Matching Items (18)
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- All Subjects: Aerodynamics
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Description
This experiment used hotwire anemometry to examine the von Kármán vortex street and how different surface conditions affect the wake profile of circular airfoils, or bluff bodies. Specifically, this experiment investigated how the various surface conditions affected the shedding frequency and Strouhal Number of the vortex street as Reynolds Number is increased. The cylinders tested varied diameter, surface finish, and wire wrapping. Larger diameters corresponded with lower shedding frequencies, rougher surfaces decreased Strouhal Number, and the addition of thick wires to the surface of the cylinder completely disrupted the vortex shedding to the point where there was almost no dominant shedding frequency. For the smallest diameter cylinder tested, secondary dominant frequencies were observed, suggesting harmonics.
ContributorsCoote, Peter John (Author) / Takahashi, Timothy (Thesis director) / White, Daniel (Committee member) / Mechanical and Aerospace Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2017-05
Description
Active flow control for airfoil designs has been researched for the past few decades. This has been achieved through steady blowing, pulsed blowing, synthetic jets, and plasma jets. These techniques have been applied to both single and dual jet configurations. This technology was examined for a wind turbine blade application so that lift and drag can be altered without needing a mechanical flap. Research was completed to also allow for thicker airfoils with more blunt trailing edges that result in the higher structural strength needed for large, heavy wind turbine blades without the negative aerodynamic effects such as boundary layer separation. This research tested steady blowing in a dual jet configuration for the S830 airfoil from the National Renewable Energy Laboratory (NREL) database of airfoils. Computational Fluid Dynamics was used in the software Ansys Fluent. Calculations were completed for a modified S830 airfoil with a rounded trailing edge surface at momentum coefficients of 0.01 for the lower jet and 0.1, 0.12, and 0.14 for the upper jet. These results were then compared to the original S830 results for the lift over drag efficiency. The design with momentum coefficients of 0.12 for the upper surface resulted in the highest increase in efficiency of 53% at an angle of attack of 12 degrees. At this momentum coefficient, the angle of attack where zero lift occurred was at -8.62 degrees, compared to the case with no blowing at -1.90 degrees. From previous research and research completed in this thesis it was concluded that active flow control is an effective technique to improve wind turbine energy collection.
ContributorsStapleton, Paige (Author) / Mertz, Benjamin (Thesis director) / Herrmann, Marcus (Committee member) / Mechanical and Aerospace Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2018-05
Description
The emerging market for unmanned aerial vehicles, or UAV's, demands the development of effective design tools for small-scale aircraft. This research seeks to validate a previously developed drag build-up method for small air vehicles. Using the method, a drag prediction was made for an off-the-shelf, remotely controlled aircraft. The Oswald efficiency was predicted to be 0.852. Flight tests were then conducted using the RC plane, and the aircraft performance data was compared with the predicted performance data. Although there were variations in the data due to flight conditions and equipment, the drag build up method was capable of predicting the aircraft's drag. The experimental Oswald efficiency was found to be 0.863 with an error of 1.27%. As for the CDp the prediction of 0.0477 was comparable to the experimental value of 0.0424. Moving forward this method can be used to create conceptual designs of UAV's to explore the most efficient designs, without the need to build a model.
ContributorsGavin, Tyler Joseph (Author) / Wells, Valana (Thesis director) / Garrett, Fred (Committee member) / Barrett, The Honors College (Contributor) / Mechanical and Aerospace Engineering Program (Contributor)
Created2014-05
Description
Each year, the CanSat Competition organizers release aerospace based engineering mission objectives for collegiate teams to compete in. This year, the design is an aerodynamically stable probe that will descend from an altitude of 725 meters at a rate between 10-30 meters/sec until it reaches an altitude of 300 meters, where it will then release a parachute as its aerobraking mechanism as it descends at 5 meters/sec until it reaches the ground. The focus of this paper is to investigate the design of the probe itself and how slender body theory and cross flow drag affect the lift and aerodynamic stability of this bluff body. A tool is developed inside of MATLAB which calculates the slender body lift as well as the lift from the cross flow drag. It then uses that information to calculate the total moment about the center of gravity for a range of angles of attack and free stream velocities. This tool is then used to optimize the geometry of the probe. These geometries are used to construct a prototype and that prototype is tested by a drop test from a 6-story building. The initial tests confirm the calculations that the probe, bluff body, is stable and self-correcting in its descent. Future work involves more high-altitude and ground-level tests that will further verify and improve on the current design.
