The droplet combining and shedding on a gradient-wetting inverted triangle surface is investigated using the lattice Boltzmann method based on the Shan-Chen pseudo-potential model. The impacts of the tip angle, wetting gradient, and Bond number are investigated. The study shows that the smaller the tip angle, the better for the droplets to merge and shed. The droplet combining and shedding process can be sped up by the triangular surface's wetting gradient. As the wetting gradient increases, the droplet combining and shedding becomes easier. Applying a wetting gradient to speed drainage is better when the original surface is more hydrophilic. The combination and shedding of droplets on the wet surface are significantly influenced by the Bond number as well.

The Rayleigh–Taylor (RT) instability in inertial confinement fusion implosions evolves at the unstable interface of two fluids when the light fluid is pushing the heavy one. The effects of the initial amplitude and transition layer on the compressible RT instability are investigated numerically by using the discrete Boltzmann method. On the one hand, during the RT evolution, higher initial amplitudes initially increase the global density gradient and non-equilibrium area, with a subsequent reversal. The increasing initial amplitude leads to an initial rise followed by a decline in the system’s maximum Mach number. On the other hand, the impact of the transition layer is generally opposite to the one of initial amplitude in the RT process. These findings offer significant insights into controlling and understanding RT instability in fusion implosion scenarios, emphasizing novel aspects relative to existing literature.

Rayleigh–Taylor (RT) instability is a classical interface instability of great importance in nature and engineering fields. In this paper, the influences of acceleration on the compressible RT instability is investigated by using the discrete Boltzmann method based on non-equilibrium statistical physics. The differences in RT systems with various accelerations have been analyzed through the physical gradients and non-equilibrium measures. It is interesting to find that the global temperature gradient, the maximum Mach number, and the non-equilibrium strength increase initially, reduce afterwards, and have peaks in the dynamic process. Specifically, in the early stage, the global temperature gradient of the fluid system is higher for a case with larger acceleration, and there is an exponential relationship between them. Moreover, the maximum Mach number is located at the heavy fluid that drops fast in the system’s midsection, rises more sharply, and reaches the peak earlier for a larger acceleration. In addition, for a larger acceleration, the non-equilibrium strength rises (reduces) faster in the early (later) stage, and presents an exponential relationship between them in the early stage as well. From the kinetic perspective, these results further enrich our understanding of the physical mechanism of the compressible RT instability with both hydrodynamic and thermodynamic non-equilibrium effects.

A lattice Boltzmann method (LBM) based on Shan-Chen pseudo-potential model is used to investigate the process of droplets merging and shedding on a gradient wetting circular surface. The effects of wetting gradient, radius, and radius ratio on droplet merging and shedding were mainly explored. The results show that applying a wetting gradient on the circumferential surface can accelerate the process of droplet merging and shedding. The velocity of droplets merging and shedding increase with the increase of the wetting gradient. The more hydrophilic the original surface, the better the optimization effect of accelerating drainage is by applying a wetting gradient. The radius and radius ratio significantly affect droplets merging and shedding on the gradient wetting surface. The larger the radius and radius ratio, the shorter the droplets merging and shedding time.

Rayleigh-Taylor (RT) instability phenomenon exists widely in nature and engineering fields. It is of great theoretical significance and practical value to clearly understand the physical mechanism of the RT instability. In this paper, the compressible RT instability is simulated by the discrete Boltzmann method (DBM), and the compressible RT instability with random multimode initial perturbations at continuous interfaces is numerically investigated by means of the DBM. The results show that with the influence of temperature gradient, the thermodynamic non-equilibrium strength related to heat flux firstly increases and then decreases. Under the action of thermal diffusion, the thermodynamic non-equilibrium strength at the interface firstly decreases and then increases, which affects the time evolution of proportion of the thermodynamic non-equilibrium region. In this respect, effects of temperature gradient and thermal diffusion on the time evolution trend of non-equilibrium strength at the interface are the same. Finally, we analyze the time evolution of the global average thermodynamic non-equilibrium strength, and find that under the joint action of macroscopic physical gradients and thermodynamic non-equilibrium area, the global average thermodynamic non-equilibrium strength firstly increases, then decreases, and finally tends to be stable. On the one hand, the increase (decrease) of the area of thermodynamic non-equilibrium region will increase (decrease) the strength of thermodynamic non-equilibrium. On the other hand, the increase (decrease) of physical gradients at the material interface also has the same effect on the global average thermodynamic non-equilibrium strength. The two physical mechanisms interact and compete with each other.

In this paper, simulation results of droplet impact motion on hydrophilic (theta=80 degrees) and hydrophobic (theta=160 degrees) orifice surfaces are obtained by a single component multiphase lattice Boltzmann model (LBM). And a piecewise relaxation time is used to improve the numerical stability under high liquid/vapor density and low droplet viscosity. The effects of Weber (We) number, Ohnesorge (Oh) number, orifice thickness, and the diameter ratio of the orifice and droplet on the deformation process of the droplet impact on hydrophilic and hydrophobic orifice plates were studied, including the phenomena of liquid slug and breakage. As a result, at a low We number, the droplet is not easy to pass through the orifice, and the liquid plug phenomenon will be formed in the hydrophilic orifice, which is because of the hydrophilic effect on the orifice surface forms capillary action. At a high We number, the droplet will break when it impacts the orifice plate. In addition, the critical We number of droplets passing through the surface of a hydrophilic orifice has a linear relationship with the thickness of the orifice, while there is a critical We number of droplets passing through the surface of a hydrophobic orifice, which corresponds to two different forms of passage: peristaltic form and rapid through the form. The state diagram of the droplet with different We number, orifice diameter and droplet diameter ratio is obtained, which can be used to predict the different states of the droplet after impacting the orifice. According to the We number and Oh number, a graph for predicting droplet rupture is obtained. The critical We number increases with the increase of The Oh number, which means that the more viscous droplet requires a larger We number to rupture.

