The 2dm file format is used to define the TUFLOW FV mesh. It is an ASCII format from the SMS Generic Mesh Module (www.aquaveo.com). The contents of the file relevant to TUFLOW FV simulations (see also the example in the attached figure) are:
Lines that commence with a “ND” are nodes, or the points that define the edges of the elements. Each ND line describes the node ID and its x, y and z (ie bed level)
Lines that commence with an “E4Q” are quadrilateral (4 sided) elements. Each E4Q line describes the element ID, the four nodes that define its connectivity and spatial extent (in a counter-clockwise direction) and the material type.
Similar to E4Q, the “E3T” lines are triangular elements. Each E3T line describes the element ID, the three nodes that define its connectivity and spatial extent (in a counter-clockwise direction) and the material type.
Lines that commence with a “NS” are nodestrings, which are used to define boundary conditions. Each NS line defines the series of nodes that form the string, the last node number is assigned as negative. The number following the negative number is the nodestring ID.
Other components of the 2dm file are not used by TUFLOW FV.