ContributorsMcCourt, Anthony Michael (Author) / Takahashi, Timothy (Thesis director) / Herrmann, Marcus (Committee member) / Mechanical and Aerospace Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2018-05
Description
This research was intended to investigate the effects of various motivational variables on high school students' declaration of a STEM major in college, focusing on PSEM majors. It made use of data from the High School Longitudinal Study of 2009, including the first and second follow-up years (2011 and 2013). The advantage of this study over others is due to this data set, which was designed to be a representative sample of the national population of US high school students. Effects of motivational factors were considered in the context of demographic groups, with the analysis conducted on PSEM declaration illuminating a problem in the discrepancy between male and female high school students. In general, however, PSEM retention from intention to declaration is abysmal, with only 35% of those students who intended towards PSEM actually enrolling.
ContributorsMangu, Daniel Matei (Author) / Middleton, James (Thesis director) / Ganesh, Tirupalavanam (Committee member) / School of International Letters and Cultures (Contributor) / Mechanical and Aerospace Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2017-12
Description
This study consisted of two fundamental experiments that examined the effects of surface parameters on baseball aerodynamics. The first experiment measured drag and lift coefficients in response to varied surface treatments of a non-spinning baseball. This experiment found that rougher surfaces (rubbing mud, increased ball usage, and scuffing) decrease drag coefficient by up to 0.05 for Reynolds numbers of up to 1.5x105 (wind speeds of 30 m/s or 67 mph). The maximum observed increase in lift coefficient was 0.20, caused by heavily scuffing the top of the ball. These results can be explained by boundary layer transition phenomena and asymmetry in the surface roughness of the ball. A decrease in drag coefficient of 0.05 can translate to an increase in the flight distance of a batted ball by as much as 50 ft (14%), and an increase of 0.20 in lift coefficient can increase flight distance by 70 ft (19%) \u2014 numbers that can easily mean the difference between a routine fly out and a monster home run. The second experiment measured drag and lift coefficients in response to varied stitch geometries of a non-spinning, 3D-printed baseball. Increasing stitch height, width, and spacing was found to increase drag coefficient, while increasing stitch length had little effect on lift coefficient. Increasing any parameter of the stitch geometry was found to increase lift coefficient. These results can be explained by boundary layer transition phenomena, blockage effects, and asymmetry in the stitch geometry of the ball. Future work would do well to repeat these experiments with a larger wind tunnel and a more sensitive force balance. These results should also be validated at higher wind speeds, and for spinning, rather than stationary baseballs. In addition, future work should explore the degree to which surface roughness and stitch geometry affect drag and lift coefficients at different ball orientations.
ContributorsDwight, Jeremiah Robert (Author) / Squires, Kyle (Thesis director) / Steele, Bruce (Committee member) / Mechanical and Aerospace Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2016-05
Description
This study examines the effectiveness of two modes of exercise on self-efficacy (SE) in adolescents with Down syndrome (DS). Thirty-nine participants were randomly divided into a voluntary cycling group (VC) (i.e., self-selected cadence), an assisted cycling group (ACT) (i.e., at least 30% faster than self-selected cadence accomplished by a motor), or a no exercise group (NC). In each cycling intervention the participant completed 30 minute cycling sessions, three times per week for a total of eight weeks. Two subsets of the Physical Activity and Self Efficacy Survey were administered prior to cycling (i.e., pretest) and after the eight week intervention (i.e., post-test). The results were consistent with the hypothesis that self-efficacy would improve after ACT, however there was not improvement after the VC condition as hypothesized. It was also hypothesized that exercise perception would improve following the ACT intervention; execise perception showed a trend of improvement after ACT, but the data did not reach significance. Limitations include the wide variability of the DS population. This limitation is responsible for the variation in mental age seen in the intervention groups and could be responsible for the non-significance of the exercise perception data. To generalize our results for parents, therapists, teachers, etc., our recommendation is for persons with DS to participate in physical activity that is easy for them at first \u2014 a simplified sport or active game, assisted cycling, brisk walking \u2014 so that they have a positive experience with exercise. Showing individuals with DS that they can be proficient exercisers will likely improve their self-efficacy and motivate them to engage in more PA over time. In conclusion, eight weeks of moderate ACT exercise demonstrated a significant trend for improved self-efficacy in adolescents with DS.
