Three-dimensional direct numerical simulation of coating flows

Many industrial processes and natural phenomena involve flows of thin viscous liquid films, such as the coating process of a solid substrate with paint or lubricant, the flow of condensed water on a clothes wire, or the flow of lava. The thinness and slowness of these flows allow us to simplify the governing partial differential equations by utilizing the lubrication approximation. These approximations simplify the numerical solution of the problem while retaining the most important nonlinear features, so that the basis of the problem can be understood.We first consider surface-tension-gradient effects on the leveling of a drying multi-component liquid. We develop a mathematical model based on the lubrication approximation, which describes the time evolution of an evaporating film. As the film dries the physical properties of the film change, therefore, we include the dependence of viscosity, surface tension, diffusivity, and evaporation rate on the resin concentration in the mathematical model. Using nonlinear numerical simulations, we demonstrate that an initially doubly-modulated sinusoidal profile can reverse its shape during the leveling process.We then consider two closely related thin-film flow problems: downhill drainage under the influence of gravity, and surface-shear-stress-driven climbing films. The stability and nonlinear finger growth mechanisms of these problems are studied in detail. The most unstable transverse wave numbers are found from the numerical solution, and are compared with published experimental results. The influence of finite contact angle is also included in the mathematical model through a disjoining-pressure model. In this study, we show that disjoining pressure is the main mechanism controlling the sideways spreading of fingers, resulting in infinitely long rivulets.Next, the spraying and spreading process on a moving substrate is considered. For this problem, we develop a mathematical model which not only captures the effects of surface tension and gravity, but also includes the moving substrate, and models different spray patterns. Under certain assumptions we find a closed-form similarity solution, which agrees well with the numerical solution.The gravitational instabilities of thin liquid films leading to drop formation are also considered. The mathematical model captures the essentials of the flow. The linear growth rates which are extracted from the nonlinear three-dimensional simulation agree very well with the analytical dispersion characteristics of the problem.Finally, we present a two-dimensional higher order lubrication approximation for the surface tension and gravity driven leveling problem. The zeroth order lubrication approximation for any flow problem is valid in the limit when the thickness of the coating is small compared to the characteristic length scale of the problem. We present the derivation of a fourth-order lubrication approximation, and show an appropriate numerical solution technique

A hierarchical life cycle cost model for a set of aero-engine components

The aero-engine is probably the most complex and vital part of civil and military aircrafts, and it is usually an important cost element of the aircraft at acquisition and operation periods. The reduction of acquisition, operation and support costs for civil and defence sectors is going to be the main driving force for aero-engine manufacturers during the next decades. Additionally, it is a well known fact that the maintenance costs of aero-engines can surpass their acquisition costs by a factor of two. Therefore, efficient and accurate prediction of aero-engine maintenance life cycle cost is vitally important for aero-engine manufacturers. For this paper we restrict ourselves to a simplified problem that deals with the life cycle cost of a set of aero-engine components, such as high pressure turbine blades, in isolation of other components of the engine. These engine components are assumed be suffering from a number of different deterioration mechanisms that may force that component to be repaired or replaced at predetermined shop visits. A hierarchical and object oriented costing model will be presented and its scope, extensibility and maintainability will be discussed

Value modelling for multi-stakeholder and multi-objective optimisation in engineering design

The work presented culminates in the development of a value model used in the conceptual phase of engineering design, with the preferences of more than one stakeholder addressed in the multi-stakeholder and multi-objective optimisation. The ‘value’ of proposed solutions is assessed in an objective way from both performance and economic perspectives, while the optimal solution is identified based on the needs of the user and manufacturer, as major stakeholders. This novel value model for consistent value assessment synthesises the multi-attribute value/utility analysis with Game Theory and Analytic Hierarchy Process (AHP) assessment methodologies. During the multi-criteria decision analysis, the deficiencies, introduced by the arbitrary numerical scales used in the AHP to convert the linguistic preferences of the user between the various attributes to numerical values, are resolved. The preferences of a group of experts/decision-makers are synthesised in the group value model through the extraction of weighting factors from the individuals’ AHP pairwise comparison matrices. Moreover, Game Theory is used in a hybrid cooperative/bargaining, non-cooperative non-zero sum game between the stakeholders as players, identifying the optimal design through the simultaneous employment of the Nash bargaining solution and the Nash equilibrium

Avoiding Resonant Frequencies in a Pipeline Application by Utilising the Concept Design Analysis Method

