Scaled Models Research Articles

Investigation of the Mechanical Behaviour of the Interface between Soil and Reinforcement, via Experimental and Numerical Modelling

The purpose of this study is to investigate the interface properties between soil and reinforcement, via experimental and numerical modelling of reinforced slopes. In particular, several scale models were built and tested under enhanced gravity in the geotechnical drum centrifuge at ETH Zurich and corresponding prototype numerical models were analyzed via a finite element stress analysis code. Optical fibre sensors were attached on the reinforcement layers of the experimental scaled models in order to measure linear strain during the increase of the g-level, and the results were compared to linear strain that was derived by the numerical analysis of the correspondent prototype reinforced slopes. The interface between soil and reinforcement was expressed in terms of normal and shear stiffness on the soil-reinforcement boundary and different values were tested in order to achieve validation of the experimental and numerical results.

Scaled models in the analysis of fire-structure interaction

A fire problem has been scaled both in terms of geometry, boundary conditions and materials thermophysical properties by means of dimensionless parameters. Both the full and scaled models have been solved numerically for two different fire power values. Results obtained by means of the full scale model and the scaled one are compared in terms of velocity and temperature profiles in order to assess the reliability of the scaled model to represent the behavior of the full scale one.

Prediction of vibration characteristics in beam structure using sub-scale modeling with experimental validation

Geometric or sub-scale modeling techniques are used for the evaluation of large and complex dynamic structures to ensure accurate reproduction of load path and thus leading to true dynamic characteristics of such structures. The sub-scale modeling technique is very effective in the prediction of vibration characteristics of original large structure when the experimental testing is not feasible due to the absence of a large testing facility. Previous researches were more focused on free and harmonic vibration case with little or no consideration for readily encountered random vibration. A sub-scale modeling technique is proposed for estimating the vibration characteristics of any large scale structure such as Launch vehicles, Mega structures, etc., under various vibration load cases by utilizing precise scaled-down model of that dynamic structure. In order to establish an analytical correlation between the original structure and its scaled models, different scale models of isotropic cantilever beam are selected and analyzed under various vibration conditions( i.e. free, harmonic and random) using finite element package ANSYS. The developed correlations are also validated through experimental testing. The prediction made from the vibratory response of the scaled-down beam through the established sets of correlation are found similar to the response measured from the testing of original beam structure. The established correlations are equally applicable in the prediction of dynamic characteristics of any complex structure through its scaled-down models. This paper presents modified sub-scale modeling technique that enables accurate prediction of vibration characteristics of large and complex structure under not only sinusoidal but also for random vibrations.

어선용 수평 냉각판 냉동장치의 냉동 효율 개선에 관한 연구

The economic efficiency for fishery products can be related to their freshness and the quality. In order to freshly storage the product, freezing equipment system is necessary for fishing vessels. For this purpose, the horizontal plate freezer (HPF) is mostly used. In this research, our major objective is to improve the freezing performance of the HPF. Therefore, it is important to analyse the relationship between the shape of channels and the cooling temperature of the HPF. In order to save calculation time while checking the trend analysis between shape and performance, we used scaled models, and evaluate the cooling temperature of full scale model based on trend analysis results. The produced HPF in domestic was used, and the same operating conditions are considered. Based on this paper, the future research will be a comparison and verification through the experiments.

Wind Tunnel Analysis of the Detachment Bubble on Bolund Island

The flow topology on two scaled models (1:230 and 1:115) of the Bolund Island is analysed in two wind tunnels, focusing on the characteristics of the detachment pattern when the wind blows from 270° wind direction and the atmospheric condition is neutral. Since the experiments are designed as the simplest possible reference cases, no additional roughness is added neither to the models surface nor to the wind tunnel floor. Pressure measurements on the surface of the 1:230 scale model are used to estimate the horizontal extension of the intermittent recirculation region, by applying the diagnostic means based in exploring the pressure statistics, proposed in the literature for characterising bubbles on canonical obstacles. The analysis is done for a range of Reynolds numbers based on the mean undisturbed wind speed, U∞ and the maximum height of the island, h[5.1×104,8.5×104]. An isoheight mapping of the velocity field is obtained using 3D hotwire (3D HW). The velocity field in a vertical plane is determined using 3D HW and 2D particle image velocimetry (PIV) on the 1:115 scale model in order to reproduce and complete already existing results in the literature.

