Subjects -> AERONAUTICS AND SPACE FLIGHT (Total: 120 journals)
 Showing 1 - 30 of 30 Journals sorted by number of followers AIAA Journal       (Followers: 1194) SpaceNews       (Followers: 826) Journal of Spacecraft and Rockets       (Followers: 773) Journal of Propulsion and Power       (Followers: 615) Acta Astronautica       (Followers: 495) Advances in Space Research       (Followers: 458) Aviation Week       (Followers: 437) Aerospace Science and Technology       (Followers: 428) IEEE Transactions on Aerospace and Electronic Systems       (Followers: 387) Journal of Aircraft       (Followers: 337) Control Systems       (Followers: 315) Journal of Navigation       (Followers: 281) IEEE Aerospace and Electronic Systems Magazine       (Followers: 280) Aircraft Engineering and Aerospace Technology       (Followers: 264) Gyroscopy and Navigation       (Followers: 260) Journal of Guidance, Control, and Dynamics       (Followers: 204) Space Science International       (Followers: 202) Space Science Reviews       (Followers: 97) International Journal of Aerospace Engineering       (Followers: 82) Progress in Aerospace Sciences       (Followers: 81) Advances in Aerospace Engineering       (Followers: 70) Journal of Aerospace Engineering       (Followers: 69) Propulsion and Power Research       (Followers: 68) Aerospace       (Followers: 60) Space Safety Magazine       (Followers: 51) Space Research Today       (Followers: 48) Proceedings of the Institution of Mechanical Engineers Part G: Journal of Aerospace Engineering       (Followers: 46) International Journal of Aeroacoustics       (Followers: 41) IEEE Transactions on Circuits and Systems I: Regular Papers       (Followers: 39) International Journal of Aerodynamics       (Followers: 37) Journal of Aerospace Information Systems       (Followers: 34) Canadian Aeronautics and Space Journal       (Followers: 34) International Journal of Aerospace Sciences       (Followers: 32) Journal of Aeronautics & Aerospace Engineering       (Followers: 31) CEAS Aeronautical Journal       (Followers: 30) Space Policy       (Followers: 29) Journal of Space Weather and Space Climate       (Followers: 27) Aviation Psychology and Applied Human Factors       (Followers: 27) Russian Aeronautics (Iz VUZ)       (Followers: 24) Egyptian Journal of Remote Sensing and Space Science       (Followers: 24) International Journal of Aerospace Psychology       (Followers: 23) Artificial Satellites       (Followers: 23) Annual of Navigation       (Followers: 22) Journal of Aerospace Information Systems       (Followers: 22) Chinese Journal of Aeronautics       (Followers: 21) Nonlinear Dynamics       (Followers: 20) Aerospace Medicine and Human Performance       (Followers: 19) Journal of Aerodynamics       (Followers: 18) Journal of Aerospace Engineering & Technology       (Followers: 18) Aerospace Scientific Journal       (Followers: 18) Journal of Wind Engineering and Industrial Aerodynamics       (Followers: 17) Research & Reviews : Journal of Space Science & Technology       (Followers: 17) International Journal of Space Structures       (Followers: 17) Aviation       (Followers: 17) Proceedings of the Human Factors and Ergonomics Society Annual Meeting       (Followers: 16) Fatigue of Aircraft Structures       (Followers: 15) Aeronautical Journal, The       (Followers: 13) International Journal of Satellite Communications Policy and Management       (Followers: 13) Frontiers in Astronomy and Space Sciences       (Followers: 12) Journal of Airline and Airport Management       (Followers: 12) Elsevier Astrodynamics Series       (Followers: 12) International Journal of Crashworthiness       (Followers: 12) International Journal of Space Science and Engineering       (Followers: 11) COSPAR Colloquia Series       (Followers: 11) Journal of Aviation Technology and Engineering       (Followers: 11) International Journal of Micro Air Vehicles       (Followers: 11) Air Force Magazine       (Followers: 10) International Journal of Space Technology Management and Innovation       (Followers: 10) Aviation in Focus - 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Uzbrojenie, lotnictwo, inżynieria bezpieczeństwa / Problems of Mechatronics. 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Similar Journals
 Microgravity Science and TechnologyJournal Prestige (SJR): 0.514 Citation Impact (citeScore): 1Number of Followers: 2      Hybrid journal (It can contain Open Access articles) ISSN (Print) 0938-0108 - ISSN (Online) 1875-0494 Published by Springer-Verlag  [2656 journals]
• A Numerical Study on Condensation Heat Transfer Characteristics of R134a
in Microchannel Under Varying Gravity Conditions
• Abstract: A large amount of heat can be dissipated more efficiently by utilizing the latent heat than the sensible heat of coolant using condensation technique. In addition, cooling by microchannel is found as a promising method to dissipate more heat than the conventional channel. The application of condensation in a microchannel under different gravity conditions becomes very important due to rising demand in space technology, where compact high-performance electronic devices experience rise in temperature beyond the tolerable limit. The present numerical model explores the effect of different gravity conditions on the fluid flow and heat transfer characteristics of R134a condensation in a two-dimensional microchannel with a diameter of 100 µm. The gravity condition is varied from zero to normal gravity as g = 0, 0.1, 0.5, 1 and 9.81 m/s2. Moreover, the effects of subcooled wall temperature, mass flux and vapour quality on two phase flow regimes, flow characteristics, temperature distribution, local and average Nusselt number behaviour are also investigated. The flow regime is significantly influenced by the gravity, wall temperature, mass flux and vapour quality and accordingly, different flow regimes are observed. The flow behaviour and temperature contour are also prominently dependent on the working parameters. The gravity condition has found to insignificantly affect the average condensation heat transfer properties in the considered microchannel.
PubDate: 2021-05-04

