Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 20 for “"Wake Interaction"”.
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Nonlinear airfoil-wake interaction in large amplitude unsteady flow
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1987.
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Heat Transfer from Multiple Row Arrays of Low Aspect Ratio Pin Fins
… with flow incidence angles experienced less wake interaction between pins than arrays with perpendicular flow, which caused a slight decrease in heat transfer in arrays with flow incidence angles. The effect of flow incidence angle on array-average Nusselt number was greater at tighter pin …
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Ram-jet combustion based on shock/flame interaction
… investigation into the effects of shock/wake and shock/flame interaction on the base pressure of axisymmetric bodies at Mach 2 has been carried out. This investigation has determined the effects of various forms of shock generator (axisymmetric cowls, twodimensional wedges and 'delta' …
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Two-dimensional Wakes and Fluid-structure Interaction of Circular Cylinders in Cross-flow
The wake of a bluff body is a representative issue in vortex dynamics that plays a central role in civil engineering, ocean engineering and thermal engineering. In this work, a flowing soap film was used to investigate the wakes of multiple stationary circular cylinders and of a single oscillating …
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Investigation of the Aerodynamic and Acoustic Performance of a Scaled eVTOL Propeller in Axial and Non-Axial Flight
… noise, a characteristic feature of Blade-Wake Interaction. Additionally, BEMT calculations predict thrust and torque within 10% accuracy of the measured data across most conditions. Supplementary calculations of the induced velocity fields offer preliminary insights into the distortion …
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Coordinated Optimal Power Planning of Wind Turbines in a Wind Farm
… and power generation among wind turbines. Wake interferences among wind turbines can lower the overall efficiency considerably, while offshore conditions pose increased loading on wind turbines. In wind farms, wind turbines* wake affects each other depending on their positions and operation …
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Computational modeling of wind turbine wake interactions
… understanding of wind turbine aerodynamics and wake interactions. The following thesis work looks to study turbulence closure methods widely used in computational fluid dynamics (CFD) and their applicability for modeling wind turbine aerodynamics. The first investigation is a parametric study of …
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Analysis of Two-point Turbulence Measurements for Aeroacoustics
… measurements taken in the first flow, a lifting wake from a rectangular NACA 0012 half wing, are used to calculate space-time correlation functions and 'pointwise' wave number frequency spectra. Two upwash spectra, calculated for locations in the region of the wake that is roughly homogenous in …
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A Fundamental Study of Advance Ratio, Solidity, Turbine Radius, and Blade Profile on the Performance Characteristics of Vertical Axis Turbines (VATs)
… the effect of advance ratio, solidity, and wake interactions were investigated. Simulations were completed in OpenFOAM using the k-ω SST turbulence model at a nominal Reynolds number of 500,000 using a NACA 0015 airfoil. To simulate the motion of the turbine, Arbitrary Mesh Interfacing (AMI) …
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Aerodynamic and Aeroacoustic Analysis of Low Reynolds Number Propellers Using Higher-Order RANS Transition Turbulence Modeling
… detailed flow features, particularly in the wake, compared to other fully turbulent and transition models, which is attributed to its Galilean invariant framework. To leverage the boundary layer information obtained from the proposed model, a semi-empirical broadband noise prediction method …
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Mean Loading and Turbulence Scale Effects on the Surface Pressure Fluctuations Occurring on a NACA 0015 Airfoil Immersed in Grid Generated Turbulence
… fluctuations resulting from turbulence/airfoil interaction. Also, measurements are compared with the theory of Amiet (1976a,b). The surface pressure response shows a dependance on angle of attack, the nature of which is related to the relative chord/turbulence scale. The dependance on turbulence …
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Vorticity control for efficient propulsion
… in a fish-like manner. Finally, we explored the interaction of a foil with oncoming vorticity to identify the processes by which vorticity can be manipulated. Throughout this thesis, digital particle image velocimetry (DPIV) is used to make quantitative multipoint measurements of the unsteady …
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Unsteady Turbulence Interaction in a Tip Leakage Flow Downstream of a Simulated Axial Compressor Rotor
… produced by a rotor operating in the vortical wakes of a set of stator vanes. The cascade, consisting of 8 GE rotor B blades, has adjustable tip gap, inlet angle of 65.1 degrees, turning angle of 11.8 degrees and solidity of 1.076. The cascade Reynolds number, based on blade chord, was 393,000. …
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Experimental Investigation of the Active Flow Control on a Two-Dimensional Wind Turbine Airfoil
… loading generated by an upstream cylinder wake was reduced by up to 12% using a proportional closed loop control algorithm at 27 degree angle of incidence. Under the same unsteady freestream conditions, the averaged lift coefficient at 19 degree angle of incidence was enhanced by up to 20% …
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Numerical investigation of air vehicle noise propagation effects
… case experimental database is used. Blade Vortex Interaction (BVI) noise, the dominant noise contributor during descent, is mainly examined. It is shown that advancing side BVI noise is affected by nonlinear distortion, while retreating side BVI noise is not. For some frequency bands the …
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Comparative Analysis of Serrated Trailing Edge Designs on Idealized Aircraft Engine Fan Blades for Noise Reduction
… blade downstream of the blade row. In the wake region, the individual trailing edge serrations tips and valleys could be seen. As the wake convected downstream, the individual tips and valleys became less visible and the wake was more uniform in profile. The tip leakage vortex was only …
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Computations of bubble dynamics with heat transfer
… by displacing liquid, particularly in the wake region behind the bubble. This, in turn, increases heat transfer from the hot surface, by continuously bringing cooler liquid into contact with the hot surface and removing hot liquid from the surface. However, despite its industrial relevance, …
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Propeller Noise Prediction of an Urban Air Mobility Vehicle in Urban Environment
… complex, unsteady aerodynamic environments where wake interactions, gust and turbulence significantly affect both performance and noise generation. Understanding these mechanisms is critical for developing quieter and more efficient eVTOL systems that meet future community noise and certification …
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Vertical axis wind turbine acoustics
… rotor; this noise was thought to be due to the interaction of the blades in the downstream half of the rotor with the wake from the blades in the upstream half. It was suggested that blade wake interaction is the dominant noise source in the typical range of peak performance for the full-scale …
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Measurement and Prediction of Rotor Noise Sources for sUAS in Outdoor and Laboratory Environments
… solidity screens were placed in the downstream wake of each rotor to delay the onset of recirculation. Placing the screens in the wake did not produce a noticeable effect on or delay recirculation within the confined testing environment. Measurements of the BPF and higher order harmonics of each …