Microgravity Science and Technology

Zahedi, Hamid; Vakili, Mohammad

doi: 10.1007/s12217-023-10063-ypmid: N/A

In this study, the vital role of fluid type in diffusion through a complex soil-like three-dimensional porous medium under gravity force was investigated by simulations performed using D3Q27 model of Lattice Boltzmann Method (LBM), with Double Relaxation Time (DRT) procedure as well as second-order discretization version of LBM. The elaborate porous medium was constructed using Image Processing technique by a detailed program written in MATLAB language. The hydrogen gas and water vapor were two fluids utilized in this project and because of small velocity of fluid, the Darcy law (with inclusion of gravity) was used extensively. Also, the satisfaction of continuity equation in different cross sections of porous medium was examined for both fluids; velocity and pressure contours were utilized also in this regard. The critical point of value of gravity acceleration g in LBM scale for different fluids was described and gLBM was calculated for 13 fluids to emphasize the vital role of fluid type in LBM simulations. For being confident regarding the role of gravity, the value of gravity acceleration was set to zero intentionally (|g| =|gLBM|= 0) in some other simulations. Because of complex nature of porous medium, the inclusion of Knudsen diffusion phenomenon in calculations of pressure change was necessary. After coupling of Darcy equation with Knudsen diffusion according to valid scientific resources, the calculation of permeability and mean pore diameter of porous medium was accomplished through special three-dimensional fitting by MATLAB. The interesting concept of Specific Surface Area (SSA) was introduced, too.Graphical Abstract[graphic not available: see fulltext]

XUE, Zhi Hu; AI, Bang Cheng; QU, Wei

doi: 10.1007/s12217-023-10056-xpmid: N/A

The gravity-effect plays important factor on the startup and thermal performance of high-temperature heat pipes (HTHPs). But the results of past studies are quite different and confusing our perception. In this paper, a sodium HTHP is fabricated and experimented to study the gravity-assisted, horizontal and anti-gravity three modes on the startup behaviors and quasi-steady thermal performance. The HTHP is designed to Φ25 × 410 mm, two wraps of 100 mesh screen, and filling mass of 15 g sodium. The HTHP is tested at the inclination angle of 0°, 90°, -30° and -90°. The results show that no startup failures are found during all the three operating modes and the startup time for HTHP fully starting at different inclination angle is the same as 10 min. However, the gravity-effect cannot be ignored and plays important influence on the HTHP startup. Compared with the horizontal mode, the gravity-assisted mode (90°) is beneficial for the starting more favorably and decreasing the temperature difference between the evaporator and condenser after the startup. The anti-gravity working mode has a significant adverse effect on the temperature rise-rate of the HTHP condenser and increase the temperature difference after the startup in a large step as the inclination angle changed from 0°, -30° to -90°.

Kanimozhi, B.; Muthtamilselvan, M.; Alhussain, Ziyad A.

doi: 10.1007/s12217-023-10065-wpmid: N/A

The ongoing research numerically examines the impact of the nanoparticle shape factor on the coupled Marangoni and buoyancy convection in a cylindrical porous annular region saturated with Ag-MgO/water hybrid nanofluid with magnetic effects. The internal wall of the annulus is considered to be hot, while the external wall is believed to be cold. The inner cylinder is fitted with a thin circular heated disc. To solve the non-dimensional governing equations, the finite difference approach with ADI, central differencing, and SOR technique is used. The major goal of the current study is to analyze the impact of the various shape factors on the Marangoni convection, magnetic field and nanoparticle volume fraction in the cylindrical annulus. The current study reveals that the spherical shaped nanoparticle outperforms in all the cases and Nu¯\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$\overline{Nu}$$\end{document} hikes with the Marangoni number and declines with Hartmann number.

Wertgeim, Igor I.; Sharifulin, Vadim A.; Sharifulin, Albert N.

doi: 10.1007/s12217-023-10061-0pmid: N/A

The three-dimensional solutions of nonlinear long-wavelength approximations for the problem of Marangoni convection in a thin horizontal layer of a viscous incompressible fluid with a free surface is being considered. The temperature distribution in the liquid corresponds to a uniform vertical gradient distorted by the imposition of a weakly inhomogeneous heat flux localized in the horizontal plane, caused by a lattice of either localized or continuously distributed heat sources and sinks. The lower boundary of the layer is solid and thermally insulated, while the upper one is free and deformable. The statement of the problem is motivated by the search for ways to control convection structures. The problem in long-wave approximation is described by a system of nonlinear transport equations for the amplitudes of temperature distribution and surface deformation. The numerical solution of the problem is based on the pseudospectral method. The dynamics of non-stationary dissipative structures is considered.

Vlasova, O. A.; Kozlov, V. G.

doi: 10.1007/s12217-023-10062-zpmid: N/A

The dynamics of spherical and cylindrical bodies in the vicinity of the cylindrical wall of the cavity filled with fluid under rotational oscillations is experimentally studied. We consider (i) the motion of a light spherical body inside a cylinder under rotational oscillations and (ii) the motion of the heavy cylindrical body in a horizontal cavity under modulated rotation. In the absence of the oscillations, the bodies are pressed against the cavity walls due to the action of (i) the buoyant force and (ii) the centrifugal force. The tangential and rotational body oscillations are studied by means of video registration. It is found that the body oscillations induce the averaged lift force that is responsible for the detachment of the body from the wall at the critical value of the amplitude of the body oscillations. The oscillation-induced repulsive force is measured by the method of the body suspension in a static field of (i) gravitational force or (ii) centrifugal force. It is found that the dimensionless lift force decreases with the distance from the wall according to the exponential law. The magnitude of the lift force is determined only by the amplitude of the velocity of the tangential body oscillation relative to the surrounding fluid while the intensity of the rotational body oscillations is of no importance. Also, the lift force does not depend on the distance to the wall and increases with the dimensionless frequency ω in the studied range ω = 10 – 90. The phenomenon of the oscillation-induced repulsion of the solid from the cavity wall is of interest for the development of an effective method for the control of multiphase media under microgravity conditions.

