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In this paper a novel numerical methodology for calculating non-uniform residual stress distributions during the glass tempering process is presented. Tempering techniques lead to non-uniform heat transfer rates causing residual stress inhomogeneities, which consequently have a direct impact on the structural behaviour of components. Nevertheless, most works in the literature do not consider the influence of local flow phenomena during thermal calculations, resulting in non-representative residual stress distributions. In this context, a novel generalised methodology based on a fluid–structure interaction one-way approach to sequentially couple the thermal and mechanical fields is presented. In this way, the unsteady and non-uniform heat transfer rate is coupled with the Narayanaswamy model to predict the non-homogeneous residual stress pattern. The obtained numerical results for the analysed impinging jet array case are in good agreement both quantitatively and qualitatively, exhibiting an average error below 10% with respect to previous experimental investigations. Finally, efforts are made to reduce the computational time. Therefore, the proposed methodology proves to be an efficient tool for understanding the underlying mechanisms and predicting the residual stress distributions during glass tempering.

Large-scale experimental programmes become unavoidable to characterise the fracture behaviour of glass. Additionally, if non-uniform residual stresses are to be considered, the total effort required increases significantly. In this work, the primary failure cumulative distribution function (PFCDF) is derived from experimental annealed glass data. In this way, a novel methodology based on the characterisation of annealed glass to assess the failure of pre-stressed glass components is presented. Similarly, a joint evaluation of annealed and tempered glass is performed, thereby ensuring a higher reliability in the derivation of the PFCDF, which results in an average error below 10%.

Different methodologies have been used in the literature to determine the absorbed vapour mass flux in falling film absorbers. So far, however, there has been little discussion about the impact of different ap- proaches in the numerical models’ performance. This study compared different methods for considering absorption in LiBr −H 2 O vertical tube-type falling film absorbers operating at both inlet subcooling and equilibrium conditions. This comparison was made based on three different criteria: the way of consider- ing the absorption, the method to determine the absorption rate, and the assumption of the existing type of diffusion at the interface. The influence of the methodology was demonstrated using 2D multiphase CFD model. The effect of different operating conditions on the methods was also examined. Finally, the results of the numerical models were compared with three experimental works, and the most suitable model was chosen, which properly agrees with them.

The paradigm of renewable energies brings a number of challenges to be solved in a short-term period. In the case of wind energy, it turns necessary to relocate onshore wind-farms in both offshore coastal regions and urban environments, so that visual and environmental impacts of current devices are reduced. This modifies the flow regime noticeably; indeed, turbulence and environmentally-induced roughness need to be accounted for, in addition to the scale-effect in case of urban wind turbines. The effects of such factors on the aerodynamic efficiency of a standard NACA0021 airfoil are tested via wind-tunnel measurements, showing the resultant decrease in aerodynamic efficiency when passing from ideal to real flow conditions. Such a decrease leads to concluding that aerodynamic tests should be undertaken with flow configurations that represent real operational conditions., Energia berriztagarrien paradigmak erronka ugari dakartza berorrekin, epe laburrean erantzun beharrekoak bederen. Energia eolikoaren kasuan, ustiapena ohiko haize-parkeetatik itsasalde edota hiriguneetara mugitzean datza, inpaktu bisuala nahiz ingurumen kalteak murrizteko asmoz. Horrek haizearen fluxu baldintzak nabarmen aldatzea dakar; bereziki, turbulentzia eta ingurumen-eragileek sorturiko gainazal-zimurtasuna hartu behar da kontuan eta, hiriguneetako kasuan, aerosorgailuen eskala aldaketa. Haize-tunel bidezko entseguak burutuz, faktore horiek NACA0021 geometriadun pala baten efizientzia aerodinamikoan duten eragina aztertu da, baldintza idealetatik errealetara igarotzean ematen den efizientzia galera ikusaraziz. Galera hori dela-eta, entsegu esperimentalak harik eta baldintza errealenetan egiteko beharra ondorioztatzen da.

