Shapes and dynamics of floating droplets under the action of an inclined temperature gradient in the presence of two-dimensional spatial modulation of the vertical component of the temperature gradient are investigated. The case when the vertical component of the temperature gradient is directed downwards is considered. The problem has been studied numerically by the finite difference method. The precursor model has been considered. It is shown that the shape of the droplet is strongly influenced by the thermocapillary stresses caused by a non-uniform substrate heating and the gravity force.

The influence of spatial inhomogeneity of temperature on the dynamics and instabilities of a droplet floating on a heated liquid substrate is investigated. The cases of one- and two-dimensional modulation are considered. The problem is studied numerically in the framework of the slender droplet approximation and the precursor model. It is shown that spatial temperature inhomogeneity leads to the liquid redistribution in the substrate toward the region of lower temperature, which is accompanied by the change of the droplet shape. The gravity flattens the droplet and freezes the droplet's shape, preventing the rupture.

The increasing duration and complexity of space missions for extra-terrestrial exploration have raised the need for developing more reliable and efficient thermal control systems (TCS). In fact, TCS are aimed at supporting life in shuttles and planetary bases and ensuring the proper operation of instrumentation for experiments. Consequently, their study is of high interest, particularly as TCS are required to reduce their weight and volume. This latter requirement has led to the introduction of two-phase heat transfer systems in place of traditional singlephase ones. As a result, two-phase heat transfer processes need to be thoroughly studied under reduced gravity conditions to ensure the adequate design of thermal control systems for space applications. In this work, the condensation heat transfer of R1233zd(E) was studied during the 84th ESA Parabolic Flight Campaign using a 3.38 mm inner diameter channel. Experiments were conducted under hyper-, micro- and normal gravity conditions at saturation temperature equal to 40 degrees C and mass fluxes equal to 30 kg m- 2 s- 1 and 40 kg m- 2 s-1. The results reveal a significant reduction in heat transfer coefficients under microgravity conditions, with annular flow patterns being predominantly observed. Notably, this study presents experimental condensation data under hyper-gravity conditions for the first time. Comparisons with HFE-7000 data (tested during a previous Parabolic Flight Campaign) and evaluations against existing correlations are presented, highlighting the need for accurate predictive models for condensation heat transfer in microgravity and hypergravity.

Recent discoveries of potential ice particles and ice-cemented regolith on extraterrestrial bodies like the Moon and Mars have opened new opportunities for developing technologies to extract water, facilitating future space missions and activities on these extraterrestrial body surfaces. This study explores the potential for water extraction from regolith through an experiment designed to test water recuperation from regolith simulant under varying gravitational conditions. The resultant water vapor extracted from the regolith is re-condensed on a substrate surface and collected in liquid form. Three types of substrates, hydrophobic, hydrophilic, and grooved, are explored. The system’s functionality was assessed during a parabolic flight campaign simulating three distinct gravity levels: microgravity, lunar gravity, and Martian gravity. Our findings reveal that the hydrophobic surface demonstrates the highest efficiency due to drop-wise condensation, and lower gravity levels result in increased water condensation on the substrates. The experiments aimed to understand the performance of specific substrates under lunar, Martian, and microgravity conditions, providing an approach for in-situ water recovery, which is crucial for establishing economically sustainable water supplies for future missions. To enhance clarity and readability, in this paper, “H2O” will be referred to as “water”.

Ice formation on aircraft surfaces poses significant safety risks, and current detection systems often struggle to provide accurate, real-time predictions. This paper presents the development and comprehensive evaluation of a smart ice control system using a suite of machine learning models. The system utilizes various sensors to detect temperature anomalies and signal potential ice formation. We trained and tested supervised learning models (Logistic Regression, Support Vector Machine, and Random Forest), unsupervised learning models (K-Means Clustering), and neural networks (Multilayer Perceptron) to predict and identify ice formation patterns. The experimental results demonstrate that our smart system, driven by machine learning, accurately predicts ice formation in real time, optimizes deicing processes, and enhances safety while reducing power consumption. This solution holds the potential for improving ice detection accuracy in aviation and other critical industries requiring robust predictive maintenance.

This study details the development and validation of a graphene-based ice detection system, designed to enhance flight safety by monitoring ice accumulation on aircraft surfaces. The system employs a semiconductive polymer (PEDOT:PSS) with graphene electrodes, interpreting resistance changes to detect water impact and ice formation in real time. The sensor’s performance was rigorously tested in a wind tunnel under various temperature and airflow conditions, focusing on resistance signal dependency on air temperature and phase change. The results demonstrate the sensor’s ability to distinguish water droplet impacts from ice formation, with a notable correlation between resistance signal amplitude and water droplet impacts leading to ice accretion. Further analysis shows a significant relationship between air temperature and the resistance signal amplitude, particularly at lower temperatures beneficial to ice formation. This underlines the sensor’s precision in varied atmospheric conditions. The system’s compact design and accurate detection highlight its potential for improving aircraft ice monitoring, offering a path toward a robust and reliable ice detection system.

