Studi eksperimen karakteristik aliran melintasi silinder sirkular yang diberi pengganggu yang berbentuk prisma segitiga sama sisi dan prisma segiempat (studi kasus untuk S/D = 0,6-0,85)

Sudahra, - (2015) Studi eksperimen karakteristik aliran melintasi silinder sirkular yang diberi pengganggu yang berbentuk prisma segitiga sama sisi dan prisma segiempat (studi kasus untuk S/D = 0,6-0,85). Undergraduate thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Penelitian tentang bentuk aliran pada silinder sirkuler sangat banyak aplikasinya di dunia engineering. Banyak cara yang dilakukan guna menurunkan koefisien drag pada silinder sirkuler, salah satunya adalah dengan menambahkan silinder sebagai pengganggu. Penelitian yang telah dilakukan menunjukkan bahwa tipe aliran berpengganggu sangat banyak dijumpai pada aplikasi engineering dan bidang mekanika fluida, seperti pada bangunan off-shore, jembatan, gedung pencakar langit, tiang kapal dan pemukiman. Oleh karena itu, sangat penting melanjutkan penelitian tentang silinder berpenganggu. Penelitian ini meneliti tentang penambahan instalasi pengganggu pada sisi upstream silinder utama guna mengurangi gaya drag pada silinder utama. Adapun pengganggu yang digunakan adalah prisma segiempat (tipe A), prisma diamond (tipe B), prisma segitiga sama sisi 300 (tipe C), prisma segitiga sama sisi 2100 (tipe D) dan silinder (tipe E). Dalam menurunkan gaya drag silinder sirkuler (D= 60 mm) digunakan lima jenis pengganggu tipe A, B, C, D dan E sebagai passive control yang diposisikan dengan variasi jarak S/D = 0,6, 0,65, 0,7, 0,75, 0,8 dan 0,85. Penelitian dilakukan ada subsonic windtunnel dengan panjang test section 1780 mm dan luas penampang 660 mm x 660 mm. Kecepatan freestream bisa ditentukan sebesar 13,954 m/s, berdasarkan pada bilangan Reynols yang digunakan Re = 5,3 x 104 (berdasarkan diameter D dan kecepatan freestream). 72 pressure tap dipasang pada dinding silinder sirkuler dengan interval jarak 50 yang dihubungkan dengan manometer inclined sehingga mampu mengukur ditribusi tekanan disekeliling silinder sirkuler. Profil kecepatan dibelakang silinder sirkuler diukur menggunakan pitot-static yang dihubungkan dengan manometer inclined. Pitot-static diletakkan dibelakang silinder sirkuler dengan jarak x/D = 3 dan frekuensi vortex shedding di belakang silinder sirkuler diukur menggunakan hot wire anemometer dengan jarak pengukuran x/D = 3,5 dan y/D = 1. Hasil penelitian ini menunjukkan adanya penurunan gaya koefisien drag pada silinder utama dengan adanya instalasi pengganggu di depan silinder utama. Pengganggu tipe A pada jarak S/D = 0,85 memberi pengaruh paling besar guna menurunkan drag pada silinder utama. Pengganggu tipe A menurunkan gaya drag silinder utama menjadi 30% dari drag silinder tanpa pengganggu. ======================================================================================================== Previous study has shown that flow configuration around a circular cylinder has an importat role in a wide range of engineering application. In order to reduce the drag coeficient of circular cylinder, some of methods were studied, such as using a small cylinder as passive control. Different studies also show that this flow configuration has many engineering applications and still present one of the challenges in fluid mechanics, such as offshore risers, bridge piers, towers, masts and stasy, etc. hatherefore it still important to continue study with cylinder circular as an object, especially on a group configuration. This study is to present the reducing of aerodynamics force on circular cylinder by upstream installation of some bluff bodies as passive control or disturbance, such as rectangular prism (type A), diamond prism (type B), equilateral triangular prism 300 (type C), equilateral triangular prism 2100 (type D) and cylinder (type E). In order to reduce the drag force on a circular cylinder (D= 60 mm), five bluff bodies; type A, B, C, D and E having a diameter d or lng side of 7,5 mm were used as a passive control. The passive control were located in various spacing positions of S/D= 0.6, 0.65, 0.7, 0.75, 0.8, nad 0.85. the experiments were carried out on subsonic open circuit windtunnel. This facility has a 1780 mm long, with test section 660 mm x 660 mm. The free stream velocity of windtunnel could be ajjusted constant to 13.954 m/s, corresponding to Reynols number Re= 5,3 x 104 (based on diameter D and free stream velocity). Seventy-two pressure tapswith interval 50 were installed on the wall of the circular cylinder and connected to and inclined kerosene manometer, which it makes it possible to measure the pressure distribution around the circular cylinder. The velocity profile behind the circular cylinder was measured using a pitot-static tube connected to the inclined manometer. The pitot-static tube was place at 18 cm at the rear of the axis of the cylindr or corresponding x/D = 3, and frequency of vortex shedding behind the cylinder was measured at x/D = 3,5 and y/D = 1 by hot wire anemometer. The experimental result show that there is reduction of drag coeficient on main cylinder by upstream installation of the some bluff body as passive control or cylinder disturbance. The passive control “type A” at S/D = 0.85 gives the highest drag reduction on the large circular cylinder situated downstream. It gives about 0.30 times the drag of a single cylinder.

Item Type: Thesis (Undergraduate)
Additional Information: RSM 620.106 4 Sud s
Uncontrolled Keywords: passive control, drag, prisma segitiga sama sisi, prisma segiempat dan silinder sirkuler.
Subjects: T Technology > TJ Mechanical engineering and machinery > TJ935 Pipe--Fluid dynamics.
Divisions: Faculty of Industrial Technology > Mechanical Engineering > 21201-(S1) Undergraduate Thesis
Depositing User: - Taufiq Rahmanu
Date Deposited: 22 Nov 2019 06:31
Last Modified: 22 Nov 2019 08:41
URI: http://repository.its.ac.id/id/eprint/71973

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