The report presents the effect of non hydrostatic pressure distribution on dam break flood wave movement. Dam break flood moves with non-hydrostatic pressure distribution in the vertical direction. However, almost all the mathematical models for dam break flows use Saint-Venant equation, which presume hydrostatic pressure in the vertical direction. In this report, an attempt has been made to use Boussinesq equations in the mathematical model.
Compared to the Saint-Venant equations, these equations have three extra terms in the momentum equation. Due to the presence of a third order term in the equations, the numerical procedure adopted is third order accurate. The mathematical model is validated against previous experimental results. The model is applied to study the effect of non-hydrostatic pressure distribution on the free surface profile and the height & propagation of dam-break flood wave for various depth ratios (i.e., ratio of initial depths downstream and upstream of the dam). The effect due to bed roughness and bed slope is also studied.
The results show that inclusions of extra terms introduce oscillations that are actually taking place in the free surface. These oscillations are significant only for depth ratios greater than 0.4. The maximum deviation of the water level is of the order of 7 %. The effect of non-hydrostatic pressure distribution exists only for a short time after the breaking of the dam. However, this may prevail for a considerable distance downstream of the dam. Out of the three extra terms used in the governing equations, first term consisting of time derivative is unimportant.
The following works are recommended for future studies:
- Inclusion of curvilinear coordinate system or two-dimensional rectangular coordinate system in the governing equations to consider the effect of two-dimensional flows
- Application of a fully coupled model using sediment transport equations
- Effect of partial dam-breaching
- Dam-break flood wave movement on a dry bed
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