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At least 631 records · Page 35

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NASA NTRS1982

Free vibration analysis of coupled fluid-structure systems

An efficient numerical technique for the eigenvalue solution in the free vibration analysis of compressible fluid-structure coupled systems is presented. The fluid is assumed to be compressible in nature and the incompressible problem is only a special case of the present generalized algorithm. A natural frequency analysis of the structure in the absence of any fluid is achieved by a combined Sturm sequence and inverse iteration technique that computes only the required eigenvalues and vectors. A special inverse iteration scheme is then developed for the coupled system that uses the computed eigenvalues as starting iteration values for convergence. Numerical results obtained by solving a number of standard test cases indicate the pattern of root convergence corresponding to various simplifying assumptions.

Gupta, K. K.↗

NASA NTRS1984

Cryogenic Fluid Management Facility

The Cryogenic Fluid Management Facility (CFMF) is a reusable test bed which is designed to be carried into space in the Shuttle cargo bay to investigate systems and technologies required to efficiently and effectively manage cryogens in space. The facility hardware is configured to provide low-g verification of fluid and thermal models of cryogenic storage, transfer concepts and processes. Significant design data and criteria for future subcritical cryogenic storage and transfer systems will be obtained. Future applications include space-based and ground-based orbit transfer vehicles (OTV), space station life support, attitude control, power and fuel depot supply, resupply tankers, external tank (ET) propellant scavenging, space-based weapon systems and space-based orbit maneuvering vehicles (OMV). This paper describes the facility and discusses the cryogenic fluid management technology to be investigated. A brief discussion of the integration issues involved in loading and transporting liquid hydrogen within the Shuttle cargo bay is also included.

Eberhardt, R. N.↗

NASA NTRS1984

Non-Newtonian fluid model incorporated into elastohydrodynamic lubrication of rectangular contacts

A procedure is outlined for the numerical solution of the complete elastohydrodynamic lubrication of rectangular contacts incorporating a non-Newtonian fluid model. The approach uses a Newtonian model as long as the shear stress is less than a limiting shear stress. If the shear stress exceeds the limiting value, the shear stress is set equal to the limiting value. The numerical solution requires the coupled solution of the pressure, film shape, and fluid rheology equations from the inlet to the outlet. Isothermal and no-side-leakage assumptions were imposed in the analysis. The influence of dimensionless speed, load, materials, and sliding velocity and limiting-shear-strength proportionality constant on dimensionless minimum film thickness was investigated. Fourteen cases were used in obtaining the minimum-film-thickness equation for an elastohydrodynamically lubricated rectangular contact incorporating a non-Newtonian fluid model. Computer plots are also presented that indicate in detail pressure distribution, film shape, shear stress at the surfaces, and flow throughout the conjunction.

Jacobson, B. O.↗

NASA NTRS1984

Fluid signatures of rotational discontinuities at the earth's magnetopause

Fluid signatures in the MHD approximation at rotational discontinuities (RD) of finite width called rotational shear layers (RSL) are examined for general flow and magnetic geometries. Analytical and geometrical arguments illustrate that the fluid speed can either go up or down across an RSL for a fixed normal mass flux. The speed profile may or may not be monotonic depending on the boundary conditions. The flow velocity may or may not be field aligned or 'jetting' as a result of traversing the RSL. In general, significant 'convection' is expected in the layer. The observable signatures of (MHD) RSL's depend on 7 (boundary condition) parameters are (1) the mass density, (2 to 5) the incident normal and transverse components of the magnetic field and fluid velocity, (6) the angle epsilon between the incident tangential flow velocity and tangential magnetic field, and (7) the size of the magnetic angular rotation implemented by the layer delta phi.

Scudder, J. D.↗

NASA NTRS1984

Physiological responses to prolonged bed rest and fluid immersion in humans

For many centuries, physicians have used prolonged rest in bed and immersion in water in the treatment of ailments and disease. Both treatments have positive remedial effects. However, adverse physiological responses become evident when patients return to their normal daily activities. The present investigation is concerned with an analysis of the physiological changes during bed rest and the effects produced by water immersion. It is found that abrupt changes in body position related to bed rest cause acute changes in fluid compartment volumes. Attention is given to fluid shifts and body composition, renal function and diuresis, calcium and phosphorus metabolism, and orthostatic tolerance. In a discussion of water immersion, fluid shifts are considered along with cardiovascular-respiratory responses, renal function, and natriuretic and diuretic factors.

