A Review of Similitude Methods for Structural Engineering

Similitude theory allows, through a set of tools known as similitude methods, to establish the conditions to design a scaled (up or down) model of a full-scale structure, usually defined as prototype. In the last years, to overcome the problems associated with full-scale testing, such as costs and setup, research on similitude methods has grown and their application has expanded in many branches of engineering. The aim of this paper is to provide a review as comprehensive as possible about similitude methods applied to structural engineering; after a brief historical introduction and a more deep analysis of the main methods, the article focuses on the applications classified by test articles

Numerical investigations about the sound transmission loss of a fuselage panel section with embedded periodic foams

Abstract The scope of this paper is to investigate the sound transmission loss of a typical fuselage panel section, as well as to propose solutions based on the inclusion of a periodic pattern inside its foam core, which aim at passively improving the acoustic performance in a mid-high range of frequencies. In detail, a new fuselage panel configuration is numerically studied, starting from the state of the art regarding the acoustic packages based on porous meta-materials. The main novelties of the present work are represented by the application of a meta-core solution inside an acoustic package of aeronautical interest, as well as a systematic investigation of the effects deriving from its geometrical parameters. In order to reach this goal, a numerical model of a fuselage panel section is studied, and the effect of several periodic patterns are simulated; more specifically, twelve configurations are taken into account, each with different radius of the inclusions and number of unit cells along the thickness. For each of these layouts, the mass increase of the so-called meta-core, compared to that of its classical homogeneous counterpart, is estimated, together with the associated mid-band frequency and amplitude of the sound transmission loss peak, which is caused by the additional acoustic modes excited by the periodic nature of the meta-core itself. Results are presented in terms of tables and graphs, which may constitute a good basis in order to perform preliminary design considerations that could be interesting for further generalizations

A Statistical Energy Analysis (SEA) model of a fuselage section for the prediction of the internal Sound Pressure Level (SPL) at cruise flight conditions

Abstract Comfort plays an increasingly important role in the interior design of airplanes. In general, comfort is defined as 'freedom from pain, well-being'; in scientific literature, indeed, it is defined as a pleasant state of physiological, psychological and physical harmony between a human being and the environment or a sense of subjective well-being. Cabin noise in passenger aircraft is one of the comfort parameter, which creates straightaway discomfort when exceeding personal thresholds. In general the cabin noise varies by the seat position and changes with flight condition. It is driven by several source types, which are transmitted through different transfer paths into the cabin. In the forward area the noise is mainly dominated by the turbulent boundary layer described by pressure vortexes traveling along the fuselage surface. In this paper evaluation of the Sound Pressure level, for the medium-high frequency range, of an aircraft fuselage section at different stations and locations inside the cabin has been performed numerically by using Statistical Energy Analysis (SEA) method. Different configurations have been considered for the analysis: from the "naked" cabin (only primary structure) up to "fully furnished" (primary structure with interiors and noise control treatments) one. These results are essential to understand which are the main parameters affecting the noise insulation. Furthermore the Power Inputs evaluation has been determined to see the contribution of each considered aeronautic component on the acoustic insulation. Finally, the effect of a viscoelastic damping layer embedded in the glass window has been evaluated

Similitude theory applied to plates in vibroacoustic field: a review up to 2020

Similitude methods are a set of tools which allow the design of scaled-up or scaled-down models of a full-scale structure called a prototype. In this way, the financial and temporal costs of experimental tests, and the problems associated with the set-up of too large (or small) test articles, may be overcome. This article provides a brief review of similitude methods applied to plates in a vibroacoustic field. Particularly, it is dedicated to a thorough analysis of similitude conditions and scaling laws for uncovering commonalities and differences, and physical interpretations, obtained from applying different scaling methods

Service Management Model Based on Lean Service and Systematic Layout Planning for the Improvement of Customer Satisfaction in an SME in the Restaurant Sector in Peru

The restaurant industry is a sector of great importance in Peru, which was one of the most affected during the pandemic due to the sanitary measures that prevented its normal operation. Once these measures were diminished and regular attention returned, the sector grew in an accelerated manner. With this growth, restaurants had to face a major problem: low customer satisfaction, as long wait- ing times and poor service became recurrent issues. Faced with this scenario, it is necessary to optimize the activities in the kitchen in order to have a better production time and to ensure the best quality in the dishes offered. Thus, a continuous improvement model based on Lean Service tools (5S, SMED, Standardized Work) is proposed to increase customer satisfaction through a faster service by making the processes in the kitchen more efficient and standardizing the quality of the dishes. In addition, Systematic Layout Planning was applied in the store to make a more efficient distribution of spaces in order to reduce waiting times. The proposal was validated through a pilot test in the case of Lean Service tools and a simulation in Arena software in the case of Systematic Layout Planning. The results obtained show a reduction in customer service time of 9.84% and an increase in customer satisfaction of 16%

Dispersion curves of infinite laminate panels through a modal analysis of finite cylinders

This work presents an approach for using a modal analysis on an equivalent finite cylindrical model, to predict the elastic waves in infinite, isotropic or composite, panels. In the description of the infinite paths, an analogy, between the classical topologies of a straight line and a circumference, is exploited and tested. Different aspects, concerning the wavemode duality and the discretization and the needed radii of curvature, are investigated to frame the problem and test the robustness of the methodology. The analysis presents a well conditioned problem and solution for any propagation wave angle by transforming the original problem into a simple modal analysis

A Linear Transformation for the Reconstruction of the Responses of Systems in Similitude

Recent years have seen an increasing interest towards similitude methods. In fact, the possibility of testing a scaled model, instead of a full-scale prototype, leads to many advantages: financial and time savings, easier experimental setups, etc. However, similitudes have drawbacks, too, mainly due to non-scalable effects and partial similitude, which prevent from an accurate reconstruction of the prototype response. For these reasons, an alternative method which can bypass these limitations is needed. A new method, called VOODOO (Versatile Offset Operator for the Discrete Observation of Objects), is herein proposed: it is based on the definition of a transformation matrix which links the outputs of a given linear systems to those belonging to another system, which may be a scaled model. The responses are acquired on a discrete number of points for both the systems. This work aims at investigating the method’s strengths and limitations of the method. The results show that, although VOODOO exhibits some lack of accuracy in off-design conditions due to the loss of spatial correlation, it is able to overcome some major restrictions that affect all similitude methods

Relationships between urban form and mobility: gender and mode of transport

With the growth of urban areas, cities are the centres of the great challenges of our society. Urban form influences the metabolism of cities in multiple ways and mobility is one of them. Depending on the type of urban fabric, population, and activities located in them, travel needs and modes of transport differences appear. As population is diverse, this relationship between urban form and mobility probably have significant gender gaps that should be investigated. The aim of this paper is to demonstrate the correlation between the type of urban fabric and people’s mobility patterns, looking for significant gender differences in the number of trips and the mode of transport. Data were collected from the survey done for the Mobility Plan of the Metropolitan Area of Valencia and cadastral information. For statistical analysis, the PSPP program and Pearson's correlation coefficient were used. This paper demonstrates significant differences in relation to gender and modes of transport. Women use more sustainable modes of transport, especially in dense and compact cities. Urban sprawl increases mobility, especially trips using private motorised modes. On the contrary, more sustainable modes, like by foot, on bike, or using public transport, are used in compact cities. Looking for sustainable mobility, women and density are key aspects which land planners must take into account when designing cities