Microgravity Science and Technology

Wuest, Simon L.; Cerretti, Geraldine; Polzer, Jennifer; Gerig, Simon; Zumbühl, Christoph; Jost, Christian; Rüfenacht, Lukas; Eberli, Robert; Krucker-Bösch, Barbara; Traversari, Julia; Horn, Melanie; Pérez, Daniel Invernot; Giger-Lange, Christina; Rattenbacher-Kiser, Karin F.; Ille, Fabian; Székely, Gerhard; Lienkamp, Soeren S.; Egli, Marcel

doi: 10.1007/s12217-024-10155-3pmid: N/A

Exposure to acute and prolonged microgravity triggers numerous physiological adaptations. To date, the underlying molecular mechanisms are not well understood, and several pathways have been proposed. Among other candidates, specific ion channels are hypothesized to be gravity dependent, but it has not been possible to conclusively demonstrate gravity dependency of specific protein entities. Therefore, we developed a miniaturized two-electrode voltage clamp (TEVC) that allowed electrophysiological experiments on Xenopus laevis oocytes using the GraviTower Bremen Prototype (GTB-Pro). The GTB-Pro is capable of flying experiments on a vertical parabolic trajectory, providing microgravity for a few seconds. As an interesting first candidate, we examined whether the nonselective mechanosensitive ion channel PIEZO1 is gravity dependent. The results showed no difference between PIEZO1-overexpressing and control oocytes under acute microgravity conditions.

Yang, Zhaodong; Wang, Zichen; Zhang, Zhijie; Wang, Yang; Liang, Wei

doi: 10.1007/s12217-024-10160-6pmid: N/A

In this paper, using propagating Lamb waves along the inclined curved surfaces, we present a technique to reduce the impact of rainy days on-camera performance. Our experimental results show that Lamb waves, generated at a location distant from a point of droplet impact, can suppress the formation of satellite droplets during partial rebound. Additionally, a high-fidelity numerical simulation model was developed, revealing that the liquid’s surface tension significantly affects the occurrence of satellite droplets during partial rebound. Moreover, by applying Lamb waves, the droplet on the curved surface can be propelled at different speeds. Combining numerical simulations, we can clearly observe the deformation of the gas-liquid interface after the droplets impact the substrate. Afterward, we systematically investigated the effects of droplet impact height, inclination angle, and applied input power on the Lamb Waves on droplet removal.

Schmitz, Andreas S.; Hanstein, Luisa; Klein, Max; Kretschmer, Michael; Lotz, Christoph; Shemakhin, Aleksandr; Thoma, Markus H.

doi: 10.1007/s12217-025-10162-ypmid: N/A

In this work we present an experiment in which we injected microspheres at low pressure into a capacitively coupled argon plasma chamber. The setup was located in the top point of the Einstein-Elevator drop tower in Hannover, Germany, where the microparticles reached their equilibrium position above the lower electrode during 1g\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$1 \, g$$\end{document}. During the fall, the trajectories of the microparticles, which were driven by the electric force, the neutral drag force and some residual gravitational force, were recorded. In addition, simulations of the plasma conditions were performed with commercial software to determine the microparticle charges via an orbital motion limit theory approach, taking into account the charge exchange in ion-neutral collisions. Based on the calculated position dependence of the microparticle charges and the electric force, the electric field present in the plasma sheath region was finally determined.

