Droplets as precursor are extensively applied in diverse fields of science and engineering. Various contributions are provided previously towards analysis of single phase and multi-phase droplets of single and multiple components. This thesis describes modelling of multi-phase (nano fluid) droplet vaporization. The evaporation of liquid phase along with migration of dispersed particles in two-dimensional plane within droplet is detailed using the governing transport equations along with the appropriate boundary and interface conditions. The evaporation model is incorporated with aggregate kinetics to study agglomeration among nano silica particles in base water. Agglomeration model based on population balance approach is used to track down the aggregation kinetics of nano particles in the droplet. With the simulated model it is able to predict different types of final structure of the aggregates formed as observed in experimental results available in literature. High spatial resolution in terms of agglomeration dynamics is achieved using current model. Comparison based study of aggregation dynamics is done by heating droplet in convective environment as well as with radiations and using different combination of heating and physical parameters. The effect of internal flow field is also analysed with comparative study using levitation and without levitation individually. For levitation, droplet is stabilized in an acoustic standing wave. It is also attempted to study the transformation of cerium nitrate to ceria in droplets when heated under different environmental conditions. Reaction kinetics based on modified rate equation is modelled along with vaporization in aqueous cerium nitrate droplet. The thermo physical changes within the droplet along with dissociation reaction is analysed under different modes of heating. The chemical conversion of cerium nitrate to ceria during the process is predicted using Kramers' reaction velocity equation in a modified form. The model is able to explain the kinetics behind formation of ceria within droplet at low temperatures. Transformation of chemical species is observed to be influenced by temperature and configuration of the system. Reaction based model along with CFD (computational fluid dynamics) simulation within the droplet is able to determine the rate of chemical dissociation of species and predict formation of ceria within the droplet. The prediction shows good agreement with experimental data which are obtained from literature.

Die Anwendungsmöglichkeiten und Potenziale des temperierten Innenhochdruck-Umformens mit flüssigen Wirkmedien (T-IHU) von Rohren aus verschiedenen Magnesium- und Aluminiumknetlegierungen werden in der vorliegenden Arbeit aufgezeigt. Neben der Werkstoff- und Halbzeugcharakterisierung, der Auslegung von temperierten Innenhochdruck-Umformanlagen und –werkzeugen, den Thermografiemessungen am Halbzeug unter Realbedingungen und der Verifizierung der Simulationsergebnisse des T-IHU-Werkzeuges war der inhaltliche Schwerpunkt die systematische experimentelle Bestimmung der maximalen Umfangserweiterung ∆u_max in Anhängigkeit von der Umformtemperatur ϑ_u, dem Werkstoff und der Wanddicke s₀ im Temperaturbereich von 22°C bis 300°C an drei Versuchsgeometrien T-Stück, Zylinder und Quader bei Innendrücken bis 800 bar. Neben dem Einfluss der Prozessparameter, der Werkstoff- und Halbzeugeigenschaften und der Ausgangswanddicke wurde der signifikante Einfluss der Umformtemperatur und der Umformgeometrie auf die erreichbaren Umfangserweiterungen herausgearbeitet und systematisch dargestellt. Es wurden Umfangsdehnungen von bis zu 120 % (bei ϑ_u = 300°C) erzielt. Die experimentelle Bestimmung der minimal auszuformenden Bauteilaußenradien erfolgte unter Anwendung der statistischen Versuchsplanung. Aus den Regressionsgleichungen wurde eine neue Berechnungsgleichung für den maximalen Innendruck p_imax generiert. Durch die Verifikation dieser Gleichung konnte die hohe Genauigkeit bei der Vorausberechnung des erforderlichen Innendruckes bei einem vorgegebenen minimalen Bauteilaußenradius R_min in Abhängigkeit von der Zugfestigkeit R_m als f (Umformtemperatur) und der Wanddicke s₀ nachgewiesen werden. Die Auslegung der T-IHU-Werkzeug- und Anlagentechnik kann damit wesentlich genauer er­folgen. Durch die Bauteilanalysen nach dem T-IHU-Prozess konnten die hohe Maß- und Formgenauigkeit und die hohe und gleichmäßigere Oberflächengüte nachgewiesen