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Effect of Wind on Near-Shore Breaking Waves

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Effect of Wind on Near-Shore Breaking Waves EFFECT OF WIND ON NEAR-SHORE BREAKING WAVES by Faydra Schaffer A Thesis Submitted to the Faculty of The College of Engineering and Computer Science in Partial Fulfillment of the Requirements for the Degree of Master of Science Florida Atlantic University Boca Raton, Florida December 2010 Copyright by Faydra Schaffer 2010 ii ACKNOWLEDGEMENTS The author wishes to thank her mother and family for their love and encouragement to go to college and be able to have the opportunity to work on this project. The author is grateful to her advisor for sponsoring her work on this project and helping her to earn a master’s degree. iv ABSTRACT Author: Faydra Schaffer Title: Effect of wind on near-shore breaking waves Institution: Florida Atlantic University Thesis Advisor: Dr. Manhar Dhanak Degree: Master of Science Year: 2010 The aim of this project is to identify the effect of wind on near-shore breaking waves. A breaking wave was created using a simulated beach slope configuration. Testing was done on two different beach slope configurations. The effect of offshore winds of varying speeds was considered. Waves of various frequencies and heights were considered. A parametric study was carried out. The experiments took place in the Hydrodynamics lab at FAU Boca Raton campus. The experimental data validates the knowledge we currently know about breaking waves. Offshore winds effect is known to increase the breaking height of a plunging wave, while also decreasing the breaking water depth, causing the wave to break further inland. Offshore winds cause spilling waves to react more like plunging waves, therefore increasing the height of the spilling wave while consequently decreasing the breaking water depth. v TABLE OF CONTENTS LIST OF TABLES ............................................................................................................ vii LIST OF FIGURES ......................................................................................................... viii 1. INTRODUCTION ....................................................................................................... 1 2. PROBLEM STATEMENT ......................................................................................... 6 3. LITERATURE REVIEW ............................................................................................ 7 4. PROJECT DESCRIPTION ....................................................................................... 10 4.1 METHODOLOGY .................................................................................................... 12 5. DATA ANALYSIS ................................................................................................... 29 5.1 DATA FOR ALL TEST CASES .............................................................................. 30 5.2 DIMENSIONAL ANALYSIS................................................................................... 44 5.3 MATLAB RESULTS ................................................................................................ 56 6. CONCLUSION ......................................................................................................... 64 7. APPENDIX ............................................................................................................... 66 7.1 SOLID WORKS DRAWINGS ................................................................................. 66 7.2 MATLAB BEACH DESIGN CODE RESULTS ...................................................... 68 7.3 BREAKING IN A SERIES RESULTS ..................................................................... 76 7.4 DIFFERENT BREAKING ANGLE VIEW ............................................................ 112 7.5 WAVE GAUGE SPECIFICATIONS ..................................................................... 116 8. BIBLIOGRAPHY ................................................................................................... 118 vi `LIST OF TABLES Table 2: Beach design configurations ............................................................................... 15 Table 3: Breaking Wave Data from MATLAB code ........................................................ 16 Table 4: Wave Gauge Layout, measured from position 0 m at wind fan end .................. 18 Table 5: Average Wind Speed Data for all Plywood Sheet Heights ................................ 26 Table 6: Wind Speed Data for Plywood Sheet Height set at Holes 4-5 ........................... 27 Table 7: MATLAB Average Wave Amplitude Results for all Cases (w=frequency rad/s, A=amplitude m) ................................................................ 56 Table 8: Wave Data at Break Point for all cases on Beach 1- Position Xb, Depth Db, and Height Hb ..................................................................................................... 