Design of an experimental set up for convective drying: experimental studies at different drying temperature

An experimental setup is designed to investigate the convective drying of moist object experimentally. All the design data, components of setup, materials and specifications are presented. Transient moisture content of a rectangular shaped potato slice (4 × 2 × 2 cm) is measured at different air temperatures of 40, 50, 60 and 70 °C with an air velocity of 2 m/s. Two different drying rate periods are observed. Results are compared with available results from literature.     

Comparison of experimental and theoretical results for the hydrostatic bulging of circular sheets

Incremental and total-strain theories have recently been used by the authors to obtain numerical solutions for the hydrostatic bulging of circular diaphragms. These solutions have incorporated the effects of anisotropy in the direction of the thickness of the sheet. This investigation was conducted to obtain test data on aluminum-killed steel sheets which contain the above mentioned anisotropy and to compare these data with the predictions of the incremental and total-strain theories solutions. The results show that the incremental theory is in better agreement with test data than the total-strain theory. Strain-path data for several volume elements shows that each volume element follows an approximately proportional strain path. However, the strain paths obtained from the total-strain theory are in gross disagreement with the data.     

Turbulent pipe flow manipulation: some experimental and computational results for single manipulator rings

The effect on developing turbulent pipe flow of blade manipulator devices has been investigated both experimentally and computationally with a view towards reducing pipeline transmission losses. Wall pressure and mean axial velocity profiles have been obtained for nine manipulator configurations. Numerical calculations have been performed for two of these manipulator configurations using a finite volume method that incorporates a low Reynolds number model of turbulence. The results suggest that nett drag reduction may be possible in this flow although at present this seems unlikely. It remains to be answered whether any benefit can be achieved in fully developed flow for which both experimental and computational studies are now underway.     

带尾翼翻转型爆炸成形弹丸试验研究

采用多点起爆方式,设计了带尾翼翻转型爆炸成形弹丸(EFP)试验装置。用X光和SVR数字相机拍摄了EFP的外形和速度;用多层纸靶测试了EFP在不同飞行距离时的飞行姿态;进行了EFP穿靶能力的检验;并利用泡沫和锯末进行了EFP的软回收。由试验结果知,EFP速度为1.56～1.72km/s,长径比最大达到了3.69,由药型罩转变为EFP的质量转换率达到了98%,EFP具有较好的尾翼结构和气动稳定外形。该EFP能穿透厚度为50mm的厚钢靶或厚度为6mm、间距各为1m的5层薄钢靶。     

Flow pattern transition for gas-liquid flow in horizontal and inclined pipes. Comparison of experimental data with theory

Experimental measurements of flow patterns for gas-liquid flow in inclined pipes are reported. The results compare well with a recently published theory for the prediction of flow patterns in horizontal and inclined pipes (Taitel & Dukler 1976).     

Comparison with experimental data of computer simulations of the expansion of spark breakdown in air

Calculated results obtained earlier by means of a computer in the simulation of the expansion of spark breakdown in air are compared with the data of an experiment.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 4, pp. 182–184, July–August, 1979.I thank V. P. Korobeinikov for supplying the originals of the photographs of [2].     

Theoretical models of vegetable drying by convection

The results of experiments are often used to model empirical phenomena. However, the term model is applied in various meanings. A model is usually treated as an abstract formal structure that can replace a material system considered as original, in respect to the aim of modeling. Certain formal structures may be treated as theoretical models of empirical phenomena. On the other hand, a material system can also be referred to as a model of an abstract system, e.g., a set of equations or a hypothesis. Such a material system, if it is a distinct empirical interpretation of the language of a given theory, is then called a real model. Both kinds of models are applied in drying technology, but the second one is more inventive. The mathematical structures are treated as empirical formulae or as theoretical models properly derived from true or legitimated promises of a given theory. The advantages of some mathematical theoretical models of drying processes versus empirical formulae are discussed. The creation of new mathematical theoretical models of convection drying kinetics of some shrinking solids is presented and analyzed. One of the above models was also hypothetically suggested for modeling the drying of cut vegetables in a fluidized-bed. Despite its initial acceptance due to peer empirical justification on cut carrots and celery, it still requires further theoretical analysis. Other models indicated here are theoretical models of vegetable drying in a tunnel drier. These models are created by deduction from laws of heat and mass transfer theory and its basic equations. XI Polish Drying Symposium, Poznań, Poland, 13–16 September 2005.     

