Numerical Simulation of Three-Dimensional Dendrite Movement Based on the CA–LBM Method

At present, the calculation of three-dimensional (3D) dendrite motion using the cellular automata (CA) method is still in its infancy. In this paper, a 3D dendrite motion model is constructed. The heat, mass, and momentum transfer process in the solidification process of the alloy melt are calculated using a 3D Lattice–Boltzmann method (LBM). The growth process for the alloy microstructure is calculated using the CA method. The interactions between dendrites and the melt are assessed using the Ladd method. The solid–liquid boundary of the solute field in the movement process is assessed using the solute extrapolation method. The translational velocity of the equiaxed crystals in motion is calculated using the classical mechanical law. The rationality of the model is verified and the movement of single and multiple 3D equiaxed crystals is simulated. Additionally, the difference between 3D dendrite movement and two-dimensional (2D) dendrite movement is analyzed. The results demonstrate that the growth of moving dendrites is asymmetric. The growth velocity and falling velocity of the dendrite in the 3D model are faster than that in 2D model, while the simulation result is more realistic than that of the 2D model. When multiple dendrites move, the movement direction of the dendrites will change due to the merging of flow fields and other factors.

Molecular dynamics study on characteristics of reflection and condensation molecules at vapor–liquid equilibrium state

The kinetic boundary condition (KBC) represents the evaporation or condensation of molecules at the vapor–liquid interface for molecular gas dynamics (MGD). When constructing the KBC, it is necessary to classify molecular motions into evaporation, condensation, and reflection in molecular-scale simulation methods. Recently, a method that involves setting the vapor boundary and liquid boundary has been used for classifying molecules. The position of the vapor boundary is related to the position where the KBC is applied in MGD analyses, whereas that of the liquid boundary has not been uniquely determined. Therefore, in this study, we conducted molecular dynamics simulations to discuss the position of the liquid boundary for the construction of KBCs. We obtained some variables that characterize molecular motions such as the positions that the molecules reached and the time they stayed in the vicinity of the interface. Based on the characteristics of the molecules found from these variables, we investigated the valid position of the liquid boundary. We also conducted an investigation on the relationship between the condensation coefficient and the molecular incident velocity from the vapor phase to the liquid phase. The dependence of the condensation coefficient on the incident velocity of molecules was confirmed, and the value of the condensation coefficient becomes small in the low-incident-velocity range. Furthermore, we found that the condensation coefficient in the non-equilibrium state shows almost the same value as that in the equilibrium state, although the corresponding velocity distribution functions of the incident velocity significantly differ from each other.

Exploration of Temperature-Dependent Thermal Conductivity and Diffusion Coefficient for Thermal and Mass Transportation in Sutterby Nanofluid Model over a Stretching Cylinder

This declaration ponders the impacts of Joule warm, separation, and warming radiation for the progression of MHD Sutterby nanofluid past over an all-inclusive chamber. The wonder of warmth and mass conduction is demonstrated under warm conductivity relying upon temperature and dispersion coefficients individually. Besides, the conventional Fourier and Fick laws have been applied in the outflows of warm and mass transport. The control model comprising of a progression of coupled incomplete differential conditions is changed over into a standard arrangement of nonlinear coupled differential conditions by reasonable likeness changes. The subsequent arrangement of articulations is systematically treated through an ideal homotopic method. The impacts of various dimensionless stream boundaries on the speed, temperature, and focus fields are delineated through diagrams. The range of some parameters involved is assumed for the convergent solution as 0 < R e < 10 , 0 < P r < 6.5 , 0 < E c < 40 , 0 < R d < 1.5 , 0 < S 1 < 0.5 , 0 < S 2 < 0.5 , 0 < L e < 0.5 , 0 < N t < 2.5 , and 0 < N b < 2.0 . The patterns of skin friction coefficient, local Nusselt, and Sherwood numbers are examined via bar charts. The principle consequence of the proposed study is that the decay of the speed for the Sutterby liquid boundary, the deterioration of the variable warm conductivity, the temperature, and the radiation increase the framework temperature. The delineation boundaries show the opposite conduct for the temperature and fixation outskirts layers.

