Interface Capture Research Articles

Surfactant-based interface capture towards the development of 2D-printed photonic structures.

This study focuses on fabricating photonic crystals (PCs) by surfactant-based particle capture at the gas-liquid interface of evaporating sessile droplets. The captured particles form interfacial films, resulting in ordered monolayer depositions manifesting iridescent structural colors. The particle dynamics behind the ordered arrangement is delineated. This arrangement is influenced by the alteration in particles' hydrophobicity, charge, and internal flow introduced by the surfactant addition. The influence of surfactant and particle concentrations on the phenomenon is also investigated. The work demonstrates a drop-by-drop technique to scale up the formation of PCs. Furthermore, the work is extended towards demonstrating the utilization of this mechanism to fabricate arbitrary PCs efficiently by direct writing technique. The particle coverage in directly written patterns is influenced by printing speed and particle concentration, which are adjusted to achieve covert photonic patterns. Finally, the replication of colloidal PC onto a flexible polymer with minimal colloid transfer is demonstrated using soft lithography.

An enhanced interface-sharpening algorithm for accurate simulation of underwater explosion in compressible multiphase flow on complex grids

In underwater explosion simulations, the accuracy is critically affected by numerical diffusion and the quality of the computational grid. An enhanced interface-sharpening algorithm, based on the five-equation model and an anti-diffusion source term, is proposed to simulate the strongly compressible multiphase flow with an arbitrary number of phases in underwater explosions. To enhance the precision of interface and maintain computational stability on nonuniform and unstructured grids, an adaptive factor algorithm and a continuous interface capture function are developed. Furthermore, a redesigned fractional step method incorporating a special iteration stop criteria is proposed to solve the volume fraction equation. A pressure–density cutoff model is used to calculate the mixture density at the saturation pressure to account for the effect of cavitation. The quadratic monotone upstream-centered scheme for conservation laws reconstruction scheme and the improved advection upstream splitting method (AUSM+-up) flux scheme are also adopted to compute the flux across the grid interfaces. The overall computational framework is constructed upon a density-based explicit finite volume method. To assess the accuracy and robustness of the proposed numerical model, four representative test cases were chosen. The results reveal that the model refines the phase interface, adeptly capturing the complexities inherent in underwater explosion scenarios with both precision and efficiency across a diverse array of conditions.

An Eulerian-like interface-capturing approach for modeling the fouling process by crystallization

Calcium carbonate (CaCO3) is an inverse solubility salt commonly scaled in heat exchangers when the fouling mechanism by crystallization occurs. Several models have been proposed to predict the fouling behavior, considering the growth of fouling mass as the difference between deposition and removal rates. Despite the different alternatives suggested in the literature to approximate these rates, there has been limited discussion regarding the fouling layer growth interface capture within a continuous domain during the time-dependent crystallization process. Hence, in this work, we propose an Eulerian interface-capturing approach for modeling the fouling process by crystallization (EICAFC). This scheme will be implemented using the standard Galerkin Finite Element Method with linear interpolation polynomials. The EICAFC procedure will be outlined employing the Bohnet fouling model. Results about fouling thickness, mass accumulation, fouling resistance, and the EICAFC performance will be discussed.

Dynamic visualization study of in situ cleaning of polystyrene microparticles off silicon wafer surface

With the improvement of chip performance, the requirements for cleaning the surface of silicon wafers are becoming higher. However, due to equipment and technology, it is difficult to observe the complex motion processes of particles at the microscopic scale. In this paper, an in situ dynamic visualization experiment on the cleaning of Polystyrene Latex (PSL) on the surface of silicon wafers is carried out by using a high-speed camera and image processing software. The mechanical behavior of PSL particles in fluid was investigated on a microscopic scale, and the trajectory and force of the polystyrene particles on the surface of the wafers were visualized, which provided a new perspective for understanding the complex cleaning process. Theoretical models were developed to explain the motion characteristics of the particles by calculating parameters such as van der Waals force, surface tension, and trailing force, and these models provide a theoretical basis for optimizing the cleaning process. There are four particle motion modes in the fluid: (1) interface capture, where the particles on the surface of silicon wafer are trapped by gas–liquid interface under surface tension; (2) particle collision, where the particles captured by the water film collide with the particles on the wafer surface to make the latter leave the silicon wafer; (3) jump attachment, where the particles jump and attach to the surface of the particle group under the action of lift; and (4) wall surface movement, where the particles start up under the action of water flow and then leave the silicon wafer quickly.