Centrifuge modeling of rocking-isolated inelastic RC bridge piers.

Experimental proof is provided of an unconventional seismic design concept, which is based on deliberately underdesigning shallow foundations to promote intense rocking oscillations and thereby to dramatically improve the seismic resilience of structures. Termed rocking isolation, this new seismic design philosophy is investigated through a series of dynamic centrifuge experiments on properly scaled models of a modern reinforced concrete (RC) bridge pier. The experimental method reproduces the nonlinear and inelastic response of both the soil-footing interface and the structure. To this end, a novel scale model RC (1:50 scale) that simulates reasonably well the elastic response and the failure of prototype RC elements is utilized, along with realistic representation of the soil behavior in a geotechnical centrifuge. A variety of seismic ground motions are considered as excitations. They result in consistent demonstrably beneficial performance of the rocking-isolated pier in comparison with the one designed conventionally. Seismic demand is reduced in terms of both inertial load and deck drift. Furthermore, foundation uplifting has a self-centering potential, whereas soil yielding is shown to provide a particularly effective energy dissipation mechanism, exhibiting significant resistance to cumulative damage. Thanks to such mechanisms, the rocking pier survived, with no signs of structural distress, a deleterious sequence of seismic motions that caused collapse of the conventionally designed pier. © 2014 The Authors Earthquake Engineering & Structural Dynamics Published by John Wiley & Sons Ltd.

A geometric scaling model for assessing the impact of aneurysm size ratio on hemodynamic characteristics

BackgroundThe intracranial aneurysm (IA) size has been proved to have impacts on the hemodynamics and can be applied for the prediction of IA rupture risk. Although the relationship between aspect ratio and hemodynamic parameters was investigated using real patients and virtual models, few studies focused on longitudinal experiments of IAs based on patient-specific aneurysm models. We attempted to do longitudinal simulation experiments of IAs by developing a series of scaled models.MethodsIn this work, a novel scaling approach was proposed to create IA models with different aneurysm size ratios (ASRs) defined as IA height divided by average neck diameter from a patient-specific aneurysm model and the relationship between the ASR and hemodynamics was explored based on a simulated longitudinal experiment. Wall shear stress, flow patterns and vessel wall displacement were computed from these models. Pearson correlation analysis was performed to elucidate the relationship between the ASR and wall shear stress. The correlation of the ASR and flow velocity was also computed and analyzed.ResultsThe experiment results showed that there was a significant increase in IA area exposed to low WSS once the ASR > 0.7, and the flow became slower and the blood was more difficult to flow into the aneurysm as the ASR increased. Meanwhile, the results also indicated that average blood flow velocity and WSS had strongly negative correlations with the ASR (r = −0.938 and −0.925, respectively). A narrower impingement region and a more concentrated inflow jet appeared as the ASR increased, and the large local deformation at aneurysm apex could be found as the ASR >1.7 or 0.7 < the ASR <1.0.ConclusionHemodynamic characteristics varied with the ASR. Besides, it is helpful to further explore the relationship between morphologies and hemodynamics based on a longitudinal simulation by building a series of patient-specific aneurysm scaled models applying our proposed IA scaling algorithm.