Patterns of non-traditional thermodynamic functions ΔrG0/n and ΔfG0(averaged) changes for cobalt minerals

This article considers general principle of predicting the difference in the reactivity of minerals and solvents in the conditions of their interaction at the interface between solid and liquid for cobalt minerals in the processing of mineral raw materials. The ideas of new properties of chemical affinity which allowed to carry out the forecast of a choice of efficiency of action of the dissolving reagent for opening of hardly soluble minerals of cobalt and the forecast of consecutive passing of the competing reaction proceeding on solid-liquid boundary at processing of mineral raw materials by a hydrochemical method at the level of an electron are stated. Previously unknown pattern of change the effectiveness of the solvent of the reagents and the sequence of passing a competing reaction was established, namely, that the effectiveness of the solvent of the reagent and the sequence of passing the subsequent reaction naturally varies with the calculated values given new chemical affinity (DrG0/n). It is practically proposed to use the average atomic energy of the formation of solids ΔfG0(averaged) and calculated value of the new chemical affinity DrG0/n to create scientific basis for the opening of cobalt minerals contained in the mineral raw materials with the least time.

Tests of Acoustic Target Strength and Bubble Dissolution Models Using a Synthetic Bubble Generator

To test methods used for converting observations of acoustic backscatter to estimates of the volume and transport of free gas escaping the seabed, a bubble generator has been constructed and used at sea. The bubble generator creates individual bubbles of the sizes commonly associated with methane seeps, 1–5-mm radii, which can be released at preplanned rates. The bubble generator was deployed off the coast of New Hampshire at a depth of 55 m, and acoustic backscatter between 16 and 24 kHz was collected from a shipboard echo sounder while transiting over the rising bubbles. Bubble sizes and compositions (either Ar or N2) were known at the source. A model for bubble evolution, accounting for changes in bubble size and composition due to hydrostatic pressure and gas diffusion across the gas–liquid boundary, was coupled with an acoustic target strength (TS) model to generate predictions of the acoustic backscatter from bubbles that had risen to different depths. These predictions were then compared with experimental observation. Good agreement between prediction and observation was found in most cases, with the exception of the largest (4 mm) gas bubbles at depths of 30 m or less. The exact cause of this bias is unknown, but may be due to incorrect assumptions in models for the bubble TS, rise velocity, or mass transfer rate.

Alternatif Penambahan Limbah Batu Kapur dan Abu Sekam Padi sebagai Bahan Stabilisasi Tanah di Kecamatan Bangorejo Kabupaten Banyuwangi

Ekspansif land having the nature of flower and dwindle, high level ground water level when the rains and will do chap when dry season. The building can experience barstly of wall and degradation of structure as in area Bangorejo Banyuwangi. So that require to be conducted by stabilization to land by adding density and inactive material, debasing surface, changing ugly land, and also add other material so that happened reaction of chemically or nature to the land. In this research is conducted by addition of materials mixture Waste Limestone and Dusty Chaff to the ekspansif land, so that can improve the nature of existing land. Sampel taken away from Bangorejo Sub-Province Banyuwangi which consist of 15 dried land example with each composition 3 example to 5 treatment phase. Result of data analysis show the existence of repair of land characteristic, that is water rate, specific gravity, liquid boundary, plastis boundary and plasticity index of land go down, so that yield low add-dwindle potency of land. At addition mixture of limestone waste 20 % and dusty chaff of paddy 5 % obtaining optimal result, that is yield strength become 0,281 kg/cm2 and energy support of land become 9,378 ton/m2.

Visualization of Microbubble Distribution Inside Turbulent Boundary Layer Along Flat and Curved Solid Surfaces

How microbubbles behave inside turbulent boundary layers are investigated experimentally. Water electrolysis is applied for generation of microbubbles in water, of which electrodes are flash mounted on the solid wall in the upstream section of the measurement area. Four kinds of solid surfaces are examined to compare the microbubble distribution. For a circular cylinder of the radius R = 22 mm at Re = 5,000, we found that microbubbles depart from the surface earlier than the liquid boundary layer. For an elliptic cylinder of the curvature radius of R = 60 mm and a hydrofoil of NACA0040, microbubble injection made the separation point move downstream in the range of 9,000 &lt; Re &lt; 90,000. To compare the effect with the cases of flat solid surfaces (R = infinity), we visualized three-dimensional distribution of microbubbles with color-coded volumetric illumination technique. The result has shown formation of microbubble clusters intermittently, which has Coulomb potential due to negative electric charge on bubble interfaces.