Milk Crown Research Articles

A volume of fluid method algorithm for simulation of surface tension dominant two-phase flows

In this article, a two-phase flow algorithm that uses an explicit Adams–Bashforth scheme coupled with volume of fluid (VOF) method in a uniform staggered Cartesian grid for surface tension dominant simulation is presented. The interface reconstruction procedure is implemented using the Weighed Linear Interface Calculation (WLIC) algorithm. The level set (LS) function instead of VOF function is adopted for calculation of not only the interface normal vectors in the WLIC algorithm but also the surface tension terms in the Navier–Stokes equations. This VOF method is compared with LS method and other experiment results in the literature for vortex deforming, milk crown, droplet impacting into deep liquid pool and bubble bursting at a free surface problems to show whether mass can be well conserved and breaking and merging phenomena can be accurately simulated.

Chemical and fermentative characteristics of agricultural byproducts and their mixtures with roughages incubated with rumen fluid from slaughtered dromedaries

In pursuit of novel strategies aimed to promote animal production while exploiting agricultural residues, using the dromedary camel rumen fluid degradation capabilities combined with a gas production (GP) technique approach, we investigated the in vitro kinetic parameters and some physical and chemical characteristics of three agro-industrial byproducts (AIBP) and their mixtures with three roughages. Chemical composition, buffering capacity, apparent degradability, pH, and in vitro GP kinetic parameters were evaluated for citrus pulp, tomato peels, apple pomace, their mixtures (50:50 % DM basis) with milk thistle, crown daisy, and polyphyte hay. GP of AIBP ranged from 200 to 240 mL/g DM. Roughages produced significantly less gas whereas mixtures gave intermediate amounts of gas. Gas from AIBP evolved with significantly (P < 0.05) shorter lag time (0.33 h) compared with roughages and mixtures. Mixing roughages with AIBP significantly (P < 0.05) increased the initial and final pH. The buffering capacity significantly increased with some mixtures and decreased with some others. In conclusion, ruminal fluid from slaughtered dromedaries, like the conventional bovine inoculum, fermented the major plant polymers and can be used in in vitro degradability trials. Rapidly fermentable AIPB mixed with roughages can improve some nutritional aspects, providing dietary fiber and correcting some in vitro kinetic parameters.

High-performance computing in simulation of milk crown

A high-performance computation with billion scales of the explicit moving particle simulation method is successfully performed for the milk crown phenomena. Through the validation study regarding the size of the particle, it is confirmed that the appropriate size for realizing milk crown should be smaller than 0.05 mm. The simulation results are rather in good agreement with the experimental ones. Namely, the tiny droplet at the tip of the milk crown, which is called the spike, and the generation of spear-type splash, which is the secondary splash formed after the milk crown, are realized well as seen in the experiment.

Three-dimensional numerical computation of gas-liquid two-phase flow under pseudo microgravity environment using a superconducting electromagnet

By using the strong magnetic field generated by a superconducting electromagnet, theoretically it is possible to produce the pseudo microgravity environment on the ground. The final goal of this research is to obtain knowledge of fluid control under a strong magnetic field using a superconducting electromagnet. In this study, in order to examine a method for accurate CFD computation, we carried out computation for a gas-liquid two-phase flow under a strong magnetic field. A milk crown phenomenon inside the bore of superconducting electromagnet is studied. The liquid is assumed to be an aqueous gadolinium nitrate solution (15%). The CLSVOF method is used for the computation of the two-phase flow and the HSMAC method is used for the pressure correction. We evaluate how much the interior of the superconducting electromagnet is in a pseudo microgravity environment by using the equation expressing the gravity level. In addition, in order to speed up the calculation, GPU parallel computation is performed, realizing about 22 times faster than CPU single computation. As a result, we succeeded in investigating a method for computation a gas-liquid two-phase flow in a strong magnetic field.

Validation of an improved lattice Boltzmann method for incompressible two-phase flows

In this communication, in order to validate a two-phase lattice Boltzmann method proposed by Inamuro et al. [14] furthermore, we simulate two-phase Poiseuille flows with density ratios of 50 and 1000 and a milk crown with density ratio of 800. In the simulations of two-phase Poiseuille flows, the computed results are compared with the analytical solution in good agreement. In the simulations of a milk crown, the droplet splashing from a crown sheet is clearly computed. Also, the crown radius evolution agrees well with theoretical predictions.

An improved lattice Boltzmann method for incompressible two-phase flows with large density differences

We propose a new lattice Boltzmann method (LBM) for two-phase fluid flows with high density ratios by improving Inamuro et al.’s method [13] without solving the pressure Poisson equation. In the proposed method, we use the lattice kinetic scheme (LKS, an extended scheme of LBM) in the same way as Inamuro et al.’s method. The velocity and pressure fields are computed by using a single equilibrium distribution function and by adjusting the speed of sound in a high density region to satisfy the incompressible continuity equation even for high density ratios. In addition, an improved LKS is used for eliminating dissipation errors, and the continuous surface force (CSF) model is used for modeling interfacial tension of thin interfaces accurately. In order to show the validity of the method, we apply the method to the simulations of a stationary drop, binary droplet collision, rising bubbles, and the impact of a drop on a thin liquid film (a milk crown). In a stationary drop, pressure and density profiles are computed, and the effect of sound speed on time evolution of the pressure field in the drop is illustrated. The stable computations can be performed for high density ratios up to 855. In the simulations of a binary droplet collision and rising bubbles, the computed results by the proposed method are compared with those by Inamuro et al.’s method in good agreement. Also, the computation time of the proposed method is about 50 times faster than that of Inamuro et al.’s method . In the simulation of a milk crown, the time evolution of the crown radius is in good agreement with theoretical predictions.