Based on lattice Boltzmann method, the numerical simulation of droplet impinging on orifice plates with different wettability was carried out. The influence of weber number (We) number, wettability of orifice surface and orifice size on different states of droplet passing through orifice plate during droplet impact was studied. The numerical simulation results show that different phenomena will occur in the process of droplet impacting the orifice plate: when the orifice plate is hydrophilic, the droplet will not detach from the surface of the orifice plate, but adhere to the lower surface of the orifice plate at a lower We number, and the droplet will rise a certain distance in the orifice channel under the action of capillarity, forming liquid plugging phenomenon. At higher We numbers, droplets will pass through the orifice plate and rupture will occur. When the orifice plate is hydrophobic, the droplets can not pass through the orifice plate and can not migrate to the lower surface at a lower We number, and finally stabilize on the orifice channel. At higher We numbers, droplets can pass through the orifice plate, and when they pass through, they will break, leaving droplets remaining on the surface of the orifice plate. When the orifice size was changed, it was found that the droplet was not easy to pass through when the orifice size was smaller or the orifice thickness was thicker.

采用基于Shan-Chen伪势模型的格子Boltzmann方法,对液滴在存在润湿梯度的倾斜表面上克服重力、自下而上运动的过程进行模拟.探究润湿梯度、液滴尺寸、Bond数以及表面倾斜角度对液滴运动的影响.计算结果表明:液滴在运动过程中,内部会出现沿斜面向上的速度矢量,润湿梯度越大,液滴运动速度越快,润湿长度也越长,且动态接触角减小速率越快.液滴尺寸和Bond数对液滴运动的影响较小,但存在临界Bond数,超过该临界Bond数时,液滴将沿梯度润湿表面向下运动.表面倾角对液滴运动有显著影响,倾角增大,液滴运动速度和润湿长度都明显减小.

Rayleigh-Taylor (RT) instability widely exists in nature and engineering fields.How to better under-stand the physical mechanism of RT instability is of great theoretical significance and practical value.At present,abundant results of RT instability have been obtained by traditional macroscopic meth-ods.However,research on the thermodynamic non-equilibrium (TNE) effects in the process of system evolution is relatively scarce.In this paper,the discrete Boltzmann method based on non-equilibrium statistical physics is utilized to study the effects of the specific heat ratio on compressible RT insta-bility.The evolution process of the compressible RT system with different specific heat ratios can be analyzed by the temperature gradient and the proportion of the non-equilibrium region.Firstly,as a result of the competition between the macroscopic magnitude gradient and the non-equilibrium region,the average TNE intensity first increases and then reduces,and it increases with the specific heat ratio decreasing;the specific heat ratio has the same effect on the global strength of the viscous stress tensor.Secondly,the moment when the total temperature gradient in y direction deviates from the fixed value can be regarded as a physical criterion for judging the formation of the vortex structure.Thirdly,under the competition between the temperature gradients and the contact area of the two fluids,the average intensity of the non-equilibrium quantity related to the heat flux shows diversity,and the influence of the specific heat ratio is also quite remarkable.

Chronic pruritus of unknown origin (CPUO) is described as chronic itch lasting longer than 6 weeks in the absence of a defined skin rash and any known causative disease process. A retrospective study was performed on biopsy samples from patients with CPUO and normal controls to compare the immune profiles of these patients with healthy individuals. We used dual CD3/T-bet and CD3/GATA3 immunohistochemical staining to assess for T-cells expressing Th1 versus Th2 transcription factors, respectively. Our data showed that CD3(+) cells of patients with CPUO co-express significantly more GATA3 compared with normal controls. Meanwhile, the normal control skin showed a much more balanced T-bet/GATA3 ratio of co-expression. Our data suggest an enrichment of Th2 cells in CPUO skin by T cell/GATA3 co-staining, supporting that CPUO is increasingly considered a type 2/Th2 cell-associated disease. We thus speculate that type 2 cytokine blockade-based therapies may represent effective treatments for CPUO.

采用单组分多相的伪势格子Boltzmann方法,在大小液滴粒径比为1.5的情况下,对大液滴竖直撞击壁面上静止小液滴的过程进行模拟,研究亲水与超疏水壁面上大液滴竖直碰撞小液滴的过程,得到液滴铺展因子和相对高度随时间的变化.结果表明:增大We数会使液滴的铺展因子增大,铺展直径变大,相对高度减小;并且随着We数的增加,在超疏水表面,液滴在铺展过程中底部会出现空腔,空腔大小随着We数增大而增加;此外,We数增加到107.35时,液滴发生了断裂.

Based on the framework of our previous work [H.L. Lai et al., Phys. Rev. E, 94, 023106 (2016)], we continue to study the effects of Knudsen number on two-dimensional Rayleigh–Taylor (RT) instability in compressible fluid via the discrete Boltzmann method. It is found that the Knudsen number effects strongly inhibit the RT instability but always enormously strengthen both the global hydrodynamic non-equilibrium (HNE) and thermodynamic non-equilibrium (TNE) effects. Moreover, when Knudsen number increases, the Kelvin–Helmholtz instability induced by the development of the RT instability is difficult to sufficiently develop in the later stage. Different from the traditional computational fluid dynamics, the discrete Boltzmann method further presents a wealth of non-equilibrium information. Specifically, the two-dimensional TNE quantities demonstrate that, far from the disturbance interface, the value of TNE strength is basically zero; the TNE effects are mainly concentrated on both sides of the interface, which is closely related to the gradient of macroscopic quantities. The global TNE first decreases then increases with evolution. The relevant physical mechanisms are analyzed and discussed.