Free-molecule flow and surface diffusion through slots and tubes A summary
Free molecule flow and surface diffusion through tubes and two-dimensional slots
FREE FLOW↗
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Study of foldable elastic tubes for large space structure applications, phase 3
A bi-convex foldable elastic tube, suitable for use in self deploying space structures, was subjected to a series of buckling tests to deterine initial buckling loads, collapse loads, and the buckling mode. The tube is cylindrical with a cross-section that is lenticular-like with flared edges. It is capable of being flattened in the center and folded compactly, storing up strain energy in the process. Upon removal of constraint, it springs back to its original straight configuration, releasing the stored strain energy. The tests showed that this type of tube has good resistance to buckling, with the initial buckling loads all falling within or above the range of those for comparable circular cylindrical tubes.
Jones, I. W.↗
Conformal mapping of a class of doubly connected regions technical report no. 8
Conformal mapping of class of doubly connected regions onto circular annulus
CONFORMAL MAPPING↗
Optimum design of columns supported by tension ties
Optimum design of thin walled cylindrical columns supported by tension ties
STRUCTURAL DESIGN↗
Asymptotic Expansions and Estimates for the Capillary Problem
The asymptotic properties for the small Bond number B of the equilibrium capillary interface interior to a circular cylindrical tube vertically dipped in an infinite reservoir of liquid are discussed. (The Bond number B is a dimensionless parameter which is the ratio of gravitational to capillary forces.) The formal expansion in powers of B of the solution to the differential equation describing the equilibrium surface (as can be obtained by standard perturbation methods) is proved to be truly asymptotic -- to all orders and uniformly in the variable and parameter gamma, the contact angle. Sequences of general estimates, in closed form, from above and from below, are also given for the solution and related functions. The M-th term in these sequences are asymptotically exact to order m. An idiosyncrasy of the problem, crucial in obtaining these estimates, is the absolute monotonicity of the structural function of the system in integral form.
Brulois, F. P.↗
Hydromagnetic buoyancy force in the solar atmosphere
A quantitative definition of the hydromagnetic buoyancy force in the solar atmosphere is presented, on the basis of a numerical analysis of the hydromagnetic characteristics of a circular flux tube. It is shown that the peripheral inhomogeneity of ambient hydromagnetic pressure in the solar atmosphere can lead to hydromagnetic buoyancy in the presence of an extraneous body. The results of the flux tube analyses showed that the strength of the force is often equal to or greater than the gravitational force of the solar atmosphere, and may be responsible for the stationary equilibria of quiescent solar prominences, as well as the outward motions of coronal transients. A diagram is presented in order to describe the field lines in the large-scale solar magnetic field in the presence of hydromagnetic buoyancy.
Yeh, T.↗
Heat Transfer and Pressure Drop in Concentric Annular Flows of Binary Inert Gas Mixtures
Studies of heat transfer and pressure drop of binary inert gas mixtures flowing through smooth concentric circular annuli, tubes with fully developed velocity profiles, and constant heating rate are described. There is a general lack of agreement among the constant property heat transfer correlations for such mixtures. No inert gas mixture data exist for annular channels. The intent of this study was to develop highly accurate and benchmarked pressure drop and heat transfer correlations that can be used to size heat exchangers and cores for direct gas Brayton nuclear power plants. The inside surface of the annular channel is heated while the outer surface of the channel is insulated. Annulus ratios range 0.5 < r* < 0.83. These smooth tube data may serve as a reference to the heat transfer and pressure drop performance in annuli, tubes, and channels having helixes or spacer ribs, or other surfaces.
