added missing check for serial execution

ellipsyswrapper/testsuite.py

@@ -192,10 +192,14 @@ class CaseRunner(object):
         elif self.exec_mode == 'shell':
             t0 = time.time()
             exepath = os.path.join(epath, self.flowfield)
-            command = 'mpirun -np %i %s' % (self.nprocs, exepath)
+            # serial computation
+            if self.flowfield == 'flowfield':
+                command = '%s' % (exepath)
+            # parallel computation
             if self.debug:
               status = subprocess.call(command, shell=True)
             else:
+                command = 'mpirun -np %i %s' % (self.nprocs, exepath)
               # Suppress output from EllipSys
               FNULL = open(os.devnull, 'w')
               status = subprocess.call(command, shell=True,stdout=FNULL)