Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1994. / Vita. Abstract. Includes bibliographical references (leaves 56-58). Also available via the Internet.

Velocity and turbulence intensity measurements were made in a linear stationary cascade of compressor blades under high angles of attack. Laser-doppler velocimetry and flow visualization were used. A method was developed for inducing propagating stall and some triggered ensemble averaged velocity records were obtained. An inviscid model was developed in order to predict the separated flow over an isolated blade. The results of this model were qualitatively compared to the pictures obtained by flow visualization. Finally initial attempts were made for extension of this model to predict the unsteady flow in a cascade. / Master of Science

Thesis (M. App. Sc.)--Carleton University, 2004. / Includes bibliographical references (p. 221-230). Also available in electronic format on the Internet.

An experimental investigation of the performance characteristics of a solid wall linear compressor cascade was conducted. The purpose of the experiments was to determine the effects of the blade row configuration parameters stagger and solidity on the pre-and post-stall behavior of the flow in the cascade. Tests were conducted at a solidity of 1.5, and for two stagger angles, 36.4 degrees and 25 degrees. The investigation included the use of high speed motion pictures with smoke flow visualization in the cascade, measurements of the total pressure and velocity of the flow upstream and downstream of the cascade, and measurements of the blade surface pressures. The experiments were conducted for a range of angle of attack from 0 degrees to 45 degrees. To determine the effects of solidity on the pre- and post-stall behavior of the flow in the cascade, the results obtained for the present 1.5 solidity cascade were compared to previous results from the same cascade tested at a solidity of 1.0. The flow in the two cascades was observed to be similar in nature, but the influence of the reduced blade loading in the high solidity cascade was apparent. For the higher solidity cascade, flow losses at low angle of attack were found to be larger, but stalling behavior was delayed. / Master of Science

This investigation was conducted to determine how design variables affect the basic flow characteristics and performance of compressor cascades with stalled flow. The performance of stalled cascades is required for analyzing with computer models stall and post stall behavior of axial flow compressors. In this investigation, the unsteadiness of the stalled flow and the stalled cascade performance as indicated by the blade normal force and total pressure loss were evaluated. The investigation consisted of both experimental and numerical phases. The effects of stagger, angle of attack and Reynolds number were investigated experimentally using a two-dimensional cascade facility. Surface flow visualization, smoke flow visualization, velocity measurements and pressure measurements were used to evaluate the flow. The flow was modeled numerically by solving the Navier-Stokes equations for a cascade of flat plates. All of the results indicate that blade stagger is a key variable in determining the performance of a stalled cascade. The smoke flow visualization revealed that propagating stall occurred for the cascades with staggers of 36.5 and 45 degrees at all angles of attack greater than or equal to the angle of full stall inception. Propagating stall was never observed for the cascade with a 25 degree stagger. The flow in the passages of the 25 degree stagger cascade was characterized by two distinct regions of flow, a potential or inviscid region with no losses and a separated region with high losses. For the two higher stagger cascades, two distinct regions did not exist. The performance data for the cascades were consistent with the qualitative results obtained in the flow visualization. When presented as a function of angle of attack, the performance parameters indicate that the loss curve is steeper, the maximum value of the normal force coefficient is lower, and the maximum normal force occurred at a lower angle of attack for the higher staggered cascades. The numerical study revealed trends in cascade performance similar to those found in the experimental study and showed that the predicted losses continue to rise as the limiting inlet angle is approached. / Ph. D.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1981. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND AERO / Includes bibliographical references. / by Saeed Farokhi. / Ph.D.

