There are many participants who have contributed to the work reported in this paper, including all the members of our project team, as well as some people from the Astronauts research and training center (ACC) and Neusoft.
This work is funded by the Strategic Priority Research Program on Space Science, Chinese Academy of Sciences: SJ-10 Recoverable Scientific Experiment Satellite (Grant No. XDA04020405 and XDA04020202-05), and by the joint fund of National Natural Science Foundation of China (U1738116).

1. Design and preparation of the experimental system
<ol>
	<li>Construct the annular liquid pool.
	<ol>
		<li>Build a copper annular liquid pool measuring Ri = 4 mm in inner diameter and Ro = 20 mm in outer diameter and d = 12 mm in height.</li>
		<li>Use a polysulfone plate measuring RP = 20 mm in diameter as the bottom of the liquid pool (see Table of Materials).</li>
		<li>Drill a small hole measuring &#981; = 2 mm in diam...

<ol>
	<li>Scriven, L. E., Sternling, C. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Marangoni+effect.">The Marangoni effect.</a> Nature. 187, 186-188 (1960).</li><li>Effects of heating mode on steady antisymmetric thermocapillary flows in microgravity. Heat Transfer in Microgravity Systems, Trans. American Society of Mechanical Engineers Available from: <a target="_blank" href="https://heattransfer.asmedigitalcollection.asme.org/">https://heattransfer.asmedigitalcollection.asme.org/</a> (1994)</li><li>Benz, S., Schwabe, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+three-dimensional+stationary+instability+in+dynamic+thermocapillary+shallow+cavities.">The three-dimensional stationary instability in dynamic thermocapillary shallow cavities.</a> Experiments in Fluids. 31, 409-416 (2001).</li><li>Schwabe, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Buoyant-thermocapillary+and+pure+thermocapillary+convective+instabilities+in+Czochralski+systems.">Buoyant-thermocapillary and pure thermocapillary convective instabilities in Czochralski systems.</a> Journal of Crystal Growth. 237-239, 1849-1853 (2002).</li><li>Kamotani, Y., Ostrach, S., Pline, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Analysis+of+velocity+data+taken+in+surface+tension+drivenconvection+experiment+in+microgravity.">Analysis of velocity data taken in surface tension drivenconvection experiment in microgravity.</a> Physics of Fluids. 6, 3601-3609 (1994).</li><li>Kamotani, Y., Ostrach, S., Pline, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+thermocapillary+convection+experiment+in+microgravity.">A thermocapillary convection experiment in microgravity.</a> Journal of Heat Transfer. 117, 611-618 (1995).</li><li>Kamotani, Y., Ostrach, S., Pline, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Some+temperature+field+results+from+the+thermocapillary+flow+experiment+aboard+USML-2+spacelab.">Some temperature field results from the thermocapillary flow experiment aboard USML-2 spacelab.</a> Advances in Space Research. 22, 1189-1195 (1998).</li><li>Kamotani, Y., Ostrach, S., Masud, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microgravity+experiments+and+analysis+of+oscillatory+thermocapillary+flows+in+cylindrical+containers.">Microgravity experiments and analysis of oscillatory thermocapillary flows in cylindrical containers.</a> Journal of Fluid Mechanics. 410, 211-233 (2000).</li><li>Schwabe, D., Benz, S., Cramer, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Experiment+on+the+Multi-roll-structure+of+thermocapillary+flow+in+side-heated+thin+liquid+layers.">Experiment on the Multi-roll-structure of thermocapillary flow in side-heated thin liquid layers.</a> Advances in Space Research. 24 (10), 1367-1373 (1999).</li><li>Schwabe, D., Benz, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Thermocapillary+flow+instabilities+in+an+annulus+under+microgravity+results+of+the+experiment+MAGIA.">Thermocapillary flow instabilities in an annulus under microgravity results of the experiment MAGIA.</a> Advances in Space Research. 29, 629-638 (2002).</li><li>Kawamura, H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Report+on+Microgravity+Experiments+of+Marangoni+Convection+Aboard+International+Space+Station.">Report on Microgravity Experiments of Marangoni Convection Aboard International Space Station.</a> Journal of Heat Transfer. 134 (3), 031005 (2012).