Matching Items (3)
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Description
Rotorcraft operation in austere environments can result in difficult operating conditions, particularly in the vicinity of sandy areas. The uplift of sediment by rotorcraft downwash, a phenomenon known as brownout, hinders pilot visual cues and may result in a potentially dangerous situation. Brownout is a complex multiphase flow problem that

Rotorcraft operation in austere environments can result in difficult operating conditions, particularly in the vicinity of sandy areas. The uplift of sediment by rotorcraft downwash, a phenomenon known as brownout, hinders pilot visual cues and may result in a potentially dangerous situation. Brownout is a complex multiphase flow problem that is not unique and depends on both the characteristics of the rotorcraft and the sediment. The lack of fundamental understanding constrains models and limits development of technologies that could mitigate the adverse effects of brownout. This provides the over-arching motivation of the current work focusing on models of particle-laden sediment beds. The particular focus of the current investigations is numerical modeling of near-surface fluid-particle interactions in turbulent boundary layers with and without coherent vortices superimposed on the background flow, that model rotorcraft downwash. The simulations are performed with two groups of particles having different densities both of which display strong vortex-particle interaction close to the source location. The simulations include cases with inter-particle collisions and gravitational settling. Particle effects on the fluid are ignored. The numerical simulations are performed using an Euler- Lagrange method in which a fractional-step approach is used for the fluid and with the particulate phase advanced using Discrete Particle Simulation. The objectives are to gain insight into the fluid-particle dynamics that influence transport near the bed by analyzing the competing effects of the vortices, inter-particle collisions, and gravity. Following the introduction of coherent vortices into the domain, the structures convect downstream, dissipate, and then recover to an equilibrium state with the boundary layer. The particle phase displays an analogous return to an equilibrium state as the vortices dissipate and the boundary layer recovers, though this recovery is slower than for the fluid and is sensitive to the particle response time. The effects of inter-particle collisions are relatively strong and apparent throughout the flow, being most effective in the boundary layer. Gravitational settling increases the particle concentration near the wall and consequently increase inter-particle collisions.
ContributorsMorales, Fernando (Author) / Squires, Kyle D. (Thesis advisor) / Wells, Valana L. (Committee member) / Calhoun, Ronald J. (Committee member) / Arizona State University (Publisher)
Created2011
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Description
This experiment investigated the effects of different vortex generator sizes and configurations on the induced drag of a 2006 Honda Accord, with comparisons to a control test. Tuft tests were carried out prior to any data collection. The tufts were placed along the roof and rear window of the vehicle

This experiment investigated the effects of different vortex generator sizes and configurations on the induced drag of a 2006 Honda Accord, with comparisons to a control test. Tuft tests were carried out prior to any data collection. The tufts were placed along the roof and rear window of the vehicle for each of the five vortex generator types. Video was taken of the tufts for each set of vortex generators, allowing a visual comparison of the flow characteristics with comparison to the control. Out of the four vortex generators tested, the two that yielded the most substantial change in the flow characteristics were utilized. The data collection was conducted utilizing the two sets of vortex generators, one large and one small, placed in three different locations along the roof of the vehicle. Over a course of four trials of data collection, each vortex generator size and configuration was tested two times along a stretch of Interstate 60, with each data set consisting of five minutes heading east, followed by five minutes heading west. Several experimental parameters were collected using an OBD II Bluetooth Adaptor, which were logged using the software compatible with the adaptor. This data was parsed and analyzed in Microsoft Excel and MATLAB. Utilizing an Analysis of Variance (ANOVA) analytical scheme, the data was generalized to account for terrain changes, steady state speed fluctuations, and weather changes per night. Overall, upon analysis of the data, the vortex generators showed little-to-no benefit to either the fuel efficiency or engine load experienced by the vehicle during the duration of the experiment. This result, while unexpected, is substantial as it shows that the expenditure of purchasing these vortex generators for this make and model of vehicle, and potentially other similar vehicles, is unnecessary as it produces no meaningful benefit.
ContributorsMazza, Seth (Author) / Walther, Chase (Co-author) / Takahashi, Timothy (Thesis director) / Middleton, James (Committee member) / Barrett, The Honors College (Contributor) / Mechanical and Aerospace Engineering Program (Contributor)
Created2022-05
166194-Thumbnail Image.png
Description
This experiment investigated the effects of different vortex generator sizes and configurations on the induced drag of a 2006 Honda Accord, with comparisons to a control test. Tuft tests were carried out prior to any data collection. The tufts were placed along the roof and rear window of the vehicle

This experiment investigated the effects of different vortex generator sizes and configurations on the induced drag of a 2006 Honda Accord, with comparisons to a control test. Tuft tests were carried out prior to any data collection. The tufts were placed along the roof and rear window of the vehicle for each of the five vortex generator types. Video was taken of the tufts for each set of vortex generators, allowing a visual comparison of the flow characteristics with comparison to the control. Out of the four vortex generators tested, the two that yielded the most substantial change in the flow characteristics were utilized. The data collection was conducted utilizing the two sets of vortex generators, one large and one small, placed in three different locations along the roof of the vehicle. Over a course of four trials of data collection, each vortex generator size and configuration was tested two times along a stretch of Interstate 60, with each data set consisting of five minutes heading east, followed by five minutes heading west. Several experimental parameters were collected using an OBD II Bluetooth Adaptor, which were logged using the software compatible with the adaptor. This data was parsed and analyzed in Microsoft Excel and MATLAB. Utilizing an Analysis of Variance (ANOVA) analytical scheme, the data was generalized to account for terrain changes, steady state speed fluctuations, and weather changes per night. Overall, upon analysis of the data, the vortex generators showed little-to-no benefit to either the fuel efficiency or engine load experienced by the vehicle during the duration of the experiment. This result, while unexpected, is substantial as it shows that the expenditure of purchasing these vortex generators for this make and model of vehicle, and potentially other similar vehicles, is unnecessary as it produces no meaningful benefit.
ContributorsWalther, Chase (Author) / Mazza, Seth (Co-author) / Takahashi, Timothy (Thesis director) / Middleton, James (Committee member) / Barrett, The Honors College (Contributor) / Mechanical and Aerospace Engineering Program (Contributor)
Created2022-05