Use Of Small-scale Models Research Articles

Experimental Simulation of Deformation Effect Propagation Due to Explosion on the Surface of a Small-Scale Model

The use of small-scale models is an important area of research today. An investigation is conducted on the response of a small-scale model’s vibrating surface. For this model, a small-scale surface explosion is used for loading. According to the article, the methodology includes procedures, model development, the explosive materials used, measurement and evaluation methods, software, and the technique used. Signal processing and response evaluation rely on a scientific method—the backward Fourier-transform principle—for frequency filtering. In this study, the simulation results are used to confirm the basic physical properties of the viscoelastic system. It is primarily investigated whether wave processes are confirmed on the new material. In terms of single wave propagation, the results summarize the characteristics of these waves (attenuation, velocity of propagation, etc.). Conclusions are targeted at the possibility of correlating three types of results: small-scale simulations, numerical simulations, and a real full-scale experiment.

Applying multiple approaches to deepen understanding of mixing and mass transfer in large-scale aerobic fermentations.

Different methods are used at Corteva® Agriscience to improve our understanding of mixing in large-scale mechanically agitated fermentors. These include (a) use of classical empirical correlations, (b) use of small-scale models, and (c) computational fluid dynamics (CFD). Each of these approaches has its own inherent strengths and limitations. Classic empirical or semi-empirical correlations can provide insights into mass transfer, blending, shear, and other important factors but are dependent on the geometry and condition used to develop the correlations. Laboratory-scale modelling can be very useful to study mixing and model the effect of heterogeneity on the culture, but success is highly dependent on the methodology applied. CFD provides an effective means to accelerate the exploration of alternative design strategies through physics-based computer simulations that may not be adequately described by existing knowledge or correlations. However, considerable time and effort is needed to build and validate these models. In this paper, we review the various approaches used at Corteva Agriscience to deepen our understanding of mixing in large-scale fermentation processes.

Small-Scale Accelerated Pavement Testing

This paper presents the results of a study conducted to explore the use of small-scale models of accelerated pavement testing devices to evaluate the performance of pavements in conjunction with full-scale tests. The motivation for the study was the availability of a model mobile load simulator (MMLS), which had been built originally to illustrate the operation of the full-scale mobile load simulator under design at the time. The scaling requirements will be different depending on whether dynamic (inertia), viscous, or gravity effects are important. One must thus decide which one of these effects controls the behavior to try to reproduce it exactly. In the preliminary tests conducted with the MMLS, emphasis had been placed in reproducing accurately the viscoelastic behavior of the asphalt layer. The possibility of obtaining valid results, even if similitude is not maintained in relation to inertia forces, is explored in this paper. The effects of load frequency or velocity and the effects of layer thicknesses are studied. The total thickness of the model pavement, which must be finite, and its effects on displacements and strains are also considered. It is concluded that even when full similitude is not satisfied, it is possible to obtain valid results that can be extrapolated to predict prototype performance if one were interested primarily in the behavior of the asphalt layer. Preliminary analyses should be conducted, however, to guide on the selection of the model dimensions.

Small scale models of complex geometry for blast overpressure assessment

In the field of blast loading and structural response assessment there is great attraction in using small scale models which yield data of satisfactory quality to allow reliable prediction of full size events. The reasons for this include cost considerations, experimentation time and aspects of safety. This paper describes a series of experiments using smooth-walled tunnels of differing geometry at (approximately) 1:45 scale and small partially-vented cubicles designed to demonstrate that meaningful results can be obtained at small scale. Results are compared with data from both larger scale and full scale experiments and show reasonable correlation, particularly with regard to peak overpressure. It is concluded that the use of small-scale models can provide a useful means of obtaining blast loading data for complex structures.

The World Oil Market: An Examination Using Small-Scale Models

This article presents the results of a series of exercises in the use of small-scale models to explain the spot price of crude oil. Small scale modeling-the use of a limited number of equations-involves a number of disadvantages: many interesting questions will have to be ignored and often a sense of realism may be sacrificed. However, small-scale models are an essential part of economic research. Compared to large, multi-equation models, small-scale models are often transparent-causal relations are clearly visible. In addition, small-scale models can often be easily updated and reexamined in the light of new information or assumptions. This is particularly important in policy-making when time and clear communication are at a premium.