59 Table 9: Wave Data at Break Point for all cases on Beach 2- Position Xb, Depth Db, and Height Hb ...................................................................................................... 60 Table 10: Matlab Beach Design Code Results for Beach Slope 1 .................................... 61 Table 11: Matlab Beach Design Code Results for Beach Slope 2 .................................... 61 Table 12: Percent Error Calculations for Beach 1 No Wind ............................................ 61 Table 13: Percent Error Calculations for Beach 2 No Wind ............................................ 62 vii LIST OF FIGURES Figure 1: Wave gauge ....................................................................................................... 11 Figure 2: Beach 1 slope layout.......................................................................................... 17 Figure 3: Beach 1 Solid Works Dimension Drawing ....................................................... 17 Figure 4: Wave Gauge Layout Beach 1 ............................................................................ 18 Figure 5: Beach 2 Solid Works Dimension Drawing ....................................................... 18 Figure 6: Cross member diagram for Beach 1, setup 1 (Left), setup 2 (Right) ................ 20 Figure 7: Beginning of setup............................................................................................. 21 Figure 8: Middle of setup (shows WG1 and WG2) .......................................................... 22 Figure 9: Continuation of setup (shows WG3). Use clock as reference ........................... 22 Figure 10: End of setup (shows WG4). Use cabinet as reference .................................... 22 Figure 11: Metal braces with holes labeled for wind speed location ................................ 25 Figure 12: Hand-held wind anemometer .......................................................................... 25 Figure 13: Wind measurement testing location (Left) and Wind testing pattern (Right) . 26 Figure 14: Comparison of Wind Velocity Data ................................................................ 27 Figure 15: Amplitude vs. Period for No Wind for Beach 1 & 2 ....................................... 30 Figure 16: Amplitude vs. Period for Wind Speed= 2.93 m/s for Beach 1 & 2 ................. 31 Figure 17: Amplitude vs. Period for Wind Speed= 3.24 m/s for Beach 1 & 2 ................. 32 Figure 18: Amplitude vs. Period for Wind Speed= 3.35 m/s for Beach 1 & 2 ................. 33 Figure 19: Amplitude vs. Period for Wind Speed= 3.7 m/s for Beach 1 & 2 ................... 34 viii Figure 20: Amplitude vs. Tank Position for Frequency ɷ= 6 rad/s for Beach 1 & 2 ....... 35 Figure 21: Estimated Breaking Locations for Amplitude vs. Tank Position for Frequency ɷ= 6 rad/s for Beach 1 & 2 ........................................................... 35 Figure 22: Amplitude vs. Tank Position for Frequency ɷ= 7 rad/s for Beach 1 & 2 ....... 36 Figure 23: Amplitude vs. Tank Position for Frequency ɷ= 8 rad/s for Beach 1 & 2 ....... 36 Figure 24: Amplitude vs. Tank Position for Frequency ɷ= 9 rad/s for Beach 1 & 2 ....... 37 Figure 25: Error Bar Plot for Amplitude vs. Tank Position for Frequency ɷ= 9 rad/s for Beach 1 ...................................................................................................... 37 Figure 26: Breaking in a series w/ No Wind on Beach Slope 1 for w=6 .......................... 40 Figure 27: Breaking in a series w/ No Wind on Beach Slope 1 for w=8 .......................... 41 Figure 28: Breaking in a series w/ Wind Speed=3.35m/s on Beach Slope 1 for w=6 ...... 42 Figure 29: Breaking in a series w/ Wind Speed=3.35m/s on Beach Slope 1 for w=8 ...... 43 Figure 33: Non Dimensional Wind Speed vs. Non Dimensional Position at Breaking ... 45 Figure 34: Non Dimensional Wind Speed vs. Non Dimensional Wavelength at Breaking .......................................................................................................... 46 Figure 35: Beach Slope vs. Non Dimensional Depth at Breaking .................................... 47 Figure 39: Non Dimensional Breaking Depth vs. Non Dimensional Wind Speed ........... 48 Figure 40: Non Dimensional Breaking Height vs. Non Dimensional Wind Speed .......... 49 Figure 41: Non Dimensional Breaking Height/depth vs. Non Dimensional Wind Speed ..................................................................................................... 50 Figure 42: Deep Water Steepness vs. Non Dimensional Breaking Depth ........................ 51 Figure 43: Deep Water Steepness vs. Non Dimensional Breaking Height....................... 52 Figure 44: Deep Water Steepness vs. Non Dimensional Breaking Height/depth............
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