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FEM 

GEO5

Geotechnical software

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Line flow

The frame "Line flow" contains a table with the list of line flows. Adding (editing) a line flow is performed in the "New line flow" dialog window.

A line flow can also be introduced using the mouse. This inputting mode is activated by clicking an appropriate button on the horizontal tool bar "Line flow". The following modes are available:

  • Adjust
 Clicking the left mouse button on already existing line flow opens the "Adjust line flow properties" dialog window, which allows for modifying its parameters.

The inputted line flows can also be edited on the desktop with the help of active objects.

Flow boundary conditions must be defined on all boundary lines. The following boundary conditions can be specified:

a) Impermeable
b) Permeable Pore pressure on a given line is equal to zero
c) Pore pressure
- distribution of pore pressure p can be specified numerically
- distribution of pore pressure can be specified by inputting the location of ground water table (by prescribing the hydraulic head h)
d) Inflow/outflow on a line q – it is specified in velocity units e.g. [m/day , ft/day] – the flow velocity into/out of the region is specified. The default setting corresponds to an impermeable boundary for which q=0.
e) Seepage surface – this boundary condition is introduced providing the boundary cannot be uniquely divided into the part with prescribed pore pressure and the part with prescribed inflow/outflow (the exit point is not known). In such a case the analysis is performed in two steps. In the first step the program locates the exit point. The actual flow analysis with known boundary conditions is then carried in the second step. In some cases both steps must be repeated several times. When enhanced input is considered the program requires entering a fictitious permeability kv in units [m/day]. This is essentially a penalty term, a sufficiently large number in general, ensuring that along an impermeable boundary the value of hydraulic head h will be equal to a y-coordinate of a given point (q=0), For a part of boundary with no flow condition we have kv=0. Variables q and h are then related by:
if>0 (S=1) inside soil body
if h<0 (S<1) inside soil body

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