Studi Numerik Pengaruh Area Ratio dan Bilangan Reynolds terhadap Karakteristik Aliran Turbulen pada Pipa Sudden Contraction dengan Rounded Inlet Edge

Mazlani, Muhammad Farhan (2026) Studi Numerik Pengaruh Area Ratio dan Bilangan Reynolds terhadap Karakteristik Aliran Turbulen pada Pipa Sudden Contraction dengan Rounded Inlet Edge. Other thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Dalam sistem perpipaan, komponen fitting berperan menghubungkan diameter pipa yang berbeda, di mana penyempitan mendadak dan kenaikan kecepatan aliran yang tajam menyebabkan pressure drop, flow separation, dan vortex yang berkontribusi besar terhadap kehilangan energi. Penelitian ini bertujuan mengkaji pengaruh area ratio dan bilangan Reynolds terhadap karakteristik aliran pada pipa sudden contraction dengan rounded inlet edge, menggunakan simulasi numerik CFD 3D melalui software ANSYS 2020 R2. Parameter utama yang ditinjau meliputi pressure drop, coefficient of losses (KL), coefficient of pressure (Cp), profil kecepatan, distribusi perubahan kecepatan, dan distribusi tekanan statis di sepanjang pipa.
Penelitian ini merumuskan tiga permasalahan utama. Pertama, variasi area ratio pada pipa sudden contraction dengan rounded inlet edge diduga berpengaruh signifikan terhadap karakteristik aliran, profil kecepatan, dan distribusi kecepatan pada kondisi turbulen. Kedua, variasi area ratio diduga menyebabkan perbedaan pada kontur tekanan, pressure drop, KL, dan Cp, di mana area ratio yang lebih besar diperkirakan menghasilkan pressure drop dan KL yang lebih kecil, Cp yang lebih stabil mendekati nol, serta memperpendek zona separasi. Ketiga, perbedaan geometri inlet antara rounded inlet edge dan baseline (sudut 90°) diduga menghasilkan perbedaan signifikan pada KL dan Cp, di mana rounded inlet edge diperkirakan lebih efektif mereduksi kerugian energi dibandingkan geometri baseline.
Hasil simulasi menunjukkan nilai loss coefficient (KL) berbanding terbalik secara konsisten dengan area ratio (AR) dan bilangan Reynolds. AR 0,694 pada Re 8 × 104 menghasilkan KL terkecil sebesar 0,19, sedangkan AR 0,174 pada Re 4 × 104 menghasilkan KL terbesar sebesar 0,36. Tren ini sejalan dengan pressure drop, yaitu terkecil ≈ 11.752,70 Pa dan terbesar ≈ 87.801,98 Pa pada kondisi yang sama. Rounded inlet edge (r/d₂ = 0,075) terbukti efektif meredam separasi aliran dan vena contracta, dengan efektivitas optimal pada AR besar. Coefficient of pressure (Cp) berdivergensi tajam di titik kontraksi, dengan AR 0,174 anjlok hingga Cp ≈ -75. Sebaliknya, AR 0,694 mengalami penurunan Cp hingga ≈ -2,2 hingga -2,4. Perbandingan geometri baseline (sudut 90°) dan rounded inlet edge pada AR 0,250 Re 8 × 104 menunjukkan modifikasi rounded inlet edge menurunkan KL hingga 52,5% (dari 0,507 menjadi 0,241). Secara keseluruhan, AR 0,694 pada Re 8 × 104 menghasilkan performa hidrodinamik paling efisien dari seluruh variasi yang diuji.
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In piping systems, fittings play an essential role in connecting pipes of different diameters. However, sudden contractions and the resulting sharp increase in flow velocity induce pressure drop, flow separation, and vortex formation, which significantly contribute to energy losses. This study aims to investigate the effects of area ratio and Reynolds number on the flow characteristics of a sudden contraction pipe with a rounded inlet edge using three-dimensional Computational Fluid Dynamics (CFD) simulations performed in ANSYS 2020 R2. The primary parameters evaluated include pressure drop, loss coefficient (KL), pressure coefficient (Cp), velocity profile, velocity distribution, and static pressure distribution along the pipe.
This research addresses three main hypotheses. First, variations in the area ratio of a sudden contraction pipe with a rounded inlet edge are expected to significantly influence flow characteristics, velocity profiles, and velocity distribution under turbulent flow conditions. Second, changes in the area ratio are anticipated to affect pressure contours, pressure drop, loss coefficient (KL), and pressure coefficient (Cp), where larger area ratios are expected to produce lower pressure drops and KL values, more stable Cp values approaching zero, and shorter flow separation regions. Third, differences in inlet geometry between the rounded inlet edge and the baseline configuration (90° sharp edged contraction) are expected to result in significant differences in KL and Cp, with the rounded inlet edge providing greater effectiveness in reducing hydraulic energy losses than the baseline geometry.
The simulation results demonstrate that the loss coefficient (KL) is consistently inversely proportional to both the area ratio (AR) and Reynolds number. The lowest KL value of 0.19 was obtained for AR = 0.694 at Re = 8 × 104, whereas the highest KL value of 0.36 occurred for AR = 0.174 at Re = 4 × 104. A similar trend was observed for the pressure drop, ranging from approximately 11,752.70 Pa to 87,801.98 Pa under the corresponding operating conditions. The rounded inlet edge (r/d₂ = 0.075) was shown to effectively suppress flow separation and reduce the vena contracta phenomenon, with the greatest effectiveness observed at higher area ratios. The pressure coefficient (Cp) exhibited a sharp divergence at the contraction region, where AR = 0.174 reached a minimum value of approximately −75, while AR = 0.694 decreased only to approximately −2,2 to −2,4. A comparison between the baseline geometry (90° sharp-edged contraction) and the rounded inlet edge at AR = 0.25 and Re = 8 × 104 revealed that the rounded inlet edge reduced the loss coefficient by 52.5%, from 0.507 to 0.241. Overall, the configuration with AR = 0.694 at Re = 8 × 104 exhibited the most efficient hydrodynamic performance among all tested variations.

Item Type:	Thesis (Other)
Uncontrolled Keywords:	Sudden Contraction, Rounded Inlet Edge, Coefficient of Losses
Subjects:	T Technology > T Technology (General) > T57.62 Simulation T Technology > TJ Mechanical engineering and machinery > TJ935 Pipe--Fluid dynamics. Tubes--Fluid dynamics
Divisions:	Faculty of Industrial Technology and Systems Engineering (INDSYS) > Mechanical Engineering > 21201-(S1) Undergraduate Thesis
Depositing User:	Muhammad Farhan Mazlani
Date Deposited:	31 Jul 2026 07:49
Last Modified:	31 Jul 2026 07:49
URI:	http://repository.its.ac.id/id/eprint/140617

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