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The fluid dynamics of curved diffuser duct flows of military aircraft is discussed. Three-dimensional parabolized Navier-Stokes analysis, and experiment techniques are reviewed. Flow measurements and pressure distributions are shown. Velocity vectors, and the effects of vortex generators are considered.
Although most of the magnetic flux observed on the sun originates in the low-latitude sunspot belts, this flux is gradually dispersed over a much wider range of latitudes by supergranular convective motions and meridional circulation. Numerical simulations show how these transport processes interact over the 11-year sunspot cycle to produce a strong 'topknot' polar field, whose existence near sunspot minimum is suggested by the observed strength of the interplanetary magnetic field and by the observed areal extent of polar coronal holes. The required rates of diffusion and flow are consistent with the decay rates of active regions and with the rotational properties of the large-scale solar magnetic field.
A finite element algorithm for the computation of confined, axisymmetric, turbulent diffusion flames is developed. The mean mixture properties were obtained by three methods based on diffusion flame concept: without using a probability density function (PDF), with a double-delta PDF, and with a beta PDF. A comparison is made for the combustion models, and the effect of turbulence on combustion are discussed.
The mechanisms that give rise to the sun's large-scale poloidal magnetic field are explored in the framework of the Babcock-Leighton (BL) model. It is shown that there are in general two quite distinct contributions to the generation of the 'alpha effect': the first is associated with the axial tilts of the bipolar magnetic regions as they erupt at the surface, while the second arises through the interaction between diffusion and flow as the magnetic flux is dispersed over the surface. The general relationship between flux transport and the BL dynamo is discussed.
The dynamic characteristics of hypersonic vehicles are reviewed, with special attention to the interactions between the airframe, engine, and structural dynamics. Based on a preliminary investigation of the dynamics of a generic vehicle configuration similar to the X-30 with Scramjet propulsion, an assessment of these interactions is presented. The control effectors include aerodynamic pitch-control surfaces, as well as engine fuel flow and diffuser area ratio. The study configuration is statically instable in pitch, and exhibits strong airframe/engine/elastic coupling in the attitude dynamics and engine responses. This strong coupling will require a highly integrated airframe-engine control system, and the performance of the attitude control system will be contingent upon the ability to adequately deal with the structural aeroelastic response and engine dynamics.
The development of an approach to the determination of the dynamic characteristics of hypersonic vehicles which is intentionally generic and basic is given. The approach involves a 2D hypersonic aerodynamic analysis utilizing Newtonian theory, coupled with a 1D aero/thermoanalysis of the flow in a scramjet-type propulsion system. In addition, the airframe is considered to be elastic, and the structural dynamics are characterized in terms of a simple lumped-mass model of the invacuo vibration modes. The vibration modes are coupled to the rigid-body modes through the aero/propulsive forces acting on the structure. The control effectors considered on a generic study configuration include aerodynamic pitch-control surfaces, as well as engine fuel flow and diffuser area ratio. The study configuration is shown to be highly statically unstable in pitch, and to exhibit strong airframe/engine/elastic coupling in the aeroelastic and attitude dynamics, as well as the engine responses.
The microgravity materials processing program has been instrumental in providing the crystal growth community with an experimental environment to better understand the phenomena associated with the growing of crystals. In many applications one may pursue the growth of large single crystals which cannot be grown on earth due to convective driven flows. A microgravity environment is characterized by neither convection of buoyancy. Consequently superior crystals are able to be grown in space. On the other hand, since neither convection nor buoyancy dominates the fluid flow in a microgravity environment, then lesser dominating phenomena can affect crystal growth, such as surface driven flows or diffusion limited solidification. In the case of experiments that are to be flown in space using the Fluid Experiments System (FES), diffusion limited growth should be the dominating phenomenon. The use of holographic and Schlieren optical techniques for studying the concentration gradients in solidification processes has been used by several investigators over the years. The Holographic Ground System (HGS) facility at MSFC has been a primary resource in researching this capability. Consequently scientific personnel have been able to utilize these techniques in both ground based research and in space experiments. An important event in the scientific utilization of the HGS facilities was the TGS (triglycine sulfate) Crystal Growth and the Casting and Solidification Technology (CAST) experiments that were flown on the International Microgravity Lab (IML) mission in March of this year. The preparation and processing of these space observations are the primary experiments reported in this work. This project provides some ground-based studies to optimize on the holographic techniques used to acquire information about the crystal growth processes flown on IML. Since the ground-based studies will be compared with the space-based experimental results, it is necessary to conduct sufficient ground based studies to best determine how the experiment in space worked. The current capabilities in computer based systems for image processing and numerical computation have certainly assisted in those efforts. As anticipated, this study has certainly shown that these advanced computing capabilities are helpful in the data analysis of such experiments.
Results are presented of a dimensional study and an experimental investigation of the pressure rise across a shock wave which causes separation of the boundary layer on a flat plate. The experimental part of the investigation was conducted at a Mach number of 3.03 for a Reynolds number range of 2 x 10 (sup) 6 to 19 x 10 (sup) 6. The available experimental data are compared with the predictions of the present study, and the significance of the results obtained is discussed relative to certain practical design problems.
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A method of successive approximations for the solution of problems in the fields of diffusion, boundary-layer flow, and heat-transfer is illustrated by solving problems in each of these fields. In most of the examples, the approximate solutions are compared with known accurate solutions and the agreement is shown to be good.
