Date of Award

Spring 5-13-2017

Level of Access Assigned by Author

Campus-Only Thesis

Degree Name

Master of Science (MS)

Department

Civil Engineering

Advisor

Lauren Ross

Second Committee Member

Shaleen Jain

Third Committee Member

Kimberly Huguenard

Abstract

Flash flooding caused by dam breaking and tsunamis commonly results in destruction of coastal and offshore structures due to wave-structure interaction. The destructive potential of the wave impact can be assessed by determining wave height, flow velocity and the impact force/pressure imposed on the structures. Accurate evaluation of such quantities is, therefore, critical for the safety and design of both coastal and offshore structures. Yet, it is challenging for mesh-based numerical methods (e.g. finite element) to precisely model the extremely violent fluid flow that results in the case of wave-structure interaction. Weakly Compressible particle-based Smooth Particle Hydrodynamics (WCSPH) method is adopted in this work due to its robustness in simulating wave-structure interaction. In particular, SPH has the capability to simulate dam breaking and tsunamis interacting with single and multiple structures.

There are three primary objectives of this thesis. First, is to present a validated and robust method for predicting local pressure on solid structures due to wave impact using SPH. The second is to assess the performance of the WCSPH method in quantifying flow characteristics (e.g. impact force, overturning moment) when the wave interacts with structures. Finally, the third objective is to implement the validated SPH methods to evaluate flow characteristics such as flow velocity and impact force to study the flood behavior on two different “city” layouts to mimic an urban flood. With these goals, five dam breaking (three dam braking on single structure and two dam breaking on multiple structures) and two tsunami (tsunami on single structure and tsunami on multiple structures) models were developed using the SPH method.

The results indicate that the newly developed local impact pressure evaluation technique is valid and accurate when compared with laboratory experiment data. The results highlight the ability of SPH to predict flood characteristics like impact force, local pressure and overturning moment compared with finite volume or finite element modeling methods. It has been found from the dam breaking on multiple structures model that the flash flood could cause more destruction if the flood impacted a city oriented at an angle to the oncoming flood waters rather than a city aligned in the flood direction. Another result of this work included the implementation of a new tsunami wave maker into SPH. It was found that the tsunami wave was generated perfectly by the new tsunami wave maker adapted in this study. In addition, other wave characteristics, such as wave height, wave velocity, impact force, and overturning moment were more accurately simulated by SPH than finite element numerical methods, when compared to laboratory experiment data.

In conclusion, SPH can address the needs of modeling the complex interactions between fluid flow and solid structures. Further, SPH can robustly cope with intricate and multipart geometry problems. Thus, the SPH model can be used as a superior and cost effective alternative for physical (laboratory) models replicating solitary wave propagation and is more precise than finite element numerical modeling. Further, this work has shown that city development and planning in flash flood prone areas should design streets to be aligned with oncoming flood waters for damage mitigation. Overall, this study can be used to advance coastal and civil engineering studies focused on better understanding and modeling solitary wave propagation and wave-structure interaction in offshore and coastal environment.

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