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The physics of cavitation bubbles in water has been extensively studied for over a century. However, our understanding of bubble dynamics in binary immiscible fluids, such as a water-oil system, is limited. These systems have recently gained a lot of interest due to their relevance in modern medical treatment, emulsification, and the food industry. In this study, we establish an accurate and inexpensive three-dimensional boundary integral (BI) model for inertial cavitation bubble dynamics in binary immiscible fluid systems. Our novel scheme for solving velocities on the flow boundaries, expressed in a matrix form, can be easily extended to complex situations where multiple bubbles are generated in different phases. Additionally, we employ a density potential method and a weighted moving least-squares method to maintain a high level of mesh regularity. Our results demonstrate that the proposed 3D model is comparable in accuracy to a 3D axisymmetric model by comparing it against analytical solutions and the results obtained from an axisymmetric model. Furthermore, we compare our numerical simulations against a purposely conducted experiment for the bubble-droplet interaction, and excellent agreement is achieved. For the first time, we present simulation results of two-bubble interactions with an initially flat fluid-fluid interface and inside a droplet surrounded by a second fluid. We also reveal the dependences of the two-bubble morphologies, flow patterns, and jet velocities on the density ratio between the two phases. Finally, we find a significant difference in the mechanism of fluid mixing by multiple bubbles compared to that of a single bubble case. • We established a 3D model for inertial bubbles in binary immiscible fluids. • Our 3D model has shown comparable accuracy to an axisymmetric model. • We reproduce the essential physics in an experiment of bubble-droplet interaction. • We unveil novel fluid-mixing mechanisms with multiple bubbles. • We explore the dependencies of two-bubble interactions on the density ratio. [ABSTRACT FROM AUTHOR]

In this study, we establish a full coupling model (FCM) to simulate strong bubble-sphere interactions based on a three-dimensional boundary integral method. Different from the conventional loose coupling model (LCM), FCM adopts several auxiliary functions to deal with the mutual dependence between the hydrodynamic force and the sphere acceleration. In addition, the weighted moving least square method, a mesh density control scheme and an adaptive mesh refinement scheme are implemented to improve the quality of mesh on the deformable bubble surface. To validate the present model, convergence tests on different mesh sizes and time steps are conducted at first. The numerical results are also compared with the axisymmetric model, in which consistent results have been achieved. We further make comparisons between the numerical results and those from several experiments under different boundary conditions. For weak interaction cases, both LCM and FCM can give the results that have good agreement with the experiment data. As the interaction effects become stronger, the advantage of the FCM over the LCM becomes increasingly obvious. Particularly, when the pulsating bubble is in contact with the sphere surface, the essential physical features of the experiments can be well reproduced by the FCM while the predictions by the LCM are significantly different from the experiment. The present 3D model can be further extended to study more complex underwater contact explosions, cavitation inception on a structure and airgun bubble dynamics. • A full coupling model is established to simulate strong bubble-sphere interaction based on 3D boundary integral method. • Auxiliary functions are introduced to deal with the mutual dependence between the force and the sphere acceleration. • By using some latest numerical techniques, the interaction between a sphere and an attached bubble is simulated. • The essential physical features of some experiments are well reproduced by the present 3D model. [ABSTRACT FROM AUTHOR]

In numerical simulations of fluid dynamics based on the smoothed particle hydrodynamics (SPH) method, the formula for the viscosity term is always complicated since it is a second-order derivative term. In this paper, for Newtonian fluids, a novel formula for the viscous force satisfying the Stokes hypothesis is proposed in the weakly compressible framework. Because of the ease of adopting only a single layer of particles to enforce the boundary condition, the normal flux method is implemented for a solid wall boundary, which should be suitable for complex geometries and thin structures. The normal flux method can mitigate the decrease in numerical accuracy caused by the lack of neighbouring particles at the boundary. Meanwhile, the kernel function at the boundary is modified to satisfy the normalization condition. The accuracy and robustness of the proposed algorithm are verified by a series of cases of numerical fluid simulations, paving the way for SPH simulations coupled with complex thin shell structures for fluid–structure interaction problems. • A novel viscous force that satisfies Stokes hypothesis is derived. • The viscous force near the single-layer boundary is presented. • Kernel function correction technique is proposed to ensure consistence near the single-layer boundary. [ABSTRACT FROM AUTHOR]