</li><li>Sato, F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hydrothermal+Wave+Instability+in+a+High-Aspect-Ratio+Liquid+Bridge+of+Pr+&gt;+200.">Hydrothermal Wave Instability in a High-Aspect-Ratio Liquid Bridge of Pr &gt; 200.</a> Microgravity Science and Technology. 25 (1), 43-58 (2013).</li><li>Yano, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Instability+and+associated+roll+structure+of+Marangoni+convection+in+high+Prandtl+number+liquid+bridge+with+large+aspect+ratio.">Instability and associated roll structure of Marangoni convection in high Prandtl number liquid bridge with large aspect ratio.</a> Physics of Fluids. 27 (2), 024108 (2015).</li><li>Yao, Y. L., Liu, Q. S., Zhang, P., Hu, L., Liu, F., Hu, W. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Space+Experiments+on+Thermocapillary+Convection+and+Marangoni+Convection+in+Two+Immiscible+Liquid+Layers.">Space Experiments on Thermocapillary Convection and Marangoni Convection in Two Immiscible Liquid Layers.</a> Journal of the Japan Society of Microgravity Application. 15, 394-398 (1998).</li><li>Zhang, P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Space+experimental+device+on+Marangoni+drop+migrations+of+large+Reynolds+numbers.">Space experimental device on Marangoni drop migrations of large Reynolds numbers.</a> Science in China. 44 (6), 605-614 (2001).</li><li>Xie, J. C., Lin, H., Zhang, P., Liu, F., Hu, W. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Experimental+investigation+on+thermocapillary+drop+migration+at+large+Marangoni+number+in+reduced+gravity.">Experimental investigation on thermocapillary drop migration at large Marangoni number in reduced gravity.</a> Journal of Colloid and Interface Science. 285, 737-743 (2005).</li><li>Kang, Q., Cui, H. L., Hu, L., Duan, L., Hu, W. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Experimental+Investigation+on+bubble+coalescence+under+non-uniform+temperature+distribution+in+reduced+gravity.">Experimental Investigation on bubble coalescence under non-uniform temperature distribution in reduced gravity.</a> Journal of Colloid and Interface Science. 310, 546-549 (2007).</li><li>Duan, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+real-time+March-Zehnder+interferometer+used+in+space+experiment.">The real-time March-Zehnder interferometer used in space experiment.</a> Microgravity Science and Technology. 20, 91-98 (2008).</li><li>Zhu, P., Zhou, B., Duan, L., Kang, Q. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characteristics+of+surface+oscillation+in+thermocapillary+convection.">Characteristics of surface oscillation in thermocapillary convection.</a> Experimental Thermal and Fluid Science. 35, 1444-1450 (2011).</li><li>Zhu, P., Duan, L., Kang, Q. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Transition+to+chaos+in+thermocapillary+convection.">Transition to chaos in thermocapillary convection.</a> International Journal of Heat and Mass Transfer. 57, 457-464 (2013).</li><li>Kang, Q., Duan, L., Zhang, L., Yin, Y. L., Yang, J. S., Hu, W. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Thermocapillary+convection+experiment+facility+of+an+open+cylindrical+annuli+for+SJ-10+satellite.">Thermocapillary convection experiment facility of an open cylindrical annuli for SJ-10 satellite.</a> Microgravity Science and Technology. 28, 123-132 (2016).</li><li>Wang, J., Wu, D., Duan, L., Kang, Q. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ground+Experiment+on+the+Instability+of+Buoyant-thermocapillary+Convection+in+Large+Scale+Liquid+Bridge+with+Large+Prandtl+Number.">Ground Experiment on the Instability of Buoyant-thermocapillary Convection in Large Scale Liquid Bridge with Large Prandtl Number.</a> International Journal of Heat and Mass Transfer. 108, 2107-2119 (2017).</li><li>Kang, Q., Jiang, H., Duan, L., Zhang, C., Hu, W. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Critical+Condition+and+Oscillation+-+Transition+Characteristics+of+Thermocapillary+Convection+in+the+Space+Experiment+on+SJ-10+Satellite.">The Critical Condition and Oscillation - Transition Characteristics of Thermocapillary Convection in the Space Experiment on SJ-10 Satellite.</a> International Journal of Heat and Mass Transfer. 135, 479-490 (2019).</li><li>Kang, Q., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+volume+ratio+effect+on+flow+patterns+and+transition+processes+of+thermocapillary+convection.">The volume ratio effect on flow patterns and transition processes of thermocapillary convection.</a> Journal of Fluid Mechanics. 868 (108), 560-583 (2019).</li></ol>

