Models results Comparison of different approaches to turbulence for flow past a heated flat plate

This paper compares the results of the well-known Spalart-Allmares (SA) model and the two-fluid model for the flow around a heated flat plate. These models represent different approaches to the problem of turbulence. The SA model is a one-parameter model and a representative of the RANS models. This model is currently the most popular and is used to solve many practical problems. The advantage of this model is that its accuracy is quite good and simple for numerical implementation. Therefore, the SA model is included in almost all the codes of the software package. The two-fluid model used in this work has been developed recently [15]. In the pioneering works, it is shown that the basis for constructing this model is the possibility of representing a turbulent flow in the form of a heterogeneous mixture of two liquids. Therefore, this model is derived from the dynamics of two liquids. In these works, it is also shown that the developed two-fluid model is able to adequately describe complex anisotropic turbulences. The fundamental difference between these two models is that the SA model uses the substance transfer equation, while the two-fluid model uses the dynamics equation. To compare the two models, we compare their numerical results with the known experimental data. It is shown that the results of both models are close to each other and are in good agreement with the experimental data.

Characterizing macropore structure of agrosoddy-podzolic soil using computed tomography

The agrosoddy-podzolic soil (Eutric Albic Glossic Retisol (Abruptic, Loamic, Aric, Cutanic)) is typical for Moscow Oblast and is used for agricultural purposes, resulting in use of various agrochemicals and pesticides. The presence of macropores and cracks in such soils leads to preferential water and substance transfer and nonequilibrium conditions. Therefore, it is important to study the numerical characteristics of the pore space of soils to adjust mathematical models of substance transfer. Undisturbed soil monoliths 10 cm in diameter taken from Ap (from 0 to 30 cm) and E, BE horizons (from 30 to 50 cm) were investigated under the field moisture conditions and after saturation using the tomographic core analyzer RKT-180 with the resolution of 200 μm/pixel. Using the X-ray computer tomography, it has been established that the plough layer of the agrosoddy-podzolic soil contains over 7% of macropores larger than 1 mm, while the subsurface layer has a porosity of about 3%. After saturation, some of the inter-aggregate pores overlap, which leads to a decrease in the total porosity to 4% in the upper and 2% in lower horizons, as well as increase in the average pore diameter. The number of macropores determined by tomographic analysis is one third higher than the values calculated using pedotransfer functions for this soil. The data obtained in this paper are recommended for use in national scenarios of migration of substances (pesticides, agrochemicals, salts) in soils.

Development of mathematical model of extraction from lupine with cheese serum by applying low-frequency mechanical vibrations

It is noted that the model is designed to create the largest possible pressure change in the cheese whey in the extractor, since the rate of transfer of the target components is proportional to the pressure difference at the ends of the capillaries. The mathematical description of impregnation as the main or important auxiliary operation is given in detail. The equations for the impregnated part of the capillary, the ratio of impregnation rates at different times are given. From the above dependencies, the equation Washburne regarding the time of impregnation. The formulas for calculating the volume of extractant passed through the capillary, serum and forced out of the capillary air taking into account the viscous resistance of the latter. After integration of the equation of the speed of capillary impregnation of the obtained expression allows to estimate the final value of the impregnation in the initial stage. For different cases of capillary impregnation expressions are written at atmospheric pressure, vacuuming and overpressure. The introduction of dimensionless values allowed to simplify the solution and to obtain an expression for calculating the time of pore impregnation. The analysis of the equation of dimensionless impregnation time taking into account the application of low-frequency mechanical vibrations is made. It is noted that the processes of impregnation and extraction occur simultaneously, so the impregnation time is often neglected, which impoverishes the understanding of the physics of the process, reduces the accuracy of the calculation. Taking into account the diffusion unsteadiness of the process of substance transfer due to hydrodynamic unsteadiness, the equation containing the effective diffusion coefficient is written. The equation of unsteady diffusion for a spherical lupine particle in a batch extractor is supplemented with initial and boundary conditions. Taking into account the balance equation, the kinetic equation of the process is obtained. We studied the distribution of pores in the particle lupine along the radii and squares, the calculated value of the porosity of the particle. The values of De and Bi are determined by the method of graphical solution of the balance equation, the equation of kinetics and the parameters included in these equations. Conclusions on the work.

Cognition and Transfer of Contagious Substance in Hindu Himalayan Pilgrim Journeys

Ideas and practices about the transfer of substances believed to be charged with positive or negative properties are significant features of pilgrimages. Oftenneglected features of pilgrimages can be addressed by adopting concepts from the Cognitive Science of Religion. Religious pilgrimages are popular phenomena that are based on ritual interaction with culturally-postulated counterintuitive supernatural agents. This article partly refers to and analyses ethnographic data gathered during fieldwork among Hindu pilgrims in Nepal and Tibet. The pilgrims received items to take home from the pilgrimage site but they also left other items there. This constituted a transfer of contagious substances that carried blessings and supernatural agency/power and it enabled the discharging of defilement, sin or evil. The aim of this article is to show how the beliefs about substance transfer are shaped by cultural institutions and by cognitive selection pressures related to psychological essentialism and concepts of agency and contagion relating to counterintuitive agents.

Numerical Simulation Model for FSW Employing Particle Method – Effect of Tool Angle on Fluid Motion

The friction stir welding (FSW) is known as non-melting joining. It used widely in the field of industry. Numerical analysis models for FSW also have been developed. In these models, the most frequently used method is a grid method (finite element method or finite difference method). However it is difficult or troublesome to calculate the advective term both for momentum and temperature employing these methods. It is also difficult to calculate the big deformation of the material's free surface. Moreover, complex process is required to analyze the dissimilar joining with respect to dealing with substance transfer. In this paper, to avoid these difficulties, particle method is adopted for FSW simulation. In particle method, advective term, substance transfer, and surface deformation are calculated automatically mainly because that Lagrangian approach is used. To verify the effectiveness of this method, fluid motion around the tool is examined by particle trace. As a result, relations between the rotating speed of the tool and area of plastic flow is evaluated.