KADIR, Abdul and Istadi, Istadi and Subagio, Agus and Iskendar, Iskendar (2024) KONSEP PEMBATASAN PUTARAN PROPELLER KAPAL MINI LIQUIFED NATURAL GAS (LNG) TIPE LANDING CRAFT TANK (LCT): MEMINIMALISASI EFEK SEDIMENTASI PADA EKOSISTEM PERAIRAN. Doctoral thesis, UNIVERSITAS DIPONEGORO.

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Abstract

Aktifitas pelayaran berpotensi menimbulkan pencemaran lingkungan dan merusak ekosistem perairan. Putaran propeller kapal menghasilkan semburan air yang dapat menimbulkan erosi pada dasar perairan dan memicu terjadinya sedimentasi. Partikel sedimen melayang akan mengendap dan menutupi areal dasar perairan yang pada kadar tertentu dapat merusak habitat biota di sekitarnya.
Penelitian ini menganalisa karakteristik kecepatan aliran air dari putaran propeller kapal Mini LNG Tipe LCT dengan diameter (Dp) 1,5 meter. Kecepatan aliran air ditentukan melalui pendekatan imperis, simulasi numerik dan percobaan model di laboratorium hidrodinamika. Kecepatan diukur pada empat rasio kedalaman perairan yaitu y/Dp=0.5, 1.0, 1.5 dan 2.0. Propeller diputar dalam empat variasi rpm masing-masing 75, 120, 230 dan 360 pada tiap rasio kedalaman. Hasil analisa yang dilakukan menunjukkan bahwa tingkat erosi dan sedimen yang terjadi berbanding lurus dengan tingkat putaran propeller, jarak propeller terhadap dasar perairan dan ukuran partikel dasar perairan. Laju sedimentasi tertinggi sebesar 78,5 mg cm-2 d-1 terjadi pada putaran propeller 360 rpm dengan rasio kedalaman y/Dp=0,5. Berdasarkan laju sedimentasi, maka konsep operasional kapal Mini LNG tipe LCT yang ramah lingkungan direkomendasikan: (a). Pada rasio kedalaman y/Dp = 0,5 atau kedalaman perairan kurang 3,25 meter, putaran propeller maksimal 120 rpm. (b). Pada rasio kedalaman 0,5 < y/Dp = 1,0 atau kedalaman perairan antara 3,25 – 4 meter, putaran propeller maksimal 230 rpm. (c). Pada rasio kedalaman 1,0 < y/Dp = 1,5, atau kedalaman perairan antara 4 – 4,75 meter, putaran propeller maksimal 360 rpm. (d). Pada rasio kedalaman y/Dp > 1,5, atau kedalaman perairan lebih dari 4,75 meter, putaran propeller disesuaikan kebutuhan.

Shipping activities have the potential to cause environmental pollution and damage aquatic ecosystems. The rotation of the ship's propeller produces water sprays that can cause erosion on the bottom of the waters and trigger sedimentation. Floating sediment particles will settle and cover the bottom area of the waters, which can damage the habitat of the surrounding biota at certain levels. This study analyzes the water flow velocity characteristics from the propeller's rotation of the LCT Type Mini LNG ship with a diameter (Dp) of 1.5 meters. The water flow velocity is determined through an imperis approach, numerical simulation and model experiments in a hydrodynamics laboratory. The speed is measured at four water depth ratios, namely y/Dp=0.5, 1.0, 1.5 and 2.0. The propeller is rotated in four rpm variations of 75, 120, 230 and 360 at each depth ratio. The analysis results show that the level of erosion and sediment that occurs is directly proportional to the propeller rotation rate, the distance of the propeller to the bottom of the water and the size of the bottom particles. The highest sedimentation rate of 78.5 mg cm-2 d-1 occurred at a propeller rotation of 360 rpm with a depth ratio of y/Dp=0.5. Based on the sedimentation rate, the operational concept of an environmentally friendly LCT type Mini LNG ship is recommended: (a). At a depth ratio of y/Dp = 0.5 or a water depth of less than 3.25 meters, the maximum propeller rotation is 120 rpm. (b). At a depth ratio of 0.5 < y/Dp = 1.0 or a water depth between 3.25 – 4 meters, the maximum propeller rotation is 230 rpm. (c). At a depth ratio of 1.0 < y/Dp = 1.5, or a water depth between 4 – 4.75 meters, the maximum propeller rotation is 360 rpm. (d). The propeller rotation is adjusted at a depth ratio of y/Dp > 1.5 or a water depth of more than 4.75 meters.

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