Due to the limitation of space resources, the volume of the equipment as a whole is only 400 mm &#215; 352 mm &#215; 322 mm, with a weight of only 22.9 &#177; 0.2 kg. This is very inconvenient when selecting and laying out experimental devices, and the establishment of the flow system becomes the critical step. Therefore, the increasing temperature difference is set at two ends of the liquid pool so that the fluid can generate a series of flow phenomena. In order to observe the entire process of the convection from stead...

Under microgravity conditions in space, many interesting physical phenomena are presented due to the absence of gravity. In a liquid with a free surface, there exists a new flow system (i.e. thermocapillary flow) that is caused by the temperature gradient or concentration gradient. Different from traditional convection on the ground, thermocapillary convection is a ubiquitous phenomenon in space environments. As it is a very important research subject in microgravity fluid physics, a number of experiments have been carried out in space as well as on the ground. Recently, space experimental studies were performed on thermocapillary convection on the SJ-10 recoverable scientific experiment satellite. The space experiment payload consisted of eight systems, namely a fluid experiment system, liquid storage and injection system, temperature control system, thermocouple measurement system, infrared thermal camera, displacement sensors, CCD image acquisition system, and electrical control system, as shown in Figure 1 (left). The space experiment payload for research on surface waves of thermocapillary convection is shown in Figure 1 (right). This study focused on the instability of flow, oscillation phenomena, and transitions, which are important characteristics in the transition process from laminar flow to chaos. Studies on these fundamental subjects have great significance for research regarding strong nonlinear flow.
Unlike buoyancy convection driven by volume force, thermocapillary convection is a phenomenon caused by surface tension within the interface between two immiscible fluids. The magnitude of surface tension changes with some scalar parameters, including temperature, solute concentration, and electric field strength. When these scalar fields distribute unevenly in the interface, there will be a surface tension gradient present on the free surface. The fluid on the free surface is driven by the surface tension gradient to move from the location with lesser surface tension to that with greater surface tension. This flow was first interpreted by an Italian physicist, Carlo Marangoni. Hence, it was named the &#34;Marangoni effect&#34;1. Marangoni flow on the free surface extends to the inner liquid by viscosity and as a result generates what is known as Marangoni convection.
Strictly speaking, for the fluid system with a free surface, thermocapillary convection and buoyancy convection always appear simultaneously under normal gravity. In general, for a macroscopic convective system, thermocapillary convection is a minor effect and is usually ignored in comparison with buoyancy convection. However, under the condition of a small-scale convective system or in the microgravity environment, buoyancy convection will be greatly weakened, or even disappear, and thermocapillary convection will become dominant in the flow system. For a long period of time, research has been focused on macro-scale buoyancy convection due to the limitations in human activities and research methods2,3,4. However, in recent decades, with the rapid development of modern science and technology such as aerospace, film, MEMS, and nonlinear science, the need for further research on thermocapillary convection has become increasingly urgent.
Studies regarding microgravity hydrodynamics have important academic significance and application prospects. Many dynamicists, physical chemists, biologists, and materials scientists have gathered to work in this field. Kamotani and Ostrach completed experiments on thermocapillary convection in an annular liquid pool under microgravity conditions2,5,6,7,8 and observed steady flow, oscillatory flow, and critical conditions. Schwabe et al. studied buoyant-thermocapillary convection in a similar annular liquid pool3,9 and found that the oscillatory flow first appeared as thermocapillary waves, and then turned to a more complex flow with the increase in temperature difference. In 2002, Schwabe and Benz et al. reported a group of experiments on thermocapillary convection in an annular liquid pool carried out on the Russian FOTON-12 satellite4,10. Their space experimental results were consistent with ground experimental results. Some Japanese scientists carried out three series of experiments on liquid bridge thermocapillary convection, named the Marangoni Experiment in Space (MEIS), on the International Space Station11,12,13. Some experimental equipment, including the camera, thermal imager, thermocouple sensors, and 3D-PTV and photochromic technology, were applied in these three tasks. The critical conditions of thermocapillary convection at different aspect ratios were determined, and three-dimensional (3D) flow structures were observed.
