Particle Accumulation Structures in a 5 cSt Silicone Oil Liquid Bridge: New Data for the Preparation of the JEREMI Experiment

Abstract

Systems of solid particles in suspension driven by a time-periodic flow tend to create structures in the carrier fluid that are reminiscent of highly regular geometrical items. Within such a line of inquiry, the present study provides numerical results in support of the space experiments JEREMI (Japanese and European Research Experiment on Marangoni flow Instabilities) planned for execution onboard the International Space Station. The problem is tackled by solving the unsteady non-linear governing equations for the same conditions that will be established in space (microgravity, 5 cSt silicone oil and different aspect ratios of the liquid bridge). The results reveal that for a fixed supporting disk radius, the dynamics are deeply influenced by the height of the liquid column. In addition to its expected link with the critical threshold for the onset of instability (which makes Marangoni flow time-periodic), this geometrical parameter can have a significant impact on the emerging waveform and therefore the topology of particle structures. While for shallow liquid bridges, pulsating flows are the preferred mode of convection, for tall floating columns the dominant outcome is represented by rotating fluid-dynamic disturbance. In the former situation, particles self-organize in circular sectors bounded internally by regions of particle depletion, whereas in the latter case, particles are forced to accumulate in a spiral-like structure. The properties of some of these particle attractors have rarely been observed in earlier studies concerned with fluids characterized by smaller values of the Prandtl number.

On the Propagation of Hydrothermal Waves in a Fluid Layer with Two-Way Coupled Dispersed Solid Particles

“…The formation of circuits spanning the entire extension of the physical domain, such as those emerging in the case of liquid bridges [23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39], is also prevented because finite-size rectangular containers lack the necessary feedback mechanisms which allow particle selforganization. The closed streamtubes playing the role of templates for the accumulation of particles in the liquid bridge do not exist in the present case.…”

“…Although the exploration of the sensitivity of these phenomena to intrinsic and environmental factors may appear as exhausted given the number of valuable efforts described above, most recently a completely new line of inquiry has been originated by the discovery that these waves can support the formation of ordered structures produced by particles (tracers initially dispersed in liquid bridges for visualization purposes). Such findings (Schwabe et al [22]) have stimulated a number of research works focusing on aspects relating to the patterning behavior in these systems for conditions in which the presence of the dispersed phase is expected not to influence the properties of the carrier flow (dilute dispersions, see, e.g., Schwabe et al [23], Schwabe and Mizev [24], Pushkin et al [25], Melnikov et al [26], Lappa [27][28][29][30], Kuhlmann et al [31], Gotoda et al [32,33], Lappa [34], Melnikov and Shevtsova [35], Capobianchi and Lappa [36][37][38], Sakata et al [39]).…”

High-Temperature Superlubricity Realized with Chlorinated-Phenyl and Methyl-Terminated Silicone Oil and Hydrogen-Ion Running-in

“…1−4 Silicone oil represents a large class of synthetic polymers 5 with excellent properties, such as extremely low volatility, nonflammability, high thermal stability, oxidative stability, low melting point, and extremely low vapor pressure. 6,7 It has an extremely wide range of applications in aerospace machinery 8,9 and electronic equipment components, 10,11 particularly in the lubrication of space-bearing mechanisms. 12,13 However, conventional methyl silicone oil exhibits poor lubricating performance, particularly in the lubrication of steel/steel and ceramic/ceramic point contacts.…”

“…In the aerospace field, the requirements for material properties are strict. Advanced ceramic materials, such as Si 3 N 4 , Al 2 O 3 , B 4 C, and SiC, are widely used in aerospace-related equipment because of their excellent mechanical reliability, fracture toughness, thermal shock resistance, and wear resistance. − Silicone oil represents a large class of synthetic polymers with excellent properties, such as extremely low volatility, nonflammability, high thermal stability, oxidative stability, low melting point, and extremely low vapor pressure. , It has an extremely wide range of applications in aerospace machinery , and electronic equipment components, , particularly in the lubrication of space-bearing mechanisms. , However, conventional methyl silicone oil exhibits poor lubricating performance, particularly in the lubrication of steel/steel and ceramic/ceramic point contacts. , In numerous studies, the molecular structure of methyl silicone oil has been modified to synthesize methyl-terminated organopolysiloxane with pentachlorophenyl-substituted groups on the pendant [chlorinated-phenyl and methyl-terminated silicone oil (CPSO)]. This modification not only improves the lubricating performance of silicone oil but also maintains its excellent temperature resistance and low volatility. − …”

Significantly Affected Lubrication Behavior of Silicone Oil Lubricated Si3N4/Glass Contact after Cleaning with Different Solvents

“…Silicone oils are a large class of synthetic polymers that can solve a wide variety of industrial problems, such as the lubrication of aerospace machinery, , electronic equipment components, , machines, medicines, , automobiles, , everyday chemical products, , and space bearings. , The performance of silicone oil as a lubricant varies significantly depending on the organic groups attached to the silicon atoms (Si–R, where R = CH 3 , C 2 H 5 , C 6 H 5 , C 6 H 4 Cl, C 3 H 4 F 3 , etc. ; chemical bond between Si and R).…”