Simulation and Analysis of Wave-Induced Near-Shore Currents

  • 許 主恩

Student thesis: Master's Thesis


This study presents the sensitivity analyses and some corresponding findings in two-dimensional near-shore current simulation based on the Coastal Reclamation and Management model (CRM model) developed by THL NCKU whose governing equations of current fields are shallow water equations The main purpose of this model was simulating near-shore sediment transportation and bed morphology evolution; however non-negligible errors were found to exist in the computed near-shore current field This might lead to meaningless predictions of sediment transportation and bed morphology evolution in that the current-field result plays a significant role in sediment transportation Consequently we commenced to devote to the investigation of near-shore current system based on CRM model The focused topics include wave models wave breaking criteria bed resistance evaluation bottom friction formulas eddy diffusion and surface roller For wave models two widely used models including RCPWave and REF/DIF 1 both of which based on mild-slope equation were taken into account The one installed in CRM model originally was RCPWave; nevertheless referred to Maa et al (2000) and Kirby (2000) REF/DIF 1 was stated to be able to capture the wave variation accurately rather than RCPWave did especially when the nonlinearity is important In addition RCPWave was found to be less stable than REF/DIF 1; hence the original CRM model was modified to be coupled with REF/DIF 1 instead of RCPWave in present study Further discussions and analysis were carried out after the comparison of wave models Since we focus on the impact factor analyses in present study the chosen experimental study or measurements should be determined carefully Visser (1991) gave the comparison of longshore current experiments in the past and proposed an improved one in his investigation which has been widely used and applied then In consequence longshore current measurements by Visser (1991) is adopted in present investigation for model verifications Finally computed results discussions suggestions and conclusions would be presented in the last two chapters of present study The modified CRM model coupled with REF/DIF 1 and surface-roller model leads to great results in current field Yet it was found that the modified CRM model still could not perform well against gravel beaches which should be attributed to the frictional energy loss estimation in wave models As for the future works this issue should have the top priority Then outcomes and conclusions of present study are expected to be applied to the field investigation and eventually the sediment transportation and bed morphology
Date of Award2015 Jul 27
Original languageEnglish
SupervisorShih-Chun Hsiao (Supervisor)

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