In the current study, an improved numerical model is proposed in the compressible fields based on Smoothed Particle Hydrodynamics (SPH), which is comprised of MUSCL interpolation in multiphase flow, enhanced particle regeneration technique (PRT) and the particle shifting technique (PST) in compressible flows. The PRT is specially proposed to deal with compressible problems, in which the volume of particles have large variation during the whole simulation process. Different to the conventional PRT [1] , an interface control (IC) method is proposed to deal with the mass conservation problem which may result in the unphysical movement of interface when modeling multifluids. The multiphase MUSCL interpolation aims at dealing with over-dissipation problem that exists in the Godunov-type SPH which may result in the wrong detection of wave front. To avoid large discontinuity between different fluids, two kinds of extrapolation schemes (constant extrapolation and isentropic extrapolation) are discussed and compared at the inspiration of the ghost fluid method (GFM). The proposed MUSCL-based compressible SPH model is validated and discussed in several challenging test cases, such as multiphase shock tube like problem, the shock wave impacting on multifluids interface problem and Richtmyer-Meshkov instability etc., in which good agreements are obtained. • An enhanced particle regeneration technique is proposed to simulate compressible multiphase flows based on SPH. • The mass conservation property is improved leading to the accurate detection of multiphase interface. • The wave front can be better predicted and higher resolution results are obtained combined with MUSCL scheme. • The strongly compressible shock tube problem and the shock wave impacting on the multiphase interface problem is simulated. [ABSTRACT FROM AUTHOR]

Hepatocellular carcinoma (HCC) is one of the major cancers with high mortality rate. Traditional drugs used in clinic are usually limited by the drug resistance and side effect and novel agents are still needed. Macrolide brefeldin A (BFA) is a well-known lead compound in cancer chemotherapy, however, with poor solubility and instability. In this study, to overcome these disadvantages, BFA was encapsulated in mixed nanomicelles based on TPGS and F127 copolymers (M-BFA). M-BFA was conferred high solubility, colloidal stability, and capability of sustained release of intact BFA. In vitro, M-BFA markedly inhibited the proliferation, induced G0/G1 phase arrest, and caspase-dependent apoptosis in human liver carcinoma HepG2 cells. Moreover, M-BFA also induced autophagic cell death via Akt/mTOR and ERK pathways. In HepG2 tumor-bearing xenograft mice, indocyanine green (ICG) as a fluorescent probe loaded in M-BFA distributed to the tumor tissue rapidly, prolonged the blood circulation, and improved the tumor accumulation capacity. More importantly, M-BFA (10 mg/kg) dramatically delayed the tumor progression and induced extensive necrosis of the tumor tissues. Taken together, the present work suggests that M-BFA has promising potential in HCC therapy. [Display omitted] [ABSTRACT FROM AUTHOR]

• An indirect ALE DG model on moving triangular meshes with mesh topological adaptability is developed. • The best features of the Lagrangian description, DG method and adaptive topology optimization strategy are incorporated. • The present scheme can handle hydrodynamics problems which involve complex deformations, large distortions and strong shock. • The new indirect ALE DG scheme is more accurate and stable than the conventional Lagrangian DG scheme. In this paper, we present a novel cell-centered indirect Arbitrary-Lagrangian-Eulerian (ALE) discontinuous Galerkin (DG) scheme on moving unstructured triangular meshes with mesh topological adaptability, aiming to deal with the strong distortions and large deformation flow problems. The scheme combines the explicit time marching Lagrangian DG methodology with the adaptive mesh topology optimization technique. The scheme consists of the following three steps. Firstly, we utilize the Runge-Kutta DG method to solve the compressible Euler equation in Lagrangian framework, and employ a nodal solver to obtain the nodal velocity and numerical fluxes across element boundaries. The physical variable and nodal position are updated in this step. Secondly, the adaptive mesh topology optimization technique, which includes the mesh refinement, edge collapse operation and mesh regularization, is implemented to eliminate the highly distorted elements and improve the mesh quality. Thirdly, the conservative remapping algorithm is employed, which can maintain the conservative interpolation of the Lagrangian solution onto the remeshed grid. The present indirect ALE DG scheme can ensure the high quality of the mesh by optimizing the topology connectivity, so that the present scheme can successfully simulate complex vortical flow problems for a sufficient simulation time. Due to the inherent Lagrangian nature, the present scheme can naturally track the multi-material flow interface, rather than using algorithms with interface reconstruction or diffuse interfaces. The scheme is validated with several benchmark flow problems. It is demonstrated that the present indirect ALE DG scheme with topological adaptability can accurately simulate flow problems with large fluid deformations and distortions. It can achieve remarkable improvements compared with the conventional Lagrangian DG method with fixed topological connectivity. [ABSTRACT FROM AUTHOR]

