Hydrodynamic Effects Research Articles

Volcano tsunamis and their effects on moored vessel safety: the 2022 Tonga event

Abstract. The explosion of the Hunga Tonga–Hunga Ha'apai volcano on 15 January 2022 (Tonga 2022) was the origin of a volcano-meteorological tsunami (VMT) recorded worldwide. At a distance exceeding 10 000 km from the volcano and 15 h after its eruption, the moorings of a ship in the port of La Pampilla, Callao (Peru), failed, releasing over 11 000 barrels of crude oil. This study delves into the profound implications of the Tonga 2022 event, investigating whether it could have led to the breaking of the mooring system. We conducted a comprehensive analysis of this significant event, examining the frequency content of the time series recorded at tide gauges, DART (Deep-ocean Assessment and Reporting of Tsunamis) buoys, and barometers in the southern Pacific Ocean. Our findings revealed that the maximum energy of the spectra corresponds to the 120 min wave period off the coast of Peru, with the arrival time of these waves coinciding with the time of the accident in the port. We used a Boussinesq model to simulate the propagation of the volcano-meteorological tsunami from the source to the port in Peru to study the impact of those waves on the mooring system. We used the synthetic tsunami recorded in the port as input for the model that simulates mooring line loads based on the ship's degrees of freedom. The results suggest that the 120 min wave triggered by the VMT could significantly increase mooring stresses due to the resulting hydrodynamic effects, exceeding the minimum breaking load (MBL). We conclude that the propagation of the long wave period generated by the VMT caused overstresses in moored lines that triggered accidents in port environments. This event showed the need to prepare tsunami early warning systems and port authorities for detecting and managing VMTs induced by atmospheric acoustic waves. The work provides new insights into the far-reaching impacts of the Tonga 2022 tsunami.

Effect of SDS Solutions on the Jamin Effect in a Capillary Tube with a Contracted Throat.

With the continuous exploitation of petroleum resources, the distribution and displacement of residual oils have become key issues in enhancing oil recovery. In a reservoir, there are various forms of residual oils caused by the capillary force, viscous force, and some other hydrodynamic effects, which lead to the Jamin effect, and they restrict the oil displacement process. In this study, the morphologies of oil droplets in a capillary tube laden with water and sodium dodecyl sulfate (SDS) solutions are experimentally investigated. The pinning behavior of the oil droplet is observed in the waterflood with a lower velocity, while depinning and rupturing behaviors occur at a higher velocity. Hereto, we build a mechanics model to analyze the evolution of the Jamin effect in a capillary tube with varying cross sections. Using this theoretical model, we obtain the two critical velocities for the depinning and rupture of the oil droplet, which agree with the experimental results. Moreover, we find that oil droplets can more easily pass through the entire capillary tube in SDS solutions compared with water. The time required for oil droplets to pass through the pore throat becomes shorter with the increase of SDS concentration. Therefore, a theoretical model is established to determine the total pressure difference and the minimum applied pressure difference. These findings are beneficial to obtain a deep insight into the detailed oil displacement and achieve a higher oil recovery rate.

Numerical and experimental study on water-sediment flow in a lateral pumping station forebay

Multiple vortex flow patterns are commonly observed in lateral pumping station forebays, particularly in basins with high sediment concentrations. These patterns can lead to pump blockage, sediment deposition, and other issues that disrupt pump station operations. The water-sediment two-phase flow in lateral pumping station forebays is significantly influenced by the start-up combination, yet our understanding remains limited. To address this, the mixture multiphase flow theory is introduced to describe water-sediment dynamics, and the mathematical model is validated with experimental data. By analyzing the characteristics and formation mechanisms of large vortex and multiple small vortex regions in the original scheme, nine different start-up combination schemes were proposed. The research results indicate that, due to the narrow channel and slope effect in the lateral forebay, some of the gravitational potential energy of the water-sediment mixture is converted into kinetic energy upon entering the forebay, thereby increasing the velocity in the main flow area. Additionally, due to the friction and dissipation effects of the two sidewalls, a pressure difference is generated in the main flow area, resulting in the formation of multi-level vortices. Furthermore, the various types of proposed start-up combinations can optimize the flow patterns in the forebay to a certain extent. The preferred scheme improved the uniformity of flow velocity by 18.63% and increased the deviation angle by 17.62°, resulting in a 75.47% reduction in vortex area compared to the original scheme. These research results provide theoretical guidance for optimizing start-up combinations and reorganizing flow field structures to achieve hydrodynamic dredging effects.