Zhang, Leigang; Ru, Meng; Zhang, Yonghai; Li, Guopei; Chen, Zhenqian; Chen, Gang; Wu, Xuehong

doi: 10.1007/s12217-024-10159-zpmid: N/A

In this study, fluid flow during condensation in a tube under different gravity conditions is simulated by utilizing centrifugal force to offset gravitational effects. The role of fins, tube diameter, and steam quality on the two-phase flow pattern, temperature distribution, and pressure drop is investigated. The results show that gravity, tube diameter, and steam quality have a significant effect on the flow pattern. The flow characteristics were also significantly affected by the operating parameters, with undulating and laminar flow dominating, while bubbling flow emerges under specific conditions. In microgravity environments, as steam quality decreases, the temperature drop diminishes progressively compared to normal gravity conditions. Under normal gravity and low flow conditions, the average temperature of finned tubes increased by 7 °C to 16.4 °C relative to bare tube temperatures, and the pressure drop escalated by up to 56%. The introduction of fins notably enhanced heat transfer efficiency and facilitated a more uniform temperature distribution. However, this enhancement in heat transfer was accompanied by an increase in pressure drop due to the heightened resistance to fluid flow caused by the presence of fins. These experimental insights offer a deeper comprehension of fluid behavior under diverse gravity conditions and lay a scientific foundation for designing future thermal management systems.

Sharifulin, V.A.; Beloborodov, P.S.; Sharifulin, A.N.; Lyubimova, T.P.

doi: 10.1007/s12217-025-10168-6pmid: N/A

In this paper, we study 2D stationary regimes of mixed convection in a square cavity with a moving lid. All walls of the cavity are considered as solid; the side walls are assumed to be perfectly thermally insulated, while the top and bottom walls are isothermal, the temperature of the bottom wall is higher. The impact of a smooth change in the velocity of the upper wall of on the convective stability of air within a square cavity is investigated both analytically, using low-mode approximation, and numerically, by the finite difference method. Calculations are performed for Grashof numbers up to values thirty times greater than the critical one. It have been shown that for each supercritical Grashof number there is a critical Reynolds number Rec\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$Re_c$$\end{document} such that with a smooth change in the Reynolds number within the interval -Rec<Re<Rec\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$-Re_c< Re < Re_c$$\end{document} the flow is continuously transformed, changing the structure from normal single-vortex to anomalous double-vortex and vice versa. If, with a change in the Reynolds number, the limits of the specified interval are exceeded, a hysteresis transition from the anomalous flow to the normal one is observed. These findings provide new insights into the complex interplay between thermal and inertial forces in convective flows. Understanding these flow structures and transitions could improve the knowledge of combustion processes.

Dong, Chao; Yang, Zhaoshu; Guo, Zhenkun; Liu, Guoping; Sun, Minzheng

doi: 10.1007/s12217-024-10157-1pmid: N/A

A compact and lightweight sensor is always expected to be embedded with the traditional micro-vibration isolator in spacecraft. It helps to detect the subtle disturbances the isolator encounters and alerts for potential harm. In this work, we developed a self-sensing micro-vibration isolator using an electret transducer. The theoretical models of the electret-based self-sensing isolator are derived from Hamilton's principle to investigate the coupled dynamics of the system and guide a model-based design. Simulations via the finite element method were also conducted to verify and extend the effectiveness of the proposed model. The results show that the electret transducer is an excellent candidate for the embedded sensor of the micro-vibration isolator. With the proper size and appropriate deployment pattern, the electret sensors can precisely detect the translation and rotation of the unsprung load.

Jiménez Blanco, Ignacio; Salgado Sánchez, Pablo; Gligor, Dan; Borshchak Kachalov, Andriy; Arshadi, Ali

doi: 10.1007/s12217-025-10165-9pmid: N/A

We present here an extensive analysis of the free surface dynamics driven by the thermocapillary effect in half-filled elliptical containers in microgravity. Depending on the cell ellipticity δ\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$\delta $$\end{document}, which selects the preferred static equilibrium via surface energy, and on the applied thermal forcing ΔT\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$\Delta T$$\end{document}, interesting dynamics are found. Simulations show that the steady, thermally-driven position of the interface — perpendicular to ΔT\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$\Delta T$$\end{document} — undergoes a pitchfork bifurcation at a critical δcr\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$\delta _\textrm{cr}$$\end{document} that breaks the vertical reflection symmetry of the system. These results are supported by (leading order) estimates of the opposing thermocapillary and surface tension forces, predicting the linear dependence of δcr\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$\delta _\textrm{cr}$$\end{document} on ΔT\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$\Delta T$$\end{document}. Finally, the free surface relaxation after switching off the thermal control is explored. As a whole, the present analysis indicates that one can combine thermocapillary flows and an adequate cell design to manipulate and control fluids in microgravity, with potential in a wide variety of applications.

