# HydroGeoSphere/Simple Grids

Simple grids can be generated for rectangular domains which are adequate for many problems. They can have uniform or variable element sizes and can be made of hexahedral block or triangular prismatic elements. Each element in the grid is given a default zone number of 1.

## Generate uniform blocksEdit

**xl, nbx**Domain length and number of blocks in the*x*-direction**yl, nby**Domain length and number of blocks in the*y*-direction**zl, nbz**Domain length and number of blocks in the*z*-direction

Generates a grid for a rectangular domain made up of uniform blocks. In this case, the grid is formed by subdividing the domain in the *x*-direction into **nbx** blocks, each of length **xl/nbx**. The domain is subdivided in a similar fashion in the *y*- and *z*-directions, using the other input parameters.

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## Generate uniform prismsEdit

Generates a grid for a rectangular domain made up of uniform prisms. Requires identical input to the routine Generate uniform blocks described above. In this case though, instead of generating block elements, this instruction generates prism elements by subdividing each block into two prism elements.

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## Generate variable blocksEdit

**nx**Number of nodes in the*x*-direction**xi(i),i=1,nx***x*-coordinates of the**nx**nodes.**ny**Number of nodes in the*y*-direction**yi(i),i=1,ny***y*-coordinates of the**ny**nodes.**nz**Number of nodes in the*z*-direction**zi(i),i=1,nz***z*-coordinates of the**nz**nodes.

Generates a grid for a rectangular domain made up of variably-sized blocks. It is almost identical to the generate uniform blocks instruction except that instead of entering a domain length in each direction we enter a list of coordinates, which are each used to define the position of a plane of nodes along that axis. The structure **xi(i),i=1,nx** is called an implied do and means that you must supply **nx** values for the array **xi**. One or more values can be entered per line until the read statement is satisfied, then a new line should be started for the next read statement.

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## Generate variable prismsEdit

Generates a grid for a rectangular domain made up of variably-sized prisms. Requires identical input to the routine Generate variable blocks described above. In this case though, instead of generating block elements, this instruction generates prism elements by subdividing each block into two prism elements.

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