In the context of improving aircraft safety, this work focuses on creating and testing a graphene-based ice detection system in an environmental chamber. This research is driven by the need for more accurate and efficient ice detection methods, which are crucial in mitigating in-flight icing hazards. The methodology employed involves testing flat graphene-based sensors in a controlled environment, simulating a variety of climatic conditions that could be experienced in an aircraft during its entire flight. The environmental chamber enabled precise manipulation of temperature and humidity levels, thereby providing a realistic and comprehensive test bed for sensor performance evaluation. The results were significant, revealing the graphene sensors’ heightened sensitivity and rapid response to the subtle changes in environmental conditions, especially the critical phase transition from water to ice. This sensitivity is the key to detecting ice formation at its onset, a critical requirement for aviation safety. The study concludes that graphene-based sensors tested under varied and controlled atmospheric conditions exhibit a remarkable potential to enhance ice detection systems for aircraft. Their lightweight, efficient, and highly responsive nature makes them a superior alternative to traditional ice detection technologies, paving the way for more advanced and reliable aircraft safety solutions.

The dynamics of a droplet on a liquid substrate in the case of an inhomogeneous heating from below has been investigated. The problem is studied numerically in the framework of the slender droplet approximation and the precursor model. The change of the stationary droplet’s shape and the rupture of the substrate layer induced by a floating droplet are investigated. The influence of the gravity force on the shape of the droplet is studied.

Ice formation on aircraft surfaces poses significant safety risks, and current detection systems often struggle to provide accurate, real-time predictions. This paper presents the development and comprehensive evaluation of a smart ice control system using a suite of machine learning models. The system utilizes various sensors to detect temperature anomalies and signal potential ice formation. We trained and tested supervised learning models (Logistic Regression, Support Vector Machine, Random Forest), unsupervised learning models (K-means clustering), and neural networks (Multi-Layer Perceptron) to predict and identify ice formation patterns. Experimental results demonstrate that our smart system, driven by machine learning, accurately predicts ice formation in real-time, optimizes de-icing processes, and enhances safety while reducing power consumption. This solution holds the potential for improving ice detection accuracy in aviation and other critical industries requiring robust predictive maintenance.

Floating droplets (liquid lenses) are widely used in engineering applications. A typical way of droplet manipulation is the non-uniform heating. In the present work, the influence of two-dimensional spatial inhomogeneity of temperature on the dynamics and instabilities of a droplet floating on a heated liquid substrate is investigated. The problem is studied numerically in the framework of the slender droplet approximation and the precursor model. It is shown that spatial temperature inhomogeneity leads to the liquid redistribution in the substrate toward the region of lower temperature, which is accompanied by the change in the droplet shape. Heating from below can lead to the substrate layer's rupture due to its monotonic instability. Symmetric and asymmetric droplets under the action of spatial temperature inhomogeneity have been obtained.

The action of vibration on Marangoni flows in a droplet on a liquid substrate heated from below is investigated. The analysis has been carried out using a closed system of strongly nonlinear equations. The problem is studied numerically in the framework of longwave amplitude equations and the precursor model. It is shown that vibrations slightly affect the average (inkpot) shape of the droplet.

Ice formation detection is important in telecommunications and aeronautics, e.g., ice on the wings of an aircraft affects its aerodynamic performance and leads to fatal accidents. While many types of sensors exist, resistive sensors for ice detection have been poorly explored. They are however attractive because of their simplicity and the possibility to install an array of sensors on large areas to map the ice formation on wings. Hygroscopic ionic conductors have been demonstrated for resistive ice sensing but their high resistance prevents the readout of sensor arrays. In this work, mixed ionic‐electronic polymer conductors (MIEC) are considered for the first time for ice detection. The polymer blend poly(3,4‐ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) is solution deposited on a pair of electrodes. The sensor displays an abrupt rise in electrical resistance during the transition phase between water liquid to solid. It is proposed that the morphology and electronic transport in PEDOT are affected by the freezing event because the absorbed water in the PSS‐rich phase undergoes dilatation upon forming ice crystals. For the aeronautics application, successful tests of integration of sensing layer in pre‐preg layers of aeronautical grade and freezing detection are carried out to validate the ice detection principle.

