add basic test for fluid solver

src/main_fluid_solver.cpp

@@ -21,6 +21,7 @@
 #include "base.hpp"
 #include "fluid_solver.hpp"
 #include <iostream>
+#include <fftw3-mpi.h>
 
 int myrank, nprocs;
 
@@ -34,6 +35,9 @@ int main(int argc, char *argv[])
     fs = new fluid_solver<float>(32, 32, 32);
     DEBUG_MSG("fluid_solver object created\n");
 
+    fftwf_execute(*(fftwf_plan*)fs->c2r_vorticity);
+    fftwf_execute(*(fftwf_plan*)fs->r2c_vorticity);
+
     delete fs;
     DEBUG_MSG("fluid_solver object deleted\n");