A time-dependent numerical analysis of flow in a mechanical heart valve: Comparison with experimental results

There is a great need to fabricate heart valves that have similar haemodynamic properties with the natural ones. Towards this goal, we examine the dynamics of fluid flow in a mechanical heart valve with one leaflet. The fluid is incompressible and Newtonian and the leaflet is a neo-Hookean material. The Arbitrary Lagrangian Eulerian method is used to model the fluid-leaflet interaction, and the system of equations is solved using the Finite Element method. The pseudo solid approach along with a set of algebraic equations are used to deform the mesh, while care is taken to avoid remeshing of the domain, at the moment of valve closure. The computational results are compared against the experimental results, and we find an excellent agreement for the time period of valve closure, the time the valve is fully opened, and the value of the maximum valve opening angle. This study indicates that the present model is capable of describing the valve dynamics in physiological geometries.     

Review of wetting and drying algorithms for numerical tidal flow models

A review of wetting and drying (WD) algorithms used by contemporary numerical models based on the shallow water equations is presented. The numerical models reviewed employ WD algorithms that fall into four general frameworks: (1) Specifying a thin film of fluid over the entire domain; (2) checking if an element or node is wet, dry or potentially one of the two, and subsequently adding or removing elements from the computational domain; (3) linearly extrapolating the fluid depth onto a dry element and its nodes from nearby wet elements and computing the velocities; and (4) allowing the water surface to extend below the topographic ground surface. This review presents the benefits and drawbacks in terms of accuracy, robustness, computational efficiency, and conservation properties. The WD algorithms also tend to be highly tailored to the numerical model they serve and therefore difficult to generalize. Furthermore, the lack of temporally and spatially defined validation data has hampered comparisons of the models in terms of their ability to simulate WD over real domains. A short discussion of this topic is included in the conclusion. Copyright © 2012 John Wiley & Sons, Ltd.     

Discrete velocity models with small data

Summary It is shown that all discrete velocity models conserving mass, momentum and energy and without self-interactions have global, uniformly bounded solutions for small enough initial data with compact support. This is interesting because of a recent example with small data inL ¹ L whose solution is not bounded, and shows the unboundedness is due to mass being fed in from infinity.

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Sommario Si dimostra che tutti i modelli con velocità discretizzate che conservano la massa, la quantità di moto e l'energia e senza autointerazioni hanno soluzioni globali, uniformemente limitate per dati iniziali a supporto compatto e abbastanza piccoli. Questo è interessante a causa di un esempio recente con dati piccoli inL ¹ L la cui soluzione non è limitata e mostra che l'illimitatezza è dovuta ad un flusso di massa dall'infinito.

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Research supported by the Natural Science and Engineering Research Council Canada under Grant No. A8560.     

Facilities on board the “Foton” automatic satellite and some experimental results

The characteristics of the facilities and the experimental conditions are described and some scientific results of experiments on single crystal growth in space relating to the hydrodynamic and heat and mass transfer processes are presented.Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 5, pp. 37–45, September–October, 1994.     

Generalized plasticity and some models for geomechanics

In this brief note, we have (a) introduced a very general form of plasticity definition; (b) indicated several types of models used for monotonic and transient loading of soil-like materials, which do not depend on time effects. The details of each form are given elsewhere but we believe that the new framework provides an easier and more general interpretation of a variety of behaviour form.     

Improved approximations for some polymer extension models

We propose approximations for force-extension dependencies for the freely jointed chain (FJC) and worm-like chain (WLC) models as well as for extension-force dependence for the WLC model. Proposed expressions show less than 1 % relative error in the useful range of the corresponding variables. These results can be applied for fitting force-extension curves obtained in molecular force spectroscopy experiments. Particularly, they can be useful for cases where one has geometries of springs in series and/or in parallel where particular combination of expressions should be used for fitting the data. All approximations have been obtained following the same procedure of determining the asymptotes and then reducing the relative error of that expression by adding an appropriate term obtained from fitting its absolute error.     