Experiments on oblique water entry of high-speed projectiles are performed to investigate cavity evolution and impact loads. The nose shape determines the cavity behavior and consequently affects the load characteristics. Each projectile used in the experiments has a truncated-cone head and a cylindrical body. The geometry of the truncated cone is defined by two dimensionless parameters. We adopt 40 kinds of head shape, while the impact velocity (41 m/s) and impact angle (30°) are kept the same. The cavity and load characteristics are investigated using a high-speed camera and an acceleration sensor, respectively. We divide the cavity dynamics into two types. In one type, the first cavity develops and coalesces with the second cavity, leading to the formation of a single continuous cavity. In the second type, the closure of the first leading cavity occurs on the truncated-cone head or the cavity may collapse onto the head in later stages, causing the two cavities develop independently without coalescence. We also find that the transient impact load and the cavity dynamics are closely related, which has not been discussed in detail in previous studies. The quantitative relationship between the load peaks and the two dimensionless parameters is revealed. [ABSTRACT FROM AUTHOR]

A 2D fluid–structure interaction (FSI) solver based on Smoothed Particle Hydrodynamics (SPH) and RKPM is established in this paper. Since we focus on the incompressible flow problem, the WCSPH is adopted to simulate the fluid. Meanwhile, the structure is modeled by the RKPM beam formulation, in which the plane strain hypothesis is adopted, and only a column of particles is needed to discretize the beam. Since the support domain of the fluid particle near the FS interface is truanted, the so-called normal-flux method is adopted to consider surface integration terms. Moreover, we propose a new excess pressure for the incompressible fluid flow based on Bernoulli's principle, which is more accurate for the simulation of incompressible FSI problems. Besides, the particle shifting scheme near the fluid–structure interface is modified. Finally, the accuracy and stability of the present FSI solver are verified by several numerical examples. [ABSTRACT FROM AUTHOR]

In this paper, by combining the boundary element method (BEM) and peridynamics (PD), a bubble-ice interaction model is established, which can investigate the dynamic interactions between a high-pressure bubble and an ice plate with particular focus on the mechanical behaviors of ice breaking. The bubble dynamics are solved by BEM based on the potential flow theory. Ice cracks initiation and propagation are simulated by the bond-based peridynamics which is validated by a three-point bending test. The fluid–structure interaction (FSI) is achieved by matching the normal velocity and hydrodynamic loads at the fluid–structure interface. To validate the proposed FSI model, an experiment is carried out in which an oscillating bubble is generated under an ice plate by underwater discharge system. The whole interaction process is captured by a Phantom V711 high-speed camera. Qualitative agreements are achieved between the numerical and experimental results. The underlying mechanism of cracks initiation, propagation, branching, and coalescence of the ice plate is found to highly depend on three parameters, i.e., bubble–ice distance, ice thickness and bubble size. The present study is expected to provide further assists in the understanding of ice breaking problems. [ABSTRACT FROM AUTHOR]

A combined RKDG-FEM approach, using the Runge-Kutta discontinuous Galerkin (RKDG) method [1,2] for fluid simulating and the finite element method (FEM) [3,4] for structure simulating, is developed to study the complex interactions between compressible multiphase flows and deformable steel and composite structures in near-field early-time underwater explosion (UNDEX). The level set method (LSM) [5,6] and the real ghost fluid method (RGFM) [7,8] are applied to capture and treat the moving gas-water interface, respectively. A GFM-based interface treating scheme [9,10] is adopted to treat the fluid-structure interface, achieving the coupling by solving simultaneously the fluid characteristic equation and the structure equation of motion at the material interface to satisfy the kinematic compatibility and pressure equilibrium conditions. The isentropic one-fluid cavitation model in [11] is employed to capture the transient flow cavitation. Accuracy and effectiveness of the combined RKDG-FEM approach are validated by five benchmark cases, and then it is applied to simulate early-time UNDEX problems near a submerged aluminum foam-cored sandwich plate and a monolithic steel plate of equivalent mass. Numerical results show that the sandwich plate has a higher underwater explosion load resistance through absorbing plastic energy by the foam core than the monolithic steel plate of equivalent mass, and that the foam core plays an important role in the fluid-structure interaction (FSI) and flow cavitation effects, which can be exploited to improve the UNDEX mitigation capability of composite sandwich structures. • A combined RKDG-FEM approach is developed for simulating UNDEX problems. • UNDEX involving shock-bubble-structure interactions and flow cavitation is simulated. • Comparison study of UNDEX near steel and composite sandwich structures is conducted. [ABSTRACT FROM AUTHOR]

