Figure 25.
The grid has a horizontal eta axis and a vertical xi axis. Three vertical grid lines and three horizontal grid lines form neighbouring cells. The labelled points are i minus 1, j plus 1, i, j plus 1, i plus 1, j plus 1, i minus 1, j, i, j, i plus 1, j, i minus 1, j minus 1, i, j minus 1, and i plus 1, j minus 1. A horizontal double arrow marks delta eta between two vertical grid lines. A vertical double arrow marks delta xi between two horizontal grid lines.Grid discretisation