Dynamics and instabilities of the droplet on the liquid substrate under the action of the gravity force have been investigated. The problem is studied numerically. The longwave approximation is applied. By heating from below, the action of the gravity can prevent the rupture of the liquid layer. The diagram of regimes in the plane "the Bond number - the Marangoni number" has been constructed. By heating from above, the gravity force flattens the droplet and suppresses the oscillations.

New concept of the experimental investigation has been proposed and successfully realized during the 73rd ESA parabolic flight campaign 2020.The evaporators' behavior is analyzed by evaluating the liquid level inside and by investigating the external condensation on the designed condenser's surface.Three evaporators made with different techniques have been tested.Analysis of the experimental data shows qualitative differences in considered evaporators.Aluminium foam provided uniform distribution of liquid close to its external surface.The evaporator with 3D-printed wick had a non-uniform distribution of liquid inside.Sintered brass wick showed the longest stabilization time.

Considering the increasing complexity of future space missions and the growth of heat fluxes to be removed in next generation satellites, thermal control systems will be asked to provide high heat dissipation rates with reduced power input, size and weight. Two-phase systems represent a reliable technical solution to meet all these specifications but their accurate design requires validated tools and a deeper understanding of the effect of gravity on heat transfer. While several experiments and numerical simulations have been conducted to investigate the gravity effect on pool and flow boiling, studies on in-tube condensation under reduced gravity conditions are still limited in the literature. In the present work, the effect of gravity is experimentally investigated during condensation of HFE-70 00 inside a 3.38 mm internal diameter channel with mass velocity ranging from 30 kg m(-2) s(-1) to 50 kg m(-2) s(-1). Condensation tests were carried out during the 70th ESA (European Space Agency) Parabolic Flight Campaign by simultaneously measuring the liquid film thickness and the heat transfer coefficient inside the channel in both normal gravity and microgravity conditions. The liquid film thickness is determined by coupling a shadowgraph technique with the measurements performed by a chromatic confocal sensor and an interferometer. The reduced gravity condition is responsible for a heat transfer penalization with respect to normal gravity, which is found to be more severe when the mass velocity decreases. The change in the gravity level affects the characteristics of the interfacial waves in terms of frequency, height and velocity. The prediction accuracy of several models for annular flow condensation is assessed against the experimental results taken in microgravity conditions. (C) 2022ElsevierLtd. Allrightsreserved.

In cardiovascular disorders, the study of thrombocytes, commonly known as platelets, is highly important since they are involved in blood clotting, essential in hemostasis, and they can in pathological situations affect the blood circulation. In this paper, single deposited platelets are measured using interferometric digital holographic microscopy. We have shown that the average optical height of platelets is significantly lower in healthy volunteers than in dialyzed patients, meaning a better spreading. It demonstrates the great interest for assessing this parameter in any patients, and therefore the high potential of analyzing single spread platelets using digital holographic microscopy in fundamental research as well as a diagnostic tool in routine laboratories, for usual blood tests.

A new concept of vapour condenser is proposed to solve the drainage problem and to provide an effective condensate flow under weightlessness conditions. The concept combines the capability of a curvilinear surface to drive liquid, and a combination of a porous media and a pump, as an active condensate retraction system. The porous media collects and stores the condensed fluid and acts as a barrier for the vapour phase. Hydrodynamic validation of the liquid flow was done against retraction overflow under terrestrial conditions. It was figured out that the time available for adjusting the retraction system to avoid film disturbances decreased non-linearly with an increase in retraction overflow. The behaviour of the proposed condenser with the retraction system was tested under weightlessness condition during the ESA parabolic flights campaign as a part of concept validation. Three porous media with different values of the pore size and material were tested. It was found that the combination of the pump and porous media helped to improve the condensate flow. It was observed that the stabilisation effect was influencing the condensate flow not only during weightlessness condition but also under acceleration disturbances during the campaign.

Early detection of ice formation on surfaces is a crucial requirement in many applications such as wind turbines, aeroplane's wings, and radar domes. This paper presents the concept of a heat-pulse ice detection system. Its principle consists of recording the temperature evolution and assessing the relaxation time after the surfaces are subject to a heat excitation generated by an electrical pulse. The sensor comprises thin graphene films embedded in pre-preg layers of aeronautical grade as well as thermocouples to record the temperatures profiles at given locations. The criterion of ice detection exploits the high thermal capacity of ice compared to the air to capture the formation of icy spots. Numerical simulations and comparison with experimental investigations have been carried out to validate the principle and criteria of the ice detection system.