Value driven conceptual design of Unmanned Air System for defence applications

The work presented concerns the development of a value driven conceptual design assessment framework for a small Unmanned Air System (UAS) to be utilized in a defence application. In the field of Multi-Disciplinary Design Optimization, most recent systematic search has been devoted to fixed topology parametric geometries, pertaining to a single concept, with very little stress put on the optimization of variable topologies describing alternative design concepts. The search is conducted in a highly novel manner, generating a broad range of combinations of UAS configurations and geometries by systematically searching alternative concepts and design configurations through the parameterization of the aircraft geometric topologies. Moreover, the “value” of proposed solutions is assessed in an objective way both from performance and economic perspectives, while the optimal solution is identified after relaxing all of the design constraints as advocated by value driven design philosophy. During the multi-criteria decision analysis, the quantification/conversion of the linguistic preferences of the user between the various attributes to numerical values has disclosed some deficiencies introduced by the unjustifiable numerical scales used in the Analytic Hierarchy Process (AHP). This problem is resolved by a novel value model synthesizing the AHP assessment methodologies with multi-attribute value-focused analysis

Value driven conceptual design of unmanned air system for a defence application

The work presented culminates in the development of a value driven conceptual design assessment framework for a small Unmanned Air System (UAS) to be utilized in a defence application. In the field of Multi-Disciplinary Design Optimisation, most recent systematic search has been devoted to fixed topology parametric geometries, pertaining to a single concept, with very little stress put on the optimization of variable topologies describing alternative design concepts. The search is conducted in a highly novel manner, generating a broad range of combinations of UAS configurations and geometries by systematically searching alternative concepts and design configurations through the parameterization of the aircraft geometric topologies. Moreover, the “value” of proposed solutions is assessed in an objective way both from performance and economic perspectives, while the optimal solution is identified based on the user’s needs after relaxing all of the design constraints. During the multi-criteria decision analysis, the quantification/conversion of the linguistic preferences of the user between the various attributes to numerical values has disclosed some deficiencies introduced by the unjustifiable numerical scales used in the Analytic Hierarchy Process (AHP) and a novel value model for consistent value assessment is introduced, synthesizing the AHP assessment methodologies with multi-attribute value-focused analysis

A prescriptive approach to qualify and quantify customer value for value-based requirements engineering

Recently, customer-based product development is becoming a popular paradigm. Customer expectations and needs can be identified and transformed into requirements for product design with the help of various methods and tools. However, in many cases, these models fail to focus on the perceived value that is crucial when customers make the decision of purchasing a product. In this paper, a prescriptive approach to support value-based requirements engineering (RE) is proposed, describing the foundations, procedures and initial applications in the context of RE for commercial aircraft. An integrated set of techniques, such as means-ends analysis, part-whole analysis and multi-attribute utility theory is introduced in order to understand customer values in depth and width. Technically, this enables identifying the implicit value, structuring logically collected statements of customer expectations and performing value modelling and simulation. Additionally, it helps to put in place a system to measure customer satisfaction that is derived from the proposed approach. The approach offers significant potential to develop effective value creation strategies for the development of new product

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