ContributorsWallace, Kellie Carter (Author) / Ringenbach, Shannon (Thesis director) / Youngstedt, Shawn (Committee member) / Hoffner, Kristin (Committee member) / School of Nutrition and Health Promotion (Contributor) / Barrett, The Honors College (Contributor)
Created2015-12
Description
The aerodynamics of golf club heads effect the forces on the club head throughout the swing. The bluff body geometry and passive flow control elements make the aerodynamics of golf club heads far more complex. The theory behind the geometry of the bluff body aerodynamics relies on the state of the boundary layer and its interaction with the golf club head. Laminar and turbulent boundary layer flow result in drag, but in varying degrees. Separation, or attachment, of the boundary layer in these laminar and turbulent boundary layer flows is part of the cause of the induced drag. Skin friction and pressure drag are the two forms of surface forces which vary according to the state of the boundary layer. To review the state of the boundary layer flow and provide validation data for the corresponding, the golf club head was tested in a wind tunnel. Drag readings from the experiment showed the lowest drag occurred while the club face was perpendicular to the flow from the range of 50 miles per hour to 90 miles per hour. Additionally, the decrease in drag varied greatly depending on the orientation of golf club head. The decrease in the coefficient for the club perpendicular to the flow was approximately 3.99*〖10〗^(-6) C_d/Re while the decrease for the club at 110° was 1.07*〖10〗^(-6) C_d/Re. The general trend of the slopes indicated the pressure drag resulted in major variations while the drag due to skin friction remained relatively constant.
For the testing of the golf club head, two probes were developed to measure the turbulent intensity in the flow. The probes, based on Rossow’s (1993) three probe system, compared the dynamic pressure of the flow with the stream-wise dynamic pressure in the flow. The resultant measurements could then produce the ratio of the cross-stream fluctuations in velocity to the time-averaged velocity. The turbulence intensity calculations would provide insight on the turbulence in the boundary layer flow and wake.
For the testing of the golf club head, two probes were developed to measure the turbulent intensity in the flow. The probes, based on Rossow’s (1993) three probe system, compared the dynamic pressure of the flow with the stream-wise dynamic pressure in the flow. The resultant measurements could then produce the ratio of the cross-stream fluctuations in velocity to the time-averaged velocity. The turbulence intensity calculations would provide insight on the turbulence in the boundary layer flow and wake.
ContributorsBrausch, Matthew James (Author) / Takahashi, Timothy (Thesis director) / Ghods, Sina (Committee member) / Mechanical and Aerospace Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2016-05
Description
This study investigated how mindset intervention in freshman engineering courses influenced students’ implicit intelligence and self-efficacy beliefs. An intervention which bolsters students’ beliefs that they possess the cognitive tools to perform well in their classes can be the deciding factor in their decision to continue in their engineering major. Treatment was administered across four sections of an introductory engineering course where two professors taught two sections. Across three survey points, one course of each professor received the intervention while the other remained neutral, but the second time point switched this condition, so all students received intervention. Robust efficacy and mindset scales quantitatively measured the strength of their beliefs in their abilities, general and engineering, and if they believed they could change their intelligence and abilities. Repeated measures ANOVA and linear regressions revealed that students who embody a growth mindset tended to have stronger and higher self-efficacy beliefs. With the introduction of intervention, the relationship between mindset and self-efficacy grew stronger and more positive over time.
ContributorsFulginiti, Alexander Ellis (Author) / Middleton, James (Thesis director) / Grewal, Anoop (Committee member) / Mechanical and Aerospace Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2021-05
Description
The following analysis was conducted at the Arizona State University open loop wind tunnel. Two 1/24-th scale NASCAR models were placed in a wind tunnel test section and were adjusted to study drafting that commonly occurs at superspeedway racetracks. The purpose of the experiment was to determine how drafting affects a leading and trailing car through changes in distance. A wind tunnel model was developed consisting of two 2019 NASCAR Chevy Camaro race car models, two bar-style load cells, and a programmed Arduino UNO. Two trials were run at each drafting distance, 0, 0.5, 1, 1.5, and 2 car lengths apart. Each trial was run at a wind tunnel velocity of 78 mph (35 m/s) and force data was collected to represent the drag effects at each drafting location. Based on previously published experimentation, this analysis provided important data that related drafting effects in scale model race cars to full-scale vehicles. The experiment showed that scale model testing can be accurately completed when the wind tunnel Reynolds number is of the same magnitude as a full-scale NASCAR. However, the wind tunnel data collected was proven to be fully laminar flow and did not compare to the flow characteristics of typically turbulent flow seen in superspeedway races. Overall, the analytical drag analysis of drafting NASCAR models proved that wind tunnel testing is only accurate when many parameters are met and should only be used as a method of validation to full-scale testing.
ContributorsOlszak, Parker T (Author) / Takahashi, Timothy (Thesis director) / Kasbaoui, Mohamed (Committee member) / Mechanical and Aerospace Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2021-05