Over the past 30 years, microgravity science has undergone prolific development in China14,15,16, and a number of microgravity experiments have been conducted in space17,18. In the field of fluid physics, the first microgravity experiment was the study of two-layer fluid on the SJ-5 recoverable satellite in 1999, and the flow structure was obtained by the particle tracing method14. In 2004, the study on thermocapillary migration of a droplet was carried out on the SZ-4, and the relationship between migration velocity and critical Mach (Ma) number was obtained15,16. In 2005, the experimental study on multi-bubble thermocapillary migration was carried out on the JB-417, and the migration rules were obtained as the Ma number was increased to 8,000. Meanwhile, problems such as bubble merging were also studied. In 2006, the study on diffusion mass transfer was carried out on the SJ-8 recoverable satellite, the Mach-Zehnder interferometer was first applied in the space experiment, the process of diffusion mass transfer was observed, and the diffusion coefficient was evaluated18.
In recent years, a series of ground experimental studies focused on oscillation and bifurcation processes in thermocapillary convection have been carried out, and the coupled effect of buoyancy and thermocapillary force has been analyzed. Experimental results show that the buoyancy effect cannot be ignored in ground experiments, as it plays a dominant role in many cases19,20,21,22. In 2016, two microgravity experiments were carried out to research thermocapillary convection in the liquid bridge on the TG-2, and thermocapillary convection in the annular liquid pool on the SJ-10 recoverable satellite23,24. The present paper introduces the experimental payload of thermocapillary convection on the SJ10, and the space experiment results. These methods will be helpful in exploring the mechanism of thermocapillary oscillation.
In order to observe the convective pattern transition, temperature oscillation, and liquid-free surface deformation, six thermocouples, an infrared thermal camera, and a displacement sensor to quantify the frequency, amplitude, and other physical quantities of the oscillation were used. Through investigations on oscillation and transition in thermocapillary convection in space, the mechanism of thermocapillary convection in the microgravity environment, which provides scientific guidance for the growth of materials in space, can be discovered and understood. Furthermore, technological breakthroughs in such space experiments, such as the techniques of liquid surface maintenance and liquid injection without bubbles, will further enhance the simplicity and technical level of microgravity experiments in fluid physics.
This paper introduces the payload development and space experiment of the thermocapillary surface wave project carried out on the SJ-10 scientific experimental satellite. As a space experiment payload, this thermocapillary convection system has a strong anti-vibration ability to prevent violent shock, especially during the satellite launching process. In order to meet the requirements of remote operation, the space experiment process is controlled automatically, and the space experimental data can be transmitted to the Ground Signal Receiving Station of the Spacecraft and then to the scientists&#39; experimental platform.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>anti-creeping liquid</td>
			<td>3M</td>
			<td>EGC-1700</td>
			<td></td>
		</tr>
		<tr>
			<td>CCD</td>
			<td>WATTEC</td>
			<td>WAT-230VIVID</td>
			<td></td>
		</tr>
		<tr>
			<td>Displacement sensor</td>
			<td>Panasonic</td>
			<td>HL-C1</td>
			<td></td>
		</tr>
		<tr>
			<td>Heating film</td>
			<td>HongYu</td>
			<td>125 Q/W335.1A</td>
			<td></td>
		</tr>
		<tr>
			<td>Hydraulic cylinder</td>
			<td>FESTO</td>
			<td>ADVU-40-25-P-A</td>
			<td></td>
		</tr>
		<tr>
			<td>Infrared camera</td>
			<td>FLIR</td>
			<td>Tau2</td>
			<td></td>
		</tr>
		<tr>
			<td>LED</td>
			<td>693 Institute</td>
			<td>10257MW7C</td>
			<td></td>
		</tr>
		<tr>
			<td>Montor</td>
			<td>PI</td>
			<td>M-227</td>
			<td></td>
		</tr>
		<tr>
			<td>Montor controller</td>
			<td>PI</td>
			<td>C-863</td>
			<td></td>
		</tr>
		<tr>
			<td>Pipe, 4mm</td>
			<td>FESTO</td>
			<td>PUN-4X0,75-GE</td>
			<td></td>
		</tr>
		<tr>
			<td>polysulfone plate</td>
			<td>507 Institute</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Refrigeration chip</td>
			<td>Zhongke</td>
			<td>9502/065/021M</td>
			<td></td>
		</tr>
		<tr>
			<td>Silicon oil, 2cSt</td>
			<td>Shin-Etsu</td>
			<td>KF-96</td>
			<td></td>
		</tr>
		<tr>
			<td>Solenoid</td>
			<td>FESTO</td>
			<td>MFH-2-M5</td>
			<td></td>
		</tr>
		<tr>
			<td>Temperature controller</td>
			<td>Eurotherm</td>
			<td>3304</td>
			<td></td>
		</tr>
		<tr>
			<td>Thermocouple, K-type</td>
			<td>North University of China</td>
			<td>ZBDX-HTTK</td>
			<td></td>
		</tr>
	</tbody>
</table>