On the experimental determination of yield surfaces and some results of annealed 304 stainless steel

Factors affecting the experimental determination of yield surfaces are discussed. They include the elastic moduli and the zero offset strain, the strain domain used to determine the yield stress, the probing path, and the strain rate of probing. To obtain yield surfaces consistently, it is necessary to account for these factors. The initial and subsequent yield surfaces of annealed AISI type 304 stainless steel have been experimentally determined in the axial-torsional stress space. Three loading paths have been studied. They are a pure axial path, a pure torsional path, and a proportional axial-torsional path. Each path includes loading, unloading, reloading, and the cyclically steady state.     

Elastoplastic models to describe experimental data on the spallation fracture under impact of plates

The processes of irreversible dynamic deformation and spallation fracture under plane impact of plates are numerically studied. The following two models for the behavior of the materials of the plates are used: a model of a damageable elastoplastic medium and a dislocation model. The computations were performed with the use of the TIS-1D software complex based on the method of separation into physical processes, the finite volume method, and moving Eulerian grids.     

Methods for generalization of experimental results in terramechanics

Due to the extreme variability of soils and different tillage and settling conditions, measurements made under a single set of conditions have little practical applicability under arbitrary conditions. Results of more general usefulness require systematic measurements to be carried out over suitable ranges of the main influencing variables. The results can then be processed to obtain dimensionally homogeneous equations, i.e. similarity equations. This method was first proposed a century ago (Buckingham, 1914) [1], and one year later, Nusselt published a fundamental paper showing how it could be used to generalize the results of heat transfer experiments and to plan new experiments (Nusselt, 1915) [2]. The method is based on the postulate that all physical processes can be expressed as relationships among dimensionless parameters, and it specifies how to find those parameters. We describe new experimental results and generalize the results using dimensional analysis to obtain similarity plots and equations that are generally applicable within the feasible range of variables.     

Stability of a supersonic flat-plate wake (Comparison of numerical and experimental results)

The stability of the wake downstream of a plat plate with a blunt trailing edge is numerically investigated at a supersonic freestream velocity. The calculated stability characteristics are compared with the experimental data.     

Comparison of experimental data with the numerical simulation of planar entry flow: Role of the constitutive equation

The goal of this research was to determine whether there is any interaction between the type of constitutive equation used and the degree of mesh refinement, as well as how the type of constitutive equation might affect the convergence and quality of the solution, for a planar 4:1 contraction in the finite eiement method. Five constitutive equations were used in this work: the Phan-Thien–Tanner (PTT), Johnson–Segalman (JS), White–Metzner (WM), Leonov-like and upper convected Maxwell (UCM) models. A penalty Galerkin finite element technique was used to solve the system of non-linear differential equations. The constitutive equations were fitted to the steady shear viscosity and normal stress data for a polystyrene melt. In general it was found that the convergence limit based on the Deborah number De and the Weissenberg number We varied from model to model and from mesh to mesh. From a practical point of view it was observed that the wall shear stress in the downstream region should also be indicated at the point where convergence is lost, since this parameter reflects the throughput conditions. Because of the dependence of convergence on the combination of mesh size and constitutive equation, predictions of the computations were compared with birefringence data obtained for the same polystyrene melt flowing through a 4:1 planar contraction. Refinement in the mesh led to better agreement between the predictions using the PTT model and flow birefringence, but the oscillations became worse in the corner region as the mesh was further refined, eventually leading to the loss of convergence of the numerical algorithm. In comparing results using different models at the same wall shear stress conditions and on the same mesh, it was found that the PTT model gave less overshoot of the stresses at the re-entrant corner. Away from the corner there were very small differences between the quality of the solutions obtained using different models. All the models predicted solutions with oscillations. However, the values of the solutions oscillated around the experimental birefringence data, even when the numerical algorithm would not converge. Whereas the stresses are predicted to oscillate, the streamlines and velocity field remained smooth. Predictions for the existence of vortices as well as for the entrance pressure loss (ΔP_ent) varied from model to model. The UCM and WM models predicted negative values for ΔP_ent.