In the first part of the thesis, we carried out direct two-dimensional (2D) multipoint measurements of the velocity fields in a turbulent Rayleigh-Benard convection cell to study the properties of small-scale convective turbulence. The local homogeneity and isotropy of the velocity field are tested using a number of criteria and are found to hold to an excellent degree. The properties of velocity circulation Gammar are also studied. The results show that the circulation appears to be more effective to capture the effect of local anisotropy than the velocity field itself. The distribution of Gammar is found to depend on the scale r, reflecting strong intermittency. It is further found that velocity circulation has the same anomalous scaling exponents as the longitudinal and transverse structure functions for low-order moments (p ≲ 5). Whereas, for high-order moments (p ≳ 5), the anomalous scaling exponents for circulation are found to be systematically smaller than the scaling exponents of the longitudinal and transverse structure functions. / In the second part of the thesis, the simultaneous visualization of the temperature and velocity fields was used to study the properties of thermal plumes. Our visualization reveals the process of the morphological evolution between sheetlike and mushroomlike plumes, which were also quantified by the height dependence of plume numbers and of vorticity fluctuations. A direct connection between the heat transport and coherent structures, i.e. thermal plumes, was established, which shows that it is plume number that primarily determines the Nu-Ra scaling relation. Individual plumes were extracted and their statistical and geometric properties were studied. It is found that the log-normal distribution is universal for thermal plumes and the log-normal statistics may be used to model them. In addition, both our quantitative characteristic and direct 3D spatial visualizations indicate that the previously-believed sheetlike plumes should be reconsidered to be only one-dimensional structures. / In the third part of the thesis, the planar laser-induced fluorescence technique was induced to study the 2D passive scalar mixing in high-Schmidt-number buoyancy-driven turbulence. The passive scalar mixing evolution was studied and various geometric properties, such as shape complexity, fractal dimension and local curvature, were used to characterize the isoconcentration contours of the 2D passive scalar fields. It is found that when the flow gets more turbulent the shape of passive scalar packets becomes closer to a circular shape and the passive scalar mixing becomes more isotropic, indicating the increased mixing and stirring of the turbulent flow. / The objective of this thesis is to address the following three key issues in turbulent thermal convection, i.e. turbulent fluctuations in small scales, coherent structures and passive scalar mixing in buoyancy-driven turbulence. / Zhou, Quan = 對流熱湍流中能量級串, 相干結構和標量場混合的实验研究 / 周全. / Adviser: Ke-Qing Xia. / Source: Dissertation Abstracts International, Volume: 70-06, Section: B, page: 3576. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references (leaves 103-117). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307. / Zhou, Quan = Dui liu re tuan liu zhong neng liang ji chuan, xiang gan jie gou he biao liang chang hun he de shi yan yan jiu / Zhou Quan.

This thesis is on the existence and uniqueness of weak solutions to the Navier-Stokes equations in R3 which govern the velocity of incompressible fluid with viscosity ν. The solution is obtained in the space of tempered distributions on R3 given an initial condition and forcing data which are dominated by majorizing kernels. The solution takes the form of an expectation of functionals on a Markov process indexed by a binary branching tree. / Graduation date: 2012

This thesis presents an investigation into the motions of the horseshoe vortices and the passage vortex, within a plane turbine blade cascade. Fluid motion was determined using a tracer gas technique. Ethylene was injected into the pressure-side and suction-side legs of the horseshoe vortex, near the leading edge of the cascade. Ethylene concentrations were determined at two downstream locations using a flame ionization detector. It was found that the pressure-side leg of the horseshoe vortex moved toward the suction side of the passage, starting the formation of the passage vortex, and was distributed throughout the passage vortex. The suction-side leg of the horseshoe vortex convected once around the periphery of the passage vortex before passing the cascade trailing edge. Downstream of the trailing edge, most of the fluid from the suction-side leg diffused into the passage vortex. However, twice as much fluid from the suction-side leg, as opposed to the pressure-side leg, mixed within the blade wake. At a location 40% of the axial chord downstream of the trailing edge, the passage vortex (shown previously to account for 60% of the overall total pressure losses) contained over 65% of the fluids from both legs. / M.S.

An investigation has been performed of the flow in a supersonic through-flow fan blade cascade. The blade shapes are those of the baseline supersonic through-flow fan (STFF) under investigation at the NASA Lewis Research Center. Measurements were made at an inlet Mach number of 2.36 over a 15° range of incidence. Flowfield wave patterns were recorded using spark shadowgraph photography and steady-state instrumentation was used to measure blade surface pressure distributions and downstream total and static pressure distributions. A two-dimensional LDV system was used to map the downstream flowfield. From these measurements, the integrated loss coefficients are presented as a function of incidence angle along with analysis indicating the source of losses in the STFF cascade. The results are compared with calculations made using a two-dimensional, cell-centered, finite-volume, Navier-Stokes code with upwind options. Good general agreement is found at design conditions, with lesser agreement at off-design conditions. Analysis of the leading edge shock shows that the leading edge radius is a major source of losses in STFF blades. Losses from the leading edge bluntness are convected downstream into the blade wake, and are difficult to distinguish from viscous losses. Shock losses are estimated to account for 70% to 80% of the losses in the STFF cascade. / Ph. D.