The objective of this study is to computationally investigate the vorticity generated by the wake of a (1) rotor blade and a (2) hydrofoil profile. The first flow is weakly compressible and is inspired by experiments carried out by Dr. Tinney at The University of Texas at Austin aimed at investigating the aeroacoustic effects of blade-vortex interactions. The second flowis inspired by experiments carried out by Dr. Irvine at the University of Chicago where a ring with a hydrofoil-shaped cross-section is pulled in water to create a coherent vortical structure. Simulations have been carried out with the high-order unstructured block-spectral code solverH3AMR. The rotor blade simulations have been performed at the nominal angle of attackof 7.4°where an unsteady vortical wake with quasi-periodic shedding was observed together with a surprising dependency of the lift coefficient on the thermal boundary conditions: the lift coefficient is predicted to increase from 0.96 to 1.14 when switching from adiabatic to isothermal no-slip conditions. The hydrofoil calculations were run with steady free-stream conditions (not matching the experiments) and showed massively separated flow on the suction side due to the high angle of attack.

Interaction of fluctuating vortex shedding with blade vibration can lead to a new class of aeromechanical instability referred as Non-synchronous vibrations. Investigating a well-known case that shows similar NSV features such as a circular cylinder can develop the understanding of physics behind NSV. A common approach to further investigating the vortex induced vibration is to control the motion of the cylinder and allowing the response of the wake to the motion to be studied in isolation. It has been found very important to carefully match the experimental conditions between free and controlled vibration. Many of research in the field of vortex induced vibration apply a rigid cylinder mounted horizontally and moving transversely to the flow stream as a paradigm for understanding the physics behind this phenomenon. Regarding the difficulties of implementation of vertically moving cylinder in experimental study, vortex dynamic and lock-in behavior of eccentrically rotating cylinder is studied in this M.Sc. Thesis. The main focus of this research is to understand to what extend a general feature of free vortex-induced vibration can be observed in the case of eccentrically rotating cylinder. If the present case captures the essential characteristics of freely oscillating cylinder the results of the forced motion via eccentrically rotating cylinder can be applied to predict the motion of an elastically mounted body. To do so a CFD model is established to predict the response, vorticity structure in near wake, timing of vortex shedding and the range of lock-in region over specific parameter space of the introduced alternative case. A commercial CFD code, Ansys/CFX, was implemented to perform this numerical study. Existences of synchronization region, striking similarity in lift force coefficient and wake mode have been observed in the current study.

The GARVEE Transportation Program started by the Idaho Transportation Department has improved parts of I-84 in Boise, Idaho. These desired improvements led to the widening of a bridge over the New York Canal (NYC) in 2009. To support the wider road, additional bridge columns were installed. The new bridge columns had a larger diameter than the existing columns and raised the number of columns from 28 to 60. Construction was completed just before the irrigation season began. During the first irrigation season it was observed that waves and oscillations were occurring within the canal immediately adjacent to the bridge structure. Throughout the irrigation season, it was observed that the intensity of the oscillations would vary. It was also observed that the wave oscillations propagated upstream and downstream from the bridge structure. Both longitudinal and transverse waves were observed. The waves appeared to originate in the section of the canal that was under the I-84 Bridge. A physical model was built in 2010 at Utah State University's (USU) Utah Water Research Laboratory (UWRL) in an attempt to simulate the oscillation phenomenon and to develop potential solutions to the problem. During the original modeling work, a thorough investigation to the causes of this phenomenon was not accomplished due to time constraints. The objective of the follow-up research presented in this thesis was to qualitatively determine the causes of the oscillations. Laboratory tests were performed using the original physical model used in the original 2010 testing.

京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第18682号 / 医博第3954号 / 新制||医||1007(附属図書館) / 31615 / 京都大学大学院医学研究科医学専攻 / (主査)教授 羽賀 博典, 教授 野田 亮, 教授 坂井 義治 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第20691号 / 工博第4388号 / 新制||工||1682(附属図書館) / 京都大学大学院工学研究科都市環境工学専攻 / (主査)教授 田中 宏明, 教授 高野 裕久, 教授 米田 稔 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