Reid, R. S.↗
Radiator Design and Installation
The fundamental principles of fluid flow, pressure losses, and heat transfer have been presented and analyzed for the case of a smooth tube with fully developed turbulent flow. These equations apply to tubes with large length-diameter ratios where the f1ow is at a high Reynolds Number. The error introduced by using these equations increases as the magnitude of the tube length and the air-flow Reynolds Number approaches the values encountered in modern radiator designs. Accordingly, heat-transfer tests on radiator sections were made and the results are presented in nondimensional form to facilitate their use and for comparison with other heat-transfer data. In addition, pressure losses were measured along smooth tubes of circular, square, and rectangular cross section and the results were also correlated and are presented in nondimensional form. The problem of a radiator design for a particular installation is solved, the experimental heat-transfer and pressure-loss data being used, on a basis of power chargeable to the radiator for form drag, for propelling the weight, and for forcing the air through the radiator. The case of an installation within a wing or an engine nacelle is considered. An illustration of radiator design is carried through for an arbitrary set of conditions. Sufficient detail is given to enable the reader to reproduce the analysis for any given case.
Brevoort, M.J.↗
Experimental Investigation of Flow Orientation Effects on Cryogenic Flow Boiling
Cryogenic flow boiling physics is of paramount importance for future cryogenic space applications employing Cryogenic Fluid Management (CFM) technologies. This experimental study investigates the two-phase flow and heat transfer performance of LN 2 flow boiling across five distinct flow orientations: vertical upflow, vertical downflow, horizontal flow, 45° inclined upflow, and 45° inclined downflow. The study employed the steady- state heating method within a circular heated tube featuring an 8.5-mm inner diameter and a 680-mm heated length. High-speed video recordings were utilized to capture two-phase flow patterns and interfacial behaviors across various flow orientations. The experiments covered a wide range of operating conditions, including mass velocities ranging from 351.80 to 1572.77 kg/m 2 s and inlet pressures from 297.14 to 1032.97 kPa, primarily with near-saturated inlet subcooling. Distinct two-phase flow patterns and regime transitions were identified for each flow orientation. Symmetrical flow patterns were evident in vertical orientations, whereas non-vertical orientations exhibited asymmetric flow stratifications, primarily influenced by the buoyancy force in a terrestrial gravity environment. Bubble dynamic parameters were quantified, and bubble collision and dispersion phenomena were visualized. Analyzing heat transfer performance based on local flow boiling curves and variations in heat transfer coefficients (HTCs), it was observed that vertical upflow demonstrated the most enhanced heat transfer performance, while vertical downflow exhibited the lowest. As mass velocity exceeded 830 kg/ m 2 s, the differences in heat transfer among orientations became less distinct, emphasizing the role of flow inertia in mitigating the influence of flow orientation. A direct comparison of microgravity HTC data from a recent study by the authors against the 1-𝘨 e HTC data indicated enhanced heat transfer performance in microgravity for flow orientation configurations in terrestrial gravity. However, this enhancement progressively diminished as the heat flux increased. Distinct HTC trends were observed as mass velocity increased for different flow orientations and gravity levels.