• Oil Drainage in a Capillary Tube: Experimental and Numerical Study
• Abstract: In this paper, we investigate experimentally and numerically the dynamics of the drainage of a transparent capillary tube (radius 0.4 mm). A non-wetting fluid (gas) displaces a wetting fluid (oil). The gas phase is continuously injected at an extremity of the capillary tube (inlet section) at a constant injection-rate $$Q_{inj}$$ , ranging from 0.1 to 10 ml/h, corresponding to capillary numbers Ca varying between $$5 \cdot 10^{ - 4}$$ and $$5 \cdot 10^{ - 2}$$ . Oil phase, initially filling the tube, leaves the system at the second opened extremity (outlet section).We consider in this work the compressibility of non-wetting fluid (gas), viscous forces in the liquid column, capillary forces and gravity. The effect of several parameters, such as $$Q_{inj}$$ j and gravity, on the progress of the gas–liquid interface has been investigated.
PubDate: 2021-04-30

• Novel Method for Surface Tension Measurement: the Drop-Bounce Method
• Abstract: The surface tension of liquids at high temperatures is generally measured with the well-established oscillating drop method in a contactless environment. However, technical difficulties in surface tension measurements make it hard to apply the oscillating drop method to the aerodynamic levitation (ADL) system, the most reliable levitation technique for liquids with low electrical conductivity. In this study, we developed a novel drop–bounce method that can be used within an ADL system to measure the surface tension of liquids. A levitated molten sample was first dropped onto an inert substrate through a splittable nozzle. The rebounded sample’s oscillatory motion behaved as it would under microgravity conditions during its free-fall, and oscillations were obtained only in the l=2, m=0 mode. Fourier transformation of the oscillation pattern provided resonant frequency of the l=2, m=0 mode and enabled the calculation of the surface tension of the sample under knowledge of its mass. Furthermore, a short experimental duration of less than 50 ms significantly reduced the possibility of surface evaporation in the sample. Our measured surface tension data from 1354 K to 1827 K for gold exhibited a standard deviation of 13.4 mJ/m2 and were consistent with the data published by Egry et al. under microgravity conditions, with a maximum deviation of 1.5% between the two fitted linear equations.
PubDate: 2021-04-26

