2,726 research outputs found
Application of context knowledge in supporting conceptual design decision making
Conceptual design is the most important phase of the product life cycle as the decisions taken at conceptual design stage affect the downstream phases (manufacture, assembly, use, maintenance, and disposal) in terms of cost, quality and function performed by the product. This research takes a holistic view by incorporating the knowledge related to the whole context (from the viewpoint of product, user, product's life cycle and environment in which the product operates) of a design problem for the consideration of the designer to make an informed decision making at the conceptual design stage. The design context knowledge comprising knowledge from these different viewpoints is formalised and a new model and corresponding computational framework is proposed to support conceptual design decision making using this formalised context knowledge. Using a case study, this paper shows the proof of the concept by selecting one concept among different design alternatives using design context knowledge thereby proactively supporting conceptual design decision making for an informed and effective decision making
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Parametric surface meshing for design optimisation using a PDE formulation
yesThe problem of parametric surface meshing for the purpose of design optimisation using finite element analysis is considered. Here the surface mesh is generated as a solution of a suitably posed boundary value problem implemented on a 2D parameter space. A robust meshing scheme is presented where an initial mesh is manipulated, with the aid of the 2D parameter space, so as to obtain a suitable surface triangulation. This meshing scheme can then be used to create suitable finite element meshes with which accurate design optimisations can be carried out
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Shape reconstruction using partial differential equations
We present an efficient method for reconstructing complex geometry using an elliptic Partial Differential Equation (PDE) formulation. The integral part of this work is the use of three-dimensional curves within the physical space which act as boundary conditions to solve the PDE. The chosen PDE is solved explicitly for a given general set of curves representing the original shape and thus making the method very efficient. In order to improve the quality of results for shape representation we utilize an automatic parameterization scheme on the chosen curves. With this formulation we discuss our methodology for shape representation using a series of practical examples
Random field sampling for a simplified model of melt-blowing considering turbulent velocity fluctuations
In melt-blowing very thin liquid fiber jets are spun due to high-velocity air
streams. In literature there is a clear, unsolved discrepancy between the
measured and computed jet attenuation. In this paper we will verify numerically
that the turbulent velocity fluctuations causing a random aerodynamic drag on
the fiber jets -- that has been neglected so far -- are the crucial effect to
close this gap. For this purpose, we model the velocity fluctuations as vector
Gaussian random fields on top of a k-epsilon turbulence description and develop
an efficient sampling procedure. Taking advantage of the special covariance
structure the effort of the sampling is linear in the discretization and makes
the realization possible
User's guide to PMESH: A grid-generation program for single-rotation and counterrotation advanced turboprops
A detailed operating manual is presented for a grid generating program that produces 3-D meshes for advanced turboprops. The code uses both algebraic and elliptic partial differential equation methods to generate single rotation and counterrotation, H or C type meshes for the z - r planes and H type for the z - theta planes. The code allows easy specification of geometrical constraints (such as blade angle, location of bounding surfaces, etc.), mesh control parameters (point distribution near blades and nacelle, number of grid points desired, etc.), and it has good runtime diagnostics. An overview is provided of the mesh generation procedure, sample input dataset with detailed explanation of all input, and example meshes
Structured grid generation for gas turbine combustion systems
Commercial pressures to reduce time-scales encourage innovation in the design and
analysis cycle of gas turbine combustion systems. The migration of Computational
Fluid Dynamics (CFD) from the purview of the specialist into a routine analysis tool is
crucial to achieve these reductions and forms the focus of this research. Two significant
challenges were identified: reducing the time-scale for creating and solving a CFD prediction
and reducing the level of expertise required to perform a prediction.
The commercial pressure for the rapid production of CFD predictions, coupled with the
desire to reduce the risk associated with adopting a new technology led, following a
review of available techniques, to the identification of structured grids as the current
optimum methodology.
It was decided that the task of geometry definition would be entirely performed within
commercial Computer Aided Design (CAD) systems. A critical success factor for this
research was the adoption of solid models for the geometry representation. Solids
ensure consistency, and accuracy, whilst eliminating the need for the designer to undertake
difficult, and time consuming, geometry repair operations. The versatility of parametric
CAD systems were investigated on the complex geometry of a combustion system and found to be useful in reducing the overhead in altering the geometry for a
CFD prediction. Accurate and robust transfer between CAD and CFD systems was
achieved by the use of direct translators.
Restricting the geometry definition to solid models allowed a novel two stage grid generator
to be developed. In stage one an initial algebraic grid is created. This reduces
user interaction to a minimum, by the employment of a series of logical rules based on
the solid model to fill in any missing grid boundary condition data. In stage two the
quality of the grid is improved by redistributing nodes using elliptical partial differential
equations. A unique approach of improving grid quality by simultaneously smoothing
both internal and surface grids was implemented. The smoothing operation was
responsible for quality, and therefore reduced the level of grid generation expertise
required.
The successful validation of this research was demonstrated using several test cases
including a CFD prediction of a complete combustion system
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