Guo, Mingjie; Liang, Zhiyi; Chen, Xue; Li, Ruizhi; Liu, Rong

doi: 10.1007/s12217-025-10161-zpmid: N/A

We studied experimentally the dynamics of a thin film coating on a fiber with different inclined angles. This type of flow is asymmetric and accompanied by rich dynamics manifested via the formation and interaction of droplets. It is found that the dynamics of the coating flows exhibits three typical regimes, i.e., oscillatory flow, steady and unsteady pearl-like flows, at different flow rates. Interestingly, at a large inclined angle, the coating flow exhibits behaviors of droplets shedding in the convective regime at high flow rates. The steady and unsteady pearl-like flows correspond to the absolute and convective instabilities, respectively, and the oscillatory flow is due to the secondary instability of the travelling wave. From the viewpoint for nonlinear dynamics, the oscillatory wave is a solution of relative periodic orbit which has fixed temporal and spacial periods. We identified the transition boundaries between different flow regimes in the θ-Q¯\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$\theta -\overline{Q }$$\end{document} plan.

Godasiaei, Seyed Hamed; Kamali, Hossein Ali

doi: 10.1007/s12217-025-10163-xpmid: N/A

This study investigates the feasibility of replacing computational fluid dynamics (CFD) techniques with machine learning (ML) models for heat transfer modeling, focusing on forced convection processes. The research leverages artificial intelligence algorithms, specifically random forests (RF), super-gradient boosting (SGBoost), and artificial neural networks (ANN), to predict key heat transfer metrics such as Reynolds number, nanoparticle size, volume percentage, and Nusselt number. Using a dataset of 210 data points, the ML models are systematically applied to forecast heat transfer outcomes. Model performance is evaluated using Root Mean Squared Error (RMSE), Pearson’s correlation coefficient (r), and Mean Absolute Error (MAE). Results indicate that SGBoost achieves an accuracy of 91%, RF 90%, and ANN 86%, with corresponding RMSE values of 1.07, 1.65, and 16.1, respectively. These findings demonstrate that ML models not only deliver high accuracy and predictive power but also outperform traditional CFD methods in computational efficiency and adaptability to new data. Unlike conventional techniques that rely on predefined physical models and require extensive computational resources, ML approaches streamline the modeling process and enhance accessibility for diverse engineering applications. This study underscores the transformative potential of ML in advancing thermal analysis and optimizing forced convection heat transfer simulations.

Subbotin, Stanislav; Shiryaeva, Mariya

doi: 10.1007/s12217-025-10164-wpmid: N/A

Inertial waves in a rotating confined fluid can focus on closed trajectories, known as wave attractors. These regimes are not eigenmodes and are related only to the frequency dependence of the wave vector. This paper presents an experimental investigation of the cylindrical cavity shape’s effect on the attractor’s spatial structure. We considered three different configurations: i) a circular cylinder with both conical axisymmetric ends; ii) a cylinder with one straight end and the other end inclined to the plane of the cross-section; iii) both ends of the cylinder are inclined parallel. The major observed difference is the azimuthal flow structure. In the axisymmetric case, the shape of the wave attractor is independent of the azimuthal coordinate, and the instantaneous vorticity field represents a system of nested rings in the cross-section. If one of the cavity ends has a constant slope, wave focusing appears in the meridional plane passing near the direction specified by the geometry. The three-dimensional law of wave reflection from inclined boundaries causes meridional trapping, which is important in real geo- and astrophysical systems with complex boundary topography.