Taylor-Couette flow in an elliptical enclosure generated by an inner rotating circular cylinder

Taylor-Couette flow between rotating cylinders is a classical problem in fluid mechanics and has been extensively studied in the case of two concentric circular cylinders. There have been relatively small number of studies in complex-shaped cylinders with one or both cylinders rotating. In this paper, we study the characteristics of Taylor cells in an elliptical outer cylinder with a rotating concentric inner circular cylinder. We numerically solve the three-dimensional unsteady Navier-Stokes equations assuming periodicity in the axial direction. We use a Fourier-spectral meshless discretization by interpolating variables at scattered points using polyharmonic splines and appended polynomials. A pressure-projection algorithm is used to advance the flow equations in time. Results are presented for an ellipse of aspect ratio two and for several flow Reynolds numbers ($Re = \omega r_i (b-r_i))/\nu$, where $\omega$ = angular velocity [rad/s], $r_i$ = radius of inner cylinder, $b$ = semi-minor axis, and $\nu$ = kinematic viscosity) from subcritical to 300. Streamlines, contours of axial velocity, pressure, vorticity, and temperature are presented along with surfaces of Q criterion. The flow is observed to be steady until $Re = 300$ and unsteady at $Re = 350$.Comment: 35 pages, 33 figure

The Design and Optimization of Jet-in-Cross-Flow (JICF) for Engineering Applications: Thermal Uniformity in Gas-turbines and Cavitation Treatment in Hydro-turbines

Jet-in-cross-flow (JICF) is a well-known term in thermal flows field. Ranging from the normal phenomenon like the volcano ash and dust plumes to the designed film cooling and air fuel mixing for combustion, JICF is always studied to understand its nature at different conditions. Realizing the behavior of interacting flows and importance of many variables lead to the process of reiterating the shapes and running conditions for better outcomes or minimizing the losses. Summarizing the process under the name of optimization, two JICF applications are analyzed based on the principles of thermodynamics and fluid mechanics, then some redesigns are proposed to reach the optimal statuses for the goals sought. Correlations and recommendations are given between the input variables and the outputs. In the first application, annular thermal mixing chamber, the cold stream penetrates the axial hot flow as circumferential inward jets. Thermal uniformity of the exit mixture is the target to maximize, and accordingly, a streamlined body is firstly suggested to be placed at the center of the chamber to divert the hot stream towards the cold one. Following the idea, the shape and dimensions (length and maximum diameter) are tested experimentally with four 3-D printed bodies expressing different aspect, blockage, and profile ratios. Later, an Analysis LED Design stage (numerical then experimental) checked the effect of adding swirlers on the best streamlined shape. Swirlers shape, number, and height are examined for the relation with the uniformity and pressure drop. By defining a decision-making variable (useful efficiency), the two contradicting variables were consolidated into one, and the swirlers performance was easier to be quantified and the most efficient one was nominated. At the final stage, a numerical study searched the optimal design(s) using design of experiment and optimization (Global and Hybrid) algorithms. The study sought the optimality of the dimensional aspects (diameter, length, and position) of the swirling streamlined body based on minimizing the contradicting objectives. The results were represented by Pareto curve, correlation matrix, parallel axes, and response surface model. It was understood that the optimization can offer improvement of 68% and 15% to the uniformity number and the pressure drop respectively. On the other hand, aeration treatment for cavitating flow in axial Kaplan turbine was considered for the second engineering application. Using CFD models of a 7.5-cm hydro-turbine, cavitation situation was simulated, then air is injected from the housing to redistribute around the blades of the rotor. The value of the vapor fraction is tracked over the blades and the hub areas throughout the time of turbine cycles. Comparison is achieved by evaluating an average value for the vapor fraction at each case. Air mass flowrate and ports distribution are found to be effective in reducing the cavitation phenomena. Proposed linear aeration distributor on the housing presented a promising technology for spreading the air over the blade chord in a better way than the circumferential distribution. The study allowed the understanding of the flow behavior (in terms of air flow, liquid pressure, and cavitation formations) and turbine performance (i.e. mechanical power) at different air injection locations and turbine rotational speeds. A broader view of research investigated the functionality of linear aeration distributor on the hub with an air supply going through a hollow shaft. The invention of the hub air injection targets the marine industry (i.e. propellers) where the housing/shrouds do not exist, but it also can be a competitor to the housing air injection technology as well. For the two aeration approaches (housing and hub), the conducted numerical investigations were based on the vapor mitigation and power regain in the Kaplan turbine, meanwhile the experimentation looked for the vapor and motor power reduction for the propeller operation. A good agreement (qualitatively and quantitatively) was found between matching cases created for such purpose using tools for high-speed imaging, statistical analysis for turbulent flow, image processing and power measurements. Finally, the dissertation sets some recommendations for the continuation of the researches on the two applications (thermal uniformity and aeration treatments) for better jets interaction with the cross flow by the consideration of the addition/orientation of guide vanes and the relocation of the jets on the turbine blades respectively