Avoiding disasters due to the problems stemming from resonance is a major concern in any construction project. This becomes particularly important for oil and gas pipeline systems as some damages may lead to leakage of flammable fluids, explosions, fires, destruction and loss of life. The proximity to the natural frequencies of forced frequencies (frequency ratio) normally leads to intolerant resonant vibrations and catastrophic failures. A relevant case study on a partial pipeline design with an unacceptable level of frequency ratio is presented. In order to assess the overall design merit of the case study, the Concept Design Analysis (CODA) method is utilised to map captured Customer Needs (CNs) into Engineering Characteristics (ECs). As the frequency ratio is an important EC of the whole system, the improved CODA method for the pipeline design introduces an avoidance type merit function that allows excluding a range of relevant ECs. This improved CODA method is demonstrated in a model whereby certain frequency ratios are successfully avoided in the final design

Value Driven Design revisited: emerging modelling concepts and applicatons

Extended product warranties, leasing, and pay-per-use schemes are few examples of how manufacturing companies are shifting their focus from selling products to offering “solutions”, combining products and services to maximise customer value. The idea of optimising a system towards the best ‘value’ is both "intuitive and sensible", and processes such as Value Driven Design (VDD), have been proposed to supplement traditional engineering design methodologies. Yet, value-driven initiatives struggle to communicate their benefits and to demonstrate how value models can solve actual problems. The aim of this paper is to shed light on the evolution of the VDD toolbox, mapping research clusters, applications and case studies from the perspective of how much (and how well) recent contributions have answered the five top-level questions of the VDD research agenda published in 2012. The results of the systematic literature review reveal the emergence of innovative modelling constructs, methods, and tools that help VDD in taking a leap forward in supporting organizations and teams in achieving the long-sought objective of designing for 'value'.open access</p

Avoiding Resonant Frequencies in a Pipeline Application by Utilising the Concept Design Analysis Method

Avoiding disasters due to the problems stemming from resonance is a major concern in any construction project. This becomes particularly important for oil and gas pipeline systems as some damages may lead to leakage of flammable fluids, explosions, fires, destruction and loss of life. The proximity to the natural frequencies of forced frequencies (frequency ratio) normally leads to intolerant resonant vibrations and catastrophic failures. A relevant case study on a partial pipeline design with an unacceptable level of frequency ratio is presented. In order to assess the overall design merit of the case study, the Concept Design Analysis (CODA) method is utilised to map captured Customer Needs (CNs) into Engineering Characteristics (ECs). As the frequency ratio is an important EC of the whole system, the improved CODA method for the pipeline design introduces an avoidance type merit function that allows excluding a range of relevant ECs. This improved CODA method is demonstrated in a model whereby certain frequency ratios are successfully avoided in the final design

Avoiding resonant frequencies in a pipeline application by utilising the concept design analysis method

Avoiding disasters due to the problems stemming from resonance is a major concern in any construction project. This becomes particularly important for oil and gas pipeline systems as some damages may lead to leakage of flammable fluids, explosions, fires, destruction and loss of life. The proximity to the natural frequencies of forced frequencies (frequency ratio) normally leads to intolerant resonant vibrations and catastrophic failures. A relevant case study on a partial pipeline design with an unacceptable level of frequency ratio is presented. In order to assess the overall design merit of the case study, the Concept Design Analysis (CODA) method is utilised to map captured Customer Needs (CNs) into Engineering Characteristics (ECs). As the frequency ratio is an important EC of the whole system, the improved CODA method for the pipeline design introduces an avoidance type merit function that allows excluding a range of relevant ECs. This improved CODA method is demonstrated in a model whereby certain frequency ratios are successfully avoided in the final desig

An integrated framework for Bayesian uncertainty quantification and probabilistic multi-criteria decision making in aero-engine preliminary design

The following paper presents a novel framework that enables making early design decisions based on probabilistic information obtained from fast, deterministic, low-fidelity tools, calibrated against high-fidelity data that is supported by experts’ knowledge. The proposed framework integrates a Probabilistic Multi-Criteria Decision Making technique with Bayesian Uncertainty Quantification concepts supported by the Kennedy and O’Hagan Framework. It allows continuous improvement of low-fidelity design tools as high-fidelity data is gathered and therefore facilitates investigation into the impacts the accumulation of high-fidelity data has on preliminary design process risk. The paper discusses theoretical concepts behind the framework and demonstrates its relevance by application in an illustrative combustor preliminary design case study