ANN modeling for diffusivity of mushroom and vegetables using a fluidized bed dryer

Drying characteristics in terms of diffusivity were studied for mushrooms and different vegetables in a fluidized bed dryer.Drying characteristics with falling rate regime were computed for all the samples.Effective diffusivity of each sample was calculated.Mass transfer coefficients were determined.Mass transfer kinetics for drying of different samples was also found out.Correlations for the diffusivity of samples were developed by relating the experimentally observed data with the different system parameters on the basis of regression analysis.The developed correlations for effective moisture diffusivity of the samples are validated by artificial neural network(ANN) modeling.Finally calculated values of diffusivity obtained through both the methods are compared with the experimentally measured values which show a very good approximation thereby indicating the wide applicability of the developed correlations for industrial uses.     

One-dimensional unsteady-state flow in a rotating grid

The article discusses the problem of determining the dynamic characteristics of rotating and fixed grids in turbine-type machines. The grid is regarded as a linear system with distributed parameters. In problems involved with determining the stability of complex systems and in control problems, the dynamic characteristics of the turbine-type machines must be known. Such characteristics have been studied, for example, in [1]. However, in [1] the discussion is limited to a system with lumped parameters, which is admissible only at small perturbation frequencies. Article [2] discusses the problem of the propagation of vibrations in a flow with a constant mean velocity. In what follows, this problem is solved with a variable velocity of the mean motion. In addition, it is assumed that, with vibrations, there is removal or supply of mechanical energy.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 5, pp. 77–83, September–October, 1971.     

Mathematical model of axisymmetric quasi-steady-state heat and mass transfer in a gas hydrate reservoir

Two problems of axisymmetric gas (gas and water) flow through a reservoir which contains a heterogeneous mixture, namely, gas hydrate, ice (water), and gas, are considered. The exact solutions to the corresponding steady-state and quasi-steady-state nonlinear problems are found. The critical diagrams are constructed for various flow regimes. The characteristic distributions of the gas hydrate, ice (water), and gas saturations are shown for various values of the parameters.     

Two-fluid magnetohydrodynamic model of plasma flows in a quasi-steady-state accelerator with a longitudinal magnetic field

This paper reports the results of numerical studies of axisymmetric flows in a coaxial plasma accelerator in the presence of a longitudinal magnetic field. The calculations were performed using a two-dimensional two-fluid magnetohydrodynamic model taking into account the Hall effect and the conductivity tensor of the medium. The numerical experiments confirmed the main features of the plasmadynamic processes found previously using analytical and one-fluid models and made it possible to study plasma flows near the electrodes. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 50, No. 3, pp. 44–55, May–June, 2009.     

Modeling of blood rheological behavior in unsteady-state shearing flows

Issues of blood flow modeling under unsteady-state conditions at moderate shear rates are considered using a blood rheological model accounting both for the viscoelastic properties and the thixotropy caused by erythrocyte aggregation. The resulting shear stress versus time relations for single shear rate steps and the dependence of the complex viscosity components on the shear rate amplitude in oscillating shear flow show good qualitative correspondence with the experimental data reported in the literature.Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 6, pp. 26–30, November–December, 1995.     

Investigation of grain mass flow in a mixed flow dryer

The numerical modeling of grain drying is a topic of great relevance to post-harvest engineering. The required type of drying process depends on the quantity of grain to be dried and the required quality of the grain. The choice of the drying system depends on the operating parameters of the drying process. The granular flow pattern of the material exerts a significant influence on the drying process. Post-harvest drying of grain is essential for better storage, handling, and processing. Therefore, it is important to know the material behavior that controls the particle flow patterns of grain in the drying equipment to guarantee the product quality and to optimize the drying process conditions. The discrete element method （DEM） was applied to investigate the particle flow pattern of wheat through a mixed-flow dryer （MFD） without airflow, and the findings were compared with experimental results in this work. The investigations were performed using dry wheat with 14 wb% moisture content.     

A general solution of 3-D quasi-steady-state problem of a moving heat source on a semi-infinite solid

The well-known Jaeger–Rosenthal asymptotic particular solution for the quasi-steady-state problem of moving heat source is proven to be inconsistent with the source constant intensity, especially at dimensionless trailing edge coordinates vx/a < −2. The problem is reduced to an equivalent Poisson’s equation by exponential transformation of moving coordinate scale. Using the method of images, the fundamental solution is found; the temperature rise function exponentially approximates to 0 along negative semi-axis. The temperature field in a semi-infinite solid for the general case of surface power intensity distribution is expressed, using the found Green’s function. The cases of point, line, and circular heat sources are considered. The found fundamental solution and particular solution for moving circular heat source explain the phenomena of martensite transformation in low-carbon steel substrate at relatively low source velocity 1.7 cm/s.     

Numerical investigation of droplet pre-dispersion in a monodisperse droplet spray dryer

Monodisperse droplet spray dryers have great advantages in particle formation through spray drying because of their ability to produce uniform sized particles. Experimental analyses of this system have shown that droplets atomized through the piezoceramic nozzle need to be sufficiently well dispersed before entering the drying chamber to achieve sufficiently dried particles. However, the dispersion dynamics cannot be readily observed because of experimental limitations, and key factors influencing the dispersion state currently remain unclear. This study carried out numerical simulations for droplet dispersions in the dispersion chamber, which allow this important process to be visualized. The systematic and quantitative analyses on the dispersion states provide valuable data for improving the design of the dispersion chamber, and optimizing the spray drying operation.     