3D numerical investigation of bubble upflow condensation behaviors during subcooled flow boiling in mini-channel with VOSET

In the subcooled flow boiling process, bubble condensation is an inevitable basic phenomenon. This paper studies the condensation phenomenon of the single, double vertical/horizontal saturated bubbles rising in a three-dimensional mini-rectangular channel based on the interface capture method VOSET (coupled volume-of-fluid and level set method) and the phase transition model. Bubble condensation behaviors are investigated at different initial diameters, inlet velocity distributions, subcooling temperatures, bubble gaps, and arrangement for the two-bubble condensing system especially. The effects of these parametric on bubble motion trajectory, shape evolution, volume variation, and condensation rate are presented. The numerical results indicated that the initial bubble size and liquid subcooling play an important role in influencing the shape and volume variation of condensing bubble behaviors significantly, while the inlet velocity distribution only affects bubble motion trajectory. Furthermore, the interaction and coalescence between the bubbles will affect the bubble behaviors and the condensation rate. Finally, the condensation heat transfer coefficients at the bubble surfaces for different cases simulated in this paper are presented, seemingly first in the literature.

A numerical model for solitary wave breaking based on the phase-field lattice Boltzmann method

This study presents a numerical investigation of a solitary wave breaking over a slope by using the phase-field lattice Boltzmann method. The incompressible two-phase flow equations are solved by using a velocity-based formulation of the two-phase lattice Boltzmann method with a central-moment collision model to accurately simulate wave breaking problems. For interface capture, a phase-field lattice Boltzmann method that ensures mass conservation is employed. The validity of the proposed method is confirmed through solitary wave propagation and transformation problems, and the obtained results are in good agreement with the experimental and calculated results. The proposed method is then employed to analyze wave breaking on a slope, demonstrating strong concordance with experimental data and existing computational findings. By analyzing the instantaneous flow characteristics and the temporal evolution of the variation in kinetic, potential, and total energy from deep to shallow water, the model can reveal the macroscopic characteristics of solitary wave breaking. Because the phase-field model effectively simulates wave breaking and air entrainment, it can depict wave energy dissipation more accurately than the single-phase lattice Boltzmann method with free surface tracking.

Implementation Of Web-Based Guest Book Information System Using Agile Method At Pt. Syntax Corporation Indonesia

The Guest Book Management Information System (SIPBT) plays a crucial role in digitalizing and enhancing the efficiency of guest recording processes. Implementing a web-based guest book system using Agile methods has proven effective in overcoming manual challenges and improving administrative processes. This study demonstrates the successful application of Agile methods in managing guest book systems. By utilizing a web-based system built with PHP, HTML, and the Laravel framework, the research achieved its goals effectively. The system provides administrators with easy management and monitoring of guest data, including a WhatsApp notification feature for efficient communication. The system also includes a user-friendly interface and webcam photo capture for easy guest identification, enhancing guest monitoring and search efficiency.

Scalable multilayered dielectric polymer film exhibiting significantly improved high-temperature energy density

Dielectric polymers, serving as crucial dielectric media in high-power-density energy storage devices, play a pivotal part in modern industries and electrical systems. However, the rapid degradation of breakdown strength and charge-discharge efficiency in elevated temperature environment imposes formidable limitations on the utilization of polymer dielectric under extreme conditions. Here, a series of polyetherimide/polysulfone alternating multilayer composite films are prepared using a non-equilibrium processing method, which effectively blocks the development of breakdown paths by the interface barriers in the multilayer structure. The deep trap sites within the interface capture the charge carriers excited at high temperatures, thus decreasing conduction loss and enhancing the efficiency and breakdown field strength of the dielectric polymer. Consequently, excellent capacitive performances including a high energy density of 5.4 J cm−3 with an efficiency exceeding 90% at 200 °C and cycle stability up to 106 cycles have been obtained. Furthermore, the multilayer polymer capacitors (MLPC) constructed from composite films also exhibit significant flexibility and thermal stability. This work provides valuable insights for the advancement of high-temperature energy storage polymers with commercial application value.