Cryogens↗
Cryogenic Flow Boiling in Microgravity: Effects of Reduced Gravity on Two-Phase Fluid Physics and Heat Transfer
With the growing interest in space exploration, cryogenic technologies involving two-phase flow and heat transfer are in high demand to successfully procure advanced space applications such as fuel depots and nuclear thermal propulsion (NTP) systems for deep space missions. However, the unique and extreme thermal properties of cryogenic fluids introduce distinct flow boiling fluid physics and energy transport phenomena, which differ significantly from those observed with conventional fluids. Understanding the unique two-phase physics in cryogenic flow boiling remains an ongoing challenge. Furthermore, the lack of readily available microgravity cryogenic steady-state heat transfer data hinders the assessment of gravitational effects on cryogenic flow boiling. This study aims to elucidate the gravitational effects on two-phase fluid physics and heat transfer by conducting the first-ever experimental measurement of cryogenic flow boiling performance using a steady-state heated method in a reduced gravity environment. Parabolic flight experiments were performed to acquire both heat transfer measurements and high-speed video of interfacial behaviors, under varying gravity levels (microgravity, hypergravity, Lunar gravity, and Martian gravity). The experiments involved flow boiling of liquid nitrogen (LN 2 ) with a near-saturated inlet along a circular heated tube of dimensions 8.5-mm inner diameter and 680-mm heated length. The operating parameters varied are mass velocity of 398.3 - 1342.8 kg/m2s, inlet quality of -0.08 to -0.01, and inlet pressure of 413.68 - 689.48 kPa. Captured microgravity flow patterns range from bubbly to annular, all having vapor structures that are larger than those under higher gravity levels. Under microgravity, absence of buoyancy yields symmetrical vapor structures without flow stratification, laying a physical foundation for the distinct two-phase heat transfer trends during LN 2 flow boiling in microgravity. Transient data collected during the flight parabolas exhibited decreasing heated wall temperature as the aircraft transitioned from hypergravity to microgravity phases. The temperature variation indicated an enhancement in flow boiling heat transfer with decreasing gravity levels and a reduction with increasing gravity levels. The effect of reduced gravity on cryogenic flow boiling heat transfer coefficient (HTC) is discussed based on steady state heat transfer analysis. Seminal HTC correlations are evaluated against the measured microgravity HTC data, of which one is identified for superior accuracy in predicting microgravity data. Finally, a new HTC correlation is proposed to improve accuracy of microgravity predictions, yet there still exists room for further improvement with future terrestrial flow boiling experiments at different flow orientations relative to Earth gravity.
Microgravity↗
Crash energy absorbing composite sub-floor structure
Static crushing tests were conducted on four different beam concepts; honeycomb sandwich, sine-wave and two integrally stiffened designs. The sine-wave beams, depending upon specimen geometry, has the highest energy absorption potential of the four concepts evaluated. All beam designs produced a progressive crushing mode similar to tube specimens. The energy absorption capability of sine-wave beam specimens were predictable from results of circular cross section tubes. A comparison of energy absorption capability was made between integrally stiffened beams fabricated from graphite/epoxy, Kevlar-49/epoxy and aluminum. The energy absorption capability of the graphite/epoxy integrally stiffened beams exceeded both the Kevlar-49/epoxy and aluminum integrally stiffened beams. The energy absorption potential of composite structures is between five and ten times that of comparable metallic structure.
Farley, G. L.↗
Thermal control of a lidar laser system using a non-conventional ram air heat exchanger
This paper describes the analysis and performance testing of a uniquely designed external heat exchanger. The heat exchanger is attached externally to an aircraft and is used to cool a laser system within the fuselage. Estimates showed insufficient cooling capacity with a conventional staggered tube array in the limited space available. Thus, a non-conventional design wes developed with larger tube and fin area exposed to the ram air to increase the heat transfer performance. The basic design consists of 28 circular finned aluminum tubes arranged in two parallel banks. Wind tunnel tests were performed to simulate air and liquid flight conditions for the non-conventional parallel bank arrangement and the conventional staggered tube arrangement. Performance comparisons of each of the two designs are presented. Test results are used in a computer model of the heat exchanger to predict the operating performance for the entire flight profile. These analyses predict significantly improved performance over the conventional design and show adequate thermal control margins.
Killough, Brian D.↗
The effects of crushing speed on the energy-absorption capability of composite tubes
The energy-absorption capability as a function of crushing speed was determined for Thornel 300-Fiberite 934 (Gr-E) and Kevlar-49-Fiberite 934 (K-E) composite material. Circular cross section tube specimens were crushed at speeds ranging from 0.01 to 12 m/sec. Ply orientations of the tube specimens were (0/ +/- theta)2 and (+/- theta)2 where theta = 15, 45, and 75 deg. Based upon the results of these tests, the energy-absorption capability of Gr-E and K-E was determined to be a function of crushing speed. The magnitude of the effects of crushing speed on energy-absorption capability was determined to be a function of the mechanisms that control the crushing process. The effects of crushing speed on the energy-absorption capability is related to whether the mechanical response of the crushing mechanism that controls the crushing process is a function of strain rate. Energy-absorption capability of Gr-E and K-E tubes ranged between 0 and 35 percent and 20 and 45 percent, respectively, depending upon ply orientation.
