Microgravity Science and Technology

Dewangan, Kush Kumar; Satbhai, Ojas; Gavel, Satish Kumar; Rokhade, Kiran Kumar

doi: 10.1007/s12217-025-10229-wpmid: N/A

In this study, a review of the state of knowledge of the propagation of evaporation waves in the superheated liquid is presented, along with the motivation for continuing research. Studies of evaporation fronts in superheated liquids have primarily been used for understanding and controlling phenomena such as explosive boiling and flash evaporation for industrial applications and safety. To understand the physics of rapid evaporation, numerous experiments have been conducted. Research findings from the past six decades have been summarized to provide an overview of the current state of knowledge regarding rapid evaporation and wave propagation. General experimental methods have been reported and compared. This review also includes the different mechanisms involved in the wave propagation of flash evaporation. The existing instrumentation of experiments for identifying the physics of rapid evaporation is still limited. Some related topics, like atomization and evaporation under microgravity, are also discussed. In this review, motivation is provided for the development of careful experiments that can be used to test the theories and reveal new phenomena.

Jin, Xin; Wang, Bing

doi: 10.1007/s12217-025-10220-5pmid: N/A

To investigate the effects of different gravity conditions on the solution flow fields and crystal growth rates during the dissolution and growth processes of InGaSb crystals utilizing the vertical gradient freezing (VGF) methods, two-dimensional numerical simulations were conducted. Nine numerical simulations were performed under a range of gravity conditions, including microgravity: 1 × 10− 4 G, 0.01 G; small gravity: 0.1 G, 0.17 G (lunar gravity), 0.38 G (Mars); normal gravity: 1.0 G, and high gravity: 2.0 G, 5.0 G, and 10.0 G. The results demonstrated that the natural convection induced by gravity significantly affects the growth rates of InGaSb crystals. The growth rates were highly sensitive to variations in gravity, decreasing as gravity increased within the range of 0.01 to 2.0 G. Under microgravity conditions (no larger than 0.01 G), growth rates values were very similar, indicating that under microgravity the InGaSb growth process is diffusion-dominant. When gravity exceeds 2.0 G, the growth rates of InGaSb stabilize, but larger non-uniform areas develop as gravity increases, compromising the quality of the grown crystals.

Zhang, Leigang; Dun, Menghao; Xu, Bo; Mao, Shang; Yue, Liwen; Zhang, Yonghai

doi: 10.1007/s12217-025-10221-4pmid: N/A

This study employs two-dimensional numerical simulation to characterize droplet migration and collision dynamics on unidirectional and symmetrical multi-level wettability gradient (WG) surfaces under Earth (g₀), Martian (0.38 g₀), and microgravity (10⁻⁶g₀). Parametric analysis reveals WG = -15/2°/mm optimizes single-droplet migration time in microgravity, exhibiting minimal sensitivity to gravity reduction, while WG = -20/2°/mm maximizes efficiency under g₀. Larger droplets (D = 3 mm) accelerate terrestrial transport but severely impede microgravity migration, where smaller droplets (D = 2 mm) excel. Peak velocity (> 0.3 m/s), governed by WG and D independent of gravity, dictates acceleration capability. Final equilibrium morphology mainly depends on WG. For dual droplets, microgravity collision requires WG = ∓ 15/2& ∓ 20/2°/mm and D = 2 mm; lower gradients or larger diameters prevent collision. The results demonstrate that reduced gravity disrupts mirror-synchronized droplet motion observed under g₀, delaying collision initiation. These findings provide critical guidelines for designing passive capillary fluidic systems in variable-gravity environments, particularly space applications.

Alabuzhev, Aleksey A.; Pyankova, Marina A.

doi: 10.1007/s12217-025-10231-2pmid: N/A

The article proposes a theoretical model of EWOD (electrowetting–on–dielectric) taking into account the saturation of the dynamic contact angle using the example of forced oscillations of an electrolyte droplet in a spatially inhomogeneous alternating electric field. This droplet is clamped between two plates, which are electrodes. The inhomogeneity of the plate surface is described by an individual function, which is a wetting parameter and a proportionality coefficient between the contact line velocity and the contact angle deviation. It is shown that the surface inhomogeneity leads to the excitation of additional modes, the spectrum of which is determined by the function describing this inhomogeneity. It is found that the surface inhomogeneity can change the saturation angle. Qualitative agreement with experiments is shown.

Zhang, Jiaqian; Du, Hui; Hu, Shuoxuan; Ji, Wei; Zhou, Lei

doi: 10.1007/s12217-025-10233-0pmid: N/A

Microgravity environments significantly impact soot formation and flame stability in laminar diffusion flames, yet the underlying mechanisms remain poorly understood, especially in high-pressure combustion systems. This study utilizes a hybrid moment method (HMOM) coupled with P1 radiation modeling to investigate the radiation-induced modifications to temperature fields, flow structures, and soot evolution in ethylene-air co-flow flames under elevated pressures (1–8 bar), comparing normal gravity and microgravity conditions. Results show that microgravity environments amplify soot volume fractions by 200–300% compared to normal gravity, due to extended reactant residence times. Radiative heat losses lower peak flame temperatures by 20–150 K, with this reduction becoming more pronounced at higher pressures due to increased radiation from both gases and soot. At critical pressure thresholds in microgravity, a transition from closed-tip to open-tip flame structures occurs in co-flow laminar diffusion flames, driven by radiative heat losses approaching 45%–60% of total chemical energy. Unlike spherical flame extinction, laminar diffusion flames experience local extinction triggered by heat release rate (HRR) decay at the flame tip, followed by the opening of the hydroxyl radical (OH) zone. This structural modification creates an oxidative boundary discontinuity, preventing the OH zone from fully encapsulating soot particles, thus allowing soot to escape oxidation pathways.

Du, Shize; Wang, Yiqing; Wang, Shengkai; Chen, Zheng

doi: 10.1007/s12217-026-10235-6pmid: N/A

As a zero-carbon fuel, ammonia (NH\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$_3$$\end{document}) has attracted great interests recently. Due to its slow propagation speed, NH\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$_3$$\end{document} flames are strongly affected by gravity and radiation. This study investigates the propagation of spherically expanding NH\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$_3$$\end{document}/air flames under the combined effects of gravity and radiation using two-dimensional simulations with detailed chemistry and transport models. The results show that gravity significantly deforms the flame front, leading to a mushroom-shaped structure in which the local flame displacement speed varies along the front due to local stretch effects. This phenomenon becomes more pronounced at lower equivalence ratios as a result of the reduced flame speed. Overall, gravity enhances the global flame propagation speed. On the other hand, radiation slows the flame propagation by lowering the flame temperature and inducing an inward flow velocity. This makes the flame more susceptible to the influence of gravity and amplifies the deformation of the flame front. Finally, the performance of various approaches for determining the unstretched laminar flame speed from spherically expanding flames under gravitational and radiational conditions is assessed. It is found that when both gravity and radiation effects are significant, the spherically expanding flame method using flame radius history is not applicable, regardless of the definition of equivalent radius, and the surface-averaged method is the only reliable approach. This study provides insights into the understanding and accurate measurement of NH\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$_3$$\end{document}/air flame propagation characteristics.