高速形状計測のための複数光路格子投影装置の開発

A multiple optical paths grating projector for high-speed shape measurement is proposed in this paper. The prototype projector has three optical paths produced with half mirrors. A grating plate and an LED device are placed on the end of each optical path. The image of the grating plate is projected onto the object by a focal lens when the corresponding LED lights up. Three grating plates are placed on the respective optical path. The positions of the grating plates are adjusted in such a way that the projected grating patterns are shifted at intervals of 1/3 periods of the grating pitch. This projector can shift the phase of the projected grating patterns quickly with switching the position of lighted LED. The evaluated maximum response speed of phase shifting using this projector is 600 kHz. High-speed shape measurements are performed with a high-speed camera and this projector. As experimental results, shape measurement of a milk crown was performed in 5 kHz with phase-shifting speed of 15 kHz and shape measurement of a rotating fan was performed in 10 kHz with phase-shifting speed of 30 kHz. It was demonstrated that the proposed multiple optical paths grating projector was available for high-speed shape measurement.

Modelling of surface tension force for free surface flows in ISPH method

PurposeThe purpose of this paper is to show how a surface tension model and an eddy viscosity based on the Smagorinsky sub‐grid scale model, which belongs to the Large‐Eddy Simulation (LES) theory for turbulent flow, have been introduced into ISPH (Incompressible smoothed particle hydrodynamics) method. In addition, a small modification in the source term of pressure Poisson equation has been introduced as a stabilizer for robust simulations. This stabilization generates a smoothed pressure distribution and keeps the total volume of fluid, and it is analogous to the recent modification in MPS.Design/methodology/approachThe surface tension force in free surface flow is evaluated without a direct modeling of surrounding air for decreasing computational costs. The proposed model was validated by calculating the surface tension force in the free surface interface for a cubic‐droplet under null‐gravity and the milk crown problem with different resolution models. Finally, effects of the eddy viscosity have been discussed with a fluid‐fluid interaction simulation.FindingsFrom the numerical tests, the surface tension model can handle free surface tension problems including high curvature without special treatments. The eddy viscosity has clear effects in adjusting the splashes and reduces the deformation of free surface in the interaction. Finally, the proposed stabilization appeared in the source term of pressure Poisson equation has an important role in the simulation to keep the total volume of fluid.Originality/valueAn incompressible smoothed particle hydrodynamics is developed to simulate milk crown problem using a surface tension model and the eddy viscosity.

F506 OpenFOAMを用いたミルククラウンの解析(F5.オープンソースCAEの新展開,フォーラム)

F506 OpenFOAMを用いたミルククラウンの解析(F5.オープンソースCAEの新展開,フォーラム)

Liquid Atomization Induced by Pulse Laser Reflection underneath Liquid Surface

We observed a novel effect of pulse laser reflection at the interface between transparent materials with different refractive indices. The electric field intensity doubles when a laser beam is completely reflected from a material with a higher refractive index to a material with a lower index. This effect appreciably reduces pulse laser ablation threshold of transparent materials. We performed experiments to observe the entire ablation process for laser incidence on the water–air interface using pulse laser shadowgraphy with high-resolution film; the minimum laser fluence for laser ablation at the water–air interface was approximately 12–16 J/cm2. We confirmed that this laser ablation occurs only when the laser beam is incident on the water–air interface from water. Many slender liquid ligaments extend like a milk crown and seem to be atomized at the tip. Their detailed structures can be resolved only by pulse laser photography using high-resolution film.

A Numerical Method for Free-Surface Flows and Its Application to Droplet Impact on a Thin Liquid Layer

We propose a simple and practical numerical method for free surface flows. The method is based various methods, the level set method of an interface capturing method, the THINC/WLIC (tangent of hyperbola for interface capturing/weighed line interface calculation) method of an interface tracking method, the CIP-CSL (constrained interpolation profile conservative semi-Lagrangian) method of a conservation equation solver, VSIAM3 (volume/surface integrated average based multi-moment method) of a fluid solver and the CSF (continuum surface force) model of a surface force model. The level set method and the THINC/WLIC method are combined by using a CLSVOF (coupled level set and volume-of-fluid) framework. The method is applied to Rayleigh-Taylor instability with surface tension force and droplet impact on a thin liquid layer (milk crown).

Study of Milk Crown

Study of Milk Crown

The Constrained Interpolation Profile Method for Multiphase Analysis

We present a review of the constrained interpolation profile (CIP) method that is known as a general numerical solver for solid, liquid, gas, and plasmas. This method is a kind of semi-Lagrangian scheme and has been extended to treat incompressible flow in the framework of compressible fluid. Since it uses primitive Euler representation, it is suitable for multiphase analysis. The recent version of this method guarantees the exact mass conservation even in the framework of a semi-Lagrangian scheme. We provide a comprehensive review of the strategy of the CIP method, which has a compact support and subcell resolution, including a front-capturing algorithm with functional transformation, a pressure-based algorithm, and other miscellaneous physics such as the elastic–plastic effect and surface tension. Some practical applications are also reviewed, such as milk crown or coronet, laser-induced melting, and turbulent mixing layer of liquid–gas interface.

Stability of a growing end rim in a liquid sheet of uniform thickness

We study the stability of a viscous liquid layer of uniform thickness subject only to viscous stresses and surface tension. We show that the growing cylindrical end rim does not typically break into droplets for moderate wavelengths. Thus, other mechanisms are needed to cause the instabilities, which, for instance, lead to the famous milk crown. The problem remains open for very large wavelengths.