meshing problem
 

hi. I'm trying to simulate an ogee weir in a channel. I want to use hexa dominant mesh in the model. but when I run it. something goes wrong and icem can't generate volume mesh. what is the problem?

I tried another method. I used surface mesh after that I ran hexa dominant with option of existing mesh. but the result was same as before. this error was showed in both case:
Running: "D:/Program Files/ANSYS Inc/v140/icemcfd/win64_amd/icemcfd/hex_dom" __hexdom_surface.uns __hexdom_volume.uns BODY
Program is running: pid = 3592
E07 Init: element 1 has measure 0.0
Application is finished.
Error: couldn't generate proper mesh
Performing a mesh flood fill...
element containing material point BODY.1 was not found
Done mesh flood fill
please help me!

any suggestion?