Experimental and numerical determination of the shoreline motion during the run-up of tsunami waves on a plain beach

Master's Thesis , 2014 , 84 Pages , Grade: 1.7

Geography / Earth Science - Oceanography

Within this master thesis the behaviour of long periodic waves during their run-up on a plain beach was investigated via physical and numerical modelling. In the experimental part, for seven leading depression, non-breaking sine waves with surf similarity parameters between 3.1 and 15.6 the wave velocity, wave height and run-up on a plain beach were determined. In addition, the motion of the initially still shoreline, i.e. run-up/ run-down process, run-up/ run-down velocity, wave acceleration, maximum run-up and maximum run-up velocity, was determined via two high-speed cameras. Comparison of the aforementioned characteristics with the theory revealed good agreement; deviations can mostly be attributed to experimental performance.
For wave generation a new volume driven wave generator was used. Long waves are generated by a pair of high capacity pumps under control of a proportional-integral-derivative controller (PID-controller). While rotating clockwise or counterclockwise water is pumped into the propagation section or extracted from it. Thereby, waves of arbitrary length can be generated.
Using the relatively new strategy of observing the shoreline motion via optical measurements gave a comparatively exact shoreline position during wave run-up. In contrast, determination of the shoreline position during run-down was less exact due to missing evidence indicating the distinct position of the shoreline. In general, the experimentally determined shoreline position agreed with the theoretical approach. The maximum run-up/ run-down occurred for waves with surf similarity parameters between 3 and 6 (interval in which transition from breaking to non-breaking occurs). The magnitude of the theoretical breaking point increased for decreasing wave non-linearity A/h. For surf similarity parameters greater equal of the theoretical breaking point and for increasing surf similarity parameters the normalized run-up and magnitude of normalized run-down decreased. The maximum run-up/ run-down was proportional to wave non-linearity, i.e. the normalized run-up and magnitude of normalized run-down decreased with increasing wave amplitude as predicted by theory. The agreement of experimental and theoretical maximum run-down/ run-up depended on tuning of the PID controller and the resulting actual curve. For longer waves suboptimal tuning of the PID controller resulted in riding waves.

Inhaltsverzeichnis

• List of Tables
• List of Figures
• List of Symbols
• Abstract
• 1 Introduction
  • 1.1 Motivation
  • 1.2 General Information on Tsunamis
  • 1.3 Scope of the Thesis
  • 1.4 Outline of the Thesis
• 2 Literature Review
  • 2.1 Long Wave Generation Techniques
    • 2.1.1 Piston-type Wave Generation
    • 2.1.2 Dam Break Analogy
    • 2.1.3 Vertical Sea Bed Motion
    • 2.1.4 Pneumatic Wave Generation
  • 2.2 The Brier Score
  • 2.3 The Shoreline Motion of Long Sinusoidal Waves
  • 2.4 Breaking Criterion for Sinusoidal Waves
  • 2.5 Optical Measurements of Long Wave Run-up
• 3 Experimental Setup
  • 3.1 Description of Instruments
    • 3.1.1 The Wave Flume
    • 3.1.2 The Wave Gauges
    • 3.1.3 The Velocity Meter
    • 3.1.4 The Pressure Sensors
    • 3.1.5 The High Speed Cameras
  • 3.2 Performance of Physical Experiments
  • 3.3 Data Processing
    • 3.3.1 Processing of Time Series
    • 3.3.2 Image Processing
    • 3.3.3 Derived Quantities: Position, Velocity and Acceleration of the Shoreline
• 4 Wave Generation
  • 4.1 Introduction
  • 4.2 The Pump-driven Wave Generator
  • 4.3 The Controller Scheme
  • 4.4 Summary
• 5 Results Of Physical Experiments
  • 5.1 Time Series
    • 5.1.1 Comparison Reference and Actual Curve, Brier Score
    • 5.1.2 Time Series of Wave Gauges
    • 5.1.3 Time Series of EMS Sensor
    • 5.1.4 Time Series of Pressure Sensors
  • 5.2 Run-up and Run-down of Long Waves
  • 5.3 Maximum Run-up and Run-down
  • 5.4 Shoreline Velocity During Run-up and Run-down
  • 5.5 Maximum Shoreline Velocity During Run-up and Run-down
  • 5.6 Wave Acceleration During Run-up and Run-down
  • 5.7 Summary
• 6 Numerical Model Test
  • 6.1 Introduction
  • 6.2 Description of the Numerical Model
  • 6.3 Results of the Numerical Model Study
    • 6.3.1 Evolution of SSH During Propagation
    • 6.3.2 Numerical Shoreline Location and Maximum Run-Up
  • 6.4 Summary
• 7 Summary and Outlook
• References
• Acknowledgements
• Statement
• Appendix A: Calibration Curves
• Appendix B: Tables for Rmax and Vmax

Zielsetzung und Themenschwerpunkte

This Master thesis aims to experimentally and numerically investigate the shoreline motion during the run-up of tsunami waves on a plain beach. The study focuses on the generation of long waves in a wave flume and the analysis of their run-up and run-down behavior. The thesis explores the relationship between the wave characteristics, the shoreline motion, and the physical processes involved in the run-up of long waves.

• Experimental determination of the shoreline motion during the run-up of long waves in a wave flume.
• Comparison of experimental results with theoretical predictions based on analytical models.
• Numerical simulation of the shoreline motion using a hydrodynamic model.
• Analysis of the influence of wave characteristics on the shoreline motion.
• Evaluation of the accuracy and limitations of the experimental and numerical methods.

Zusammenfassung der Kapitel

Chapter 1 introduces the motivation for the study, provides general information on tsunamis, and outlines the scope and structure of the thesis. Chapter 2 reviews relevant literature on long wave generation techniques, the Brier score, the shoreline motion of long sinusoidal waves, breaking criteria for sinusoidal waves, and optical measurements of long wave run-up. Chapter 3 describes the experimental setup, including the wave flume, instruments used, and data processing methods. Chapter 4 focuses on the wave generation process, including the pump-driven wave generator and the controller scheme. Chapter 5 presents the results of the physical experiments, including time series analysis, run-up and run-down measurements, and shoreline velocity and acceleration. Chapter 6 describes the numerical model test, including the model description and results. Chapter 7 summarizes the findings of the study and provides an outlook for future research.

Schlüsselwörter

The keywords and focus themes of the text include shoreline motion, tsunami waves, run-up, run-down, long wave generation, wave flume, experimental methods, numerical modeling, hydrodynamic model, Brier score, wave characteristics, and physical processes.

• College: University of Hamburg (Institute of Oceanography Hamburg)
• Course: Physical Oceanography
• Grade: 1.7
• Author: Ulrike Drähne (Author)
• Publication Year: 2014
• Pages: 84
• Catalog Number: V280860
• ISBN (eBook): 9783656743804
• ISBN (Book): 9783656743774
• Language: English
• Tags: experimental