DOC PREVIEW
GVSU EGR 365 - CYLINDER DRAG

This preview shows page 1-2 out of 7 pages.

Save
View full document
Premium Document
Do you want full access? Go Premium and unlock all 7 pages.
Access to all documents
Download any document
Ad free experience

Unformatted text preview:

Grand Valley State University The Padnos School of Engineering CYLINDER DRAG EGR 365 FLUID MECHANICS Brad Vander Veen June 10 2003 Lab Partners Julie Watjer PURPOSE The purpose of this exercise is to experimentally determine the drag on a cylinder in crossflow using a momentum balance in the wake of the cylinder THEORY Consider the diagram of the flow in Figure 1 below Notice that the view is from directly above the cylinder Figure 1 Experimental Setup Using the control volume shown above it is possible to show that the total drag force on the cylinder is H D LV 2 u2 1 V 2 H 1 where D is the drag force is the fluid density L is the height of the cylinder V is the undisturbed fluid velocity u is the disturbed wake velocity and H to H is the width of the wake This result can be put into non dimensional form CD H D 2 u2 1 V 2 0 5 LdV 2 d H 2 where CD is the drag coefficient and d is the diameter of the cylinder The flow speed can also be put into non dimensional form Re d Vd 3 where Red is Reynolds Number and is the dynamic viscosity of the fluid The undisturbed air velocity can be calculated using pt p s 0 5 V 2 where pt is the total pressure ps is the static pressure and V is the air velocity APPARATUS ITEM Wind Tunnel Pressure Measuring Device Manometer 4 Scale PROCEDURE 1 Assemble the experimental setup as seen in Figure 1 2 Place rake in the wake of the object 3 Turn wind tunnel on to desired speed 4 Measure and record the pressures in the wake at each rake tine 5 Measure total pressure in the wind tunnel at the entrance to test section and at the rake RESULTS tine distance from zero ft dynamic pressure in of H2O 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 0 000 0 008 0 015 0 023 0 030 0 038 0 045 0 053 0 060 0 068 0 075 0 083 0 090 0 098 0 105 0 113 0 120 0 128 0 135 1 08 0 92 0 90 0 88 0 82 0 75 0 66 0 57 0 41 0 35 0 33 0 35 0 42 0 54 0 67 0 76 0 83 0 86 0 88 Table 2 Experiment Results ANALYSIS In Figure 3 below the experimental results can be seen This figure plots the undisturbed air velocity in pink and the disturbed wake velocity in blue The velocity was calculated using Equation 4 from the theory section in the lab report Notice also the propagated error in yellow Velocity vs Position in Wake 9 00 Velocity ft s 8 00 Air Velocity 7 00 Constant Velocity Upper Error 6 00 Low er Error 5 00 4 00 0 00 0 02 0 03 0 05 0 06 0 08 0 09 0 11 0 12 0 14 distance ft Figure 3 Fluid Velocity From Figure 3 above it is clear that the fluid velocity in the wake is much slower that the undisturbed air velocity Notice that the fluid velocity is the slowest directly behind the cylinder and that the fluid velocity on the edge of the wake is very close to the undisturbed fluid velocity This data can also be shown in non dimensional form as seen below in Figure 4 Normalized Velocity vs Position in Wake 1 25 1 Nomalized Velocity U 2 V 2 0 75 Normalized Constant Upper Error 0 5 Low er Error 0 25 0 0 00 0 02 0 03 0 05 0 06 0 08 0 09 0 11 0 12 0 14 distance ft Figure 4 Normalized Fluid Velocity Note from Equations 3 and 4 that the area between these two curves is directly proportional to the drag force and the drag coefficient Using Riemann Sums between to approximate the area between the curves yields H u2 1 V 2 00446 ft 0048 ft H It is also known that 00238 slugs ft 3 L 11 in V 8 37 ft s d 5 in Using Equation 1 the drag force can be found D 0 0068lbf 0 0008lbf Using Equation 2 the drag coefficient can be found CD 2 14 0 23 Using Equation 3 Reynolds number can be found Re d 2220 CONCLUSION In this lab a round cylinder was placed in a wind tunnel When fluid was forced past the cylinder a wake was created behind it This wake was experimentally measured and analyzed The drag force on the cylinder was found to be 0 0068 lbf 0 0008 lbf The drag coefficient was found to be 2 14 0 23 Reynolds Number was found to be 2220 and since no measuring error is associated with Reynolds Number there was no propagated error


View Full Document
Download CYLINDER DRAG
Our administrator received your request to download this document. We will send you the file to your email shortly.
Loading Unlocking...
Login

Join to view CYLINDER DRAG and access 3M+ class-specific study document.

or
We will never post anything without your permission.
Don't have an account?
Sign Up

Join to view CYLINDER DRAG and access 3M+ class-specific study document.

or

By creating an account you agree to our Privacy Policy and Terms Of Use

Already a member?