Zhang, Yufeng; Liu, Rong; Chen, Xue

doi: 10.1007/s12217-023-10064-xpmid: N/A

In the present paper, we investigated experimentally the dynamics of coating flow on a vertical fiber immersed in a liquid phase environment. This flow exhibits rich dynamics which is different from the coating flow in air. In the experiments, it is found that the dynamics of immersed coating flow at different flow rates exhibited three flow regimes, i.e., highly regular beads chain, bound state and beads-like flow with irregular coalescence. The regular and irregular beads-like flows correspond to absolute instability and convective instability, respectively. The bound state flow occurs at the boundary of absolute instability and convective instability. The behavior of immersed coating flow is examined by analyzing the spatiotemporal diagram. In addition, we quantitatively investigated three important characteristic parameters of the immersed coating flow, i.e., wave thickness, wave spacing and wave speed in different flow regimes.

Khemili, Faycel; Najjari, Mustapha

doi: 10.1007/s12217-023-10067-8pmid: N/A

In this study, a one-dimensional, two-phase transient model has been developed to study the transient behavior of water transport in the porous gas diffusion layer (GDL) of a proton exchange membrane fuel cell PEM fuel cell. This model based on the numerical resolution of the mass transport of liquid water and oxygen in the porous GDL is used to gauge the effects of various design and operational parameters, namely, the current density, GDL thickness and GDL permeability, on the overall performance of the system.

Hughes, Ariel M.; Vandenbrink, Joshua P.; Kiss, John Z.

doi: 10.1007/s12217-023-10066-9pmid: N/A

The future of space exploration will be contingent upon the use of plants in bioregenerative life support systems. Unfortunately, the microgravity of space can cause stress in plants, which can reduce growth. The Random Positioning Machine, RPM, is a device designed to provide an analogue for the effects of microgravity on Earth by rotating specimens in three dimensions. In this study, we compare the results from experiments conducted on the International Space Station with those conducted using the RPM (in the 3D clinostat mode) on the ground. Seedlings of Arabidopsis thaliana wildtype and phytochrome mutants were grown in true microgravity and in the omnidirectional gravity on a rotating RPM on the ground. We found that the RPM treatment caused less stress in the seedlings than did true microgravity. We also report that phytochromes A and B play roles in phototropic responses to unilateral light and that these roles differ in the two gravitational environments. Finally, we conclude that while root phototropism in unilateral red and blue differs significantly between the microgravity and omnidirectional stimuli, the RPM can serve as a reasonable analogue of microgravity conditions for assessment of shoot phototropism.

Xie, Gengxin; Yang, Jing; Xu, Yuxuan; Zhang, Yuanxun; Qiu, Dan; Ding, Jinghang

doi: 10.1007/s12217-023-10058-9pmid: N/A

For humanity to complete its ambitious solar system exploration, it is crucial to comprehend how terrestrial life reacts to differing planet gravity. We followed the life trajectory of an earth cotton seed's germination, development, and ultimate fate after prolonged exposure to extremely low temperatures using the life-regeneration ecosystem carried by Chang'e 4 probe, which landed on the Moon on January 3rd, 2019, for the first time in human history. In a controlled environment with similar characteristics, such as temperature, humidity, air pressure, and nutrition, we compared this life trajectory on the moon to that on Earth, except for the differences in gravity, light, and radiation. We discovered that the 1/6 g moon gravity speeds up seed germination. Surprisingly, Moon seed-lings demonstrated rapid acclimatization to super-freezing (below minus 52 degrees Celsius) under 1/6 g lunar gravity, maintaining upright and green despite exposure to long-term extremely cold temperatures for 18–24 hours. Based on cellular and molecular reactions caused by moon-low gravity, we suggest probable mechanisms for cold resilience. These unique findings will enhance our understanding of how plants adapt to suboptimal environmental conditions in space.

Zhang, Chu; Yang, Chao; Hu, Liang; Chen, Shuyang; Zhao, Yifan; Duan, Li; Kang, Qi

doi: 10.1007/s12217-023-10060-1pmid: N/A

Drop tower is an important facility for conducting microgravity experiments on the ground. Since the Beijing drop tower was put into operation in 2003, a large number of scientific experiments have been carried out in the fields of microgravity fluid physics, combustion, materials science and fundamental physics. The drop tower has two operation modes: single capsule falling and double capsule falling, with the microgravity levels reaching 10−2g ~ 10−3g and 10−5g respectively. In order to meet the demand of multi-level microgravity levels in ground microgravity experiments, a double capsule microgravity level control system based on the cold-gas micro thruster is developed. The micro thrusters are mounted in the inner capsule of the double capsule system. During the fall of the double capsule, the cold-gas micro thrusters thrust in the opposite direction of the movement of the structure, which increases the resistance of the inner capsule to realize the control of microgravity level. The measurement results of the high-precision accelerometer show that the 10–3 ~ 10−5g microgravity level can be controlled by this system.