An application-agnostic procedure is outlined for checking the validity of momentum-deficit-based drag measurements performed under different turbulent conditions in a wind tunnel. The approach defines a two-step methodology: the first stage characterizes the turbulent flowfield generated downstream a passive grid through a set of statistical parameters. Acceptable values for such parameters are determined by means of two criteria: compliance with the threshold value set by an analysis of the experimental uncertainties, and fulfilment of the isotropic condition for ensuring a well-established turbulent flowfield. Those two prerequisites define a set of turbulent configurations for which the momentum-deficit-based technique applies feasibly. The second stage of the procedure is configuration-specific, and undertakes drag measurements upon a NACA0021 airfoil subjected to a set of different turbulent configurations. It is shown that performing measurements under invalid turbulent conditions leads to inconsistent drag curves, which serves for defining a validity map based on the testable cases.

Butterfly valves are widely used industrial piping components as on-off and flow controlling devices. The main challenge in the design process of this type of valves is the correct dimensioning to ensure proper mechanical performance as well as to minimise flow losses that affect the efficiency of the system. Butterfly valves are typically dimensioned in a closed position based on mechanical approaches considering uniform hydrostatic pressure, whereas the flow losses are analysed by means of CFD simulations. The main limitation of these approaches is that they do not consider either the influence of the dynamics of the manoeuvring stage or coupled phenomena. Recent works have included the influence of the flow on the mechanical behaviour for different opening angles by means of one-way FSI approach. However, these works consider steady-state flow for the selected angles, not capturing the effect of the transient flow evolution during the manoeuvring stage. Two-way FSI modelling approach could allow overcoming such limitations providing more accurate results. Nevertheless, the use of this technique is limited due to the increase in the computational cost. In the present work, the applicability of FSI one-way and two-way approaches is evaluated for the analysis of butterfly valves, showing that not considering fluid-structure coupling involves not capturing the most critical situation for the valve disc.

This paper describes a smart system to monitor high temperature in industrial applications. The solution includes a semipassive microchip which allows logging data and wireless reading. Protection for the electronics against high temperature environment is provided by a vacuum packaging. Thermal isolation at 150°C and 800°C ambient temperature allows the system to work properly during 14 and 2 minutes respectively.

The goal of the present work is to characterise the influence of static prestrain on the elastic and dissipative properties of constrained viscoelastic films. Dynamic mechanical analysis (DMA) technique is considered for measuring the dynamic properties under several static prestrain levels, and a new material constitutive model is presented for characterising the frequency–prestrain dependence of the viscoelastic material. The results indicate that the static prestrain strongly affects the elastic and dissipative properties of the analysed viscoelastic material. The proposed material constitutive model properly describes the frequency–prestrain dependence of the tested viscoelastic material., Peer Reviewed, Postprint (published version)

