Browsing by Subject "Computational cost"

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An equivalent orifice for short conduits in SWMM5+
(2024-08) Pazhoor Abraham, Adithya ; Hodges, Ben R.; Bartos, Matthew
Model time steps in the US EPA Storm Water Management Model (EPA SWMM) are typically controlled by the shortest links in the network. This problem is exacerbated in the finite-volume SWMM5+ hydraulic solver due to the need to provide at least three computational elements in each link. In EPA SWMM, the typical approach to this problem is to artificially lengthen short elements, which addresses the problem but at the cost of model fidelity. Herein, we propose an equivalent orifice algorithm that replaces a short conduit link with an orifice whose behavior mimics the expected head loss using the energy equation. This algorithm eliminates the need to artificially lengthen links. The underlying idea is demonstrated to be workable, but the implementation in the SWMM5+ code requires further modification of finite-volume element-to-face interpolation schemes.
Dynamic response of laterally-loaded piles
(2009-05) Thammarak, Punchet; Tassoulas, John Lambros
The laterally-loaded pile has long been a topic of research interest. Several models of the soil surrounding a pile have been developed for simulation of lateral pile behavior, ranging from simple spring and dashpot models to sophisticated three-dimensional finite-element models. However, results from the available pile-soil models are not accurate due to inherent approximations or constraints. For the springs and dashpots representation, the real and imaginary stiffness are calculated by idealizing the soil domain as a series of plane-strain slices leading to unrealistic pile behavior at low frequencies while the three-dimensional finite-element analysis is very computationally demanding. Therefore, this dissertation research seeks to contribute toward procedures that are computationally cost-effective while accuracy of the computed response is maintained identical or close to that of the three-dimensional finite-element solution. Based on the fact that purely-elastic soil displacement variations in azimuthal direction are known, the surrounding soil can be formulated in terms of an equivalent one-dimensional model leading to a significant reduction of computational cost. The pile with conventional soil-slice model will be explored first. Next, models with shear stresses between soil slices, including and neglecting the soil vertical displacement, are investigated. Excellent agreement of results from the proposed models with three-dimensional finite-element solutions can be achieved with only small additional computational cost.