);

	+double select_time_step(double tau, double re, double dx, double dy,
	+ int nx, int ny, double U, double V);
	+
	#endif