werden. Trotz der beginnenden dynamischen Rekristallisation lag bei allen Versuchswerkstoffen eine Erhöhung der Werkstofffestigkeit in der Umformzone vor. Bei den Untersuchungen bzgl. des T-IHU des Realbauteiles „PKW-Querträger vorn“ konnten die Kenntnisse der Grundlagenuntersuchungen auf ein komplex geformtes Realteil übertragen und erweitert werden. Es zeigte sich, dass der Einsatz von T-IHU-Magnesiumbauteilen ein erhebliches Potenzial für weitere Gewichtsreduzierungen von Leichtbaukonstruktionen besitzt. / This paper presents the potential applications of temperature-supported hydroforming of various magnesium and aluminium alloy tubes using active liquid media. It includes details of material and semi-finished product characterisation, the design of temperature-supported hydroforming equipment and tools, thermography measurements on the semi-finished product under real conditions and verification of simulation results for the temperature-supported hydroforming tool. The main focus, however, was the systematic, experimental approach to determining the maximum increase in perimeter ∆u_max as a function of the forming temperature ϑ_u, the material and the wall thickness s₀ in the temperature range 22°C to 300°C for three trial geometries (T‑piece, cylinder and cuboid) at internal pressures of up to 800 bar. In addition to studying the effect of process parameters, material properties, semi-finished product characteristics and initial wall thickness, the paper also presents the finding that forming temperature and forming geometry have a significant impact on achievable increases in perimeter. Perimeter expansions of up to 120 % were attained (at ϑ_u = 300°C). Statistically designed experiments were used to determine the minimum component outside-radii to undergo the forming process. A new equation for calculating the maximum internal pressure p_imax was generated from regression equations. By verifying this equation, it was possible to demonstrate the high level of accuracy in predicting the internal pressure required for a given minimum component outside-radius R_min as a function of the tensile strength R_m as f(forming temperature) and of the wall thickness s₀. This means that the temperature-supported hydroforming tool and system equipment can be designed far more accurately. Component analyses after the temperature-supported hydroforming process demonstrated the high level of dimensional and geometrical accuracy and the high quality and more consistent surface finish. Despite the onset of dynamic re-crystallisation, the strength of the material was increased in the forming zone in all the materials tested. The knowledge gained from researching the fundamental principles was applied to a real component with a complex shape in studies of temperature-supported hydroforming of the "front car cross-member", which provided further useful insights. It was found that the use of temperature-supported hydroforming magnesium components has considerable potential for further weight reduction in lightweight constructions.

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The simulation of physical systems in the early stages of conceptual designs has shown to be a key factor for adequate decision making and avoiding big and expensive issues downstream in engineering projects. In the case of aircraft cabin design, taking into account the thermal comfort of the passengers as well as the proper air circulation and renovation can make this difference. However, current numerical fluid simulations (CFD) are too computationally expensive for integrating them in early design stages where extensive comparative studies have to be performed. Instead, Zonal Models (ZM) appear to be a fast-computation approach that can provide coarse simulations for aircraft cabin flows. In this thesis, a Zonal Model solver is developed as well as a geometry-definition and meshing framework, both in Matlab®, for performing coarse, flexible and computationally cheap flow simulations of user-defined cabin designs. On one hand, this solver consists of a Fractional Step approach for coarse unstructured bi-dimensional meshes. On the other, the cabin geometry can be introduced by hand for simple shapes, but also with Computational Aided Design tools (CAD) for more complex designs. Additionally, it can be chosen to generate the meshes from scratch or morph them from previously generated ones. / <p>The presentation was online</p>