圆柱体涡激振动缩尺实验的相似关系研究

提出了一种基于雷诺相似的圆柱体涡激振动(VIV)实验方法。涡旋的泄放模式与雷诺数Re密切相关，目前圆柱体涡激振动的研究中，缩尺模型实验往往基于弗汝德相似而雷诺数不相似，因此，模型与原型的涡泄模式不同，由此可以推断，模型的涡激振动响应与原型不相似。这就意味着基于弗汝德相似准则的模型实验结果不能准确地预测原型的涡激振动响应。对基于雷诺数相似的模型与原型的涡激振动实验相似关系进行了推导，采用CFD方法对原型和3种不同相似准则条件下的缩尺模型进行了涡激振动仿真计算, 同时引入实验进行对比。数模结果表明，仅满足雷诺数相似的模型与原型的涡泄模式相似，这个结果与弗汝德数和雷诺数均相似的结果一致，而仅弗汝德数相似条件下，模型与原型之间的涡泄模式和尾流场完全不同。实验结果表明，仅满足雷诺数相似时，模型与原型涡泄周期满足相应缩尺比，而仅满足傅汝德数相似时，模型与原型涡泄周期不满足相应缩尺比。因此，缩尺实验中仅满足傅汝德数相似模型的涡激振动特性不可能与原型相似，应采用雷诺相似准则。An experimental method, based on Reynolds number similarity, of the vortex-induced vibration (VIV) of circle cylinders is proposed to achieve VIV similarity between prototype and tested model. The VIV response of a circle cylinder is closely related to Reynolds number because the mode of vortex shedding highly depends on Re. However, the scaled model test of circle cylinder’s VIV is designed based on Froude number similarity but Reynolds number is not similar under the same fluid for both model and prototype. Therefore, the VIV response of tested model is not similar to that of the prototype because they have different vortex shedding modes. It means that the test results can not be used to predict the VIV response of the prototype according to the scaling law based on Froude number similarity. The prototype and three scaled models with different simi-larity schemes have been simulated using CFD to validate the method and at the same time, expe-riments are compared. The numerical results show that the similarity between prototype and model is satisfying by Reynolds number similarity, and it is in accordance with both Froude number and Reynolds number similarity. But the similarity between prototype and model is not satisfying by Froude number similarity. The experimental results show that the similarity of period of the vortex shedding is satisfying by Reynolds number similarity but not satisfying by Froude number similarity. As a result, Reynolds number similarity should be used in the scale model test instead of Froude number similarity when studying the characteristics of VIV.

Establishment of structural similitude for elastic models and validation of scaling laws

Scaled down models are widely used for experimental investigations on huge structures due to the limitation in the capacities of testing facilities, and, moreover, the experimentation on scaled models is less expensive. Also small scale models are often built with materials dissimilar to those of the prototype. However, only few studies have been carried out on the similitude laws for the prototype structures with small scale models built with a different material. In the present study, an attempt has been made to develop a scaling law for models to carry out the free vibration analysis of structures, based on the similitude requirement. The established scaling laws are validated analytically using simple test problems. The similitude relationship between the prototype and the model is validated with the aid of a case study using finite element analysis software.

Comparison of the insertion loss of diffusive noise barriers using scale model experiments

A new design of an environmental friendly noise barrier was suggested which can be assembled by unit blocks. It was anticipated to decrease of noise levels because the shape of the blocks is so diffusive that it may reflect and diffuse the sound. The unit blocks also contain the soil and vegetation for landscape which can contribute the noise control as well. Four different designs of noise barriers were suggested considering various practical conditions of construction. In order to investigate the acoustical performances of the various diffusive noise barriers, different size of unit block including 30, 25, 20 and 15cm were introduced. 1/10 scaled models were made and the insertion loss of each model was measured in an anechoic chamber. Also, the difference of diffusive and flat surfaces of noise barriers was analyzed. As a result, it was found that there is no difference of insertion losses depend on the distance from the noise barriers. It was also revealed that the diffusive noise barriers have larger insertion loss than flat noise barriers. And the bigger the unit block is, the larger noise insertion losses were acquired.

