OpenFOAM: negative volumes on good looking mesh. Empty sample results.

blockMesh defined with incorrect topology:


Far nodes:


4   5
0   1


Near nodes:

7  6
3  2


I used topo 0 1 2 3 4 5 6 7 and the mesh created okay, with warnings during blockMesh:

 Creating block mesh topology
--> FOAM Warning :
    From function cellModel::mag(const labelList&, const pointField&)
    in file meshes/meshShapes/cellModel/cellModel.C at line 128
    zero or negative pyramid volume: -1.66667e-05 for face 0



(ignored, obviously).  On sample, tets could not be created.  checkMesh showed all cells to be stretched and negative volume; paraFoam showed them as okay.

Anyway, using the (correct) topo  : 3 2 1 0 7 6 5 4

fixed all this.