Comparison between structural and residual error formulations of an optimum design mechanism problem

Summary The model formulation of the objective function is one of the most important steps for solving an optimization problem. Generally, the objective function of an optimal design mechanism problem can be mathematically formulated either with structural or residual errors. In this paper we have conducted some comparisons between the results obtained by the structural and residual error formulations utilized in solving the optimum design of a four-bar linkage. The optimization problem is defined as a nonlinear least-squares problem. The damped Gauss-Newton algorithm is utilized for computing the solution, which ensures a local convergence for almost all nonlinear least-squares problems.

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Sommario La formulazione matematica della funzione obiettivo è uno degli aspetti più delicati nella soluzione di un problema di ottimizzazione. Generalmente la funzione obiettivo di un problema di progettazione ottima di un meccanismo può essere formulata sia mediante l'errore strutturale che residuo. In questo lavoro sono stati eseguiti dei confronti tra i risultati ottenuti mediante le due precedenti formulazioni, in riferimento al problema della progettazione ottima di un quadrilatero articolato. Il problema di ottimizzazione viene definito come un problema nonlineare ai minimi quadrati la cui soluzione numerica è ottenuta mediante l'algoritmo damped di Gauss-Newton.

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This paper was partially discussed at theII Congegno di Meccanica Computazionale, Roma, 1987.     

Similarity between unsteady-state conduction in a planar slab for short times and steady-state conduction in a uniform,straight fin

The principal goal of this study is two-fold. First, to elucidate an analogy between unsteady-state conduction in a planar slab for short times and steady-state conduction in a straight fin of uniform cross section. Second, to present approximate analytical solutions of the transient heat conduction equation for short times in a plane having a uniform initial temperature and subjected to a uniform surface temperature (Dirichlet boundary condition). Use was made of a hybrid computational method, theTransversal Method Of Lines (TMOL) to bypass the classical solution techniques for partial differential equations and exploit the physical analogy with the steady-state, heat conduction in a straight fin. The resulting quasi-steady, approximate analytical solution is very easy to employ and is suitable for obtaining quality short-time temperature distributions in the slab.     

Amorphous particle deposition and product quality under different conditions in a spray dryer

Deposition of amorphous particles, as a prevalent problem particularly in the spray drying of fruit and vegetable juices, is due to low-molecular weight sugars and is strongly dependent on the condition of the particles upon collision with the dryer wall. This paper investigates the condition of the amorphous particles impacting the wall at different drying conditions with the aim of elucidating the deposition mechanism and physical phenomena in the drying chamber. A model sucrose-maltodextrin solution was used to represent the low-molecular-weight sugar. Particle deposits were collected on sampling plates placed inside the dryer for analyses of moisture content, particle rigidity (using SEM) and size distribution. Moisture content was adopted as a general indicator of stickiness. Product particles collected at the bottom of the experimental dryer were found to have higher moisture than particle deposits on samplers inside the dryer. Moisture content profile in the dryer shows that apart from the atomizer region, where particles are relatively wet, particle deposits at other regions exhibit similar lower moisture content. At the highest temperature adopted in the experiments, particles became rubbery suggesting liquid-bridge formation as the dominant deposition mechanism. Further analysis on particles size distribution reveals a particle segregation mechanism whereby smaller particles follow preferentially to the central air stream while larger particles tend to re-circulate in the chamber, as predicted in past CFD simulation. The findings from this work will form the basis and provide validating data for further modeling of wall deposition of amorphous particles in spray drying using CFD.     

Experimental investigation of the characteristics of unsteady-state breakaway zones arising in a supersonic flow at a needle with a screen

An experimental investigation of unsteady-state flow in a breakaway zone arising at a needle installed ahead of a conical screen and ahead of a screen located in a cylindrical resonance cavity was made.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 4, pp. 98–104, July–August, 1977.     

Numerical modeling of large deformations in soil structure interaction problems using FE,EFG, SPH,and MM-ALE formulations

Present design practice for soil structure interaction (SSI) problems most frequently assumes linear elastic properties of the soil and disregards geometrical nonlinearities, treating the displacements as small. However, there are numerous problems that require a more advanced approach. This paper presents an application of such numerical approaches to modeling SSI problems in the presence of large soil deformations. Simulations using Lagrangian finite element, element-free Galerkin, smoothed particle hydrodynamics (SPH), and multi-material arbitrary Lagrangian Eulerian (MM-ALE) approaches were performed for two previously conducted experimental tests: (1) large-scale steel pad penetration into silty clay with sand and (2) standard cone penetration test performed on poorly graded sand. In this paper, the usefulness and the efficiency of the methods was assessed in terms of modeling robustness and computational cost. Results show that to some extent each of the utilized methods is able to capture large deformations. However, the most robust turned out to be SPH and MM-ALE methods as the only two that were successful in simulating both experiments.     

Comparison of the standard Euler-Euler and hybrid Euler-Lagrange approaches for modeling particle transport in a pilot-scale circulating fluidized bed

Particle transport phenomena in small-scale circulating fiuidized beds （CFB） can be simulated using the Euler-Euler, discrete element method, and Euler-Lagrange approaches. In this work, a hybrid Euler-Lagrange model known as the dense discrete phase model （DDPM）, which has common roots with the multiphase particle-in-cell model, was applied in simulating particle transport within a mid-sized experimental CFB facility. Implementation of the DDPM into the commercial ANSYS Fluent CFD package is relatively young in comparison with the granular Eulerian model. For that reason, validation of the DDPM approach against experimental data is still required and is addressed in this paper. Additional difficulties encountered in modeling fluidization processes are connected with long calculation times. To reduce times, the complete boiler models are simplified to include just the combustion chamber. Such simplifications introduce errors in the predicted solid distribution in the boiler. To investigate the conse- quences of model reduction, simulations were made using the simplified and complete pilot geometries and compared with experimental data. All simulations were performed using the ANSYSFLUENT 14.0 package. A set of user defined functions were used in the hybrid DDPM and Euler-Euler approaches to recirculate solid particles.