add a h_min value as well

grudge/symbolic/operators.py

@@ -742,6 +742,26 @@ def h_max_from_volume(ambient_dim, dim=None, dd=None):
                 )
             )**(1.0/dim)
 
+def h_min_from_volume(ambient_dim, dim=None, dd=None):
+    """Defines a characteristic length based on the volume of the elements.
+    This length may not be representative if the elements have very high
+    aspect ratios.
+    """
+
+    import grudge.symbolic.primitives as prim
+    if dd is None:
+        dd = prim.DD_VOLUME
+    dd = prim.as_dofdesc(dd)
+
+    if dim is None:
+        dim = ambient_dim
+
+    return NodalMin(dd_in=dd)(
+            ElementwiseSumOperator(dd)(
+                MassOperator(dd_in=dd)(prim.Ones(dd))
+                )
+            )**(1.0/dim)
+
 # }}}
 
 # vim: foldmethod=marker