Accuracy of scale models for flutter prediction of cross-ply laminated plates

This study demonstrates the applicability of the similitude theory and scaled models in the prediction of the flutter speed of cross-ply laminated plates subjected to supersonic flow. Such a study is important since it provides the necessary scaling laws and corresponding scale factors, which affect the accuracy of the scale models. In this study, based on structural similitude, the necessary scaling laws are derived using governing equations of the system. These scaling laws are employed to predict the flutter speed of the prototypes by projecting the flutter speed of the model. Both models with complete and partial similarities are discussed. Based on the results of this analytical study, for the special case of the ply level scaling, the complete similarity can be achieved. Furthermore, distorted models with different thicknesses, number of plies, material properties, and mode shapes than those of the prototypes are capable of predicting the flutter speeds of prototypes with good accuracy. The results of this study can be applied to the design of an accurate scale model for flutter analysis of composite plates.

Pressure Fluctuation Characteristics of Complex Turbulent Flow in a Single Elbow With Small Curvature Radius for a Sodium-Cooled Fast Reactor

A multi-elbow piping system is adopted for the Japan sodium-cooled fast reactor (JSFR) cold-legs. Flow-induced vibration (FIV) is considered to appear due to complex turbulent flow with very high Reynolds number in the piping. In this study, pressure measurement for a single elbow flow is conducted to elucidate pressure fluctuation characteristics originated from turbulent motion in the elbow, which lead potentially to the FIV. Two different scale models, 1/7- and 1/14-scale simulating the JSFR cold-leg piping, are tested experimentally to confirm whether a scale effect in pressure fluctuation characteristics exists. A distinguishing peak can be seen in each power spectrum density (PSD) profile of pressure fluctuation obtained in and downstream of the flow separation region for both scaled models. When nondimensionalized, the PSD profiles show good correspondence regardless of scale model and even of Reynolds number simulated in this study.

Scale modelling of aircraft fuselage: an innovative approach to evaluate and improve crashworthiness

Scale modelling of an aircraft fuselage and its measure of accuracy was investigated and determined with 1/5th, 1/10th, 1/15th and 1/20th times scaled models of an aircraft fuselage. Non-linear Finite Element Method (FEM) solver LS DYNA 3-D has been employed to analyse the experimental 1/20th scale aircraft fuselage model. The results were validated with the experimental scaled drop test model. The focus of this paper is to evaluate the scaling concept and its possible incorporation into the crashworthiness evaluation of fuselage as a potential crashworthiness evaluation tool. The impact design requirement for the 1/20th scale model fuselage section is to maintain 500 g floor-level acceleration for a 30 ft/s vertical impact velocity onto a rigid surface. This impact requirement corresponds to 25 g floor-level acceleration for a geometrically and constitutively similar full-scale fuselage section. Sub-floor concepts were then evaluated by conducting dynamic tests and confirmed with analytical calculations by performing finite element analysis using LS-DYNA. Finally, an assessment of model accuracy is provided with suggestions for improvements to achieve a better correlation result. These tests are carried out to determine the fuselage crashworthiness level and safe limit loads prescribed by the Federal Aviation Administration (FAA), and to satisfy the design goals for improved crashworthiness. A thorough investigation has been made on the existence of scaling effects and to demonstrate the application of scale model technology in the development of a new feasible methodology to evaluate the crashworthiness of the transport aircraft fuselage. Percentage error linearity of scaling is a major achievement of this study. This innovative and cost-effective crash test technique has a great potential to play a major role in the cost-saving methodology to evaluate the structure crashworthiness of the aircraft fuselage. The 1/20th scale model was built, tested and simulated with the LS-DYNA FEM package and the results were validated with the experimental drop test.

Scaled models for predicting buckling of delaminated orthotropic beam-plates

This study investigates the applicability of scaled models for predicting the buckling behavior of delaminated composites. Such a study is important since it provides the necessary scaling laws, and the factors which affect the accuracy of the scale models. Employment of similitude theory to establish similarity among structural systems can save considerable expense and time, provided that the proper scaling laws are found and validated. In this study a number of parametric studies are performed. The limitations and acceptable intervals of all parameters and corresponding scale factors are investigated. Particular emphasis is placed on the case of delamination buckling of orthotropic plates. Both complete and partial similarities are discussed. This study indicates that models with a different delamination size, depth and number of delaminations than those of the prototype are capable of predicting buckling loads of the prototypes with good accuracy.

