Pengaruh variasi jarak antar ring berbentuk segi empat pada permukaan silinder terhadap koefisien drag

Abstract

Abstrak:

Dalam aplikasi engineering banyak ditemukan peralatan yang menggunakan silinder seperti tiang penyangga jembatan,cerobong asap, tiang pancang pengeboran minyak lepas pantai dan sebagainya. Peralatan-peralatan tersebutmengalami hembusan udara setiap saat, yang menyebabkan kekuatan konstruksinya berkurang, akibat adanya drag.Tujuan dari penelitian ini adalah untuk mengetahui pengaruh variasi jarak antar ring berbentuk segi empat padapermukaan silinder terhadap koefisien drag. Penelitian ini dilakukan pada wind tunnel (lorong udara) yang terdiri dariblower (untuk menghembuskan udara), pipa pitot, U tube manometer, inclined manometer, neraca digital, silinderdengan ring segi empat. Pada penelitian ini, dilakukan dengan memvariasikan Jarak antar ring yaitu 30 mm, 40 mm, 50mm, 60 mm dan 70 mm. Silinder diletakkan vertikal dalam wind tunnel dengan diameter D = 60 mm. Gaya dragdiperoleh dengan menggunakan neraca digital yang mencatat besarnya massa, kemudian dikalikan dengan percepatangravitasi. Distribusi tekanan diperoleh dengan mengukur tekanan pada permukaan silinder menggunakan inclinedmanometer pada 36 titik dengan interval 10o. Hasil penelitian menunjukkan semakin besar jarak antar ring koefisiendrag semakin besar. Koefisien Drag terendah terjadi pada jarak antar ring L = 30 mm atau L/D = 0.50, besarnya CD =0,606352. Besarnya penurunan drag dibandingkan tanpa ring adalah 29,3 %.Kata kunci: Silinder, ring segi empat, jarak antar ring, koefisien drag

Abstract:

In many engineering applications there are many types of equipment that use cylinders, such as smoke chimney, bridgesupport column, etc. The equipment is undergoing drag due to the airflow that flows through it. The existence of the dragwill reduce its lifetime. One of the efforts to reduce drag is to create a rectangular ring on the surface of the cylinder. Thepurpose of this study was to determine the effect of variations in the distance between the ring of a rectangular ring onthe cylinder surface on the drag coefficient.This research was conducted in wind tunnel which consists of a blower (forblowing air), pitot pipe, U-tube manometer, inclined manometer, digital balance, cylinder with a rectangular ring. Theresearch was carried out by varying the distance between the ring i.e. 30 mm, 40 mm, 50 mm, 60 mm and 70 mm,respectively. The cylinder is placed in a vertical wind tunnel with a diameter D = 60 mm. The drag force is obtained byusing a digital balance that records the amount of mass, and then multiplied by the acceleration due to gravity. Thepressure distribution is obtained by measuring the pressure in the cylinder surface using inclined manometer on 36points with 10o intervals. The results showed that the greater the distance between the rings increased the dragcoefficient. The lowest drag coefficient was achieved at rhe distance between ring L = 30 mm or L/D = 0.50, with the CDvalue = 0.606352; that is equivalent to 29.3% drag reduction.Keywords: Cylinder, rectangular ring, space between ring, drag coefficient