Applications of similitude to the structural mechanics of reactors

The structural mechanics of a reactor involves the prediction of the behavior of the components of the reactor and the entire reactor system under a combination of gravitational and other force fields, electrical and magnetic fields, thermal fields and radiation fields. The nature of the materials and components is such that under the operational conditions imposed, the behavior is often nonlinear, with the result that the application of the usual techniques of mathematical analysis to predict behavior often results in lengthy computations based on assumptions that are somewhat subjective. Although computer techniques have proven very helpful in many instances, they are often limited in scope through size of available computer storage. The direct approach, that of cut-and-try design, is often not appropriate because of the possibility of release of radioactive materials in the event of a faulty design or a failure of the containment or other materials. In addition, economics, as well as safety, usually precludes construction of a complete operating unit without preliminary analysis Under these conditions of complex mathematical analysis and expensive construction the use of small scale models is suggested as a method of obtaining data from which realistic predictions may be made. In the design of small scale models the theory of similitude is used in the same way that it has been used in many fields of engineering. It is also pertinent to consider current power reactors in the 400-MW range as models of projected reactors in the 2000-MW range. Direct application of the principles of similitude leads to a series of design conditions that cannot be satisfied simultaneously. In such a situation the application of distorted model theory is mandatory. The application of distorted model theory requires the determination of the prediction factors associated with the pertinent distortion factors derived from the significant parameters that are distorted. Evaluation of the prediction factors as functions of the distortion factors may be accomplished experimentally or analytically, and the remainder of the presentation is devoted to consideration of the applicable methods and procedures for determining the prediction factors. The analytical procedures may be classed as those based on well established laws and those based on fundamental principles. Specific illustrations of the application of the principles includes fuel element containment, distortion of primary containment, performance of containment shells as a result of sudden release of energy within or from external disturbances, and thermal strains resulting from loss of coolant and subsequent sudden cooling. As the numerical examples will illustrate, distorted model theory often enables one to make practical judgments concerning which distortions are significant and which will have a trivial influence upon the results.

STRUCTURAL MODEL ANALYSIS WITH THERMOPLASTICS

The use of small scale models as an experimental method of analysing structural behaviour offers an attractive solution to many problems, and thermoplastics can be considered profitably as structural materials for such models. Xylonite was probably the first thermoplastic used in this way, but its relatively poor dimensional stability often proved a serious disadvantage.In the present paper vybak is advocated as a superior material, for which bonding and strain gauging techniques have been established. Comparisons are made between the material properties of vybak and other thermoplastic materials, and examples of experimental work with vybak models are given.

TECHNIQUE NOUVELLE DE MODÈLES RÉDUITS POUR LA PROSPECTION ÉLECTRIQUE

AbstractThe use of small scale models in the interpretation of results of electric prospecting involves two majors difficulties: (1) the dimensions of the models and of the tanks in which the experiment is performed must be of unwieldy large sizes if one wants to be quite free from side effects; (2) the precise geometrical relation, in respect to the model, of the successive points where the interesting data are measured, requires an intricate installation, and is costly in both time and money.The technique which is described in this paper eliminates these difficulties as well as some others. The surface of the ground is represented by the lower face of a thick horizontal plate of plexiglas which is laid at the surface of the liquid filling the tank. This plate is pierced by a great number of small holes whose coordinates have been measured initially with the necessary precision. The electrodes are then introduced into these holes without creating any perturbation in the distribution of the lines of current flow. A solution of copper sulphate is used as the liquid in conjunction with copper electrodes. In this way, a D.C. excitation is possible, combining precision with convenience.

Part III: An Investigation into the Surging of Ball Mills

The problem of surging in ball mills has been investigated by the use of small-scale models and, although a complete analysis of all the variables has not been made, a criterion has been obtained by use of which it is possible to determine, whilst the design is still on the drawing board, whether the charge of a proposed mill is likely to surge. The validity of the proposed criterion has been demonstrated by comparison with the published results relating to industrial mills; this comparison showing that all the mills considered are operated under conditions which are in accordance with those laid down in the present work. So far as is known, such a criterion has not previously been propounded, and it is believed that it is of considerable value to the designer and to the mill operator. For the purpose of predicting the existence or non-existence of surging in a mill, it is only necessary to establish within which of two possible zones on a certain graph the point corresponding to the operating conditions of the mill falls; the relevant graph having for the abscissae the value of the ratio of the mill diameter to the ball diameter and for the ordinate the product of the mill filling and the mean coefficient of friction of the ball and powder charge of the mill. Thus, in order that a mill shall not surge, it is necessary that the mill filling and the ratio of mill diameter to ball diameter shall be so chosen in relation to the coefficient of friction, which is fixed by the nature of the material being ground, that the operating point for the mill shall fall within the non-surging zone on the graph mentioned. It is suggested that if a mill can be operated under ‘non-surging’ conditions, then, for lower first costs and maintenance costs, plain liners should be adopted, but if the mill cannot be operated under these conditions, then heavy lifters should be provided to suppress surging—even though the cost is thereby increased.

The New American Wind Tunnels

Much has been learnt, in many branches of science and engineering, from the use of small scale models. The earliest successful experiments in humanly contrived flight with heavier-than-air craft, were made with small scale prototypes of the man-carrying machine of a later day : experiments with man-carrying craft, kite, glider and power-driven, followed.