• Particle Accumulation Structures in a 5 cSt Silicone Oil Liquid Bridge:
New Data for the Preparation of the JEREMI Experiment
• Abstract: Systems of solid particles in suspension driven by a time-periodic flow tend to create structures in the carrier fluid that are reminiscent of highly regular geometrical items. Within such a line of inquiry, the present study provides numerical results in support of the space experiments JEREMI (Japanese and European Research Experiment on Marangoni flow Instabilities) planned for execution onboard the International Space Station. The problem is tackled by solving the unsteady non-linear governing equations for the same conditions that will be established in space (microgravity, 5 cSt silicone oil and different aspect ratios of the liquid bridge). The results reveal that for a fixed supporting disk radius, the dynamics are deeply influenced by the height of the liquid column. In addition to its expected link with the critical threshold for the onset of instability (which makes Marangoni flow time-periodic), this geometrical parameter can have a significant impact on the emerging waveform and therefore the topology of particle structures. While for shallow liquid bridges, pulsating flows are the preferred mode of convection, for tall floating columns the dominant outcome is represented by rotating fluid-dynamic disturbance. In the former situation, particles self-organize in circular sectors bounded internally by regions of particle depletion, whereas in the latter case, particles are forced to accumulate in a spiral-like structure. The properties of some of these particle attractors have rarely been observed in earlier studies concerned with fluids characterized by smaller values of the Prandtl number.
PubDate: 2021-04-10

• Experimental Study on the Enhanced Thermal Performance of Two-Phase Closed
Thermosyphon Using Mechanical and Chemical Treated MWCNTs Nanofluids
• Abstract: Nowadays the two-phase closed thermosyphon (TPCT) has been widely used as an important heat transfer medium for passive cooling systems. Since the enhancement of the performance of electronic device releases a considerable amount of heat, the development of working fluids which can improve thermal performance of the TPCT is necessary. In this experiment, two different type of MWCNT nanofluids were successfully made by using ball-mill process and alkaline treatment. The morphological and structural analysis were conducted by using transmission electron microscope (TEM), fourier-transform infrared spectroscopy (FT-IR). Also thermal conductivity of modified MWCNT nanofluids were investigated by introducing transient hot wire method. The results of TEM, FT-IR and thermal conductivity showed that the MWCNTs were successfully functionalized as well as had higher thermal conductivity. The TPCT was fabricated with copper tube and total length of the TPCT is 700mm, in which the evaporator section, the adiabatic section and the condenser section are 150mm, 400mm, and 150mm, respectively. The experiment of the thermal performance of the TPCT was evaluated by introducing RMS value of the temperature of the evaporation section, thermal resistance and heat transfer coefficient at five different filling ratios, 10%, 30%, 50% and 70% by ratcheting up heat loads in five levels, 5W, 8W, 10W, 13W and 15W. The overall results showed that the both of modified MWCNT nanofluids can decrease thermal resistance and increase the heat transfer coefficient, especially at 10% filling ratio with 8W. M-CNT nanofluid can even enhance the thermal performance of TPCT at 30% filling ratio with all heat loads.
PubDate: 2021-04-02

• Effect of Novel Designed Bodygear on Gastrocnemius and Soleus Muscles
during Stepping in Human Body
• Abstract: Muscle atrophy occurs in human musculature system due to inactivity of muscles in microgravity environment. Herein, a novel designed countermeasure gravitational load modulation bodygear is developed to enhance muscle activity. The bodygear is devised to compress the body through axial loading from shoulder to feet. The time and frequency domain parameters of electromyography (EMG) signals showed that the activity of gastrocnemius and soleus muscle was increased by 87% and 90% respectively in comparison to without bodygear during stepping. The enhanced muscle activity might be due to the increase in the recruitment of extra motor units, increase in contraction and more potential firing in muscles with bodygear. The results of analysis of variance confirmed that the root mean square, peak and mean frequency values were increased significantly (p < 0.05). Overall, the present bodygear is simple yet highly efficient to enhance muscle activity by providing enough loading during exercise. The bodygear demonstrates potential as a exercise countermeasure device by providing axial loading and can mimic the muscle activity of standing position in bed ridden patients. Further, it may serve as an rehabilitation device for speedy recovery of patients after further design refinement.
PubDate: 2021-04-02