Corium interface flow dynamics investigation during severe accident in pressurized water reactors using compressive advection interface capturing method

Past nuclear accident occurrences raised strong concerns which led to research on nuclear safety. One of the major causes of nuclear accidents is the impeded circulation of core coolant, leading to decay heat removal cessation and rapid temperature rise. If uncontrolled, this results in critical heat flux, loss of coolant accidents, and core dryout. Detailed melted core relocation (i.e., nuclear fuel, graphite, and zircaloy) needs to be investigated through interface capture and multimaterial flow model coupling, which have not been done in previous studies. This work aims to investigate the impacts of temperature and core material composition on the flow dynamics during core relocation. In this study, mass fraction is discretized using a streamlined upwind Petrov–Galerkin method spatially and a modified Crank–Nicolson method temporally to accurately capture fluid interfaces using a high-order accurate flux-limiter. Two core material composition cases (individual material properties case and bulk material properties case) were considered to assess the impact of temperature and core materials composition on both flow dynamics and computational time. Temperature has a significant impact on core material transport and corium flow dynamics during core relocation. Bulk materials properties case has greater impact of temperature on its corium resulting in faster materials transport, but with higher computation time.

Scale effects on the hydrodynamic performance of a submerged body

The increasing development and utilization of submerged bodies in ocean exploration have led to significant challenges due to their unique working environment. Conducting experiments with a full-scale submerged body is exceptionally difficult. To investigate scale effects on the hydrodynamic characteristics of submerged bodies, a three-dimensional numerical model for submerged bodies was established based on the Reynolds-averaged Navier–Stokes (RANS) equations and utilizing the Realizable k-ɛ turbulence model. The volume of fluid (VOF) method was used for interface capture. Initially, the reliability of the numerical model was verified through result validation and convergence analysis of the grid and time steps. Subsequently, SUBOFF model of different scales were adopted using the established numerical model considering the influence of the Froude number (Fr). The present study focused on investigating the effect of model scales on the wave pattern, resistance characteristics, and nominal wake fields. Research has shown that the scale effects on the frictional resistance and the wake field of the submerged body are significant. The numerical model used in the present study demonstrated good accuracy. A comprehensive analysis of the scale effects on submerged bodies was conducted, providing valuable insights for the application of model data to full-scale scenarios.

Droplet impact simulation with Cahn–Hilliard phase field method coupling Navier-slip boundary and dynamic contact angle model

As a highly promising interface capture tool, the phase field method (PFM) has gained fast development in the past 20 years or so including in the simulation of droplet impact. The mobility tuning parameter χ of PFM, however, is hard to determine since it ambiguously reflects the relative strength between advection and diffuse effects that are difficult to quantify. This problem becomes even more complex when it is coupled with the contact line movement modeling, i.e., the dynamic contact angle (DCA) model, which is closely related to the effective slip (Ls,e) and the Navier-slip (Ls). This study systematically investigated the factors that would take effect at the interface capture and the contact line movement in droplet impact simulation. The value and the scaling law of Ls,e as for its dependence on χ and interface thickness (ε) was first confirmed, and an approximation scheme for defining the DCA model was proposed based on the difference between the apparent contact line moving velocity (Ucl) and the Navier-slip velocity at the contact line (Ucl′), which is inherently determined by Ls,e and Ls, respectively. After validation with the experiments, the scaling law of χ with ε, i.e., the sharp-interface limit, was finally obtained, which provides improved droplet impact simulation.

Controlling gas–liquid flow and enhancing heat transfer in a T-junction microchannel by wettability-engineered walls

Characteristics of gas–liquid flow and heat transfer in a cross-flow T-junction microchannel with wettability-engineered walls are numerically investigated in this paper. The validated diffuse interface method is adopted for interface capture. First, the effects of wall wettability on bubble formation and transportation are studied. Three flow patterns are observed due to different combinations of the bottom and the top wall contact angles. On this basis, two methods are proposed to enhance the heat transfer. One is to increase the two-phase interfacial contact area by dividing the microchannel into three functional regions, which can promote the heat exchange at the two-phase interface. The other is to increase the velocity fluctuation intensity by alternating the contact angle along the channel, which can enhance mixing between the hot liquid layer adjacent to the wall and the cool liquid core. These two methods are applicative for steady and unsteady problems, respectively. The flow states, velocity vectors, and streamlines are used to analyze the fluid and thermal mixing mechanism. Meanwhile, a quantitative comparison of the wall temperature is made at a given wall heat flux. The obtained results can provide fresh insights into the gas–liquid flow control and the heat transfer enhancement in a microchannel, which are valuable for the design of microreactors and radiators.