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Researchers have investigated several factors that could alter fetal growth, including nutrient restriction (Valiente et al., 2021), hair shedding (Gray et al., 2011), and extreme hot and cold temperatures (Davidson et al., 2022). Hot temperatures and increased humidity percentages in the southeast United States caused researchers to investigate the hair coats of Angus cattle in the commercial production setting. An improvement in fiber digestibility and calf birth and weaning weights has been observed in Angus dams that shed 50% of the winter hair coat by May (Gray et al., 2011; Burnett et al., 2021). Our objective of this experiment was to investigate the nutrient digestibility of Angus calves born to cows that on average, shed early compared to calves from cows that shed later. Newly weaned, purebred Angus bull calves (early; n = 6, late; n = 6) were housed in metabolism crates for 10 d. Prior to the trial, calves had a 14 d adaption period to a 14% CP textured feed (CPC 14% Developer, CPC Commodities, Fountain Run, KY) and offered ad libitum Cynodon dactlyon hay and water. After 3 d crate acclimation period, urine, feces, orts, and hay samples were collected for 7 d. Concentrate was offered at 0.25% of average BW. Approximately 5% samples were taken of feces, and urine samples had 1-1.5% of 25% metaphosphoric acid added to prevent ammonia volatilization, and both collections were composited by animal. Orts were collected at 0600 h daily, dried, and composited by animal. Laboratory analysis included dry matter (DM), organic matter (OM), Ash, neutral detergent fiber (NDF), acid detergent fiber (ADF), Kjeldahl N (CP), and fat. Data were analyzed using the GLM procedure of SAS 9.4 in a completely randomized design with calf as the experimental unit. Significant (P ≤ 0.05) means were separated using Fischer’s protected LSD. The model for intake included average daily DM and OM (kg) and adjusted by body weight (BW%). For digestibility analysis, the model included: DM, OM, ash, NDF, ADF, hemi-cellulose (HC), CP, and fat. The N retention model included: N retained (g/d), N retained/consumed (%), and N retained/DM intake (%). There were no differences between early or late calves for DM intake (5.502 ± 0.2774 kg/d; 2.251 ± 0.1247 %BW), or OM intake (5.199 ± 0.2591 kg/d; 2.128 ± 0.1166 %BW). There were no differences in digestibility for either group for DM, OM, Ash, NDF, ADF, HC, CP, or fat (Table 1.). There were also no differences in N retention in either group of calves (3.686 ± 2.0242 g/d; 4.366 ± 2.3964 %; 0.064 ± 0.0355 %). Replication and further research are needed in this area to adequately understand factors influencing nutrient digestibility in calves born from early and late shedding dams.

Experiments have been performed using the Air Force Research Laboratory (AFRL) Blade-Row Interaction (BRI) rig to investigate interactions between a loaded stator and transonic rotor. The BRI rig is a high-speed, highly loaded compressor consisting of a swirler/deswirler, a transonic rotor and a stator. The swirler/deswirler of the BRI rig is used to simulate an embedded transonic fan stage with realistic geometry which produces a wake through diffusion. Details of the unsteady flow field between the stator and rotor were obtained using Particle Image Velocimetry (PIV). Flow visualization images and PIV data that facilitate analysis of vortex shedding, wake motion, and wake-shock-interactions in the blade row are analyzed for three stator/rotor axial spacings and two stator loadings. The data analysis focuses on measuring and comparing, for the different spacings and loading, the vortex size, strength, and location as it forms on the stator trailing edge and propagates downstream into the rotor passage. It was observed that more than one vortex was shed with the passing of a rotor bow shock. These vortices were categorized as small and large vortices with a ~20% decrease in strength. The large vortices were compared at similar location and results show that vortex strength increased as spacing between stator and rotor decreased due to the increased strength of the rotor bow shock impacting the stator trailing edge. Changes in stator loading also affected shed vortex strength. A decrease in stator loading resulted in a decrease in the strength of the vortex shed. The smaller vortices were not affected by a change in spacing but strength was directly related to the loading.

Control of vortex-driven instabilities was demonstrated via a scaled-down, cold-flow simulation that modeled closed-end acoustics. When vortex shedding frequencies couple with the natural acoustic modes of a choked chamber, potentially damaging low-frequency instabilities may arise. Although passive solutions can be effective, an active control solution is preferable. An experiment was performed to demonstrate an active control scheme for the reduction of vortex-driven oscillations. A non-reacting experiment using a primary flow of air, where both the duct exit and inlet are choked, simulated the closed-end acoustics. Two plates, separated by 1.27 cm, produced the vortex shedding phenomenon at the chamber's first longitudinal mode. Two active control schemes, closed-loop and open-loop, were studied via a cold-flow simulation for validating the effects of reducing vortex shedding instabilities in the system. Actuation for both control schemes was produced by using a secondary injection method. The actuation system consisted of pulsing compressed air from a modifed, 2-stroke model airplane engine, controlled and powered by a DC motor. The use of open-loop only active control was not highly effective in reducing the amplitude of the first longitudinal acoustic mode, near 93 Hz, when the secondary injection was pulsed at the same modal frequency. This was due to the uncontrolled phasing of the secondary injection system. A Pulse Width Modulated (PWM) signal was added to the open-loop control scheme to correct for improper phasing of the secondary injection flow relative to the primary flow. This addition allowed the motor speed to be intermittently increased to a higher RPM before returning to the desired open-loop control state. This proved to be effective in reducing the pressure disturbance by approximately 46%. A closed-loop control scheme was then test for its effectiveness in controlling the phase of the secondary injection. Feedback of the system's state was determined by placing a dynamic pressure transducer near the chamber exit. Closed-loop active control, using the designed secondary injection system, was proven as an effective means of reducing the problematic instabilities. A 50% reduction in the FFT RMS amplitude was realized by utilizing a Proportional-Derivative controller to modify the phase of the secondary injection.