Greenleaf, J. E.↗

NASA NTRS1986

Flowmeter for Clear Fluids

Electronic flowmeter measures flow rate of clear or translucent fluids. Instrument produces electrical signal proportional to volume of fluid flowing through it per unit time. Optoelectronic instrument generates electrical signal proportional to fluid-flow rate.

White, P. R.↗

NASA NTRS1984

Lateral fluid forces acting on a whirling centrifugal impeller in vaneless and vaned diffuser

Fluid forces on a rotating centrifugal impeller in whirling motion were studied. A two dimensional impeller installed in a parallel-walled vaneless and vaned diffuser whirled on a circular orbit with various positive and negative angular velocities. It is shown that the fluid forces exert a damping effect on the rotor in most operating conditions, but become excitatory when the impeller operates at very low partial discharge while rotating far faster than the whirl speed. The fluid forces were expressed in terms of mass, damping and stiffness matrices. Impellers with the same geometry and whirl condition are calculated. Quantitative agreement is obtained especially in positive whirl.

Ohashi, H.↗

NASA NTRS1984

Analysis of dynamic characteristics of fluid force induced by labyrinth seal

Flow patterns of the labyrinth seal are experimentally investigated for making a mathematical model of labyrinth seal and to obtain the flow induced force of the seal. First, the flow patterns in the labyrinth chamber are studied on the circumferential flow using bubble and on the cross section of the seal chamber using aluminum powder as tracers. And next, the fluid force and its phase angle are obtained from the measured pressure distribution in the chamber and the fluid force coefficients are derived from the fluid force and the phase angle. Those are similar to the expression of oil film coefficients. As a result, it is found that the vortices exist in the labyrinth chambers and its center moves up and down periodically. The pressure drop is biggest in the first stage of chambers and next in the last stage of chambers.

Iwatsubo, T.↗

NASA NTRS1985

Spray applicator for spraying coatings and other fluids in space

A self contained spray application is developed for one handed operation in a zero gravity vacuum environment by a free flying astronaut not attached to any spacecraft. This spray applicator eliminates contamination of the operator by back spray. This applicator includes a rigid accumulator containment of a fluid within a flexible bladder the fluid being urged out of the accumulator under pressure through a spray gun. The spray gun includes a spring loaded lockable trigger which controls a valve. When in an open position, the fluid passes through the valve into the ambient environment in the form of a spray. A spray shield is provided which directs the flow of the spray from the applicator by trapping errant particles of spray yet allowing the passage of escaping gases through its material.

Kuminecz, J. F.↗

NASA NTRS1985

Technology requirements to be addressed by the NASA Lewis Research Center Cryogenic Fluid Management Facility program

The NASA Lewis Research Center is responsible for the planning and execution of a scientific program which will provide advance in space cryogenic fluid management technology. A number of future space missions were identified that require or could benefit from this technology. These fluid management technology needs were prioritized and a shuttle attached reuseable test bed, the cryogenic fluid management facility (CFMF), is being designed to provide the experimental data necessary for the technology development effort.

Aydelott, J. C.↗

NASA NTRS1985

Technology requirements to be addressed by the NASA Lewis Research Center Cryogenic Fluid Management Facility program

Aydelott, J. C.↗

NASA NTRS1985

Measurement of the Density of Base Fluids at Pressures 0.422 to 2.20 Gpa

The influence of pressure on the density of six base fluids is experimentally studied for a range of pressures from 0.422 to 2.20 GPa. An important parameter used to describe the results is the change in relative volume with change in pressure dv sub r/dp. For pressures less than the solidification pressure (p ps) a small change in pressure results in a large change in dv sub r/ps. For pressures greater than the solidification pressure (p ps) there is no change in dv sub r/dp with changing pressure. The solidification pressures of the base fluids varies considerably, as do the slopes that the experimental data assumes for p ps. A new formula is developed that describes the effect of pressure on density in terms of four constants. These constants vary for the different base fluids tested.

Hamrock, B. J.↗

NASA NTRS1985

NASA Lewis Research Center low-gravity fluid management technology program

A history of the Lewis Research Center in space fluid management technology program is presented. Current programs which include numerical modeling of fluid systems, heat exchanger/radiator concept studies, and the design of the Cryogenic Fluid Management Facility are discussed. Recent analytical and experimental activities performed to support the Shuttle/Centaur development activity are highlighted.