thermocapillary convection space experiment on the sj-10 recoverable satellite

Thermocapillary convection is an important research subject in microgravity fluid physics. The experimental study on surface waves of thermocapillary convection in an annular liquid pool is one of the 19 scientific experimental projects on the SJ-10 recoverable satellite. Presented is a design for a payload for space experimental study on thermocapillary convection that includes the experimental model, measurement system, and control system. The specifics for the construction of an experimental model of an annular liquid pool with variable volume ratios is provided. The fluid temperatures are recorded by six thermocouples with a high sensitivity of 0.05 &#176;C at different points. The temperature distributions on the liquid free surface are captured by means of an infrared thermal camera. The free surface deformation is detected by a displacement sensor with a high accuracy of 1 &#181;m. The experimental process is fully automated. The research is focused on thermocapillary oscillation phenomena on the liquid-free surface and convective pattern transitions through analyses of experimental data and images. This research will be helpful to understand the mechanism of thermocapillary convection and will offer further insights into the nonlinear characteristics, flow instability, and bifurcation transitions of thermocapillary convection.

The accurate volume ratio was defined, and the liquid surface topography was reconstructed based on the images captured by the CCD. The critical instability condition was determined, and the oscillation characteristics were studied through analyses on single point temperature signals and displacement oscillating signals. The structure of the flow field was obtained, and the transition of the flow pattern was determined through the change of the infrared image with time. The flow character...

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Thermocapillary Convection Space Experiment on the SJ-10 Recoverable Satellite

A protocol for the space payload design, the space experiment on thermocapillary convection, and analyses of experimental data and images are presented in this paper.

Thermocapillary convection is an important research subject in microgravity fluid physics. The experimental study on surface waves of thermocapillary ...

