Permodelan Numerik Aliran Pada Pelimpah Bertangga Menggunakan Program OpenFOAM

Izzati, Afkarina (2021) Permodelan Numerik Aliran Pada Pelimpah Bertangga Menggunakan Program OpenFOAM. Masters thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Aliran pada pelimpah berkemiringan tinggi memiliki kecepatan dan energi yang besar. Sehingga berpotensi menimbulkan kavitasi dan gerusan dasar sungai. Stepped spillway merupakan alternatif konstruksi yang dikembangkan untuk mengurangi kecepatan aliran dan meredam energi secara bertahap sepanjang pelimpah. Dewasa ini, permodelan eksperimen maupun numerik dengan berbagai geometri anak tangga telah banyak dilakukan untuk mengetahui pengaruhnya terhadap peredaman energi. Model numerik memiliki kelebihan dibandingkan model eksperimen dari segi waktu pelaksanaan, dan biaya penelitian. Hasil model numerik dengan berbagai program dari penelitian sebelumnya menunjukkan performa yang baik. OpenFOAM merupakan salah satu program open source yang dapat memodelkan kasus multiphase. Oleh sebab itu, OpenFOAM dipilih untuk memodelkan aliran pada pelimpah bertangga. Data yang dibutuhkan dalam penelitian ini yaitu data dari permodelan eksperimen sebelumnya berupa data tangga, data pelimpah, data aliran, dan parameter hidraulik. Data tangga meliputi jumlah anak tangga (N), tinggi anak tangga (h) dan lebar anak tangga (l). Data pelimpah meliputi lebar (B), panjang puncak (Lcrest), radius upstream puncak (R1), radius downstream puncak (R2), nilai kekasaran (ks) dan kemiringan pelimpah (θ). Data aliran yaitu debit (Q). Seluruh data tersebut digunakan sebagai input dalam permodelan numerik. Hasil model tersebut divalidasi dengan parameter hidraulik hasil model eksperimen. Dalam penelitian ini, terdapat lima simulasi dengan berbagai debit. Hasil simulasi meliputi profil muka air (d), kecepatan aliran (v), dan peredaman energi (ΔE). Performa model numerik, sensitivitas model, dan peredaman energi dihitung dari hasil simulasi. Hasil penelitian menyatakan bahwa model numerik OpenFOAM memiliki performa yang baik. Rentang nilai RMSE ditinjau dari profil muka air antara 0,006–0,013, ditinjau dari kecepatan aliran antara 0,086–0,217, dan ditinjau dari peredaman energi antara 0,036–0,103. Ukuran mesh merupakan parameter yang paling berpengaruh terhadap hasil model. Aliran pada pelimpah bertangga hasil model numerik dengan debit antara Q=0,179 m3/s atau dc/h=1,50 – Q=0,083 m3/s atau dc/h=0,90 menghasilkan peredaman energi antara 51% – 68%. ================================================================================================================= The flow over steep slope spillways has high velocity and flow energy. It has potential to cause cavitation and scour the riverbed. Stepped spillway is an alternative construction developed to reduce flow velocity and reduce flow energy gradually along the spillway. Recently, experimental and numerical modeling by various geometric of steps have been developed to get the effect of energy dissipation. Numerical modeling has strength over experimental modeling in terms of time and research cost. The results of numerical modeling using various program of the previous research indicated that the models have a good performance. OpenFOAM is one of the open source program that able to modeling the multiphase case. Therefore, OpenFOAM program was choosen to modeling the flow over stepped spillway for this research. The data used in this research obtained from previous eksperimental research, such as geometri of spillway data, flow data, parameter hydraulic for validation. Steps data consist of the number of steps (N), the height of the steps (h) and the width of the steps (l). Spillway data consist of width (B), crest length (Lcrest), crest upstream radius (R1), crest downstream radius (R2), roughness value (ks) and slope of spillway (θ). Flow data is discharge (Q). All of that data was used as input in numerical modeling. The results of this numerical model were validated using hydraulic parameter of the previous experimental laboratory model. This study performed five simulation using various discharge. Hydraulic parameter such as water level profile (d), water velocity (v), and energy dissipation (ΔE) are obtained from simulation. Numerical modeling performance, model sensitivity, and energy dissipation are calculated from simulation result. The results indicated that numerical modeling using OpenFOAM have a good performance. The range of RMSE In term of water level profile is 0,006–0,013, In term of flow velocity is 0,086–0,217, and in term of energy dissipation is 0,036–0,103. The size of mesh is the most influential parameter to the model result. The flow over stepped spillway of numerical modeling by discharge Q=0,179 m3/s or dc/h=1,50 – Q=0,083 m3/s or dc/h=0,90 generates energy dissipation 51% – 68%.

Item Type: Thesis (Masters)
Uncontrolled Keywords: Pelimpah bertangga, peredaman energi, permodelan numerik OpenFOAM, performa model, stepped spillway, energy dissipation, numerical modeling OpenFOAM, model performance
Subjects: T Technology > TC Hydraulic engineering. Ocean engineering > TC555 Spillways. Energy dissipation. Hydraulic jump.
Divisions: Faculty of Civil, Planning, and Geo Engineering (CIVPLAN) > Civil Engineering > 22101-(S2) Master Thesis
Depositing User: Afkarina Izzati
Date Deposited: 06 Mar 2021 05:27
Last Modified: 06 Mar 2021 05:27
URI: https://repository.its.ac.id/id/eprint/83652

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