Scale Modeling of the 96th Floor of World Trade Center Tower 1

This paper presents an experimental investigation of the World Trade Center Tower 1 (WTC1) collapse using a 1/20-scale model. The WTC1 fire on the 96th floor is reconstructed on a small scale, and structural members including the floor trusses and the exterior wall subsystem are built and tested under scaled fire load. Scaling rules are used to determine the values of the insulating material on the structural systems. This experimental study demonstrates the use of scaled models to investigate a real-world fire disaster. Results from the experimental investigation are compared to analytical results and visual evidence compiled in the National Institute of Standards and Technology report on the investigation of the collapse of WTC towers. This study helps engineers and researchers better understand the fire behavior and the associated structural response in WTC1, and a more solidly grounded collapse hypothesis can therefore pursued.

Geostatistical Analysis of data on AIR Temperature and Plant Phenology From Baden-Württemberg (GERMANY) as a Basis for Regional Scaled Models of Climate Change

The rise of the air temperature is assured to be part of the global climatic change, but there is still a lack of knowledge about its effects at a regional scale. The article tackles the correlation of air temperature with the phenology of selected plants by the example of Baden-Württemberg to provide a spatial valid data base for regional climate change models. To this end, the data on air temperature and plant phenology, gathered from measurement sites without congruent coverage, were correlated after performing geostatistical analysis and estimation. In addition, geostatistics are used to analyze and cartographically depict the spatial structure of the phenology of plants in spring and in summer. The statistical analysis reveals a significant relationship between the rising air temperature and the earlier beginning of phenological phases like blooming or fruit maturation: From 1991 to 1999 spring time, as indicated by plant phenology, has begun up to 15 days earlier than from 1961 to 1990. As shown by geostatistics, this holds true for the whole territory of Baden-Württemberg. The effects of the rise of air temperature should be investigated not only by monitoring biological individuals, as for example plants, but on an ecosystem level as well. In Germany, the environmental monitoring should be supplemented by the study of the effects of the climatic change in ecosystems. Because air temperature and humidity have a great influence on the temporal and spatial distribution of pathogen carriers (vectors) and pathogens, mapping of the environmental determinants of vector and pathogen distribution in space and time should be performed in order to identify hot spots for risk assessment and further detailed epidemiological studies.

Nonlinear scaled models in 3D calculation of transformer magnetic circuits

PurposeTo make easier and faster the designing of transformers using scale models.Design/methodology/approachThe scale modeling in designing of transformers is included. Both computer and physical models of high leakage reactance (HLR) and 3‐phase (TP3C) transformers have been considered. The 3D field computations have been executed for the scaled models, and the results were recalculated to the full‐scaled ones.FindingsIt is possible to calculate the scale coefficients for nonlinear models of transformers using finite element method (FEM) software. Obtained coefficients are useful in the designing process. Measurements confirm correctness of the scaling laws.Research limitations/implicationsThe calculations were done only for transformers and the eddy current was not taken into account.Practical implicationsPresented formulae for scale model calculation are very useful for designing of transformers by the engineers. It is possible to design a series of transformers. Only one physical model must be manufactured for experimental verification.Originality/valueThis paper offers an innovative approach to non‐linear scaled modelling of transformers using FEM.

A new model of Mercury’s magnetospheric magnetic field

Two new missions will arrive at Mercury within the next decade. Interest in this enigmatic planet has therefore been revived in the magnetospheric community, and new models of Mercury’s magnetic field are demanded. In the past, there have been several attempts to model the magnetosphere of Mercury based on simply scaling models of the Earth’s magnetosphere. Although these scaled models have enjoyed many successes, their global magnetic configurations are determined by measurements made at the Earth, not at Mercury. In this paper, we develop a new empirical model of the Hermean field which is constrained wherever possible by the Mariner 10 dataset. We also explore the response of the model to upstream solar wind conditions. Data-based empirical models are an invaluable tool in magnetospheric physics at the Earth, and will doubtless prove to be just as useful at Mercury. The model developed here is generally applicable, and can be used to fit a much larger spacecraft dataset when it becomes available.

