Microgravity - Science and Technology

Shankhwar, Vishwajeet; Singh, Dilbag; Deepak, K. K.

doi: 10.1007/s12217-021-09899-zpmid: N/A

Muscle atrophy in humans mainly occurs due to aging, lack of physical activity, and exposure to microgravity leading to decreased muscle volume and power. Several exercises coupled with various bodysuits have been used to cope with muscle atrophy. But, all state of arts failed to provide complete prevention from atrophy. Hence, a new countermeasure gravitational load modulating bodygear (CGLM bodygear) has been developed. Herein, squats exercise coupled with bodygear was used to increase the lower limbs muscle activity and evaluated by electromyography (EMG). The study was conducted by performing the squats by thirty subjects with and without bodygear. The EMG signals from the biceps and rectus femoris muscle were recorded to evaluate the electrical activity produced in both the muscles. The time domain results of EMG analysis revealed that the bodygear has enhanced biceps and rectus femoris muscle activity by 50% and 90% respectively. The frequency domain results revealed that the rate of fatigue was higher when squats was performed with bodygear as compared to without bodygear. Overall, the study has concluded that squats coupled with bodygear can be a promising countermeasure to muscle atrophy by generating higher muscle activity in lower limbs.

Cao, Xianqi; Gao, Dongyan; Huang, Yongping; Liu, Xiangdong

doi: 10.1007/s12217-021-09903-6pmid: N/A

An improved single-relaxation-time lattice Boltzmann model of the melting with natural convection in a cavity submitted to an inhomogeneous magnetic field is developed and comparatively investigated in this paper, which can not only reduce the numeric diffusion at the phase boundary obviously but also recover the macroscopic energy equations correctly. Three numerical benchmark cases are performed, including the half-space conduction melting, convection-dominated melting, and natural convection under an inhomogeneous magnetic field. Impacts of the dimensionless magnetic force parameter and the magnetic field inclination angle on the melting process are presented in relation to the average Nusselt number, liquid fraction, temperature profile, melting front and pressure distribution. The results show that the numerical predictions based on the current model agree with analytical solutions and present better accuracy than those reported in previous studies. Like the buoyancy force, the magnetic force also has a vital influence on the natural convection development in the melting process. Compared with the case without a magnetic field, the magnetic field angle can be adjusted to enhance and suppress the melting process by employing the coupling effect of the magnetic force and gravity. Moreover, there exists an optimal magnetic field inclination angle for maximizing the melting heat transfer performance. Besides, increasing the dimensionless magnetic parameter expands the gain of melting enhancement while expanding the range of inclination angles that enhances melting performance.

Perminov, A. V.; Lyubimova, T. P.; S.A.Nikulina,

doi: 10.1007/s12217-021-09898-0pmid: N/A

The influence of high-frequency vibrations on the convection of a liquid in an infinitely long horizontal cylinder of square cross-section, which undergoes vertical vibrations, is investigated. The problem was solved numerically on the basis of the averaged equations of thermal vibrational convection, written in terms of the vorticity of the average velocity and stream functions of the average and pulsating flows. The influence of vibrations on the system was determined by a dimensionless vibration parameter V proportional to the ratio of vibrational acceleration to gravitational acceleration and independent of the temperature difference. The values V ≥ 1 correspond to the case of low gravity conditions. The intensity of gravitational convection was characterized by the Grashof number Gr. All calculations were performed for the fixed value of the Prandtl number Pr = 100. For values 0 ≤ V ≤ 10 the evolution of average convective regimes was studied and a map of these regimes was plotted on the Gr—V parameter plane. The stability boundary of stationary average convection is determined. It is shown that after the loss of stability by a stationary average flow in a cavity, two oscillatory average convective regimes with different symmetries can be realized.

