The kinematic-wave flow model has been recently used in the computation of dam-break flood waves (Hunt, 1982). Hunt concludes in his study that the kinematic-wave solution is asymptotically valid. Since the diffusion model has a wider range of applicability for varied bed slopes and wave periods than the kinematic model (Ponce et al., 1978), the diffusion model approach should provide an extension to the referenced kinematic model.

Because the diffusion modeling approach leads to an economic two-dimensional dam-break flow model (with numerical solutions based on the usual integrated finite-difference or finite element techniques), the need to include the extra components in the momentum equation must be ascertained. For example, evaluating the convective acceleration terms in a two-dimensional flow model requires approximately an additional 50-percent of the computational effort required in solving the entire two-dimensional model with the inertia terms omitted. Consequently, including the local and convective acceleration terms increases the computer execution costs significantly. Such increases in computational effort may not be significant for one-dimensional case studies; however, two-dimensional case studies necessarily involve considerably more computational effort and any justifiable simplifications of the governing flow equations is reflected by a significant decrease in computer software requirements, costs and computer execution time.

Ponce (1982) examines the mathematical expressions of the flow equations which lead to wave attenuation in prismatic channels. It is concluded that the wave attenuation process is caused by the interaction of the local acceleration term with the sum of the terms of friction slope and channel slope. When local acceleration is considered negligible, wave attenuation is caused by the interaction of the friction slope and channel slope terms with the pressure gradient or convective acceleration terms





21
[Back to DHM Home] [Back to Research] [Cover] [Table of Contents 1] [Table of Contents 2] [Table of Contents 3]
[<-- Previous Page]  11   12   13   14   15   16   17   18   19   20   21   22   23   24   25   26   27   28   29   30   31   [Next Page -->]