Towards jet flow LES of conceptual nozzles for acoustic predictions

Progress in simulating chevron nozzle jet flows using ILES/RANS-ILES approaches and using the Ffowcs Williams and Hawkings (FW-H) surface integral method to predict the radiated far field sound is presented in this paper. With the focus on the realistic chevron geometries, SMC001 and SMC006, coarse and fine meshes are generated in the range of 3∼13 million mesh cells. Throughout this work, to minimize numerical dissipation introduced by mesh quality issues, the hexahedral cell type is used. Numerical simulations are then carried out with cell-vertex and cell-centered codes. Despite the modest grids, mean velocities and turbulent statistics are found to be in reasonable accord with measurements. Also, far field sound levels predicted by the FW-H post processor are encouraging. Copyright © 2008 by the American Institute of Aeronautics and Astronautics, Inc.

Redesigning the design process through interactive simulation: A case study of life-cycle engineering in jet engine conceptual design

Many aerospace companies are currently making the transition to providing fully-integrated product-service offerings in which their products are designed from the outset with life-cycle considerations in mind. Based on a case study at Rolls-Royce, Civil Aerospace, this paper demonstrates how an interactive approach to process simulation can be used to support the redesign of existing design processes in order to incorporate life-cycle engineering (LCE) considerations. The case study provides insights into the problems of redesigning the conceptual stages of a complex, concurrent engineering design process and the practical value of process simulation as a tool to support the specification of process changes in the context of engineering design. The paper also illustrates how development of a simulation model can provide significant benefit to companies through the understanding of process behaviour that is gained through validating the behaviour of the model using different design and iteration scenarios. Keywords: jet engine design; life-cycle engineering; LCE; process change; design process simulation; applied signposting model; ASM. Copyright © 2011 Inderscience Enterprises Ltd.

Modelo simple para la permeabilidad dinámica de fluidos viscoelásticos

In the present work a simple form to obtain analytical expression for the dynamic permeability of Maxwellian fluids is presented. This expression gives the frequency dependent form of this dynamic permeability. In particular case, the analytic expression for the sinusoidal pressure pump fluid is illustrated in the configuration space. As an example of the feasibility of this expression the flow of human blood in a tube is presented finding that the human heart frequency has the same order that the frequencies where the dynamic permeability shows resonances. In order to make clear the above aspect of the dynamic permeability a model of pulsing pressure drops (gaussian like) are analyzed.

Preliminary evaluation of conceptual mechanical designs

Computational Design has traditionally required a great deal of geometrical and parametric data. This data can only be supplied at stages later than conceptual design, typically the detail stage, and design quality is given by some absolute fitness function. On the other hand, design evaluation offers a relative measure of design quality that requires only a sparse representation. Quality, in this case, is a measure of how well a design will complete its task.

The research intends to address the question: "Is it possible to evaluate a mechanical design at the conceptual design phase and be able to make some prediction of its quality?" Quality can be interpreted as success in the marketplace, success in performing the required task, or some other user requirement. This work aims to determine a minimum level of representation such that conceptual designs can be usefully evaluated without needing to capture detailed geometry. This representation will form the model for the conceptual designs that are being considered for evaluation. The method to be developed will be a case-based evaluation system, that uses a database of previous designs to support design exploration. The method will not be able to support novel design as case-based design implies the model topology must be fixed.