Supersonic wind tunnel nozzles: A selected, annotated bibliography to aid in the development of quiet wind tunnel technology

This bibliography, with abstracts, consists of 298 citations arranged in chronological order. The citations were selected to be helpful to persons engaged in the design and development of quiet (low disturbance) nozzles for modern supersonic wind tunnels. Author, subject, and corporate source indexes are included to assist with the location of specific information

NASA patent abstracts bibliography: A continuing bibliography. Section 1: Abstracts (supplement 40)

Abstracts are provided for 181 patents and patent applications entered into the NASA scientific and technical information system during the period July 1991 through December 1991. Each entry consists of a citation, an abstract, and in most cases, a key illustration selected from the patent or patent application

Review of fluid flow and convective heat transfer within rotating disk cavities with impinging jet

International audienceFluid flow and convective heat transfer in rotor-stator configurations, which are of great importance in different engineering applications, are treated in details in this review. The review focuses on convective heat transfer in predominantly outward air flow in the rotor-stator geometries with and without impinging jets and incorporates two main parts, namely, experimental / theoretical methodologies and geometries/results. Experimental methodologies include naphthalene sublimation techniques, steadystate (thin layer) and transient (thermochromic liquid crystals) thermal measurements, thermocouples and infra-red cameras, hot-wire anemometry, laser Doppler and particle image velocimetry, laser plane and smoke generator. Theoretical approaches incorporate modern CFD computational tools (DNS, LES, RANS etc). Geometries and results part being mentioned starting from simple to complex elucidates cases of a free rotating disk, a single disk in the crossflow, single jets impinging onto stationary and rotating disk, rotor-stator systems without and with impinging single jets, as well as multiple jets. Conclusions to the review outline perspectives of the further extension of the investigations of different kinds of the rotor-stator systems and their applications in engineering practice

Bibliography on aerodynamics of airframe/engine integration of high-speed turbine-powered aircraft, volume 1

This bibliography was developed as a first step in the preparation of a monograph on the subject of the aerodynamics of airframe/engine integration of high speed turbine powered aircraft. It lists 1535 unclassified documents published mainly in the period from 1955 to 1980. Primary emphasis was devoted to aerodynamic problems and interferences encountered in the integration process; however, extensive coverage also was given to the characteristics and problems of the isolated propulsion system elements. A detailed topic breakdown structure is used. The primary contents of the individual documents are indicated by the combination of the document's title and its location within the framework of the bibliography

Aeronautical engineering: A continuing bibliography with indexes (supplement 266)

This bibliography lists 645 reports, articles, and other documents introduced into the NASA scientific and technical information system in May 1991. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics

Aeronautical engineering: A continuing bibliography with indexes (supplement 321)

This bibliography lists 496 reports, articles, and other documents introduced into the NASA scientific and technical information system in Sep. 1995. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment, and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics

Aeronautical engineering: A continuing bibliography with indexes (supplement 251)

This bibliography lists 526 reports, articles, and other documents introduced into the NASA scientific and technical information system in April 1990. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics

Aeronautical Engineering: A special bibliography with indexes, supplement 39

This special bibliography lists 417 reports, articles, and other documents introduced into the NASA scientific and technical information system in December 1973