Bubble flow analysis using multi-phase field method

In simulations of gas-liquid two-phase flows using conventional interface capture methods, we observed that when bubbles come close to each other, they tend to merge numerically, despite experimental evidence indicating that they would repel each other. Given the significant impact of sequential numerical coalescence on flow patterns, it is necessary to regulate the merging behavior of close bubbles. To address this issue, we introduced the Multi-Phase Field (MPF) method, which mitigates bubble coalescence by applying an independent fluid fraction function to each bubble. In this study, we employed the MPF based on the N-phase model [7] to minimize numerical errors associated with surface interactions at triple junction points. Additionally, we implemented the Ordered Active Parameter Tracking (OAPT) method [9] to efficiently store several hundreds of fluid fraction functions. To validate the MPF method, we conducted analysis of turbulent bubbly pipe flows and compared the results against experimental data from Colin et al [12]. The validation results showed reasonable agreements with respect to the bubble distribution and the flow velocity profiles.

A high-order simulation method for compressible multiphase flows with condensed-phase explosive detonation in underwater explosions

This study introduces an efficient method designed for the simulation of compressible multiphase flows associated with explosive detonation, primarily in the context of underwater explosions. The proposed approach integrates three core components: the compressible Euler equations, the level-set equation, and the program burn model. Spatial terms of the compressible Euler equations undergo discretization using a fifth-order accuracy weighted essentially non-oscillation reconstruction, while the third-order total variation diminishing Runge–Kutta scheme manages the temporal terms. The level-set method ensures accurate tracking of the multiphase interface. To detail the transition from solid, non-reactive explosives to gaseous detonation products in the condensed charge's detonation reaction zone, the program burn model based on Zeldovich, von Neumann, Doering theory. The efficacy and accuracy of the incorporated program burn model and the multiphase interface capture method are employed through four benchmark tests, exhibiting excellent agreement with previously published data from alternative numerical methods or commercial software. In conclusion, applying the proposed method to four distinct engineering scenarios facilitates a comprehensive understanding of the inherent dynamics associated with detonation and shock wave generation and propagation.

Evaporative phase separation in polymer microdroplets with confinement and internal flow

Evaporation can drive initially homogeneous multiphase liquid systems out of equilibrium to induce liquid-liquid phase separation (LLPS). Here, we demonstrate evaporative LLPS in microfluidic-generated emulsion microdroplets of polymer mixtures. The evaporation produces distinct polymer phases within the microdroplets. Phase separation occurs even with polymer combinations that do not form distinct phases in sessile droplet evaporation. We attribute this aspect to evaporation-driven solutal Marangoni flows and the interface capture accumulating the nuclei at the apex where the evaporation rate is the maximum. A fast coalescence and growth of the accumulated polymer nuclei occurs inside the droplets, unlike the capillary-flow-induced spread-out of the nuclei along the contact line in sessile drops. Our method of evaporation of the droplet cluster may facilitate studying LLPS in volume-limited environments and have implications for understanding LLPS in biological systems.

Numerical simulation on underwater vertical launching process under effect of initial gas

The exiting-tube process is the basis and premise of the underwater vertical launching process. which is a multiphase, rapid, nonlinear, complex issue. Based on RANS method, combined the VOF multiphase flow model, high-resolution interface capture (HRIC) and overlapping grid (zero gap) technology, a complete mathematical model to describe the underwater exiting-tube process of the vehicle is established. The effects of the initial gas and launch parameters on the flow field and the load characteristics of the vehicle are systematically obtained. The research results indicated that: With the increase of the initial pressure of the initial gas, the force period of the vehicle increases, and the evolution process of the initial gas slows down. The initial gas pulsation period can be shortened by increasing the launch depth, while increasing the pressure at the shoulder of the vehicle and suppressing the natural cavitation of the vehicle. The increase of the lateral flow velocity will significantly increase the lateral force and deflection moment of the vehicle. The initial gas's pulsation process has a greater influence on the deflection moment and lateral force of the vehicle.

Endpoint Detection Based on Optical Method in Chemical Mechanical Polishing.

