Microgravity Science and Technology

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Localization of Melt Components in a Crucible as a Result of Inserting Anisothermic Rod with Non-wettable Boundaries

Concentration-induced convection of a binary metal melt in a rectangular crucible has been studied numerically in the case of a mixture with a eutectic phase diagram. The calculations are performed for realistic parameters which correspond to the pair of metals Sn-Pb. A solid rod with non-wettable boundaries and a non-uniform longitudinal temperature distribution on the surface is immersed into the melt vertically at the center of the crucible. The condition of complete non-wetting allows us to ...

Vibration Induced Reciprocating Sliding Contacts between Nanoscale Multi-Asperity Tips and a Textured Surface

Microgravity and vacuum are two main environments in outer space. In the microgravity environment, vibration is a typical phenomenon, and it will induce a reciprocating sliding contact between a journal and a bearing in a clearance joint. In vacuum environment, the adhesion effects are severe, and the friction forces are much higher than the ground environment. Nanoscale textures can reduce the contact area and trap the wear particles, which are beneficial to the friction reduction. Most of the ...

In order to reveal the impact mechanism of gravity acceleration on thermocapillary convection instability in two-layer system, the flow characteristics of two-layered thermocapillary convection in annular pool under various gravity levels is investigated by 3D numerical simulation, in which the outer and inner walls are differentially heated. The interface of fluids is assumed to be a flat non-deformable interface, where thermocapillary forces act on. The computational results show that, with th...

Numerical Simulation on Interface Evolution and Pressurization Behaviors in Cryogenic Propellant Tank on Orbit

The interface distribution and self-pressurization phenomenon are the most important problems in the storage of cryogenic liquid on orbit, which are difficult to be predicted and assessed exactly due to the complex non-equilibrium thermal behavior. In this paper, one 3-D CFD model based on volume of fluid (VOF) method is established to investigate the interface evolution and self-pressurization process in the liquid oxygen (LOX) tank in microgravity environment with various heat loads and gravit...

The theory of long nonlinear oscillating wave packets (breathers) in a stratified fluid with a small density difference in a gravitational field is developed. The theory is based on the Gardner equation and its modifications, which are fully integrable with modern methods of the nonlinear wave theory. Examples of the breather generation are given and the conditions for their stability are discussed.

Liquid degassing takes place in several space processes (cooling and lubrication of hardware, combustion of liquid propellants etc.) during launching and re-orbiting of rockets and workstations. The present work studies the effect of hypergravity acceleration on the two phase flow that is developed during the degassing of a liquid jet. Liquid is initially saturated with dissolved gas at 200 kPa and 400 kPa and is then injected at the bottom of a liquid column having its top open to atmospheric p...

Analysis of three different equations of state suitable for describing fluids near the thermodynamic critical point is performed. Numerical simulation of the piston effect (adiabatic heating) with the use of the equations of state is carried out. The range of temperature distances to the critical point in which the calculated time of the piston effect is equal to the analytical time is defined. The reasons of discrepancy between the calculated and analytical times of the piston effect beyond the...

The capillary driven seepage in porous media under microgravity conditions is investigated. Experiments on the flow of a liquid in an inhomogeneous artificial porous medium are presented. A non-stationary mathematical model of the flow of a multiphase fluid in a sample of a porous medium is described. The experimental data are compared with the results of a three-dimensional numerical simulation of the multiphase seepage process. The behavior of the imbibition front when passing through a bounda...

This paper is addressing the challenge related to understanding the experimental results obtained by Taylor dispersion technique when working under high pressure with supercritical carbon dioxide (CO2). We discuss typical experimental problems that arise when using the Taylor dispersion method for measuring diffusion coefficients in the supercritical fluids. The diffusion coefficients of the two samples in supercritical carbon dioxide were measured along the isobars at different temperatures. Th...

Inhibition of Cell Cycle Progression, Induction of Apoptosis, and Changes in Surface Markers of MEG-01 Megakaryoblastic Cells Exposed to a Random Positioning Machine

One cause of thrombocytopenia in astronauts after spaceflight is decreased platelet production. To increase our understanding of thrombopoiesis in humans while in space, we investigated the effects of simulated microgravity, achieved using a random positioning machine (RPM), on megakaryoblastic cells (MEG-01 cell line). Exposure of MEG-01 cells to simulated microgravity for up to one week significantly increased cellular apoptosis compared to the static group (1 g-control). Flow cytometry analys...

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