• Heat Loss Analysis of Flow Boiling Experiments Onboard International Space
Station with Unclear Thermal Environmental Conditions (1st Report:
Subcooled Liquid Flow Conditions at Test Section Inlet)
• Abstract: Two series of flow boiling experiments have been conducted onboard the International Space Station (ISS) as a part of the TPF (Two-Phase Flow) experiment promoted by JAXA during July 2017–March 2018, February 2019–July 2019. Microgravity data on two-phase flow and heat transfer in flow boiling of n-Perfluorohexane (FC-72) have been obtained by a copper heated test tube and a transparent glass heated tube in a wide experimental range of mass velocity, liquid subcooling, vapor quality and heat flux. Furthermore, detailed two-phase flow behaviors have been observed by using high frame rate camera in the unheated observation section. In order to elucidate the accurate influence of gravity on flow boiling, it is essential to compare the heat transfer data and two-phase flow behaviors obtained under normal (terrestrial) gravity and microgravity environments at the same flow and heating conditions. However, both experiments cannot be performed by using the same experimental apparatus and under the same thermal environmental conditions. In addition, the heat loss cannot be negligible due to the forced avionics air flow inside the experimental apparatus in ISS. Therefore, exact evaluation of the fluid conditions at the inlet of the heated test tube requires the heat loss model with high-accuracy. In the present paper, the heat loss models for evaluating the degree of liquid subcooling at the inlet of the heated test tube and net heat flux from the heated tube to test fluid has been developed by using the results of preliminary heat loss experiments conducted onboard ISS. The correction of the degree of liquid subcooling by the proposed heat loss models is not negligible for the accurate analysis of gravity effects. The accuracy of the heat loss models has been verified through the evaluation of heat transfer coefficients for single-phase turbulent forced convection obtained from the heating experiments onboard ISS.
PubDate: 2021-03-27

• Numerical Investigation of Successively Nucleating Bubbles During
Subcooled Flow Boiling of FC-72 in Microgravity
• Abstract: For the present study numerical simulations of subcooled flow boiling of FC-72 in microgravity have been conducted to accompany boiling experiments performed in microgravity on the International Space Station (ISS). The numerical domain represents the geometry of the experimental test cell. For all simulations the open source framework OpenFOAM was employed, including extensions to the interFoam solver, which have been developed at the authors’ institute. A reference case has been defined applying intermediate values from the experimental parameter range as system parameters. This case has been examined thoroughly with regards to hydrodynamic phenomena and heat transfer during multiple, successive bubble cycles. Based on this reference case, the system parameters flow velocity, input heat flux, pre-heating time, and subcooling of the liquid bulk have been varied, and the impact of these quantities on bubble growth and movement as well as heat transfer have been studied. It was found, that an increased flow rate as well as increased subcooling lead to smaller bubbles and increased time between subsequent nucleations. A high input heat flux, an increased pre-heating time, and a decreased subcooling lead to a rapid cycle of bubble nucleation and coalescence.
PubDate: 2021-03-25

• Tsinghua University Freefall Facility (TUFF): A 2.2 Second Drop Tunnel for
Microgravity Research
• Abstract: Ground-based freefall facilities are to create microgravity environment on earth for studying the space-related or fundamental sciences, which have been widely used in the field of combustion, fluid, physics and material sciences. Aiming to serve for the broader microgravity science and preliminary tests for projects onboard the upcoming assembly of Chinese Space Station, a 2.2 second freefall facility was designed and built in the Lee Shau Kee Science and Technology Building on the campus of Tsinghua University in Beijing. This facility is composed of five systems: (I) freefall tunnel and safety cables; (II) release and retrieve system; (III) the capsule; (IV) brake system; (V) electrical control and safety interlock system. The capsule consists of an outer drag shield and an inner rig of which the total weight is 280 kg. The capsule is released by a pneumatic chuck that minimizes disturbance of the release operation. The eddy current brake modules made of several permanent magnets are applied to decelerate the capsule without power supply. This paper primarily discusses the tests designed and conducted to characterize the performance of such facility in many aspects. The results show that during freefall, the microgravity level of 10-3 g can be achieved for 2.2 second. Concerning movement of the inner rig relative to the drag shield during freefall, the clearance of 0.43 m and relative velocity of 0.62 m/s were specified. The deceleration can be controlled within 15 g. The terminal velocity of capsule in the brake system ranges from 0.4 to 0.5 m/s depending on the actual weight of capsule. The noise level in the entrance section of brake system is about 75.6 dB. The duration of this noise is very short (<1 s), suggesting that the operation of facility is environmentally friendly to the operators and people working in the building.
PubDate: 2021-03-25

