Numerical Simulation of Bed Level Changes Around Structure Due to Waves and Current
DOI:
https://doi.org/10.5614/jts.2017.24.3.2Keywords:
Hydrodynamic simulation, simulation of waves, sediment transport, groin structure, scour, and bed level change.Abstract
Abstract
Interactions between sediments in the marine environment with the dynamics of the ocean can generate sedimentmovement. Sedimentation and erosion is the result of these interactions, which often have a negative impact on theharbor waters or coastal environment. The purpose of this research is to understand the process of sedimenttransport caused by the dynamics of currents and waves on the basis of morphological changes and the potentialthat can lead to scour for coastal protection structures (groin).Coupled model of hydrodynamic model, spectralwave and sediment transport were conducted to study the pattern of sediment movement. Simulations carried out byvarying the waveform specification that propagates to the domain model. Verification of maximum velocity magnitudedue to Van Rijn (1987), Nurdjaman and Ningsih (2003), and Adilantip (2012) shows good agreement with thedifferences value below 5%. While verification of wave height and wave stress radiation with analytical calculationshows good comparison with the mean of differences value 15%. The results of the study indicate that scour depthof 0,955 m was formed at the end of the simulation by the discharge input only. When the discharge combined withthe various wave height and periods, scour depth increases by about 3 - 14%. Location of the scour depth coincideswith the location of the maximum velocity at the tip of the groin structures to the left side.
Abstrak
Interaksi antara sedimen di lingkungan laut dengan dinamika laut dapat menghasilkan pergerakan sedimen. Prosessedimentasi dan erosi merupakan hasil dari interaksi tersebut yang tak jarang berdampak negatif terhadapperairan pelabuhan ataupun lingkungan pesisir. Tujuan dari penelitian ini yaitu untuk memahami proses transporsedimen yang diakibatkan oleh dinamika arus dan gelombang terhadap perubahan morfologi dasar dan potensinyayang dapat mengakibatkan gerusan terhadap struktur pelindung pantai (groin). Dilakukan model kopelhidrodinamika, gelombang spektral, dan transpor sedimen untuk mempelajari pola pergerakan sedimen. Simulasidilakukan dengan memvariasikan perbedaan spesifikasi gelombang yang menjalar terhadap domain model.Simulasi dilakukan dengan memvariasikan spesifikasi waveform yang merambat ke model domain. Verifikasibesarnya kecepatan aliran maksimum dari hasil model oleh Van Rijn (1987), Nurdjaman dan Ningsih (2003), danAdilantip (2012) menunjukkan kesesuaian yang baik dengan perbedaan nilai di bawah 5%. Sedangkan verifikasitinggi gelombang dan radiasi tegangan gelombang dengan perhitungan analitik menunjukkan perbandingan yangbaik dengan rata-rata perbedaan nilai 15%. Hasil penelitian menunjukkan bahwa kedalaman gerusan 0,955 mterbentuk pada akhir simulasi dengan input debit sungai saja. Bila ddebit sungai dikombinasikan dengan berbagaitinggi dan perioda gelombang, kedalaman gerusan meningkat sekitar 3 - 14%. Lokasi kedalaman gerusanbertepatan dengan lokasi kecepatan aliran maksimum pada ujung struktur groin sisi kiri.
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