- In this Section , we shall present the concept of { Flow Net } ,
- a quasi-empirical method from { Soil Mechanics } .

- This then give rise to the notion of :
- using the { General-Random-Type Six-Face Object } as the [ finite element ] in { Fluid Mechanics Analysis } .

- { Flow Net } is simply a quasi-empirical method used in { Soil Mechanics } :
- Let us look , for a brief moment , at the seepage of water under a Dam , as per this diagram below :

- The { Flow Net } method is then as follows :
- First , we draw-in , roughly what we think are the { Stream-Lines } for the flow :
- as marked by the { blue-color lines } in the diagram below .

- Next , we draw-in , lines that intersect the { Stream-Lines } at [ Right-Angles ] :
- as marked by the { green-color lines } in the diagram below .
( Right-Angles ] are [ 90-degrees angles ] )

- as marked by the { green-color lines } in the diagram below .
- If the { intersection angles } do not look-like [ Right-Angles ] ,
- we simply make adjustments to the { blue-color lines } and the { green-color lines } :
- until the { intersection angles } do look-like [ Right-Angles ] .

- we simply make adjustments to the { blue-color lines } and the { green-color lines } :

- First , we draw-in , roughly what we think are the { Stream-Lines } for the flow :
- We shall not go into the full details of the { Flow-Net } method , but will simply note here :
- that each { Finite Element } in the { Flow Net } is a { planar surface } with 4 [ nodal-points ] ,
as marked in { orange-color } in the diagram above .

( see [ Soil Mechanics in Engineering Practice - Karl Terzaghi and Ralph B. Peck ] - ISBN 0-471-85273-2 for full details . )

- that each { Finite Element } in the { Flow Net } is a { planar surface } with 4 [ nodal-points ] ,

- We simply note here that with 4 { nodal-points } , we can always form :
- a planar [ Finite Element ] with 4 [ straight-edges ] ,
- which is essentially a { quadrangle } .

- a planar [ Finite Element ] with 4 [ straight-edges ] ,
- When we extend this to { 3-D Space } , we can always use :
- the { General-Random-Type Six-Face Object } as the [ Finite Element ] ,
- which has 8 { nodal-points } and exactly 6 [ faces ] which are all [ planar surfaces ] .

We then have a clear and distinct advantage here :

- each [ face ] of the [ finite element ] here is always in { full contact } with the corresponding { face } of the adjacent [ finite element ] ,
- so that there are no [ gaps ] in-between and unbroken { continuity } can always be achieved and maintained , if so desired .

- the { General-Random-Type Six-Face Object } as the [ Finite Element ] ,

- Next , we shall look at the usage of this type of [ finite elements ] in a { steady flow } situation .