• Additive Manufacturing Under Lunar Gravity and Microgravity
• Abstract: Mankind is setting to colonize space, for which the manufacturing of habitats, tools, spare parts and other infrastructure is required. Commercial manufacturing processes are already well engineered under standard conditions on Earth, which means under Earth’s gravity and atmosphere. Based on the literature review, additive manufacturing under lunar and other space gravitational conditions have only been researched to a very limited extent. Especially, additive manufacturing offers many advantages, as it can produce complex structures while saving resources. The materials used do not have to be taken along on the mission, they can even be mined and processed on-site. The Einstein-Elevator offers a unique test environment for experiments under different gravitational conditions. Laser experiments on selectively melting regolith simulant are successfully conducted under lunar gravity and microgravity. The created samples are characterized in terms of their geometry, mass and porosity. These experiments are the first additive manufacturing tests under lunar gravity worldwide.
PubDate: 2021-03-24

• Experimental Study of the Processes of Formation, Drift and Levitation of
Vapor–Gas Bubbles in Water Containing Surfactant Under the Action of
Ultrasound
• Abstract: The work is devoted to the investigation of the peculiarities of the formation, dynamics and coalescence of vapor–gas bubbles as a result of continuous ultrasonic (US) exposure to a liquids containing anionic surfactant of various concentrations. It is found that large bubbles of millimeter size which are formed in pure water due to coalescence processes, freely rise to the surface. With time, the number of bubbles in water decreases according to a law close to an inverse proportionality. In the presence of surfactant, the area of bubbles recorded by the camera does not change over time; this is apparently associated with the formation of only small bubbles of the order of ten microns, which is caused by the process of inhibition of coalescence by surfactant. Small bubbles are not able to rise to the surface, due to the prevalence of viscous forces over the buoyancy force. Thus, it can be supposed that the surfactant reduces the rate of the liquid degassing process.
PubDate: 2021-03-23

• Numerical Investigation of the Effects of High Reynolds and Marangoni
Numbers on Thermocapillary Droplet Migration
• Abstract: This paper presents the results of the thermocapillary motion of a spherical droplet under Marangoni flow conditions, which takes place in a zero-gravity environment where buoyancy effects become insignificant. In such an environment the droplet moves from the cold region to the warm region due to the variation of surface tension induced by the temperature gradient. This two-phase flow problem is formulated using a 3D CFD model linked with four user-defined functions (UDFs) where the liquid–liquid interface is tracked using the “volume of fluid (VOF)” method and the “geometric reconstruction” scheme. The droplet interface was captured using the “Piece-wise Linear Interface Calculation (PLIC)” approach as a part of the VOF method. A constant temperature gradient was assumed in the stagnant liquid bounded medium. The results obtained cover low, intermediate, and high thermal Marangoni numbers (MaT ≤ 105), which were not covered before in numerical or space onboard experimental results. It was found that the droplet deforms as it elongates in the direction of the temperature gradient. The scaled droplet velocity decreases as the thermal Marangoni number increases for the full range of MaT. In addition, the scaled droplet velocity has been correlated with the thermal Marangoni number of a single droplet migrating in the zero-gravity condition, based on the results of the present work.
PubDate: 2021-03-22

• Analysis of the Significance of the Influence of Various Components of the
Disturbance from a Temperature Shock on the Level of Microaccelerations in
the Internal Environment of a Small Spacecraft
• Abstract: The paper analyzes the influence of various disturbing components arising from a temperature shock of large elastic elements of a small spacecraft structure on the level of microaccelerations of the internal environment. The stability loss of a flat equilibrium shape of an elastic element of a small spacecraft is considered, as well as its all-round expansion when it moves from the shadow area to the illuminated part of the orbit. Conclusions are drawn about the significance of the influence of various factors in modeling the microacceleration field. The results obtained can be used in the design of small technological spacecraft.
PubDate: 2021-03-12

