Pemodelan Fisik 2-D untuk Mengukur Tingkat Efektivitas Perforated Skirt Breakwater pada Kategori Gelombang Panjang
DOI:
https://doi.org/10.5614/jts.2010.17.3.7Keywords:
Gelombang panjang, Perforated skirt breakwater, Hubungan bilangan tak-berdimensi, Koefisien transmisi.Abstract
Abstrak. Efektifitas pemecah gelombang dapat diukur dengan mengukur koefisien transmisi (KT). Semakin kecil koefisien transmisi maka semakin efektif pemecah gelombang ini. Pengujian model fisik dilakukan untuk mengetahui nilai koefisien transmisi dari Perforated Skirt Breakwater (PSB). Model PSB diuji dalam saluran gelombang 2-D di Laboratorium Gelombang Teknik Kelautan FTSL ITB, untuk mengetahui keefektifannya terhadap kategori gelombang panjang (periode prototipe, Tp = 7 detik). Penskalaan untuk model PSB menggunakan prinsip Keserupaan Froude dimana bilangan Froude model setara dengan bilangan Froude prototipe (Frm=Frp). Saluran gelombang dilengkapi dengan 5 sensor gelombang tipe tahanan listrik dan 8 saluran DAS (Data Acquisition System). Data tinggi gelombang (H) dan periode gelombang (T) diamati secara manual melalui pengamatan visual dan diperoleh melalui rekaman sensor gelombang (yang selanjutnya diproses menggunakan metode "zero mean up-crossing"). Tinggi gelombang datang di depan PSB (Hi) dan tinggi gelombang transmisi di belakang PSB (Ht) diukur dan diproses untuk mendapatkan koefisien transmisi (KT). Selanjutnya, hubungan antara KT dan bilangan tak-berdimensi, kedalaman sirip / tinggi gelombang datang (S/Hi) dianalisis dan nilai koefisien transmisi (KT) untuk berbagai kondisi lingkungan diperoleh.Abstract. The effectiveness of a breakwater can be measured by quantifying the transmission coefficient (KT). The smaller the coefficient, more effective the performance of the breakwater. A physical modeling on the proposed breakwater was conducted to identify the coefficient of Perforated Skirt Breakwater (PSB). The PSB model was tested in 2-D wave flume at Ocean Wave Research Laboratory FTSL ITB, to obtain the effectiveness of PSB for long-period waves (prototype periods, Tp= 7 second). The scaling of PSB models applies the principle of Froude Similarity, where the Froude number in the model equals to the Froude number in prototype (Frm=Frp). The wave flume is equipped with 5 resistance-type wave probes and 8-channels of DAS (Data Acquisition System). Wave heights (H) and wave periods (T) data were observed both manually by visual observation and from wave probes record (processed later with method of "zero mean up-crossing" technique). The incoming wave heights (Hi) and transmitted wave heights (Ht) - before and after PSB, respectively - were measured and processed to obtain the transmission coefficient (KT). The relationships between KT and non-dimensional variables (skirt draft / incident wave height, S/Hi) are analyzed and the calculated KT for varied environmental condition are obtained.
References
Ariyarathne, H.A.K.S., 2007, Efficiency Of Perforated Breakwater And Associated Energy Dissipation, Thesis. Civil Engineering of Texas A&M University.
Armono, H.D., Hall, K.R., 2002, Wave Transmission On Submerged Breakwaters Made Of Hollow Hemispherical Shape Artificial Reefs, Canadian Coastal Conference.
Bergmann, H., Kudella, M., Oumeraci, H., 1998, Wave loads and pressure distribution on permeable vertical walls. Copenhagen, Denmark: Proceedings International Conference Coastal Engineering (ICCE), ASCE, No. 26, 2 pp.
Bloxam, M., Maxted G., Murray J., 2003, Wave Energy Dissipating Wharf: Raffles Marina Breakwater, Singapore, Coasts & Ports Australasian Conference Paper No. 95.
Hagiwara, K., 1984, Analysis of Upright Structure for Wave Dissipation Using Integral Equation, Proc. 19th Conf. on Coastal Engineering A.S.C.E. pp. 2810-2826.
Jarlan, G.E., 1961, A Perforated Vertical Wall Breakwater. Dock Harbour Auth. XII 486 (1961), pp. 394-398.
Kondo, K., 1979, Analysis of Breakwaters Having Two Porous Walls, Proc. Coastal Structures '79 Alexandria, VA, pp. 962-977.
Quinn, A., 1972, Design and Construction of Ports and Marine Structures. New York: McGraw Hill.
Suh, K.D., Choi, J.C., Kim, B.H., Park, W.S., and Lee, K.S., 2001, Reflection of Irregular Waves From Perforated-Wall Caisson Breakwaters, Coastal Engineering 44, pp. 141-151.
