FLOWNET DIAGRAMS - THE USE OF FINITE DIFFERENCES AND A SPREADSHEET TO DETERMINE POTENTIAL HEADS

This paper shows how to use spreadsheet programmes for desktop computers to construct flownets. The seepage of water is governed by a Laplace- type partial differential equation for the potential head of water, which is solved approximately using finite difference methods. In a previous paper, Smyrell showed how to solve such a finite difference equation using spreadsheet methods, and applied it to torsional stiffness. For a seepage problem, the area of ground considered is divided into a square grid, and cells in the spreadsheet are allocated to each node point of the grid. The cells are filled with formulae to calculate the potential head or values of the known potential head at the corresponding point. Formulae for the various boundary conditions are entered into suitable cells in the spreadsheet's top area. They are stored in a master file for repeated use. Iterations are continued until there is no significant change in the calculated values. The number required depends on the grid size. The calculations for a numerical example are presented, for a 12m wide 8m deep cofferdam. For many situations, the method described is sufficiently accurate. However, the finite difference equations can be modified in various ways, to reduce calculation time and solve more complex problems such as those involving orthotropy, grid grading and soil layers.

  • Availability:
  • Corporate Authors:

    Thomas Telford Limited

    London,   United Kingdom 
  • Authors:
    • WILLIAMS, B P
    • SMYRELL, A G
    • LEWIS, P J
  • Publication Date: 1993-6

Language

  • English

Media Info

  • Features: References;
  • Pagination: p. 32-8
  • Serial:
    • GROUND ENGINEERING
    • Volume: 26
    • Issue Number: 5
    • Publisher: EMAP CONSTRUCT LIMITED
    • ISSN: 0017-4653

Subject/Index Terms

Filing Info

  • Accession Number: 00663417
  • Record Type: Publication
  • Source Agency: Transport Research Laboratory
  • Files: ITRD
  • Created Date: Aug 24 1994 12:00AM