Wang, Zhibin; Su, Hongshi; Chen, Ying; Li, Yuxiu; Li, Shuzhe

doi: 10.1007/s12217-021-09868-6pmid: N/A

Using a laser to heat microfluid has the advantages of non-contact local operation, high accuracy, and good adjustability. In this study, a focused infrared laser with a 1550-nm wavelength was applied to heat an oil–water-oil double-emulsion droplet in a microchannel. The Finite Volume Method was used to numerically study the thermocapillary flow and heat transfer of this laser-heating process. In the simulation, the laser energy distribution was modeled using a volumetric Gaussian heat source. The attention was focused on the heat transfer and thermocapillary flow of the double-emulsion droplet. The influences of laser parameters (power and beam diameter) and the temperature coefficient of interfacial tension were studied. We found that the intensity of the thermocapillary flow and the temperature linearly increased with input power; they first decreased and then increased as the size of the input beam increased because of the combined effect of absorbing energy and energy concentration. Moreover, there were four and two thermocapillary vortices inside the middle water phase when the sign of the temperature coefficient of interfacial tension in the double interfaces was the same and different, respectively. In all cases, the uneven temperature coefficient of the inner droplet was lower than that of the middle water phase, but the average temperatures of both regions were extremely close. These results can prove useful in the future operation of double-emulsion droplet-based microfluidics using a laser as a precise and sensitive heating source for drug discovery and delivery, cell analyses, and micro/nanoparticle synthesis.

Tong, Ruiting; Han, Bin; Zhang, Xiao; Zhang, Tao; Zeng, Quanren; Liu, Geng

doi: 10.1007/s12217-021-09896-2pmid: N/A

In this paper, a collision friction model for a double-layer MoS2 film is proposed considering the microgravity induced collision in space environment. A modified REBO (Reactive Empirical Bond Order) potential is used to describe interactions among the atoms in the MoS2 film. The collision friction process of the MoS2 film is simulated by vibrations in the y and z directions, and the dependence of average friction force is analyzed. The influence of a single vibration in the y direction on the friction forces can be ignored, while the vibration in the z direction shows great influence. The effects of vibration frequency and amplitude on frictional behaviors of the MoS2 film are investigated. The average friction forces during the collision friction process correlate with the frequency of the vibration in the z direction, and the relationship shows four stages. As the frequency increases, average friction forces show low values in the first stage, and they are increased as the frequency in the second stage. In the third stage, the average friction forces are decreased, and they come to a stable level in the fourth stage. Increasing the vibration amplitude at different frequencies leads to an increase in average friction force, due to that the increased amplitude results in a high indentation depth. The puckering phenomenon occurs at a specific frequency, which is a reason that the average friction force is increased during this collision friction process.

Moatimid, Galal M.; Amer, Mohamed F. E.; Mohamed, Mona A. A.

doi: 10.1007/s12217-021-09885-5pmid: N/A

Electrohydrodynamics (EHD) instability of a vertical cylindrical interface is tackled in the present study. The interface separates two viscous, homogeneous, porous, incompressible, and dielectric fluids which totate about the common cylindrical axis with different uniform angular velocities. A uniform axial electric field acts upon the considered system. Additionally, the influence of heat transfer is incorporated into the buoyancy term as well as the surface tension parameter, giving rise to the thermo-capillary effect. In this context, the viscous potential theory as well as the standard normal modes analysis are employed. The distributions of temperature, pressure, and velocity fields are evaluated. The linear stability approach resulted in an exceedingly complicated transcendental dispersion relation. The non-dimensional analysis revealed some physical Ohnesorge, Darcy, Rayleigh, Prandtle and Weber numbers. Actually, the dispersion relation has no closed form solution. Consequently, a numerical technique is utilized to display the stability profile. The relation between the growth rate and the wavenumber of the surface waves is constructed. The influences of various physical parameters on the stability profile are illustrated. It is found that the Ohnesorge number plays a dual role in the stability configuration.

Romero-Calvo, Álvaro; Herrada, Miguel Ángel; Hermans, Tim H. J.; Benítez, Lidia Parrilla; Cano-Gómez, Gabriel; Castro-Hernández, Elena

doi: 10.1007/s12217-021-09894-4pmid: N/A

The sloshing of liquids in low-gravity entails several technical challenges for spacecraft designers due to its effects on the dynamics and operation of space vehicles. Magnetic settling forces may be employed to position a susceptible liquid and address these issues. Although proposed in the early 1960s, this approach remains largely unexplored. In this paper, the equilibrium meniscus and axisymmetric oscillations of a ferrofluid solution in a cylindrical tank are studied for the first time while subject to a static inhomogeneous magnetic field in microgravity. Coupled fluid-magnetic simulations from a recently developed inviscid magnetic sloshing model are compared with measurements collected at ZARM’s drop tower during the ESA Drop Your Thesis! 2017 campaign. The importance of the fluid-magnetic interaction is explored by means of an alternative uncoupled framework for diluted magnetic solutions. The coupled model shows a better agreement with experimental results in the determination of the magnetic deformation trend of the meniscus, but the uncoupled framework gives a better prediction of the magnetic frequency response which finds no theoretical justification. Although larger datasets are required to perform a robust point-by-point validation, these results hint at the existence of unmodeled physical effects in the system.

