Master of Science (M.S.), University of Dayton, 2020, Aerospace Engineering

Velocity measurement inside of a wind tunnel is an extremely useful quantitative data for a multitude of reasons. One major reason is that velocity has a mathematical relationship with dynamic pressure which in turn influences all the aerodynamic forces on the test model. Many devices and methods exist for measuring velocity inside wind tunnels. At the same time, Doppler wind lidar (light detection and ranging) has been used for decades to make air speed measurements outdoors at long ranges. Lidar has been proven effective for many applications, and it has the potential to solve many of the problems faced by current velocimetry techniques inside wind tunnels. Despite this, minimal research has been performed with Doppler wind lidars inside wind tunnels. While multiple commercial systems exist for making air speed measurements at longer ranges, there are currently no widely available commercial devices designed to work well inside wind tunnels. In this research, initial work is described for the design and development of a continuous wave (CW), coherent wind lidar system. The system is for use as an alternative non-intrusive velocimetry method inside wind tunnels relying on the Doppler effect. A scaled down wind lidar designed to operate at much shorter ranges than current commercial wind lidars can be simpler, less expensive, and require less power. A first iteration of the design was constructed for proof of concept testing with a small-scale wind tunnel at low speeds (7.5-9 m/s). Testing showed that the lidar system could take one-dimensional speed measurements of seeded flow that closely matched Pitot static tube data. When not adding tracer particles to the flow, the lidar return signal was not strong enough for the photodetector used to measure the beat frequency. This research is focused on the process for designing the Doppler wind lidar system, constructing the experimental setup, and studying methods for data analysis. Results of testing presente (open full item for complete abstract)

Committee: Sidaard Gunasekaran (Advisor); Aaron Altman (Committee Member); Paul McManamon (Committee Member) Subjects: Aerospace Engineering; Atmosphere; Atmospheric Sciences; Engineering; Optics; Technology

Master of Science (M.S.), University of Dayton, 2011, Electro-Optics

Multi-aperture imaging has been used to receive high resolution images from arrays of sub-apertures. The use of sub-aperture arrays allows for more compact optical systems and enables conformal aperture imaging. Images collected from these arrays are processed to obtain the high resolution image. A High resolution image is created from an accurate representation of the pupil plane fields in each sub-aperture. Data processing to create an image is time consuming and computationally heavy. Compensating for the unknown piston phase error between the different sub-apertures is one of the more time consuming corrections required to process the image data into a single image. Sub-aperture phasing simulations are used to explore the processing of multi-aperture arrays. The data is processed for several sub-aperture arrays, including 2 and 3 in-line sub-aperture arrays, and hex 7 and 19 sub-aperture arrays. A scheme is proposed for measuring the piston phases in each sub-aperture. It is shown through numerical simulations that a system that measures the piston phase could significantly reduce the processing time required to phase the images from a multi aperture system into a single high resolution image.

Committee: Paaul McManamon (Advisor) Subjects: Electrical Engineering; Optics

Master of Science (M.S.), University of Dayton, 2010, Electro-Optics

Sparse frequency, linearly frequency modulated laser radar (ladar) signals achieve improved range resolution comparable to a larger signal bandwidth. From basic radar/ladar principles it is known that the bandwidth of a signal is inversely proportional to range resolution. Hence, the effective bandwidth of a ladar signal using sparse frequency techniques is larger than the bandwidth of each modulated laser frequency. Previous experiments have validated range resolution and peak to sidelobe ratio derived from models utilizing two segmented bandwidths. This thesis discusses the modeling with three segmented bandwidths. The model is verified against an experimental setup using three frequency offset lasers.The two segmented bandwidth, sparse frequency ladar signal is reexamined to include Doppler effects. The new modeling utilizes a coherent on receive setup allowing for phase information to be processed from the signal. The extracted phase information can be used to determine characteristics about a target, namely its speed and direction with respect to the receiver. This modeling was experimentally verified for cases where the target was next to the receiver, at a distance (simulated through a fiber delay line), and for multiple targets. As a final check of the modeling, the velocity determined from the phase information was compared against the velocity readout of a stage with a built in optical encoder.

Committee: Peter Powers PhD (Advisor); Dierking Matthew PhD (Committee Member); Haus Joseph PhD (Committee Member) Subjects: Engineering; Optics; Physics