An efficient and accurate method of added mass for evaluating the seismic hydrodynamic effect of deep‐water piers

AbstractDue to the effects of complex fluid‐structure interaction, deep‐water bridges are more prone to damage under strong earthquakes. Quantification of seismic fluid‐structure interaction can be crucial for evaluating the seismic performance of deep‐water bridges. Currently, there is a lack of suitable methods for rapidly calculating hydrodynamic added mass for deep‐water piers with complex cross‐sectional shapes in the seismic performance assessment of deep‐water bridges. In light of this, the present paper proposed an efficient and accurate method for calculating the hydrodynamic added mass of piers with different cross‐sectional shapes. Taking circular, rectangular, and dumbbell‐shaped piers as examples, the proposed method was employed to calculate the hydrodynamic added mass for deep‐water bridge piers. Comparison of the seismic responses obtained from the analytical formula, fluid‐structure coupling refined numerical model and the proposed method in this paper validated the accuracy of the proposed method. Finally, the hydrodynamic coupling effects of deep‐water bridge piers were also investigated. It was concluded that the proposed method can be efficient and accurate for obtaining the added mass of deep‐water piers.

Microwave-induced plasma on spherical flame dynamics of spark-ignited hydrogen-air under water dilution

Microwave-assisted spark ignition (MAI) offers a commercially feasible way to enhance conventional spark ignition performance under extreme conditions. While previous studies suggested microwave pulses had no obvious effect on self-sustained flame from the perspective of energy deposition, the hydrodynamic effect of microwave plasma remained under-explored. This study experimentally investigated the effect of the microwave-induced plasma on lean hydrogen flame dynamics (Lewis number ∼ 0.35), examining the influence of water content (rH2O) in this process under different pulse repetition frequency (PRF) and pressures. Using a linear high-speed shadow imaging system coupled with electrical diagnostics, we synchronously recorded the flame and plasma morphology evolution while monitoring spark and microwave energy. Results revealed that microwave pulses during spark ignition generated wrinkles and perturbances accelerating the cracking and cellularization of the subsequent self-sustained flame. This effect intensified with increasing PRF from 1 to 10 kHz, particularly at high rH2O. The overall microwave impact on early flame development was more pronounced at high rH2O, attributed to stronger interactions between the microwave plasma jet and flame front due to reduced distance. Interestingly, electrical diagnostics showed an inversed relationship between total absorbed microwave energy and rH2O, highlighting the crucial role of the first microwave pulse at 1 kHz PRF. This study demonstrates that early microwave pulses can influence hydrogen flame dynamics even in the self-sustained stage, offering new insights into MAI mechanisms. These findings open avenues for research into active control of self-sustained flame dynamics, potentially leading to improved ignition strategies in challenging combustion environments.

Real-time simulation of ship overtake maneuvering at different water depths with a ship motion controller

This study aimed to predict ship trajectories in deep and shallow waters in real-time by properly accounting for the effects of hydrodynamic interactions on ship maneuvering. Ship maneuverability and motion control were investigated under hydrodynamic interactions arising from the effects of water depth, ship speed, and lateral distance between interacting ships on parallel courses. The Maneuvering Modeling Group (MMG) model was used, and the hydrodynamic interaction effect was estimated using an efficient three-dimensional potential-flow code that can run in real time. The influence of water depth on ship maneuverability was analyzed. The ship velocity response to the hydrodynamic interactions and maneuvering motion was simulated during the overtaking process of two ships at a range of water depths, lateral distances, and speeds. The findings suggest that, in shallow waters, changing the heading of the ship becomes more difficult, and the course deviation associated with the overtaking maneuver of two ships also increases. A conventional proportional-integral-derivative (PID) controller was employed for course-keeping. When the ratio of the water depth to ship draft was less than 2.0, the PID controller continued to perform effectively for the overtaking ship. For the overtaken ship, the effectiveness of the controller was diminished owing to the relatively low rudder effect at slow speeds.

