Kajian Hidraulika Pelimpah Gergaji di Bendung Gandong Kerik, Kabupaten Magetan

Lativa, Dika Khulashotul (2023) Kajian Hidraulika Pelimpah Gergaji di Bendung Gandong Kerik, Kabupaten Magetan. Diploma thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Mercu karet di Bendung Gandong Kerik sobek. Oleh karena itu, dilakukan penggantian bendung karet menjadi bendung tetap. Perencanaan bendung tetap menerapkan tipe pelimpah gergaji. Perubahan tipe pelimpah menyebabkan perubahan aspek hidraulis. Maka kajian ini dilakukan untuk mengetahui pengaruh desain pelimpah gergaji terhadap aspek hidraulika aliran agar aman untuk hulu-hilir, memenuhi kebutuhan irigasi, dan memperkecil pembongkaran konstruksi eksisting. Perencanaan pelimpah gergaji didasarkan pada Perencanaan Hidraulik Pelimpah Gergaji 2004. Tinggi muka air (H) dan mercu (P) masing-masing direncanakan 0.75m dan 1.2m agar memenuhi syarat 0≤H/P≤0.65. Pelipatan panjang pelimpah lg/b adalah 2.08 sehingga panjang pelimpah menjadi 62.5m. Konstruksi hilir mempertahankan lantai transisi, terjunan, dan kolam olak. Fr di hilir terjunan adalah 4.96. Pola loncatan hilir adalah y2'<y2 sehingga dipasang rip rap dengan diameter 25cm dan ketebalan 100cm untuk mengurangi erosi. Dimensi Kolam Olak USBR Tipe III rencana sama dengan dimensi eksisting sehingga tidak memerlukan pembangunan baru. Analisis backwater menunjukkan panjang aliran balik 248.9m sehingga tidak mempengaruhi Bendung Jejeruk yang berjarak 21km. Video hasil simulasi aliran dengan ANSYS-Fluent menggambarkan olakan akibat perubahan geometri pelimpah (penyempitan), terjunan melalui pelimpah, serta loncatan hidraulik di kolam olak. Kontur water volume fraction mengonfirmasi hasil analisis profil muka air yang melalui gigi depan dan belakang pelimpah gergaji dari perhitungan manual. Kontur kecepatan menunjukkan kecepatan tinggi di aliran dari pelimpah ke lantai transisi. Kontur eddy viscosity menunjukkan turbulensi tinggi terjadi di loncatan hidraulik. Perhitungan manual maupun ANSYS-Fluent menunjukkan tidak adanya luapan aliran yang melebihi tanggul eksisting.
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The rubber material at the Gandong Kerik Weir was torn. Therefore, the rubber will be replaced with a fixed weir. The fixed weir applies the labyrinth weir. Changes in the weir type cause changes in the hydraulic aspect. Accordingly, this study is conducted to determine the effect of the labyrinth weir design on the hydraulic aspects of the flow so that it is safe for upstream and downstream, fulfilling irrigation needs, and minimizing demolition of existing construction. The design of the labyrinth weir is based on the Labyrinth Weir Hydraulic Planning 2004. The water level (H) and crest (P) are planned to be 0.75m and 1.2m respectively to meet the requirements of 0≤H/P≤0.65. The multiplication of the weir length (lg/b) is 2.08 hence the overflow length becomes 62.5m. The downstream construction preserved the transition floors, falls, and stilling basin. The Froude Number downstream is 4.96. The downstream jump pattern is y2'<y2. Consequently, a rip rap with a diameter of 25cm and a thickness of 100cm is installed to reduce erosion. The dimension of the planned USBR Type III Stilling Basin is the same as the existing dimension so no new construction is required. Backwater analysis shows a backflow length of 248.9m. Therefore, it does not affect the Jejeruk Dam which is 21km away. Video of flow simulation results using ANSYS-Fluent represents the turbulence due to changes in the geometry of the weir (narrowing), falls through the weir, and hydraulic jumps on the stilling basin. The water volume fraction contour confirms the result of manual calculation for water profile analysis through the front and behind labyrinth weir. The velocity contour shows the high velocity in the flow from the crest to the transitional floor. The eddy viscosity contour indicates high turbulence occurring in the hydraulic jumps. Manual calculations and ANSYS-Fluent analysis show that no overflow exceeds the existing embankment.

Item Type:	Thesis (Diploma)
Uncontrolled Keywords:	ANSYS-Fluent, bendung, loncatan hidraulik, pelimpah gergaji, profil muka air, hydraulic jump, labyrinth weir, water surface profile, weir
Subjects:	T Technology > TC Hydraulic engineering. Ocean engineering > TC555 Spillways. Energy dissipation. Hydraulic jump.
Divisions:	Faculty of Vocational > Civil Infrastructure Engineering (D4)
Depositing User:	Dika Khulashotul Lativa
Date Deposited:	16 Nov 2023 01:57
Last Modified:	16 Nov 2023 01:57
URI:	http://repository.its.ac.id/id/eprint/103131

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