Liquid fuel dispersion in practical systems is typically achieved by spraying the fuel into a polydisperse distribution of droplets evaporating and burning in a turbulent gaseous environment In view of the nearly insurmountable difficulties of this two-phase flow, a systematic study of spray evaporation and burning in configurations of gradually increasing levels of complexity, starting from laminar sprays to fully turbulent ones, would be useful. A few years ago we proposed to use an electrostatic spray of charged droplets for this type of combustion experiments under well-defined conditions. In the simplest configuration, a liquid is fed into a small metal tube maintained at several kilovolts relative to a ground electrode few centimeters away. Under the action of the electric field, the liquid meniscus at the outlet of the capillary takes a conical shape, with a thin jet emerging from the cone tip (cone-jet mode). This jet breaks up farther downstream into a spray of charged droplets - the so-called ElectroSpray (ES). Several advantages distinguish the electrospray from alternative atomization techniques: (1) it can produce quasi-monodisperse droplets over a phenomenal size range; (2) the atomization, that is strictly electrostatic, is decoupled from gas flow processes, which provides some flexibility in the selection and control of the experimental conditions; (3) the Coulombic repulsion of homopolarly charged droplets induces spray self-dispersion and prevents droplet coalescence; (4) the ES provides the opportunity of studying regimes of slip between droplets and host gas without compromising the control of the spray properties; and (5) the compactness and potential controllability of this spray generation system makes it appealing for studies in reduced-gravity environments aimed at isolating the spray behavior from natural convection complications. With these premises, in March 1991 we initiated a series of experiments under NASA sponsorship (NAG3-1259 and 1688) in which the ES was used as a research tool to examine spray combustion in counter-flow and co-flow spray diffusion flames, as summarized below. The ultimate objective of this investigation is to examine the formation and burning of sprays of liquid fuels, at both normal and reduced gravity, first in laminar regimes and then in turbulent ones.
Methods and apparatus are provided for a blood pump bearing system within a pump housing to support long-term high-speed rotation of a rotor with an impeller blade having a plurality of individual magnets disposed thereon to provide a small radial air gap between the magnets and a stator of less than 0.025 inches. The bearing system may be mounted within a flow straightener, diffuser, or other pump element to support the shaft of a pump rotor. The bearing system includes a zirconia shaft having a radiused end. The radiused end has a first radius selected to be about three times greater than the radius of the zirconia shaft. The radiused end of the zirconia shaft engages a flat sapphire endstone. Due to the relative hardness of these materials a flat is quickly produced during break-in on the zirconia radiused end of precisely the size necessary to support thrust loads whereupon wear substantially ceases. Due to the selection of the first radius, the change in shaft end-play during pump break-in is limited to a total desired end-play of less than about 0.010 inches. Radial loads are supported by an olive hole ring jewel that makes near line contact around the circumference of the shaft to support high speed rotation with little friction. The width of olive hole ring jewel is small to allow heat to conduct through to thereby prevent heat build-up in the bearing. A void defined by the bearing elements may fill with blood that then coagulates within the void. The coagulated blood is then conformed to the shape of the bearing surfaces.
An apparatus is provided for a blood pump bearing system within a pump housing to support long-term highspeed rotation of a rotor with an impeller blade having a plurality of individual magnets disposed thereon to provide a small radial air gap between the magnets and a stator of less than 0.025 inches. The bearing system may be mounted within a flow straightener, diffuser, or other pump element to support the shaft of a pump rotor. The bearing system includes a zirconia shaft having a radiused end. The radiused end has a first radius selected to be about three times greater than the radius of the zirconia shaft. The radiused end of the zirconia shaft engages a flat sapphire endstone. Due to the relative hardness of these materials a flat is quickly produced during break-in on the zirconia radiused end of precisely the size necessary to support thrust loads whereupon wear substantially ceases. Due to the selection of the first radius, the change in shaft end-play during pump break-in is limited to a total desired end-play of less than about 0.010 inches. Radial loads are supported by an olive hole ring jewel that makes near line contact around the circumference of the Ir shaft to support big speed rotation with little friction. The width of olive hole ring jewel is small to allow heat to conduct through to thereby prevent heat build-up in the bearing. A void defined by the bearing elements may fill with blood that then coagulates within the void. The coagulated blood is then conformed to the shape of the bearing surfaces.
Methods for a blood pump bearing system within a pump housing to support long-term high-speed rotation of a rotor with an impeller blade having a plurality of individual magnets disposed thereon to provide a small radial air gap between the magnets and a stator of less than 0.025 inches. The bearing system may be mounted within a flow straightener, diffuser, or other pump element to support the shaft of a pump rotor. The bearing system includes a zirconia shaft having a radiused end. The radiused end has a first radius selected to be about three times greater than the radius of the zirconia shaft. The radiused end of the zirconia shaft engages a flat sapphire endstone. Due to the relative hardness of these materials a flat is quickly produced during break-in on the zirconia radiused end of precisely the size necessary to support thrust loads whereupon wear substantially ceases. Due to the selection of the first radius, the change in shaft end-play during pump break-in is limited to a total desired end-play of less than about 0.010 inches. Radial loads are supported by an olive hole ring jewel that makes near line contact around the circumference of the shaft to support high speed rotation with little friction. The width of olive hole ring jewel is small to allow heat to conduct through to thereby prevent heat build-up in the bearing. A void defined by the bearing elements may fill with blood that then coagulates within the void. The coagulated blood is then conformed to the shape of the bearing surfaces.
Packaging engineers can avoid unnecessary and costly redesign of product through use of tools such as the SINDA '85/FLUINT software system for predicting thermal performance of electronic aviation equipment. SINDA '85/FLUINT is an acronym for Systems Improved Numerical Differencing Analyzer and Fluid Integrators. It is a program for solving the physical problems governed by flow and diffusion type equations and is most widely used as a general thermal analyzer.