• Lattice Boltzmann Study on Influence of Gravitational Acceleration on Pool
Nucleate Boiling Heat Transfer
• Abstract: Under both normal gravity and microgravity conditions, pool boiling is an efficient mode of heat transfer which has been widely applied in practice. Studying the influence of gravitational acceleration on boiling heat transfer is not only of academic significance, but also helpful for the design of space equipment related to boiling. With the development of computer technology, numerical method has been a new reliable way to investigate the boiling heat transfer under different gravities. Pseudopotential lattice Boltzmann (i.e., LB) model is one of the most popular multiphase LB models, in which the phase interface could be formed, disappeared and migrated naturally. In this paper, the Multi-Relaxation-Time (i.e., MRT) pseudopotential LB model coupled with phase-change model was applied to simulate the pool boiling heat transfer under different gravitational accelerations and wall superheats. Pool boiling curves under different gravities were obtained. It’s found that: 1) the pool boiling heat transfer coefficient at a given wall superheat decreases with a decrease in gravity; 2) the wall superheat, as well as heat flux, at the CHF (i.e., critical heat flux) point and ONB (i.e., onset of the nucleate boiling) decrease gradually with a decrease in gravity. In addition, based on the numerical results, a new gravity scaling model was proposed to predict the influence of gravitational acceleration on the nucleate boiling heat transfer under different wall superheats. Finally, the new gravity scaling model was proved to be capable of predicting the heat flux during the nucleate boiling under different wall superheats and gravities.
PubDate: 2021-03-05

• Analysis of Circulation Reversal and Particle Transport in Evaporating
Drops
• Abstract: We report experimental evidence of circulation reversal in evaporating drops. The internal flow patterns and particle distribution inside the evaporating water droplet with suspended polystyrene particles was studied using the Particle Image Velocimetry (PIV) technique. Droplet placed on externally heated substrate showed two symmetric and counter rotating Marangoni convection cells at the beginning of evaporation process. Towards the final stages of evaporation, the two counter rotating Marangoni convection cells reversed the direction of circulation. Interestingly, it was observed that between these two stages four symmetric and counter rotating convection cells appeared inside the evaporating droplet. Our results are in support of recent theoretical investigations on circulation reversal in evaporating drops. The flow patterns were driven by the surface tension gradient caused by the surface temperature distribution along the droplet-air interface. The surface temperature distribution is not only dependent on the non-uniform evaporation flux but also on the conduction path from the substrate to the droplet surface. Towards the end of evaporation, the fluid flow becomes radially outward from the center to the pinned edge of the droplet. We have also investigated the evaporating droplets placed on a curved substrate. Unlike the case of flat substrate, the evaporation from curved surface resulted monotonic temperature profile. The particle distribution and resulting deposition patterns was strongly influenced by the internal fluid flow pattern and was observed to be different from that of a flat substrate.
PubDate: 2021-02-15
DOI: 10.1007/s12217-020-09866-0

• Coherent Particle Structures in High-Prandtl-Number Liquid Bridges
• Abstract: Clustering of small rigid spherical particles into particle accumulation structures (PAS) is studied numerically for a high-Prandtl-number (Pr = 68) thermocapillary liquid bridge. The one-way-coupling approach is used for calculation of the particle motion, modeling PAS as an attractor for a single particle. The attractor is created by dissipative forces acting on the particle near the boundary due to the finite size of the particle. These forces can dramatically deflect the particle trajectory from a fluid pathline and transfer it to certain tubular flow structures, called Kolmogorov–Arnold–Moser (KAM) tori, in which the particle is focused and from which it might not escape anymore. The transfer of particles can take place if a KAM torus, which is a property of the flow without particles, enters the narrow boundary layer on the flow boundaries in which the particle experiences extra forces. Since the PAS obtained in this system depends mainly on the finite particle size, it can be classified as a finite-size coherent structure (FSCS).
PubDate: 2021-02-11
DOI: 10.1007/s12217-020-09845-5