This dissertation presents the experimental and numerical dynamic analysis of press-formed viscoelastic sandwich structures composed by two thin metallic face layers and a constrained viscoelastic film. Such structures can be formed by classical sheet metal forming processes, but the relative displacement given between the elastic face layers subjects the viscoelastic core to a static prestrain. Besides the temperature and the frequency, the dynamic properties of the viscoelastic core also depend on such static prestrain, which must be taken into consideration to properly determine the dynamic response of formed sandwich parts. The viscoelastic core is characterized in function of the frequency, temperature and static prestrain by two different experimental techniques. The frequency dependence is characterized by a new analysis method developed for identifying the dynamic properties of high damping and strong frequency-dependent viscoelastic materials from the dynamic response measured by the forced vibration test with resonance technique. By contrast, the temperature and the static prestrain dependence is characterized by conducting dynamic mechanical analysis (DMA) tests. The dynamic properties characterized by both experimental techniques are compared and discussed. Different material constitutive models are considered to characterize the dynamic properties of the viscoelastic core in function of the three variables. The frequency dependence is described by a four-parameter fractional derivative model, the influence of the temperature is included by the frequency-temperature superposition principle making use of the Arrhenius equation, and a new material constitutive model to describe the frequency-prestrain dependence is proposed. In addition, a higher order eigensensitivities-based numerical method is presented for the dynamic analysis in frequency domain of viscoelastically damped systems characterized by a structural damping matrix. Two different schemes are prop, Doktorego tesi honetan konformatuak izan diren bi azal metalikoz eta film biskoelastiko batez eraturiko sandwich egituren portaera dinamikoa aztertzen da bai esperimentalki, baita zenbakizko metodoen bidez ere. Egitura hauek ohiko prozesuen bidez konformatu badaitezke ere, bi azalen artean ematen den desplazamentu erlatiboa dela eta nukleo biskoelastikoa era iraunkorrean deformaturik geratzen da. Tenperatura eta maiztasunaz gain, aurre-deformazio honek material biskoelastikoaren propietate mekanikoetan eragina aintzat hartu beharreko aldagaia da, konformatuak izan diren sandwich egituren portaera dinamikoa egoki aurreikusteko. Nukleo biskoelastikoaren propietate dinamikoak maiztasuna, tenperatura eta aurredeformazioaren arabera karakterizatu dira bi teknika esperimental ezberdinekin. Maiztasunari dagokionez, moteltze-maila altuko eta maiztasunarekiko menpekotasun nabaria duten material biskoelastikoen propietate dinamikoak egoki zehazteko, habe erako laginen erantzun dinamikoan oinarritutako metodo berri bat garatu da. Tenperaturaren eta aurre-deformazioaren menpekotasuna, aldiz, erresonantzia gabeko saiakuntza dinamikoen bidez aztertu da. Era berean, bi tekniken bidez karakterizatutako propietate dinamikoak alderatu eta bateratu dira. Nukleo biskoelastikoaren propietate dinamikoek hiru aldagaiekiko duten menpekotasuna deskribatzeko material-eredu ezberdinak erabili dira. Maiztasunaren eragina lau parametroko deribatu frakzionarioen ereduaz deskribatu da. Tenperaturaren efektua, tenperatura-maiztasuna gainezarpen printzipioaz barneratu da Arrhenius-en ekuazioa erabiliz. Azkenik, aurre-deformazioaren eragina eredu berri baten bidez zehaztu da. Bestalde, autobalio eta autobektoreen goi mailako deribatuetan oinarritzen den zenbakizko metodo berri bat proposatu da material biskoelastikoen bidez moteldutako egituren portaera dinamikoa kalkulatzeko. Bi eskema ezberdin proposatu dira, batetik egituraren parametro-modal konplexuak zehazteko eskema iteratiboa, eta bestetik, m, Las estructuras sándwich de núcleo viscoelástico son una alternativa efectiva para la atenuación de las vibraciones y así, mejorar el confort vibro-acústico, la seguridad o al ciclo de vida de los productos. La utilización de un film viscoelástico situado entre dos capas metálicas permite obtener laminados que pueden ser conformados mediante los procesos convencionales de transformación de chapa. El diseño de piezas con estas estructuras sándwich conlleva determinar correctamente su respuesta dinámica, por lo que es necesario conocer la dependencia de las propiedades dinámicas del núcleo viscoelástico con la frecuencia, la temperatura y la predeformación que se induce por el desplazamiento relativo de las dos capas metálicas al ser conformadas. Además, esta dependencia se debe incluir en un modelo constitutivo del material, que junto con los métodos numéricos adecuados permitan predecir la atenuación vibratoria que aportan estos laminados en componentes industriales. Así, en esta tesis doctoral se ha analizado el comportamiento dinámico de estructuras sándwich conformadas, tanto de forma experimental como numérica. El núcleo viscoelástico se ha caracterizado en función de la frecuencia, la temperatura y la predeformación mediante dos técnicas experimentales. La dependencia con la frecuencia se ha establecido mediante un nuevo método de análisis a partir de la respuesta dinámica obtenida con la técnica de vibraciones forzadas con resonancia. El método desarrollado permite identificar las propiedades dinámicas de materiales viscoelásticos con alto amortiguamiento y fuerte dependencia en frecuencia. Por otro lado, la influencia de la temperatura y la predeformación se ha determinado mediante ensayos de vibraciones forzadas sin resonancia. Así, empleando ambas técnicas experimentales, se han identificado las propiedades dinámicas en un amplio ancho de banda. La influencia de cada variable se ha descrito mediante diferentes modelos constitutivos de material. La dependencia co