Flow Visualization: Lab: Flow Visualization

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Lab 1: Flow Visualization
Jintark Kim
Purdue University
ME309 lab Section 009 Abstract The purpose of this experiment is to visualize and analyze the flow patterns formed by objects in different conditions: cylinders in different diameter at different flow rate, and airfoils with different angle of attack at a constant flow rate. Properties of water at measured temperature and flow conditions for each trial were used to compute the Reynolds number. Red-dye ejector was used to traces the flow field around experiment objects. The cylinders with 2 different diameters (6.35mm and 25.4mm) at different water channel speed (1.25 in/sec and 3.00 in/sec) were used to observe flow patterns in 4 different Reynolds numbers. In addition, an
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The Von Karman vortex street becomes more turbulent with increasing Reynolds number. In the airfoil experiment, the airfoil with 0° angle of attack shows the laminar and smooth flow pattern while the airfoil with 20° shows the turbulent flow pattern. The result of this experiment strongly supports the validity of using Reynolds number to predict the flow pattern. Predicting rough conjecture of flow pattern without experiments can reduce the time consumption for design projects related to flow. Accordingly, the flow pattern analysis from this experiment contributes to engineering development. Introduction Flow visualization is a classic technique that visualizes flow patterns by using colored dye, or other tracking material. The visualized flow pattern is recorded by camera subsequently. Flow visualization is needed when designing and testing any components related to fluid flow such as car body, jet engine, aircraft, etc. Many fields of industry are related to analyze how an object is affected by surrounding flow field. The Reynolds number is used to predict the flow patterns. Reynolds number is given in Equation 1 (Fox, Pritchard, & McDonald, 2009). Re=ρ VL/μ (Eq.1) …show more content…
The Flow Pattern of Airfoil at Different Angles The other experiment object is airfoil. The separation point at 0° angle is located on the back of the airfoil, which only causes small wake. On the other hand, with increased angle of attack, the separation point is located on the front part causing large wake and turbulent flow. The flow pattern regarding airfoil at different attack of angle is shown in figure 2 (“Angle of attack,” n.d.). The purpose of this experiment is to determine how Reynolds number is related to the behavior of wake shedding. The red dye ejector was used to visualize the streak line of the flow system in each test case. Different flow patterns were observed with different diameter, flow rate, and angle of attack. Some assumptions were made for this experiment: The fluid is incompressible. The temperature of the fluid does not change throughout the experiment. The injected dye does not affect fluid properties. The system is in steady state at least 30 seconds after frequency

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