Visualization of the flows in precessing tanks with internal baffles

This paper presents an experimental investigation of some fluid flows inside a precessing right circular cylindrical tank. The first aim was to determine the extent to which a wave modal description of the fluid flow, which is physically realizable for a tank with no internal baffles, is sustained when the geometry of the tank is modified by baffle plates. The second was to determine if a baffle plate configuration could be found that forestalled the development of low-order modes. This second aim is directed toward the goal of eliminating low-order mode resonances in the fuel tanks of spinning spacecraft. Instabilities of such spacecraft have been successfully minimized at the design stage by the incorporation of baffle plates optimized by empirical drop tests. The ability of a baffle plate to eliminate low-order resonances, provided it is of a particular optimal configuration, is confirmed in this paper. This result suggests the use of flow visualizations as a means of simplifying expensive empirical drop-test programs. I. Introduction I N recent years, increasing proportions of the masses of spacecraft have been made up of fluids. These are the liquid fuels required to make small corrections to the orbits of communications satellites that are becoming more complex and must stay in operation for longer times. Spinning interplanetary probes must also carry more liquid fuels to execute increasingly complex missions. The stability of such spacecraft must be insured at the design stage. A rigid spacecraft will spin stably about either its axis of least inertia or its axis of greatest inertia. However, if energy is dissipated when a spacecraft is spinning about its axis of least inertia (a common configuration for a satellite in geostationary transfer orbit), this configuration is unstable. The spacecraft's nutation angle diverges as it tends to a spin about its axis of greatest inertia, this being the state of lowest energy for a given angular momentum. In a spacecraft containing liquid fuels, dissipation can include the transfer of energy from the rigid spacecraft's motion to the fluid. The fluid motion could occur on a variety of spatial scales, ranging from the large (low wave number waves) to the small (turbulence). In addition, viscous friction causes energy losses in boundary or shear layers. Drop-test experiments1 were carried out on scaled models of the Eurostar spacecraft bus. The internal liquid-containing tanks in both the models and the prototype spacecraft were right circular cylinders with hemispherical ends. In a drop-test experiment, a scale model of the spacecraft and its contained fluids is spun up at the top of a shaft. The model is dropped and briefly experiences free fall. During its fall, the model's overall angular velocity is recorded so that the prototype's stability in orbit may be inferred. Exponential growth of the nutation angle 0 of the spinning model was reported; the model was unstable. The nutation angle diverged according to 0<xet/T, with experimental time constants T of order 1 s. This occurred even with virtually full fuel tanks. Corresponding scaled time constants for the prototype spacecraft of about 20-30 s (or 10-15 revolutions of the spacecraft) were unaccept

Rheological and tectonic modeling of salt provinces

Abstract Technological improvements and a more-rigorous research approach have led the petroleum industry to renew and expand its interest in physical modeling of faulting associated with halokinesis. Salt tectonics and the formation of structural hydrocarbon traps can be reproduced in models using viscous polymers for the substratum and frictional plastic granular materials for the overburden. The fault patterns simulated in these dynamically scaled models are remarkably similar to those in depth-converted seismic sections. Scale models are, therefore, useful for generating new concepts and for reconstructing the structural evolution of hydrocarbon traps. Although even unsealed models may help generating ideas, the full transfer of quantitative data requires that models be dynamically scaled to their natural prototypes. Previously, published scaling theory for salt tectonics has erroneously assumed fluid behaviour of the overburden. This paper provides a sound scaling approach for geological deformations involving brittle overburdens on ductile substrata. Rheological data from overburden rocks and salt are compiled and compared to model rheologies using dimensions of laboratory analogs and other, intrinsic material properties. Scaling approaches are compared and rules are formulated for achieving dynamic similarity in models of salt tectonics, including those with synkinematic sedimentation.