Liu, Xiaoke; Lu, Xiaoxiao; Wang, Xiaoqing; Yu, Qiang; Liu, Laijun; Wang, Yuehai; Ning, Keqing

doi: 10.1007/s12217-021-09890-8pmid: N/A

The containerless method is generally used to study the intrinsic properties of materials, especially the thermophysical properties of melt droplets. The calculation of the melt droplet density and thermal expansion coefficient is related to its volume, while density is the dependent variable for determining the surface tension and viscosity coefficient. Evidently, the accuracy of the thermophysical properties of materials essentially depend on the precision of volume measurement. The melt droplet volume is obtained by analysing the image, thus, the precise volume of the melt droplet depends on the image quality and contour extraction algorithm. Restricted by external conditions, most of the obtained melt droplet images are of low quality and are severely polluted by noise, which complicates the determination of the thermophysical characteristics. Herein, a shape-supervised super-resolution convolutional neural network method is presented to improve image resolution and using its sub-network to extract the contour of the melt droplet directly and accurately. Compared with the existing method, this approach improves the accuracy of evaluating the thermophysical properties of the material and reduces the computational complexity by simplifying the two-step calculation process to a one-step procedure.

Ando, Shion; Shimada, Kei; Eto, Daijiro; Moriue, Osamu

doi: 10.1007/s12217-021-09893-5pmid: N/A

To investigate the effect of ethanol concentration on the cool flame characteristics of isolated binary fuel droplet, experiments and numerical simulations on n-decane/ethanol droplet were conducted, varying the volume fractions of ethanol. Ambient pressure was set to atmospheric pressure and the temperature was varied from 600 to 660 K. Under these conditions, although cool flame was observed for n-decane, it did not induce hot flame ignition. CCD camera and K-type thermocouple were used to measure the droplet diameter and cool flame temperature, respectively. Moreover, one dimensional numerical simulation was performed with the fully transient numerical model. In addition to the assumptions on species flux, temperature continuity, fugacity equilibrium was assumed to simulate the evaporation process of multicomponent droplet. After the n-decane droplet was inserted into the hot ambience, evaporation was suddenly promoted and the temperature near the droplet surface decreased due to the cooling effect of evaporation. After the ignition of cool flame, the thermocouple nearest to the droplet showed the highest temperature, which implies that large heat release occurred near the droplet. When ethanol was added to n-decane, the cool flame ignition delay became longer. This is probably because the vapor formation of n-decane was delayed due to the high volatility of ethanol. However, the cool flame temperature was not significantly varied by the volume fraction of ethanol. This is probably because n-decane and OC10H19OOH accumulating at the cool flame location was almost the same for all conditions.

Karchevsky, A. L.; Cheverda, V. V.; Marchuk, I. V.; Gigola, T. G.; Sulyaeva, V. S.; Kabov, O. A.

doi: 10.1007/s12217-021-09892-6pmid: N/A

The paper presents a new tool “the method of IR transparent thick plate” that can be used to study the heat and mass transfer processes in the air-liquid-solid contact line area. Its distinctive feature as compared to the previously known methods is the solution of the initial-boundary problem for the heat conductivity equation, which in terms of mathematics is a correct problem. Currently, the heat and mass transfer processes in the area of the contact line are not completely understood because of its small size and a limited set of applied research methods. The challenges in modeling of contact line phenomena have to do with the fact that several physical effects such as evaporation, viscous flow, surface tension, thermocapillary stresses, London-van der Waals forces, disjoining pressure, nonequilibrium effects are coupled together and all significant in this highly localized region. This leads to difficulties in both mathematical modeling and design of experiments. The experimental part of the study includes the evaporation of a liquid drop on a sapphire substrate. The upper part of the sapphire glass is coated with a high heat-resistant black graphite paint (Graphit 33), which is a non-transparent for visual and IR-rays. Measurements of various physical, chemical and geometrical properties of this coating have been done by electron microscopy and other techniques. Trial experiments on the drop evaporation were carried out. The sapphire surface temperature fields after single drop deposition were obtained using the IR-scanner. The experimental local heat flux distribution at drop evaporation on the sapphire surface with two small local highs close to the contact line regions has been measured.