Farley, Gary L.↗
Diamagnetic force on a flux tube
The diamagnetic force on a straight flux tube is elucidated. The case when the flux tube has a circular cross section is considered, and the result is generalized to the case of noncircular cross section. The result shows that when the external magnetic field is uniform, the diamagnetic force is simply equal to the vector multiplication of the internal conduction current and the external magnetic field. It is independent of the size and shape of the cross section of the flux tube. This is analogous to the Kutta-Joukowski theorem that the aerodynamic lift force is proportional to the vector multiplication of the unperturbed flow velocity and the circulation around the airfoil. When the external magnetic field is nonuniform, the diamagnetic force has an additional contribution which is proportional to the gradient of magnetic pressure and to the volume of the flux tube. The constant of proportionality, which is shown to be equal to two for a circular cross section, indicates the enhancement of the nonuniformity of the external magnetic field in the vicinity of the periphery by the polarization current.
Yeh, T.↗
Fabrication and testing of composite ring specimens
The tooling and techniques used in the fabrication of composite laminate tubes of any desired ply orientation and stacking sequence are described along with techniques for cutting ring specimens under internal pressure. The method consists of laying up the tube on a central circular mandrel, and by means of internal pressure, expanding the prepreg tube against the cavity wall of an external mold tool, which forms the geometric curing envelope for the tube. Tube quality is assessed by laminate wall thickness measurement, by hoop strength measurement on rings cut from the ends of the tube, and by ultrasonic inspection.
Liber, T.↗
The effects of crushing speed on the energy-absorption capability of composite material
The energy-absorption capability as a function of crushing speed was determined for Thornel 300/Fiberite 934 (Gr/E) and Kevlar-49/Fiberite 934 (K/E) composite material. Circular cross section tube specimens were crushed at quasi-static, 6 m/sec, and 12 m/sec speeds. Ply orientations of the tube specimens were (0/+ or - theta) sub 2 and (+ or - theta) sub 3 where theta=15, 45, and 75 degress. Based on the results of these tests the energy-absortion capability of Gr/E and K/E was determined to be a function of crushing speed. The crushing modes based on exterior appearance of the crushed tubes were unchanged for either material. However, the interlaminar crushing behavior changed with crushing speed.
Farley, Gary L.↗
Solid state imagers and their applications; Proceedings of the Meeting, Cannes, France, November 26, 27, 1985
Topics treated include the use of semiconductor imagers in high energy particle physics, an X-ray image sensor based on an optical TDI-CCD imager, and an electron-sensitive CCD readout array for a circular-scan streak tube. Papers are presented on the pan-imager, high resolution linear arrays, the reduction of reflection losses in solid-state image sensors, a high resolution CCD imager module with swing operation, large area CCD image sensors for scientific applications, and new readout techniques for frame transfer CCDs. Consideration is given to advanced optoelectronical sensors for autonomous rendezvous/docking and proximity operations in space, the testing and characterization of CCDs for the Rosat star sensors, an advanced radial camera for the Hubble Space Telescope, and scanning or staring infrared imagers.
Declerck, Gilbert J.↗
Two-Dimensional Vernier Scale
Modified vernier scale gives accurate two-dimensional coordinates from maps, drawings, or cathode-ray-tube displays. Movable circular overlay rests on fixed rectangular-grid overlay. Pitch of circles nine-tenths that of grid and, for greatest accuracy, radii of circles large compared with pitch of grid. Scale enables user to interpolate between finest divisions of regularly spaced rule simply by observing which mark on auxiliary vernier rule aligns with mark on primary rule.
Juday, Richard D.↗