Determination of Drag Coefficients for Various Sphere Types
Determination of Drag Coefficients for Various Sphere Types
Adriana Carbon, Jessica Lake, Jonathan Bessler
ChE 341 Experiment 1
March 6, 2015
Abstract
“A wind tunnel is a specially designed and protected space into which air is drawn, or blown, by mechanical means in order to achieve a specified speed and predetermined flow pattern at a given instant” . The flow over a specific object can be observed from outside the wind tunnel through transparent windows that enclose the test section and the flow characteristics can be measured through specialized instruments.
In this experiment an open-type wind tunnel was used to observe the flow over different types of spheres and the experimental results were used to calculate each sphere’s flow characteristics, such as the coefficient of drag force (CD).
From our experimental results, we determined that the balls all displayed a sharp drop in drag coefficient at the turbulent transition with drag values in reasonable ranges when comparing these results to the literature values.
Introduction:
The total drag of an object may be due to pressure as well as frictional effects. In this situation the coefficient of drag, CD, is defined as
Equation 1 where F is the force, AP is the projected area of the surface, is the density of the fluid, and v∞ is the free-stream fluid velocity. The quantity is often called the dynamic pressure. This equation can be used to solve for the coefficient of drag from experimental data. The force and the air velocity can be measured during an experiment, the projected area is easily calculated from measured dimensions, and the density of the air can be measured or assumed.
The drag coefficient can be calculated from experimental results and parameters. It depends on parameters such as the body’s shape, Reynolds number and surface roughness. The power (energy ratio) obtained in the test section versus the power input from the fan is described as
Equation 2
Adriana Carbon, Jessica Lake, Jonathan Bessler
ChE 341 Experiment 1
March 6, 2015
Abstract
“A wind tunnel is a specially designed and protected space into which air is drawn, or blown, by mechanical means in order to achieve a specified speed and predetermined flow pattern at a given instant” . The flow over a specific object can be observed from outside the wind tunnel through transparent windows that enclose the test section and the flow characteristics can be measured through specialized instruments.
In this experiment an open-type wind tunnel was used to observe the flow over different types of spheres and the experimental results were used to calculate each sphere’s flow characteristics, such as the coefficient of drag force (CD).
From our experimental results, we determined that the balls all displayed a sharp drop in drag coefficient at the turbulent transition with drag values in reasonable ranges when comparing these results to the literature values.
Introduction:
The total drag of an object may be due to pressure as well as frictional effects. In this situation the coefficient of drag, CD, is defined as
Equation 1 where F is the force, AP is the projected area of the surface, is the density of the fluid, and v∞ is the free-stream fluid velocity. The quantity is often called the dynamic pressure. This equation can be used to solve for the coefficient of drag from experimental data. The force and the air velocity can be measured during an experiment, the projected area is easily calculated from measured dimensions, and the density of the air can be measured or assumed.
The drag coefficient can be calculated from experimental results and parameters. It depends on parameters such as the body’s shape, Reynolds number and surface roughness. The power (energy ratio) obtained in the test section versus the power input from the fan is described as
Equation 2
References: 1. Welty, James R., Charles E. Wicks, Robert E. Wilson, and Gregory L. Rorrer. Fundamentals of Momentum,Heat, and Mass Transfer. 5th ed. John Wiley & Sons, 2008. 138-141. Print. 2. Asal, Takeshi. "The Physics of Football." Physics World. Institute of Physics, 1 June 1998. Web. 5 Mar. 2015. <http%3A%2F%2Fphysicsworld.com%2Fcws%2Farticle%2Fprint%2F1998%2Fjun%2F01%2Fthe-physics-of-football>. 3. Libii, Josué Njock. Wind Tunnels in Engineering Education. Fort Wayne: INTECH Open Access, 2011.IntechOpen. Indiana University-Purdue University. Web. 5 Mar. 2015.