Studi Eksperimen dan Numerik Karakteristik Sseparation Bubble pada Aliran Dua Dimensi Melintasi Thick Plate-Rounded Leading Edge (r/t = 0,2) dengan Pengaruh Reynolds Number (Ret = 5,08×10^4 dan Ret = 8,46×10^4) dan Panjang Aksial (c/t = 6,5 dan c/t = 10)

Rahayu, Cholifatus E. (2020) Studi Eksperimen dan Numerik Karakteristik Sseparation Bubble pada Aliran Dua Dimensi Melintasi Thick Plate-Rounded Leading Edge (r/t = 0,2) dengan Pengaruh Reynolds Number (Ret = 5,08×10^4 dan Ret = 8,46×10^4) dan Panjang Aksial (c/t = 6,5 dan c/t = 10). Undergraduate thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Berbagai penelitian untuk meningkatkan efisiensi penggunaan bahan bakar pada kendaraan terus dilakukan. Salah satu faktor konsumsi bahan bakar kendaraan adalah pada sisi desain aerodinamika kendaraan itu sendiri yang menentukan besar kecilnya drag force. Beberapa cara dalam menurunkan drag force diantaranya dengan mekanisme flow control yang dapat berupa active dan passive flow control yang membantu mencegah separasi aliran. Fenomena terbentuknya bubble separation dapat dimanfaatkan untuk menunda terjadinya separasi aliran permanen di daerah buritan. Penambahan panjang bidang tumpu aliran dapat juga dimaknai sebagai upaya memperbesar jarak antara dua titik potensi separasi depan dan belakang diduga dapat mempermudah proses reattachment aliran yang terseparasi setelah leading edge. Penelitian mengenai dugaan tersebut dilakukan secara analisa 2 dimensi melalui eksperimen dengan wind tunnel dan numerik dengan Ansys (Fluent) 19.1 dengan membandingkan model turbulen k-Ω SST dengan Transition k-kl-ω untuk mengetahui model yang paling tepat dalam menganalisa kasus ini. Benda uji yang digunakan berupa thick plate–rounded leading edge (r/t = 0,2) serta variasi panjang aksial c/t = 6,5 dan c/t = 10 dengan pengaruh Reynolds number Ret = 5,08×104 dan Ret = 8,46×104. Penelitian ini dilakukan dengan menganalisa karakteristik separation bubble (tebal, panjang dan sudut), koefisien tekanan, profil kecepatan, turbulent kinetic energy dan shape factor serta titik reattachment dan massive separation di daerah buritan. Hasil yang didapatkan dalam penelitian ini adalah variasi Reynolds number dan panjang bidang tumpu aliran dapat mempengaruhi karakteristik separation bubble yang terbentuk. Sedangkan dengan memperpanjang bidang tumpu dan memperbesar Reynolds number akan mempercepat terjadinya reattachment dengan membentuk separation bubble yang lebih pendek. Dengan demikian aliran dapat lebih cepat bertransisi dari laminar ke turbulen yang mana akan menambah momentum aliran untuk melawan adverse pressure, yang kemudian dapat menunda separasi massif di buritan. Secara umum variasi panjang bidang tumpu aliran (c/t = 6,5 dan c/t = 10) memberikan pengaruh yang lebih signifikan dalam penundaan separasi massif di daerah buritan daripada variasi bilangan Reynolds (Ret = 5,08×104 dan Ret = 8,46×104). Kata kunci: boundary layer transition, separation bubble, massive separation ================================================================================================================== Abstract Various studies to improve the efficiency of fuel consumption in vehicles continue to be done. One of the factors of vehicle fuel consumption is on the aerodynamic design of the vehicle itself which determines the magnitude of the drag force. Some ways to reduce drag force include flow control mechanisms such as active and passive flow control. which helps to prevent flow separation. The phenomenon of the formation of bubble separation can be utilized to delay the occurrence of permanent flow separation on the downstream. The addition of the length of the fulcrum field can also be interpreted as an effort to enlarge the distance between the two potential points of the front and back separations allegedly can facilitate the process of reattachment of the after the leading edge. This research was carried out in 2-dimensional analytics through experiments with wind tunnels and numerically with Ansys (Fluent) 18.1. The specimens used were thick plate - rounded leading-edge r / t = 0.2 and axial length c / t = 6.5 and c / t = 10. This research was conducted by analysing the characteristics of separation bubble (thickness, length, and angle), pressure coefficient, velocity profile, turbulent kinetic energy, and shape factor also reattachment point and massive separation at downstream. The results obtained are the variation of the Reynolds number and axial length affect the characteristics of the separation bubble. By elongation of the axial length and increasement od Reynolds number will accelerate the reattachment by forming shorter separation bubble. This phenomenon causes the acceleration of laminar to turbulent boundary layer transition and increases the flow momentum to counter the adverse pressure, which is the massive separation at the downstream will be delayed. The variation of axial length has more significant effect on the delay of massive separation at the downstream than the variation of Reynolds number. Keywords: boundary layer transition, separation bubble, massive separation

Item Type: Thesis (Undergraduate)
Uncontrolled Keywords: boundary layer transition, separation bubble, massive separation
Subjects: T Technology > TJ Mechanical engineering and machinery > TJ820 Wind power
T Technology > TJ Mechanical engineering and machinery > TJ935 Pipe--Fluid dynamics.
Divisions: Faculty of Industrial Technology > Mechanical Engineering > 21201-(S1) Undergraduate Thesis
Depositing User: Cholifatus Eka Rahayu
Date Deposited: 23 Aug 2020 15:14
Last Modified: 23 Aug 2020 15:14
URI: http://repository.its.ac.id/id/eprint/79405

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