Occurrence and Favorable Enrichment Environment of Lithium in Gaoping Coal Measures: Evidence from Mineralogy and Geochemistry

The Carboniferous-Permian coal measure strata in the Qinshui Basin exhibit highly lithium (Li) enrichment, with substantial exploitation potential. To further explore the enrichment mechanism of lithium in coal measure strata, the No. 15 coal of the Taiyuan Formation from the Gaoping mine is taken as the research object, and its mineralogical and geochemistry characteristics are evaluated using optical microscopy, X-ray diffraction, scanning electron microscopy, inductively coupled plasma mass spectrometry, X-ray fluorescence, and infrared spectral. The results show that the No. 15 coal is semi-anthracite coal with low moisture, low ash, low volatility, and high sulfur. Organic macerals are primarily vitrinite, followed by inertinite, and liptinite is rare; the inorganic macerals (ash) are dominated by clay minerals (predominantly kaolinite, cookeite, illite, and NH4-illite), calcite, pyrite, quartz, siderite, gypsum, and zircon. The average Li content in the coal is 66.59 μg/g, with higher content in the coal parting (566.00 μg/g) and floor (396.00 μg/g). Lithium in coal occurs primarily in kaolinite, illite, cookeite, and is closely related to titanium-bearing minerals. In addition, Li in organic maceral may occur in liptinite. The No. 15 coal was formed in the coastal depositional system, and the deposition palaeoenvironment is primarily a wet–shallow water covered environment in open swamp facies; the plant tissue preservation index is poor, and aquatic or herbaceous plants dominate the plant type. The reducing environment with more terrestrial detritus, an arid climate, and strong hydrodynamic effects is favorable for Li enrichment in coal. The results have important theoretical significance for exploring the enrichment and metallogenic mechanisms of Li in coal.

Experimental study on fragmentation characteristics of molten stainless steel discharged into liquid Lead-Bismuth Eutectic pool

The LFR is a candidate for the Generation-IV nuclear systems, where the process of MFCI differs from that occurred in LWRs and SFRs. In the absence of experimental study and widely applied theoretical models for LFRs, experiments on the interaction between molten SS and liquid LBE are conducted in this study under eight conditions. The morphological characteristics and fragment sizes of the products are analyzed based on the hydrodynamic effect parameter (We) and thermal effect parameter (Tic). Simplified thermal fragmentation models are established, where the innermost layer of the solidified shell is subjected to the maximum tangential compressive stress, while the outermost layer is subjected to the maximum tangential tensile stress. As the shell thickness increases, the total tangential stress of the outermost layer decreases. The fragmentation will occur when the maximum tangential stress on the shell exceeds the shell tensile strength.

