Kajian Alternatif Desain Bangunan Pelimpah Tipe Gergaji pada Bendungan Bener, Purworejo.

Rinantya, Indy Hemawandari (2026) Kajian Alternatif Desain Bangunan Pelimpah Tipe Gergaji pada Bendungan Bener, Purworejo. Other thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Pelimpah eksisting tipe Ogee pada Bendungan Bener memiliki margin keamanan (safety margin) yang terbatas saat menampung debit banjir ekstrem QPMF outflow sebesar 2649.55 m³/dt. Kajian ini dilakukan sebagai upaya preventif guna memitigasi risiko peluapan (overtopping) pada bendungan tipe CFRD tersebut. Sebagai solusi, direncanakan desain alternatif berupa pelimpah tipe gergaji (labyrinth weir) berbentuk trapesium dengan variasi sudut kemiringan dinding 10°, 12°, dan 15°. Penelitian ini mengombinasikan perhitungan hidraulika di Microsoft Excel dengan validasi simulasi 3D berbasis Computational Fluid Dynamics (CFD) menggunakan software ANSYS Fluent. Kesimpulan dari kajian alternatif ini menunjukkan bahwa pelimpah gergaji trapesium sudut 10° memberikan kinerja paling optimal dengan meningkatkan panjang mercu efektif secara signifikan menjadi 235,25 m menggunakan konfigurasi 5 pias gigi pada lebar saluran tetap 90 m. Melalui penelusuran banjir waduk (flood routing), konfigurasi sudut 10° mampu menurunkan tinggi tekan air secara drastis sehingga meningkatkan jarak bebas (freeboard) bendungan dari 0.94 m menjadi 2.52 m pada kondisi banjir QPMF. Pada bagian transisi dan saluran peluncur, kondisi profil hidraulis aliran terbukti stabil pada kondisi superkritis serta aman dari risiko aliran getar (slug flow). Pada area hilir, struktur peredam energi tipe USBR II menghasilkan peredaman energi yang efektif, di mana menghasilkan loncatan hidraulis kuat yang stabil dengan efisiensi reduksi energi 80.04% menjadi 81.22%. Hasil visualisasi 3D dari ANSYS Fluent dan kontur water volume fraction secara akurat mengonfirmasi serta memvalidasi kesesuaian profil muka air hulu-hilir dari hasil perhitungan manual.
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The existing Ogee-type spillway at the Bener Dam had a limited safety margin when accommodating an extreme flood discharge with a QPMF outflow of 2649.55 m³/s. This study was conducted as a preventive measure to mitigate the risk of reservoir overtopping on the CFRD dam structure. As a solution, a labyrinth weir spillway with a trapezoidal geometry was proposed as an alternative design, evaluated under wall inclination angle variations of 10°, 12°, and 15°. This study combined manual hydraulic calculations in Microsoft Excel with 3D simulation validation based on Computational Fluid Dynamics (CFD) using ANSYS Fluent software. The conclusion of this alternative study indicated that the trapezoidal labyrinth spillway with a 10° angle yielded the superior performance by successfully expanding the effective crest length to 235.25 m using a 5-cycle configuration within a fixed channel width of 90 m. Reservoir flood routing simulation demonstrated that the 10° alternative significantly reduced the hydraulic head, thereby increasing the freeboard from 0.94 m to 2.52 m under the extreme QPMF flood condition. Furthermore, hydraulic profile analysis along the spillway chute confirmed that the flow remained supercritical and completely safe from the risk of pulsating or slug flow. In the downstream area, the USBR Type II energy dissipation structure effectively reduced the flow energy, producing a strong and stable hydraulic jump with an energy dissipation efficiency ranging from 80.04% to 81.22%. The three-dimensional visualizations from ANSYS Fluent and the water volume fraction contours accurately confirmed and validated the agreement between the upstream and downstream water surface profiles obtained from the manual calculations.

Item Type:	Thesis (Other)
Uncontrolled Keywords:	ANSYS, Bendungan Bener, Computational Fluid Dynamics, Pelimpah ogee Pelimpah tipe gergaji., ANSYS, Bener Dam, Computational Fluid Dynamics, Labyrinth weir, Ogee spillway
Subjects:	T Technology > TC Hydraulic engineering. Ocean engineering > TC167 Dams, reservoirs T Technology > TC Hydraulic engineering. Ocean engineering > TC555 Spillways. Energy dissipation. Hydraulic jump.
Divisions:	Faculty of Vocational > 22301-Civil Infrastructure Engineering (D4)
Depositing User:	Indy Hemawandari Rinantya
Date Deposited:	04 Aug 2026 07:07
Last Modified:	04 Aug 2026 07:07
URI:	http://repository.its.ac.id/id/eprint/143222

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