# Characterisation of Flow Around a Sphere

Powerful Essays
SPHERE TEST: REVISIT WIND TUNNEL TURBULENCE

ABSTRACT
One of the most widely used methodologies in characterising the quality of a wind tunnel is to study the flow over a sphere.The flow around the bluff body was characterised using smoke test, and the region of flow separation was analysed. The drag characteristics of 3 spheres of different diameters were studied for a wide range of Reynolds number. The Reynolds number at which the transition occurs is strongly dependent on the degree of turbulence in the wind tunnel. Based on the following tests, the quality of the wind tunnel was determined. The turbulence level in the wind tunnel was experimentally studied. The sphere test results were in good agreement with the literature and the quality of the wind tunnel was found to be fairly good.

CHAPTER 1 INTRODUCTION

FIGURE 1.1. Flow around a sphere

FIGURE 1.1 shows that whenever a flow encounters a body, the flow tends to curve around that body. As air flows around the sphere, the flow gets deflected due to the shape and there is a difference in pressure at various points on the sphere. Pressure decreases as we move from front to the top point and increases as we move from top to the rear. For the latter part there is a chance for flow separation due to adverse pressure gradient. Spheres are known to have a distinct critical Reynolds number above which the flow on the upstream face of the sphere is fully turbulent causing the drag coefficient to drop dramatically. This is because the turbulent boundary layer results in separation further aft than a laminar boundary layer, thus producing a smaller wake. The critical Reynolds number for the three spheres was determined by examining the measured drag coefficient CDp as a function of Reynolds number. To understand the quality of flow in the test section, turbulence level is the flow quality parameter. In this experiment, the level of turbulence and resultant turbulence factor for the wind tunnel was

References: 1. J.D. Anderson, Jr.”Fundamentals of Aerodynamics”, McGraw-Hill, 2001. 2. E.L .Houghton and P.W. Carpenter “Aerodynamics for Engineering Students” Fifth Edition, Butterworth-Heinemann publications, 2003. 3. B.R Munson, P.F Young, T.H Okiishi, ”Fundamentals of Fluid Dynamics” John Wiley & Sons, 2002. 4. Barlow, J.B., Rae Jr., W.H., Pope, A., Low-Speed Wind Tunnel Testing Wiley & Sons, Inc., New York, 1999. pp 147-150. 5. Robert C. Platt,”Turbulence Factors of NACA Wind Tunnels As Determined Sphere Tests”1937. 6. Dryden, H.L., Keuthe, A.M., “Effect of Turbulence in Wind Tunnel Measurements” NACA Report 342, 1929. 21

## You May Also Find These Documents Helpful

• Good Essays

Celestial Sphere Terminology 1 Celestial Sphere:What we see, it contains the stars, planets, Sun, and Moon Celestial Equator- the imaginary line that divides the planet into Northern and Southern hemispheres. The celestial equator is a similar imaginary circle around the celestial sphere, also known as the visible universe. The celestial equator divides the visible universe in two, creating the Northern and Southern celestial hemispheres. This helps us locate celestial bodies. Ecliptics -an imaginary…

• 1009 Words
• 5 Pages
Good Essays
• Satisfactory Essays

Characterisation: Abigail Williams The Crucible is a play written by Arthur Miller, and is set in the fiercely Puritan Salem, Massachusetts in 1692. Abigail Williams, above all else, is the least complex. As the antagonist of the play, she’s dominant and clearly puts herself out there as the opposition. Abigail is 17-year-old niece of Reverend Parris. She is unmarried, and an orphan, meaning her position on the social ladder is fairly low. Abigail Williams is a young lady with a vicious…

• 265 Words
• 2 Pages
Satisfactory Essays
• Good Essays

Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science http://pic.sagepub.com/ A Study of Turbulent Flows in Pipe Bends W N Al-Rafai, Y D Tridimas and N H Woolley Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 1990 204: 399 DOI: 10.1243/PIME_PROC_1990_204_120_02 The online version of this article can be found at: http://pic.sagepub.com/content/204/6/399 Published by: http://www…

• 5404 Words
• 22 Pages
Good Essays
• Good Essays

. It can be argued that the development of characters in gothic literature follows the separate spheres theory which suggests that in the 18th and 19th century each gender was bounded by specific traits and "God-given domains" with women's sphere evolving around caring for the household, their husband and children; a role Elizabeth has been fulfilling and the men's sphere evolving around working, providing money and political involvement. Elizabeth is described as "a being heaven-sent, and bearing…

• 166 Words
• 1 Page
Good Essays
• Good Essays

“The idea that a public sphere to which everyone can contribute on equal terms is simply a fantasy.” To believe that there exists a public sphere where every single member contributes on an equal level is highly unrealistic. Correspondingly, many academics have critically supported as well as argued against this view. There will be discussion of the public sphere and various writer’s views and concepts regarding it, with specific references to Howley (2007) and Turnbull (2006), as well as Hackett…

• 1842 Words
• 8 Pages
Good Essays
• Good Essays

Throughout the 1700’s, men and women were confined to culturally predefined spheres of responsibility. “A woman’s place is in the home” was the prevailing opinion in America under the Separate Spheres ideology during the eighteenth century. Women were thought to be biologically inclined to excel in the domestic sphere of childrearing and homemaking while men were thought to be biologically inclined to excel in the public sphere of economics and politics. Some early feminist pioneers like Abigail Adams…

• 906 Words
• 4 Pages
Good Essays
• Powerful Essays

Outline the key features of Habermas’ public sphere. Discuss how healthy the public sphere is today, with reference to the forces of commerce and politics. The focus point of this paper is to outline the key features of Jurgen Habermas’ public sphere while discussing how healthy the public sphere is today, with reference to the forces of commerce and politics. Jurgen Habermas’ concept of a public sphere is an area within social life that allows for a public opinion to be formed. First introduced…

• 2044 Words
• 6 Pages
Powerful Essays
• Good Essays

The spheres of influence are: the government, the workforce and workplace, association and interests groups, and the community. Policy formation may occur in more than one sphere at a time, with action in one sphere can influence the action in another sphere (O'Grady, Mason, Outlaws, & Gardner, 2016). “Nursing places a significant role in influencing nursing and nursing practice” (O’Grady et al., 2016, p. 13). There are many ways that nurses can influence policy formation in governmental sphere, for…

• 381 Words
• 2 Pages
Good Essays
• Powerful Essays

CHARACTERISATION: Macbeth In William Shakespeare’s "Macbeth", the audience witness’s one man’s overriding ambitions resulting in consequences both for himself and those around him. In the play the main character is heavily influenced and persuaded by external forces, particularly the supernatural and the immense ambition of Lady Macbeth In Act I, Shakespeare set the scene for what is to prove the pivotal part of the play, the death of King Duncan. Therefore, through act one the audience’s perception…

• 1612 Words
• 7 Pages
Powerful Essays
• Good Essays

the “Separate Spheres” theory was still applied to how women and men were supposed to act in society. The theory is that women should remain at home, because they are “delicate, fragile creatures” who shouldn’t be out in a “man’s world”. Men should be masculine and tough; they should be in charge of financially supporting his family and be in the “dangerous business world”. That left the women at home to take care of the household and children. The logic behind “Separate Spheres” was that “women…

• 492 Words
• 2 Pages
Good Essays