Experimental study on in-situ emulsification of heavy oil in porous media

Under the strategic goal of “dual-carbon”, reducing oil viscosity by in-situ emulsification using chemical method has become a new direction for high-efficiency and low-carbon development of heavy oil reservoirs. This technology can transform the originally immovable heavy oil into movable dispersed oil droplets through in-situ emulsification, and thus enhances heavy oil recovery. However, there is still a lack of sufficient understanding about the characteristics and influencing laws of in-situ emulsification of heavy oil in porous media. So, this paper carried out experimental studies on in-situ emulsification and influencing factors for heavy oil in porous media. The results show that, due to the transport and adsorption loss of viscosity reducer in porous media, the emulsification area expands gradually from the inlet to the outlet. At the same sampling position, with the increase of injection volume, the dispersed oil droplet size decreases, the distribution density increases, and the color of produced liquid changes from light yellow to dark brown. Under the same injection volume, the closer to the outlet, the smaller the particle size of the dispersed oil droplets and the higher the distribution density, which is resulted from the shearing effect of the porous media. With the increase of injection rate, the hydrodynamic shear effect is enhanced, so the in-situ emulsification of heavy oil starts earlier and the emulsification oil ratio curves have a higher slope and distribute more densely. With the increase of agent concentration, the adsorbed number of viscosity reducer molecules on the oil–water interface is increased, making it easier to emulsify the remaining oil. With the increase of pre-conversion oil recovery, the remaining oil in the porous media is more dispersed and the oil–water contact surface increases, so the emulsification is easier and the percentage of dispersed oil droplets in the produced oil phase increases. The research results based on sampling analysis deepen our understanding on in-situ emulsification of heavy oil in porous media, which provides valuable reference for designing suitable viscosity reducer agent and effectively enhancing heavy oil recovery in the future.

Enhancing carbon mineralization of slag leachate using amine-functionalized magnetic nanoparticle clusters

Carbon mineralization—converting carbon dioxide (CO2) into stable carbonate minerals, such as calcium carbonate (CaCO3)—has attracted much attention as a permanent way to sequester CO2. In this study, we developed a novel method for improving the efficiency of carbon mineralization using amine-functionalized magnetic nanoparticle clusters (A-MNCs). To prepare them, magnetic nanoparticle clusters composed of tens of small Fe3O4 nanoparticles were treated with 3-aminopropyltriethoxysilane to functionalize amine groups on their surfaces. When CO2 was bubbled into a NaOH solution, the rate of CO2 dissolution was enhanced in the presence of A-MNCs, mostly due to physical effects such as grazing and hydrodynamic effects that improved mass transfer between the solution and CO2 bubbles. In addition, A-MNCs promoted carbon mineralization in a NaOH solution containing Ca2+ by providing an additional mineralization route via carbamate formation, resulting in a threefold increase in efficiency to 81 %. We demonstrated that A-MNCs could be applied to leachate from slag, a byproduct of commercial steelmaking, increasing the efficiency by 2.6 times compared to the absence of A-MNCs. The resulting CaCO3 precipitate was confirmed to be calcite using X-ray diffraction and scanning electron microscopy. Furthermore, after the mineralization, A-MNCs were easily separated from the solution using a permanent magnet, while retaining their performance.

Analytical study on hybrid thrust foil bearing, structural characterization and measurement of static performance

This work presents a novel hybrid foil thrust bearing (HFTB) with an outer diameter of 154 mm, along with simulation and test results. The HFTB incorporates a high-pressure air/gas injection to the taper portion of the thrust foil bearing, boosting the hydrodynamic effect on the main bearing surface and hydrostatic load capacity at zero speed. The bearing has high load capacity, low power loss, and no friction/wear during startup and shutdown. Firstly, push-pull tests were conducted on a double-acting HFTB configuration to evaluate the nonlinear structural stiffness of the bump foil structure. The measured nonlinear stiffness model was adopted to predict the overall bearing performance under various speeds and loads. The simulation uses an advanced model which predicts the 2D plate top foil deflection with physical bump locations mapped from the actual hardware. The simulation confirms that the hybrid operation significantly increases the load capacity compared to hydrodynamic bearing due to the boost effect of hydrostatic pressure in the main film. Tests were conducted at 10krpm, 15krpm, and 20krpm to measure load capacity, power loss, and average film thickness. At 20krpm, a maximum axial load of 1711 N was achieved before bearing failure. Ultimately, the novel HFTB shows excellent static performance with potential for use in Organic Rankine Cycle (ORC) generators and other large oil-free turbomachines.

