Kajian Alternatif Desain Mercu Dan Peluncur Bertangga Pada Spillway Bendungan Cijurey Menurut Kriteria Hidraulis Berbasis Computational Fluid Dynamic (CFD)

Zaky, Muhamad Wildan (2026) Kajian Alternatif Desain Mercu Dan Peluncur Bertangga Pada Spillway Bendungan Cijurey Menurut Kriteria Hidraulis Berbasis Computational Fluid Dynamic (CFD). Diploma thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Ketidakpastian hidrologi akibat perubahan iklim menuntut evaluasi dan optimalisasi kapasitas infrastruktur pengendali banjir, salah satunya pada Bendungan Cijurey, Kabupaten Bogor. Desain bangunan pelimpah (spillway) eksisting yang menggunakan mercu ogee dan peluncur bertangga terindikasi memicu fenomena loncatan aliran (free-jet) berdasarkan pra-pemodelan numerik, yang berisiko mengancam ketahanan struktur. Oleh karena itu, penelitian ini bertujuan untuk mengevaluasi kinerja desain eksisting serta merumuskan alternatif desain yang lebih optimal menggunakan mercu labirin (labyrinth weir) dan modifikasi peluncur. Metode yang digunakan meliputi analisis hidrologi historis, penelusuran banjir (flood routing), perhitungan hidrolika analitik, evaluasi stabilitas struktur, serta pemodelan numerik komparatif berbasis Computational Fluid Dynamics (CFD) tiga dimensi untuk memvalidasi profil aliran pada kondisi ekstrem tanpa harus menggunakan uji model fisik. Hasil analisis hidrologi menetapkan debit banjir rancangan sebesar 459,3 m³/s (Kala Ulang 1000 Tahun) dan 1334,7 m³/s (Probable Maximum Flood/PMF). Pada tahap penelusuran banjir, desain mercu labirin terbukti memberikan margin tinggi jagaan (freeboard) yang jauh lebih aman (1,82 m) dibandingkan desain ogee eksisting (0,45 m), meskipun tingkat reduksi puncaknya sedikit lebih rendah (11,27% berbanding 14,35%). Ditinjau dari kriteria hidrolis dan disipasi energi, desain Alternatif 1 (mercu labirin dengan peluncur bertangga modifikasi tinggi 1,8 m) ditetapkan sebagai desain paling optimal. Desain ini mampu menstabilkan regim aliran menjadi skimming flow penuh, mengeliminasi bahaya free-jet, menghindari potensi kavitasi tanpa memerlukan aerator tambahan, serta menyisakan tinggi energi di hilir sebesar 30,249 m. Validasi CFD mengonfirmasi tidak adanya risiko overtopping akibat aliran getar. Lebih lanjut, analisis mekanika teknik mengonfirmasi bahwa desain modifikasi terpilih aman dan stabil terhadap bahaya guling, geser, eksentrisitas, maupun penurunan daya dukung tanah pada berbagai skenario pembebanan (Normal, gempa OBE, dan gempa MDE).
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Hydrological uncertainty due to climate change demands the evaluation and optimization of flood control infrastructure capacity, one of which is the Cijurey Dam in Bogor Regency. The existing spillway design using an ogee crest and stepped chute is indicated to trigger the free-jet phenomenon based on preliminary numerical modeling, which poses a risk to the structural integrity. Therefore, this study aims to evaluate the performance of the existing design and formulate a more optimal design alternative using a labyrinth weir and modified chute. The methods used include historical hydrological analysis, flood routing, analytical hydraulic calculations, structural stability evaluation, and comparative numerical modeling based on three-dimensional Computational Fluid Dynamics (CFD) to validate flow profiles under extreme conditions without the need for physical model testing. The results of the hydrological analysis determined a design flood discharge of 459.3 m³/s (1000-Year Recurrence Interval) and 1334.7 m³/s (Probable Maximum Flood/PMF). At the flood tracing stage, the labyrinth weir design proved to provide a much safer freeboard margin (1.82 m) compared to the existing ogee design (0.45 m), although the peak reduction rate was slightly lower (11.27% compared to 14.35%). From the perspective of hydraulic criteria and energy dissipation, Alternative Design 1 (labyrinth weir with a modified stepped spillway height of 1.8 m) was determined to be the most optimal design. This design is capable of stabilizing the flow regime to a full skimming flow, eliminating the risk of free-jet, avoiding potential cavitation without requiring additional aerators, and leaving a downstream energy height of 30.249 m. CFD validation confirms the absence of overtopping risk due to vibrational flow. Furthermore, the engineering mechanics analysis confirms that the selected modified design is safe and stable against rolling, sliding, eccentricity, and soil bearing capacity reduction under various loading scenarios (Normal, OBE earthquake, and MDE earthquake).

Item Type:	Thesis (Diploma)
Uncontrolled Keywords:	Pelimpah Labirin, Pelimpah Bertangga, CFD, Hidrolika, Stabilitas Guling, Stabilitas Geser
Subjects:	T Technology > TA Engineering (General). Civil engineering (General) > TA357 Computational fluid dynamics. Fluid Mechanics T Technology > TC Hydraulic engineering. Ocean engineering > TC424 Water levels T Technology > TC Hydraulic engineering. Ocean engineering > TC555 Spillways. Energy dissipation. Hydraulic jump.
Divisions:	Faculty of Vocational > 22301-Civil Infrastructure Engineering (D4)
Depositing User:	Muhamad Wildan Zaky
Date Deposited:	04 Aug 2026 08:07
Last Modified:	04 Aug 2026 08:07
URI:	http://repository.its.ac.id/id/eprint/139675

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