This thesis describes the flow of ground water with a free water table, in an isotropic and homogeneous soil overlying a horizontal impermeable layer, from a surface-applied rainfall or irrigation supply to a system of horizontal tube drains. The idealized representation of this situation is in terms of a potential flow towards line sinks. The tube drains (sinks) may be at atmospheric pressure (free flow) or under back-pressure (submerged flow). After describing the flow to systems of drains at uniform depth and equal spacings, the thesis shows the effect of horizontal, vertical and combined misalignments of a single line sink on the free surface, the flow pattern and the rates of flow to each sink. The study was carried out by viscous-flow and electrical analogues, by a numerical method (Relaxation), and by the exact solution of equations based on physical approximations. In theory the extent of the effect of any misalignment is infinite. Experimentally it was found that the vertical misalignment had a significant effect on the free surface, discharge and flow net over the whole range of the experiment, while the horizontal one had a noticeable effect only extending over one spacing on either side of the misaligned drain. An approximate mathematical solution for the horizontal displacement has been obtained. Experiments on the viscous-flow model revealed the importance of the effect on the free surface etc. of the back pressure. The distribution of the effect along the free surface and the correlation between the free surface height and the back pressure are also presented. A new approach was used to elucidate the effect of negative pressure (capillary rise) on the free surface and obtain the surface of atmospheric pressure. An equation, independent of the geometrical scale ratio was derived to relate the various parameters for the unsteady flow to the scaling laws. The introduction of a reference potential at a fixed point in the field provides a method for the correction of the change with time in the position of equipotentials and represents a new technique. The variations of free surface heights with discharge, as observed on the viscous-flow model, were compared with the results of s some recent theories and showed discrepancies between the experiment and theories.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:602187 |
| Date | January 1963 |
| Creators | El-Dujaili, Ahmed Mehdi |
| Publisher | Imperial College London |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/10044/1/13226 |
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