Synergistic thermal and hydrodynamic effects in 3D-printed heat sinks with intricate microchannel patterns

Synergistic thermal and hydrodynamic effects in 3D-printed heat sinks with intricate microchannel patterns

A correlation for U-value for laminar and turbulent flows in concentric tube heat exchangers

This paper introduces a novel empirical correlation designed to predict the overall heat transfer coefficient (U) in concentric tube heat exchangers. The study utilizes a comprehensive dataset of 2700 data points from CFD simulations, examining the impact of critical variables including hot and cold fluid Reynolds numbers (Reh, Rec), Prandtl numbers (Prh, Prc), and heat exchanger dimensions (tube hydraulic diameter Dh, annular space hydraulic diameter Dc, and overall length L). The analysis incorporates a range of fluid combinations in the tube and annular sections – air–air, air–water, water-air, and water–water – across Reynolds number ranges from 1000 to 20000, covering both laminar and turbulent flow regimes. The correlation was developed using the Adam optimizer to minimize the Weighted Mean Squared Error (WMSE), achieving an impressive convergence to an average prediction error of 6.7% compared to actual U values. The model categorizes flow into four distinct categories, each corresponding to a combination of flow patterns in the tube and annular spaces regimes – Laminar–Laminar, Laminar–Turbulent, Turbulent–Laminar, and Turbulent–Turbulent – integrating both hydrodynamic and thermal entry effects to enhance prediction accuracy. Rigorous error analysis revealed a median error of 5.18%, substantially outperforming existing models. Notably, 10% of the predictions deviate by less than 1%, with 90th percentile errors staying below 15%. Parameters were finely tuned through extensive numerical simulations, ensuring accurate application of the correlation across diverse operational conditions. The study concludes by highlighting the model’s potential to significantly enhance the design and efficiency of heat exchangers and proposes future enhancements to further improve its predictive accuracy.

Finite element method-based investigation of heat exchanger hydrodynamics: Effects of triangular vortex generator shape and size on flow characteristics

Heat exchangers (HEs) play a critical role in numerous industrial and engineering applications by facilitating efficient thermal energy transfer. In the pursuit of enhancing the performance of such systems, this study focuses on the hydrodynamic effects of two distinctive vortex generators (VGs) within a turbulent airflow channel, operating under steady-state conditions. Arranged in a staggered manner, the first vortex generator (VG) adopts a rectangular structure positioned in the upper section, while the second VG, triangular in shape, is situated on the opposing wall at varying heights, ranging from 40 to 80 mm in 10 mm increments. A further examination of the triangular VG includes two cases, one featuring an inclined front-face and the other showcasing an inclined rear-face. The turbulent airflow within the channel is accurately represented using the Newtonian fluid model and the standard k-epsilon turbulence model, while the governing equations are solved through the finite element method. A non-uniform mesh, consisting of triangular and square elements with a specific focus on refining the mesh near walls, is designed to capture boundary layer effects and effectively resolve intricacies in near-wall flow dynamics. The investigation unveils dynamic responses within the channel, characterized by notable flow distortions and prominent regions of recirculation, demonstrating the effectiveness of both rectangular and triangular VGs. Importantly, the analysis shows that tilting the triangular VG’s back-face notably improves the hydrodynamic structure of the HE channel, leading to enhanced recirculation cells and substantially increased performance. In particular, increasing the height of triangular VGs significantly enhances flow velocity within the channel. For instance, the axial velocity increased by 33.8% when the VG height was raised from 40 to 80 mm in the first triangular case, while an increase of about 37.9% was observed in the second triangular case at the lowest inlet velocity of 7.8 m/s. In addition, triangular VGs with an inclined back-surface achieved higher axial velocities compared to those with an inclined front-surface, with a 13.5% increase at the smallest height and a 17.0% increase at the maximum height. Furthermore, increasing the inlet velocity to 9.8 m/s resulted in a 17.1% higher axial velocity in the second model, reaching 55.4 m/s compared to 47.3 m/s in the first model. These findings underscore the importance of optimizing the triangular VG shape, height, and inlet conditions to maximize the hydrodynamic performance of HE systems, leading to potential energy savings and improved efficiency.