• Steady-state Measurements of Ternary Mixtures in Thermogravitational
Microcolumn Using Optical Digital Interferometry
• Abstract: Steady-state measurements in a thermogravitational microcolumn using optical digital interferometry are presented here for the first time in the literature in the case of ternary mixtures. These measurements enabled the subsequent obtaining of thermodiffusion coefficients of a ternary mixture once convection reaches the steady-state. The ternary mixture used was the benchmark one, tetrahydronaphthalene (THN) – isobutylbenzene (IBB) and n-dodecane (nC12) with mass fraction of 0.8-0.1-0.1 respectively. Contrast factors due to the change in the concentration field were measured and compared with the corresponding ones in the literature. Uncertainty in the results was found to be of similar order of magnitude as in the case of Selectable Optical Diagnostic Instrument (SODI), which means that the condition number of that contrast factor matrix is almost equal to the present one. Final values of thermodiffusion coefficients were compared with the results reported from other optical techniques, as well as with the results obtained by the traditional long opaque thermogravitational columns (TGC). Some proposals were then made in order to improve accuracy reducing the condition number of the contrast factor matrix.
PubDate: 2021-02-08
DOI: 10.1007/s12217-020-09861-5

• Research on Melt Wettability Measurements Under Microgravity
• Abstract: Wetting and the interaction between liquid and solid phases are significantly affected by gravity. In recent years, Chinese scientists have carried out wettability experiments in space, but the limitations of experimental facilities have hindered their ability to carry out in-situ observations of the dynamic process of wettability in space. The future Chinese space station will provide a platform for real-time observation of the melt wettability in space. To study the wettability of melt under microgravity, a research method for real-time observation on orbit is proposed. The change in the image contour is determined on the basis of Hu moments, according to changes in the image, to control the acquisition frame rate. This can greatly reduce the memory required to store the images. At the same time, the proposed method uses the binarization method to process the images, and then performs target searching and positioning. Furthermore, it uses the Canny multi-level edge detection operator to extract the target contour. The Young-Laplace equation is used to fit the contour of the droplet. Finally, it obtains the surface tension and contact angle of the melt droplet in real time. The experimental results show that the data storage capacity can be reduced by 90% nearly using this method, and the change in the contact angle and surface tension in the melting process can be obtained in real time.
PubDate: 2021-02-03
DOI: 10.1007/s12217-020-09860-6

• Critical Modes of Thermoelectric Convection Instabilities in a Vertical
Slot
• Abstract: Investigation of the natural convection in a dielectric fluid confined inside a vertical slot subject to a constant horizontal temperature gradient and a high-frequency electric field was revisited. The thermoelectric coupling produces a dielectrophoretic force which contains a term called electric buoyancy associated with an electric gravity. Similar to the Archimedean buoyancy, this force can induce thermo-electro-convective instability in a stable fluid flow. Including the feedback effect of the electric field on the flow, a three-dimensional linear stability analysis is performed to characterize the instability induced by this force. Different critical modes are found depending on the intensity of the electric field: stationary hydrodynamic modes, oscillatory thermal modes and stationary electric modes. The threshold of the electric modes is independent of the Prandtl number in contrast with the threshold of the hydrodynamic and thermal modes. The obtained results are compared with those of previous studies.
PubDate: 2021-01-25
DOI: 10.1007/s12217-020-09856-2

• The Payload Development and the Experiments for Studying Thermocapillary
Convection in TG-2 Liquid Bridge
• Abstract: The development of space experiment payload for studying thermocapillary convection in the liquid bridge with large Pr number on TG-2 space laboratory as well as the experiments are presented in detail in this paper, and the objectives of the space experiments are confirmed. The functions of the payload are analyzed, and the technical and engineering specifications are determined. Detailed designs and experimental verifications are performed on the structure of liquid bridge columns, the method of bubble removing in the liquid, the bridge cleaning system, the accurate control of aspect ratio and volume ratio, and the high-sensitivity measurement of fluid temperature. Matching experiments on the ground according to space experiment properties are carried out, 5cSt silicone oil is selected as the fluid medium in space experiments. And the states of liquid bridge and temperature oscillation signals obtained from space experiments are presented at the end of this paper. Specific summarizations and discussions to the experiment project on fluid science in space are conducted in this paper, which will provide a useful reference for scientists participating space experimental research in the future.
PubDate: 2021-01-23
DOI: 10.1007/s12217-020-09859-z

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