Endpoint detection is an important technology in chemical mechanical polishing (CMP), which is used to capture the material interface and compensate the variations of consumables and incoming wafer thickness. This paper aimed to apply optical detection in metal CMP. An in situ optical measurement system was developed for a 12-inch CMP tool. Kinematic analysis of the scanning trajectory of the laser device indicated the relative position relationship between the device and the wafer. Average optical data within the wafer described the material removal of metal CMP. Furthermore, optical data and location described the non-uniformity of the entire wafer surface. In this research, the polishing condition and the residual of the wafer edge are characterized by optical trace. Pauta Criterion is used to discriminate the inflexion point of the material interface. The results reveal that the interface capture is accurate and effective.

A coupled level-set and volume-of-fluid (CLSVOF) method for prediction of microgravity flow boiling with low inlet subcooling on the international space station

The present study is part of a series of NASA-supported investigations of flow boiling of n-perfluorohexane (n-PFH, C6F14) under microgravity on the International Space Station (ISS). The fluid physics and heat transfer characteristics of flow boiling with low inlet subcooling are explored using the Flow Boiling and Condensation Experiment (FBCE) (which is actual name of the test facility), the largest endeavor in microgravity two-phase research conducted to date. Experimental data are collected from the FBCE's Flow Boiling Module (FBM), which features a rectangular channel with 5.0-mm x 2.5-mm cross-section and 114.6-mm heated length. Results for three flow rates are used to explore the effects of mass velocity on flow structure and heat transfer characteristics in the absence of the body force. A Computational Fluid Dynamics (CFD) model is constructed to predict the measured FBM results. The CFD model employs the Coupled Level-Set and Volume-of-Fluid (CLSVOF) method, which is modified with improved interface capture and additional force terms in the momentum equation to determine the bubble dynamics more accurately. Validity of the CFD model is assessed in two ways, by comparing predictions against video-captured interfacial behavior and heat transfer data. The CFD model shows good ability to capture detailed evolution of the interfacial structure both across and along the flow channel, including bubble nucleation, growth, departure, and coalescence, as well as axial development of dominant flow patterns. Details of the flow structure are examined via axial development of both flow velocity and void fraction profiles. Similarly, heat transfer results are presented in terms of streamwise variations of both wall temperature and fluid temperature, which are also predicted accurately with the CFD model. Overall, this study proves the CFD model is an effective method for both design and performance assessment of flow boiling subsystems in space vehicles.

A peridynamic model for coupled thermo-mechanical-oxygenic analysis of C/C composites with SiC coating

The oxidation induced by coating cracking is a general failure mode of high-temperature composites such as C/C and C/SiC. However, this failure mode has not been fully investigated due to the lack of a method suitable for both crack simulation and oxidation interface capture. In this paper, a coupled thermo-mechanical-oxygenic peridynamic model is proposed for SiC-coated C/C composites in an oxidizing environment. The ordinary state-based peridynamics is extended to plane strain thermoelastic problems for orthotropic media to calculate the crack distribution. Cracks in the coating are modeled as oxygen diffusion channels and the peridynamic oxidation equation is developed to simulate the oxidation of the C/C substrate. Furthermore, the peridynamic non-Fourier heat transfer equation is employed to consider the finite thermal propagation speed and the model is validated by experimental results. Numerical examples are presented to investigate the oxidation failure after thermal shock, non-Fourier thermal shock fracture, and stress oxidation failure of SiC-coated C/C composites.

Generation of incident wave in two-phase flow simulation based on field decomposition

Field decomposition is an effective strategy for reducing numerical dissipation and dispersion. This strategy was employed by Li et al. (2021) to generate incident waves in two-phase flow simulations. This study attempts to improve previous methods in two ways. First, the density gradient in the additional source term, i.e. a delta function at the interface, is explicitly discretised. Although the explicit calculation simplifies the implementation, an additional pressure translation correction method is proposed to ensure numerical stability and accuracy. Second, the coupled level-set and volume-of-fluid method is used for interface capture. The calculation of the additional source term is more precise using the level-set function. The two proposed improvements result in a second-order spatial accuracy for the wave amplitude. A test on wave propagation over a flat bottom shows that the proposed method provides more accurate predictions of the wave amplitude compared with the previous method. In other test cases, including wave propagation over two-dimensional breakwater and three-dimensional shoal, the simulation results show good agreement with the experimental data.