The Dynamics of Debris Disk Creation in Neutron Star Mergers

The detection of GW170817/AT2017gfo inaugurated an era of multimessenger astrophysics, in which gravitational-wave and multiwavelength photon observations complement one another to provide unique insight into astrophysical systems. A broad theoretical consensus exists, in which the photon phenomenology of neutron star mergers largely rests upon the evolution of the small amount of matter left on bound orbits around the black hole or massive neutron star remaining after the merger. Because this accretion disk is far from inflow equilibrium, its subsequent evolution depends very strongly on its initial state, yet very little is known about how this state is determined. Using both snapshot and tracer particle data from a numerical relativity/MHD simulation of an equal-mass neutron star merger that collapses to a black hole, we show how gravitational forces arising in a nonaxisymmetric, dynamical spacetime supplement hydrodynamical effects in shaping the initial structure of the bound debris disk. The work done by hydrodynamical forces is ∼10 times greater than that due to time-dependent gravity. Although gravitational torques prior to remnant relaxation are an order of magnitude larger than hydrodynamical torques, their intrinsic sign symmetry leads to strong cancellation; as a result, hydrodynamical and gravitational torques have a comparable effect. We also show that the debris disk’s initial specific angular momentum distribution is sharply peaked at roughly the specific angular momentum of the merged neutron star’s outer layers, a few r g c, and identify the regulating mechanism.

Hydrodynamic disintegration effects assessment by CFD modelling integrated with bench tests

The hydrodynamic disintegration process depends, among others, on operational parameters like rotational speed or introduced energy. The study presents an interdisciplinary approach to the hydrodynamic disintegration parameters impact assessment on the internal processes and disintegration effects on the example of sewage sludge treatment. Three rotational speeds were considered, including fluid properties change at selected disintegration stages. Disintegration effects were measured in the bench tests. Soluble chemical oxygen demand (SCOD) and volatile fatty acids (VFA) were measured before and after disintegration process. The assessment of the effects of disintegration employed the disintegration degree and the assessment of the course of methane production employed biochemical methane potential (BMP) tests. Fluid properties change during the disintegration stages does not cause a significant change in the flow structure. Due to the mathematical modelling results, at 1500 rpm no cavitation phenomenon was observed. Although, the bench tests results indicates, for the rotational speed 1500 rpm, organic compounds released to the liquid were characterised by higher susceptibility to biological decomposition than those released for 2500 and 3000 rpm (as suggested by the low SCOD/VFA values for 1500 rpm). Obtained results have confirmed, that the main phenomenon responsible for the disintegration effect is mechanical shredding not cavitation.

Nonlinear Dynamic Analysis of High-Strength Concrete Bridges under Post-Fire Earthquakes Considering Hydrodynamic Effects

This study employed the linear interpolation method to ascertain the curve relationship between the elastic modulus and stress of high-strength concrete C60 with temperature, and the nonlinear dynamic analysis of high-strength concrete bridge structures subjected to post-fire earthquake action at varying water levels was subsequently evaluated. It was established that both the hydrodynamic effects and the temperature effects have a considerable impact on the structural dynamic response of bridges. The presence of water has been observed to increase the dynamic response of pier structures. At water levels of 0 m and 10 m, the temperature effect results in a reduction in the fundamental frequencies of acceleration and displacement responses by 73.68% and a decrease in the fundamental frequency of stress responses by 83.33%. At a water level of 20 m, the fundamental frequencies of the acceleration, displacement, and stress responses decrease by 53.49%. In consideration of the acceleration and displacement at the pier top and stress at the pier base at a water depth of 10 m, the superposition of temperature effects and hydrodynamic effects results in an increase of 59.06% in acceleration, 25.93% in displacement, and 49.53% in stress than combination effects, respectively. At a water depth of 20 m, the superposition of temperature and hydrodynamic effects results in an increase of 92.82%, 100%, and 127.85% in acceleration, displacement, and stress, respectively. The combined effects of hydrodynamic and temperature effects cannot be described merely as a linear superposition of the two single actions. The research findings provide a significant theoretical basis for understanding the impact of multiple disasters, such as fires and earthquakes, on bridge structures.

