Dalam aplikasi engineering banyak ditemukan peralatan yang menggunakan silinder, seperti tiang penyangga jembatan, cerobong asap, dan sebagainya. Peralatan-peralatan ini mengalami hembusan udara setiap saat, yang menyebabkan kekuatan konstruksinya mengalami penurunan, hal ini disebabkan adanya drag yang arahnya searah dengan arah aliran. Upaya yang dilakukan untuk mengurangi drag adalah dengan memanipulasi medan aliran fluida. Manipulasi aliran fluida dapat dilakukan secara pasif antara lain dengan menambahkan helical strake pada permukaan silinder, menambahkan penghalang di depan silinder dan sebagainya. Dalam penelitian ini manipulasi aliran fluida dilakukan dengan menambahkan O-ring pada permukaan silinder. Tujuan penelitian ini adalah menganalisa pengaruh variasi diameter O-ring terhadap koefisien drag. Penelitian ini dilakukan pada sebuah wind tunnel yang terdiri dari blower, pipa pitot, manometer, timbangan digital, dan silinder. Penambahan O-ring diletakkan pada permukaan silinder dengan variasi diameter O-ring yaitu 3mm, 4mm, 5mm, 6mm dan jarak antar O-ring 30mm. Silinder diletakkan ke arah vertikal. Bilangan Reynolds berdasarkan diameter silinder (60mm) adalah Re = 3,64 x .Dari hasil penelitian menunjukkan bahwa terjadi penurunan koefisien drag dibandingkan tanpa variasi O-ring. Nilai koesisien drag terendah didapat dari variasi diameter O-ring 5mm atau d/D=0,08 dengan nilai 0,650259, dimana terjadi penurunan drag sebesar  24,15% dibandingkan dengan silinder tanpa O-ring.

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One of the ways to preserve energy on the air plane is by decreasing the drag. Drag is closely related to the flow separation, the faster the separation, then the drag will increase more. Because of that, efforts were conducted to decrease drag is by manipulating a fluid flow field that is by installing triangle rod obstacle in front of the cylinder. The purpose of this research is to analyze the effect of installing triangle rod obstacle in front of the cylinder by various air flow velocity on the drag cofficient. In this research, the experiment was conducted in the wind tunnel, which consists of blower, pitot pipe, manometer, cylinder pipe, and triangle rod. The air flow velocity was varied from 6.

There are so many equipment using cylinder in its application, such as bridge support column, smoke chimney, pole pillar of offshore oil drilling etc. When those kind of equipment is affected by air flow continuously, it would reducing the strength of those equipment construction. This strength reduction is caused by the drag force that is emerged due to the air flow and its direction are having the same direction with flow direction. So that it is necessary to do something to reduce the drag, one of it is by adding the rectangular ring at the cylinder surface. The rings is placed at the cylinder surface in 100sloping position and then its ring distance would be varied. The aim of this research is to discover the influences of distance variation between the ring with sloping position on the cylinder surface to the drag coefficient. This research is conducted in the wind tunnel that consist of blower, pitot pipe, U manometer, inclined manometer, digital weight, cylinder, quadrangular rings (attached on the cylinder). The cylinder is placed in vertical position within the distance between the rings is varied as L/D = 0.5, 0.67, 0.83, 1.00, and 1.17. The Reynold number based on silinder diameter D = 60 mm is Re = 3.64 X 104. Pressure distribution is determined by measuring cylinder surface pressure at 36 points with 100interval. The result of this research showed that the lowest drag coefficient value occurs at the distance between the ring of L/D = 0.5 is 0.485. The large decreasing of the drag coefficient compare to without rings is 43.5%.