Understanding the effects of oscillation and bifurcation in thermocapillary convection is important for the study of a strong nonlinear flow in space. Due to limited space resources and conditions, the experimental payload should be small in size, light in weight, and possess anti-vibration abilities. Space technology breakthroughs, such as performing liquid surface maintenance and the liquid injection without bubbles, can further enhance the technical capacity of microgravity experiments in fluid physics.Observing the convection transition, temperature oscillation, and the surface deformation of a liquid requires the use of thermocouples an infrared thermal camera, and a displacement sensor. Demonstrating the procedure will be Wang Jia, Wu Di, and Hu Liang, technicians from my laboratory. Begin by constructing a copper annular liquid pool with an inner radius of four millimeters in diameter and an outer radius of 20 millimeters in diameter and a height of 12 millimeters.Use a 20-millimeter-diameter polysulfone plate as the bottom of the liquid pool, and drill a small, two-millimeter-diameter hole six millimeters away from the center of the plate as the liquid injection hole. Add sharp, 45-degree-angle corners on the inner and outer side walls, and apply anti-creeping liquid to the inner and outer walls to a height greater than 12 millimeters. Next, select an appropriate low-viscosity silicone oil as the working fluid, and heat the liquid to 60 degrees Celsius.To discharge any gas from the oil, apply less than 150 pascals of pressure for six hours, followed by vacuuming of the liquid storage system until the pressure reaches just below 200 pascals. Then, relieve the valve to allow the silicone oil to fill in the vacuumed cylinder without gas. To set up the injection system for the working liquid, select a step motor to drive the injection and suction of liquid, and apply a solenoid valve to control the on/off switch of the injection system.Use a universal joint to connect the step motor to the liquid cylinder, and use a four-millimeter-outer-diameter pipe to successively connect the liquid cylinder, solenoid valve, and injection hole. To establish the measurement system, place six thermocouples inside the liquid pool to measure the temperatures at different points, as illustrated in the figure. Place an infrared camera directly above the liquid surface, and rotate the lens to adjust the focus and to collect the temperature field information on the liquid-free surface.Adjust the displacement sensor to measure the displacement of a specific point of interest on the liquid surface, and use the CCD camera to focus on the liquid surface. Then, record the change of the free surface. To begin the experiment, start the experiment control software, and turn on the power button.To perform the liquid injection, apply 12 volts to the solenoid valve to open the valve. Next, turn on the motor button to start the motor at a step of 2.059 millimeters to inject 10, 305 milliliters of silicone oil into the liquid pool. When all of the oil has been delivered, turn off the solenoid valve power to close the solenoid valve.To perform linear heating, set the heating target temperature to 50 degrees Celsius, the cooling target temperature to 15 degrees Celsius, and the heating rate to 0.5 degrees Celsius per minute. For data collection, set the sampling frequency of the infrared imager to 7.5 hertz, the thermocouple frequency and the displacement sensor to 20 hertz, and the CCD frequency to 24 hertz. When all of the parameters have been set, click the data collecting system button, and monitor the temperature, displacement, and other information of interest in the computer software.At the end of the analysis, turn off the power. These experimental model and measurement methods were integrated in this payload on the SJ-10 satellite. 23 microgravity experiments on surface wave thermocapillary convection are finished.In these infrared thermal images of the temperature distributions on a liquid-free surface in thermocapillary convection, a variety of oscillatory flow patterns can be observed, including radial oscillations and clockwise and counterclockwise circumferential rotations. In this representative experiment, the temperatures inside the fluid increased linearly with the temperature difference increase, with the temperature field fluctuating periodically once the temperature difference exceeded a certain threshold, indicating that the thermocapillary convection developed from a steady state to an oscillatory state. In addition, the amplitude of the oscillatory temperature grew as the flow field evolved, as indicated in this spectrum analysis, showing that the critical oscillation frequency was 0.064 hertz.Although the buoyancy convection of the small-scale ground system was weakened, the flow was still a coupling of thermocapillary and buoyancy convections, with different results observed in space experiment results, compared results obtained in ground experiments. By comparing a large number of deformation data for the liquid-free surface measured by the displacement sensor and the temperature data of the fluid measured by the thermocouples, it was also observed that the surface deformation and the temperature field in the fluid began to oscillate at the same time and at the same frequency. These two key technologies, the maintenance of a fluid surface and the injection of liquids without bubble formation, play essential roles in experiment space research.We hope that the present work can provide a scientific basis and technical support for viewers interested in attempting these techniques.

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Gravitation

SCIENTISTS IN ACTION

6.4K visualizações.  Chinese Academy of Sciences. Compreender os efeitos da oscilação e bifurcação na convecção termocapar é importante para o estudo de um forte fluxo não linear no espaço. Devido a recursos e condições de espaço limitados, a carga experimental deve ser pequena em tamanho, leve em peso e possuir habilidades anti-vibração. Avanços da tecnologia espacial, como a realização da manutenção da superfície líquida e a injeção líquida sem bolhas, podem aumentar ainda mais a capacidade técnica de experimentos ...