Numerical study of hydrodynamic drag effects of streamwise riblet structures on SUBOFF bare hull model

This study performs a full-scale numerical simulation on meter-scale underwater vehicles (UWVs) with micrometer-scale V-type streamwise riblet structures, focusing on hydrodynamic drag using the SUBOFF model. The periodic simulation along the azimuthal direction enables the full-scale analysis. Two main scenarios are discussed: (1) effect of riblet structure size on drag at a constant maneuvering speed and (2) effect of maneuvering speed on drag for representative riblet cases. In scenario (1), the average wall shear stress at the central region of the body exhibited significant reduction of approximately 50%. However, owing to larger effective area at the central surface of the body fixed with riblets, the friction drag may either decrease or increase depending on the riblet size. Consequently, R100 case showed maximum total drag reduction of ∼3%, whereas R500 case showed maximum increase in drag of ∼3%, where R100 and R500 indicate riblet-applied SUBOFF models with riblet heights of 100 and 500 μm, respectively. In scenario (2), friction drag in riblet-applied region exhibited smaller variations in R100 case, showing universal drag reduction effect at all speeds. In contrast, R500 case showed significant variations, with drag increments ranging from minimum of 1% to maximum of 12% at all speeds.

Searching for the grand tack in exoplanetary data

The grand tack model, more generally called the Masset and Snellgrove mechanism, is a planetary migration model whereby two giant planets via interactions with their natal disk migrated to larger orbital radii. While its relevance in our own Solar System remains in question, the fact that the Masset and Snellgrove mechanism is a general hydrodynamical effect implies that it may have occurred in another planetary system. In this study I searched through exoplanet data for evidence of the Masset and Snellgrove mechanism, which requires that (1) the inner of the two planets is more massive than the outer planet; (2) the planets are sufficiently massive that their gravity-induced gap overlaps; and (3) they orbit at sufficiently close radii that their co-rotation regions also overlap. The last two requirements are met when the planets orbit with a 3:2 mean motion resonance. I do not find conclusive evidence for a grand tack-like system, but find some evidence for planet formation at the edge of a planet-induced protoplanetary disk gap in three systems.

Analysis of Thermoelastic Contact of Gas-Lubricated Rough Sealing Faces.

Friction and wear are the main failure sources of face seals. When the surfaces of sealing rings exhibit greater roughness, the level of friction might increase and lead to sealing failure. Therefore, in this paper, based on the elastic contact hypothesis of rough and wavy surfaces and the influence of temperature on the elastic modulus of materials, a thermoelastic contact lubrication model of a gas-lubricated end seal is established. The novelty and advantage of this study is that it takes the effect of surface roughness into consideration during thermoelastic analysis of gas-lubricated seals. The film pressure, temperature, contact force and deformation of a gas spiral groove-faced seal are numerically determined. The influence of surface roughness on the contact distribution, deformation and temperature of the end-face seal at different speeds and pressures is analyzed. The film thickness increases as the rotational speed increases from 1 rpm to 2000 rpm, while the contact pressure sharply decreases from 0.25 kPa to 0. The analysis shows that the roughness contact mainly happens on the inner side of the rings due to convergent distortion of the seal faces, which easily causes partial wear of the seal faces. Moreover, it can also be found that the spiral grooves on the sealing surface can produce obvious hydrodynamic pressure effect due to the function of shear speed when the speed increases to 2000 rpm, while the film temperature increases from 293.3 K to about 306 K. The greater surface roughness results in a larger temperature rise under low-rotational-speed and lower-seal-pressure conditions, which further increases the risk of severe wear or even failure of the seal faces.