• A weakly compressible ULPH model is developed for multiphase flows. • A new surface tension formula combined with interface sharpness force is developed in the ULPH multiphase flow model. • The intermediate configuration is considered in the computational algorithm. • Validations of ULPH multiphase flow model show good accuracy, stability and convergence. In this paper, a weakly compressible updated Lagrangian particle hydrodynamics (ULPH) model [1] has been developed for multiphase flows with high density ratios and viscosity ratios. To enhance computation stability and prevent penetrations near the multiphase flow interface, a new surface tension resultant formulation based on the Continuum Surface Force (CSF) formulation [2] , combined with the interface sharpness force, is also developed within the framework of ULPH method. The intermediate configuration is considered in the computational algorithm, and a modified predictor-corrector scheme is adopted to solve governing equations, which significantly improve the accuracy and efficiency of the ULPH model. Several numerical examples are presented to compare with either analytical or computational results obtained by using different numerical methods such as Smoothed Particle Hydrodynamics (SPH) method, Moving Particle Semi-implicit (MPS) method and Level Set (LS) method within the framework of Finite Element Method (FEM). The results indicate that the ULPH method has good accuracy, stability, and convergence properties in simulations of multiphase flows. [ABSTRACT FROM AUTHOR]

Highlights: [•] Highly ordered silica with small pores is synthesized and characterized. [•] Short-chain cationic–anionic mixed surfactant system was used as template. [•] Synthesis reported here should facilitate the large-scale applications of mesoporous silica with small pores. [ABSTRACT FROM AUTHOR]

A new interface treating method is proposed to simulate compressible two-medium problems with the Runge-Kutta discontinuous Galerkin (RKDG) method. In the present work, both the Euler equation and the level-set equation are discretized with the RKDG method which is compact and of high-order accuracy. The linearized interface inside an interface cell is recovered by the level-set function. The new solution of this cell is taken as a convex combination of two auxiliary solutions. One is the solution obtained by the RKDG method for a single-medium cell with proper numerical fluxes, and the other one is the intermediate state of the two-medium Riemann problem constructed in the normal direction. The weights of the two auxiliary solutions are carefully chosen according to the location of the interface inside the cell. Thus, it ensures a smooth transition when the interface leaves one cell and enters a neighboring cell. The entropy-fix technique is adopted to minimize the overshoots or undershoots in problems with large entropy ratio across the interface. The scheme is justified in a 1-dimensional situation and extended to 2-dimensional problems. Several 1-dimensional two-medium problems, including both smooth and discontinuous examples, are simulated and compared with exact solutions. Also, three 2-dimensional benchmark problems are simulated to validate the present method in two-medium problems. • A new interface treating method is proposed to simulate compressible multi-medium problems. • Runge-Kutta discontinuous Galerkin method is used to discretize both the Euler equations and the level set equations. • The new solution in the interface cell is taken as a convex combination of two auxiliary solutions. [ABSTRACT FROM AUTHOR]

Background: Varicose veins (VVs), a common vascular disease, are functionally characterized by dilation and tortuosity and are widely prevalent in the adult population. The pathophysiology and molecular mechanism of VVs are still unclear. A genetic risk for VVs has been demonstrated, although no genetic variant pertaining to VVs has been identified. Matrix metalloproteinases (MMPs) and their endogenous tissue inhibitors (TIMPs), which can prevent excessive extracellular matrix (ECM) degradation, greatly impact vascular remodeling and may play a vital role in patients with VVs. We evaluated a potential association between polymorphisms in the promoters of MMP-9 and TIMP-2 and the risk for VVs in the Chinese population. Materials and Methods: Genotyping of the promoter region polymorphisms -1562C/T in MMP-9 and -418G/C in TIMP-2 was performed with PCR and restriction fragment length polymorphism (PCR-RFLP) assays with a group of 60 patients with VVs and 60 healthy controls. Purified PCR products were sequenced. Results: A significant correlation was found between patients with VVs and controls at -1562C/T in MMP-9. The TIMP-2 gene polymorphism -418G/C was also associated with VVs. Conclusions: Our results suggest that polymorphisms in the promoter region of MMP-9 and TIMP-2 are associated with VVs in the Chinese population [ABSTRACT FROM AUTHOR]