# Drag on a Cylinder

Topics: Reynolds number, Fluid dynamics, Aerodynamics Pages: 11 (3180 words) Published: March 13, 2012
Drag on a cylinder
ENME432L section 0101
Date of the Experiment: Feb. 21, 2012
Date submitted: Feb. 28, 2012
Instructor: Anilchandra Attaluri
Prepared by:
Ku Choe: ________ Dwight Hofstetter: _________
Benjamin DiDonato: _______
Lab report checklist:
x Have you included the raw (handwritten) data sheet?
x Have you included your pre-lab report which has been signed by your TA or instructor? x Have you typed the measured data and include them into your report? x Have you included enough data so that the instructor can calculate the final results himself? x Have you included detailed methods so that your younger brother or sister can understand what you did? x Have you included one or two figures for the experimental setup to help the instructor understand how you made those measurements? x Have you included a description of your experimental protocol? x Have you provided a table for all the parameters you obtained from other textbook? x Have you performed the uncertainty analysis on at least one indirectly measured variables? x Have each member of your group read the lab report?

Abstract
In this experiment, the drag coefficient of a cylinder was calculated from data obtained by performing tests in an air bench. Two methods of analysis were used to calculate drag measurements on the cylinder: direct measurement of the drag force and applying the Reynolds Transport Theorem to control volume enclosed by the test section. In the first method, the drag coefficient can be determined by directly measuring the drag force exerted on the cylinder. The drag force by weight measurement is given by the weight, which have to be added on the weight pan to balance the cylinder at air speed. In contrast, the second method was carried out by measuring the outlet dynamic pressure at different location in the exit plane along the transverse direction on the cylinder. A comparison was then made between the results and error obtained by the two methods analysis and data acquisition. Objective

The objective of this experiment is to determine the drag force and drag coefficient for a circular cylinder by two methods: direct measurement of the drag force and applying the Reynolds Transport Theorem to the control volume enclosed by the test section. Introduction

Understanding the drag characteristics of a body as it moves through a fluid is great engineering importance in aerodynamics. Designing airplane wings or vehicles shapes which have a small drag is fundamental for reducing the power necessary for their movements. The phenomenon of drag can be simulated and measured by recreating air flow over an object. Analytical tools such as Bernoulli Equation and the Reynolds Transport Theorem may be combined with experimental data to study the behavior of flow around an object. In this experiment, air bench is used to analyze the effects of air flow over a cylinder. For convenience the cylinder is fixed in space and the air is forced to flow around it. The Reynolds number used was Re = 20000, which is the flow may be considered laminar. The drag caused by the cylinder can be calculated through two different methods: direct measurement of the drag force and applying the Reynolds Transport Theorem to control volume enclosed by the test section. These experimentally obtained pressure and velocity measurements provide the necessary data required to find the coefficient of drag of the cylinder for this experiment. The equations used to calculate the drag coefficient is described in the Material and Method. With these two methods of obtaining the drag coefficient, the air flow around the cylinder can be observed, analyzed, and compared.

Materials and Methods
For this analysis of drag on a cylinder using the TecQuipment AF-10, two methods are employed. The first method is performed via force balance while the second utilizes the Reynolds Transport Theorem. A...