Studi numerik evaluasi sudut divergensi (20) = 8 derajat dan (20) = 12 derajat terhadap karakteristik aliran fluida di dalam symetric flat- walled diffuser dengan aspect ration konstan

Faila, Rizka Nur (2015) Studi numerik evaluasi sudut divergensi (20) = 8 derajat dan (20) = 12 derajat terhadap karakteristik aliran fluida di dalam symetric flat- walled diffuser dengan aspect ration konstan. Undergraduate thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Diffuser merupakan salah satu konstruksi yang mampu mengendalikan perilaku fluida. Performa diffuser dapat ditunjukkan dengan nilai koefisen tekanan (Cp) fluida yang mengalir di dalamnya. Adverse pressure gradient (APG) menyebabkan boundary layer berkembang dengan cepat sehingga dapat mengakibatkan separasi aliran dan Cp menjadi rendah. Untuk menunda separasi perlu dievaluasi penelitian lebih lanjut tentang diffuser dengan modifikasi sudut bukaan untuk optimasi nilai koefisen tekanan (Cp) diffuser. Penelitian ini bertujuan untuk mengevaluasi karakteristik aliran fluida pada symmetric flat-walled diffuser dengan aspect ratio konstan dengan dua sudut divergensi (2θ1) = 8° dan 12°. Pada penelitian ini digunakan bilangan Reynolds 8.7 x 104 dan 12.9 x 104 berdasarkan tinggi dan kecepatan inlet diffuser. Test section penelitian terdiri dari 3 bagian yaitu symmetric diffuser, upstream channel, dan downstream channel. Symmetric diffuser memiliki panjang (L1) = 500 mm, upstream channel memiliki panjang (L2) = 500 mm, dan downstream channel memiliki panjang (L3) = 1000 mm. Test section secara keseluruhan memiliki lebar inlet span (b1) = 100 mm, lebar outlet span sudut 8° (b2) = 239.8 mm dan lebar outlet span sudut 12° (b3) = 312.5 mm serta tinggi inlet diffuser (W1) = 50 mm, tinggi outlet diffuser sudut 8° (W2) = 119.9 mm dan tinggi outlet diffuser sudut 12° (W3) = 155 mm. Penelitian ini menggunakan metode numerik dengan software Fluent 6.3.26 dengan turbulence model k-ω shear stress transport (SST). Hasil yang diperoleh dari penelitian menunjukkan bahwa tidak terjadi separasi aliran pada bidang midspan vertikal pada sudut bukaan diffuser (2θ1) = 8° dan 12°. Namun berdasarkan visualisasi vektor kecepatan, separasi aliran dapat diamati pada bidang midspan horizontal untuk sudut bukaan diffuser (2θ1) = 8° ditunjukkan terjadinya separasi pada daerah setelah inlet diffuser, yaitu pada x/L1 = 1,4 hingga x/L1 = 1,6, sedangkan untuk sudut bukaan diffuser (2θ1) = 12° ditunjukkan terjadinya separasi pada daerah sesaat setelah inlet diffuser, yaitu pada x/L1 = 1,2 hingga x/L1 = 1,4 pada ReW1 = 8,7 x 104 dan ReW1 = 12,9 x 104. Peningkatan bilangan Reynolds sebesar 48.3% tidak menunjukkan terjadinya penundaan separasi diakibatkan pengaruh adverse pressure gradient yang besar. ========================================================================================== Diffuser is one of the construction that is able to control the behavior of the fluid. Performance of diffuser can be indicated by the value of the pressure coefficient (Cp) fluid that flowing in it. Adverse pressure gradient (APG) causes boundary layer develops rapidly so that it causes separation and Cp becomes low. So that need to evaluating divergence angle of diffuser to delay the separation to get optimization Cp of diffuser. This study aimed to evaluate the characteristics of fluid flow in a symmetric flat-walled diffuser with a constant aspect ratio with two divergence angle (2θ1) = 8 ° and 12 °. In this study used the Reynolds number 8.7 x 104 and 12.9 x 104 based on the height and speed of the inlet diffuser. Test section consisted of three parts, namely symmetric diffuser, upstream channels, and downstream channels. The symmetric diffuser has a length (L1) = 500 mm, the upstream channel length (L2) = 500 mm, and the downstream channel has a length (L3) = 1000 mm. Overall test section inlet width span (b1) = 100 mm, the width of the outlet span angle of 8 ° (b2) = 239.8 mm and the width of the outlet angle of span 12 ° (b3) = 312.5 mm and height of the inlet diffuser (W1) = 50 mm, height outlet diffuser angle of 8 ° (W2) = 119.9 mm and height of the outlet diffuser angle of 12 ° (W3) = 155 mm. This study uses a numerical method with software Fluent 6.3.26 with k-ω turbulence model of shear stress transport (SST). The results of the study showed that there is no flow separation on the field at midspan vertical diffuser (2θ1) = 8 ° and 12 °. However, based on the velocity vector visualization, flow separation can be observed at midspan plane horizontal to diffuser (2θ1) = 8 ° indicated the occurrence of separation in the area after the inlet diffuser, ie at x / L1 = 1.4 and x / L1 = 1.6, while for the diffuser (2θ1) = 12 ° is shown the occurrence of separation in the area shortly after the inlet diffuser, are at x / L1 = 1.2 to x / L1 = 1.4 at ReW1 = 8.7 x 104 and ReW1 = 12 x 104. Increasing of the Reynolds number of 48.3% did not show a separation delay caused by adverse pressure gradient effect.

Item Type: Thesis (Undergraduate)
Additional Information: RSM 620.106 4 Fai s
Uncontrolled Keywords: adverse pressure gradient; aspect ratio; symmetric flatwalled diffuser
Subjects: T Technology > TJ Mechanical engineering and machinery
T Technology > TJ Mechanical engineering and machinery > TJ935 Pipe--Fluid dynamics.
Divisions: Faculty of Industrial Technology > Mechanical Engineering > (S1) Undergraduate Theses
Depositing User: - Taufiq Rahmanu
Date Deposited: 08 Oct 2018 03:04
Last Modified: 08 Oct 2018 03:04
URI: http://repository.its.ac.id/id/eprint/59752

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