Aydelott, J. C.↗

NASA NTRS1985

Endocrine and fluid metabolism in males and females of different ages after bedrest, acceleration and lower body negative pressure

Space shuttle flight simulations were conducted to determine the effects of weightlessness, lower body negative pressure (LBNP), and acceleration of fluid and electrolyte excretion and the hormones that control it. Measurements were made on male and female subjects of different ages before and after bedrest. After admission to a controlled environment, groups of 6 to 14 subjects in the age ranges 25 to 35, 35 to 45, 45 to 55 to 65 years were exposed to +3 G sub z for 15 minutes (G1) and to LBNP (LBNP1) on different days. On 3 days during this prebedrest period, no tests were conducted. Six days of bedrest followed, and the G sub z (G2) and LBNP (LBNP2) tests were run again. Hormones, electrolytes, and other parameters were measured in 24-hour urine pools throughout the experiment. During bedrest, cortisol and aldosterone excretion increased. Urine volume decreased, and specific gravity and osmolality increased. Urinary electrolytes were statistically unchanged from levels during the non-stress control period. During G2, cortisol increased significantly over its control and bedrest levels. Urine volume, sodium, and chloride were significantly lower; specific gravity and osmolality were higher during the control period or bedrest. The retention of fluids and electrolytes after +G sub z may at least partially explain decreased urine volume and increased osmolality observed during bedrest in this study. There were some who indicated that space flight would not affect the fluid and electrolyte metabolism of females or older males any more severely than it has affected that of male astronauts.

Leach, C. S.↗

NASA NTRS1985

Fluid leak indicator

A fluid leak indicator for detecting and indicating leaks in visually inaccessible fluid tubing joints, such as those obstructed by insulation includes a bag system and a wicking system surrounding or wrapping the joints under the visual obstructing material. Leaking fluid is collected in the bag or on the wicking material where it is conducted along the wicking material to a visily accessible capturing transparent indicator bulb for providing a visual indication of the leak without requiring a chemical change in the capturing indicator bulb.

Anderson, G. E.↗

NASA NTRS1985

Fluid behavior in microgravity

An experiment designed to study some fundamental aspects of microgravity fluid dynamics has been built and is scheduled for flight. The purpose of the experiment is to investigate differences in behavior of wetting and nonwetting fluid systems at low Bond numbers. Methods were developed to determine liquid quantity, estimate vapor contact area and measure liquid layer thickness. Both the responses of the fluid systems to external perturbations and the transfer of liquid through a connection between two containers can be studied.

William W. Durgin↗

NASA NTRS1985

Volume and density changes of biological fluids with temperature

The thermal expansion of human blood, plasma, ultrafiltrate, and erythrocycte concentration at temperatures in the range of 4-48 C is studied. The mechanical oscillator technique which has an accuracy of 1 x 10 to the -5 th g/ml is utilized to measure fluid density. The relationship between thermal expansion, density, and temperature is analyzed. The study reveals that: (1) thermal expansion increases with increasing temperature; (2) the magnitude of the increase declines with increasing temperature; (3) thermal expansion increases with density at temperatures below 40 C; and (4) the thermal expansion of intracellular fluid is greater than that of extracellular fluid in the temperature range of 4-10 C, but it is equal at temperatures greater than or equal to 40 C.

Hinghofer-Szalkay, H.↗

NASA NTRS1985

Fluid and electrolyte control in simulated and actual spaceflight

Effects of microgravity on body fluid distribution and electrolyte and hormonal levels of astronauts have been studied since the early manned space missions. Bedrested subjects have been used as controls to separate effects of microgravity from those of hypokinesia. These investigations have led to documentation of the physiological effects of spaceflight and to a unified theory of response to microgravity. During flight, crewmembers have decreased thirst and a net loss of body water, sodium, and potassium. These changes seem to be initiated by passive transfer of extracellular fluid resulting in increased central venous pressure (CVP), to which the homeostatic mechanisms respond. A new equilibrium state is maintained during flight; it does not change in response to negative calcium and nitrogen balances during flight. On reexposure to gravity, profound water and salt retention occurs to replete extracellular fluid. Attempts to avoid cardiac deconditioning by repleting water and salt before leaving microgravity have somewhat ameliorated postural hypotension but have had little effect on CVP, cardiac chamber size or electrolyte dynamics.

Leach, C. S.↗