Aspects of Turbulence and Stochastic Processes in Fluid Mechanics

1 online resource (217 pages) : PDF

2018

University of North Carolina at Charlotte

Three experimental studies are executed to examine aspects of turbulence and stochastic processes in fluid mechanics. Each experimental study is conducted in a different medium; water, wind and vibrated grain piles. Each study requires upgrades to existing equipment and data analysis hardware. The first two studies were conducted to develop a better understanding of the physics of flow conditions in general, and more specifically around a bluff body, while the third study utilizes a proposed experimental method to use macroscopic scale grains for studying molecular hydrodynamics. The first experimental study examines wake structures in the flow past a bluff body utilizing the university hydrodynamic water channel and upgraded tomographic particle image velocimetry system. This volumetric PIV method utilizes an asymmetric camera configuration. This method allows for an accurate instantaneous visualization and characterization of flow structures present in the wake region without stitching multiple planes together to generate a time-averaged volume. One advantage of the updated system is that the flow can be realized on the time scale of the image capture, therefore wake motions can be seen as a function of time at the velocity tested. Tests were conducted to determine the best surface color of the model to improve processing methods. The results of this volumetric flow study are then compared to the benchmark diagrams. The second study examines flow structures and pressure correlations in the wind tunnel utilizing a 100 Hz standard 2D PIV and five pressure sensors to gather data on the walls of the bluff body as well as eight pressure sensors in the floor of the wake region. Three seeding materials are tested to determine which provided the most reliable and uniform results. The pressure data is utilized to determine if there is a correlation in the pressures on the sides of the bodies, specifically in the reattachment zones with pressures along the top of the body. The PIV data is then compared with the data analyzed in the previous study.The third study examines molecular hydrodynamic processes in dense liquids and gases. This experiment utilizes a standard vibratory polishing rig and high speed camera to gather images to be used in a non-traditional PIV process which allows for macroscopic observations of a variety of dynamical processes. This data, coupled with force and vibration data demonstrate the framework of an analog method for studying molecular hydrodynamics, which is historically studied using photonic or neutron beam scattering techniques. Utilizing this unique experimental set up, the packing density as well as kinematic and dynamic viscosities are determined for seven different types of solid media.

doctoral dissertations

Mechanical engineering
Fluid mechanics

Ph.D.

Bluff Body Aerodynamics
Molecular Hydrodynamics
Particle Image Velcoimetry
Wake Structures
Water Channel
Wind Tunnel

Mechanical Engineering

Tkacik, Peter

Keanini, Russell
Hellman, Samuel
Kakad, Yogendra
Lim, Jae Hoon

Thesis (Ph.D.)--University of North Carolina at Charlotte, 2018.

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Dahlberg_uncc_0694D_11889

http://hdl.handle.net/20.500.13093/etd:1415