THE APPLICATION OF THE BOUNDARY ELEMENT METHOD TO SOLVE VISCOUS FLOW PROBLEMS BASED ON PRIMITIVE VARIABLES FORMULATION

The boundary element method is applied to the solution of incompressible fluid flow problems governed by the continuity and Navier-Stokes equations. The differential equations are transformed into integral equations. Indication of the transformation is given in detail. Application to simple flow cases such as the driven cavity and forward facing step is presented. Convergence difficulties are indicated, which have limited the applications to flows of low Reynolds numbers.

Specifications for modelling fuel cell and combustion-based residential cogeneration device within whole-building simulation programs

This document contains the specifications for a series of residential cogeneration device models developed within IEA/ECBCS Annex 42. The devices covered are: solid oxide and polymer exchange membrane fuel cells (SOFC and PEM), and internal combustion and Stirling engine units (ICE and SE). These models have been developed for use within whole-building simulation programs and one or more of the models described herein have been integrated into the following simulation packages: ESP-r, EnergyPlus, TRNSYS and IDA-ICE. The models have been designed to predict the energy performance of cogeneration devices when integrated into a residential building (dwelling). The models account for thermal performance (dynamic thermal performance in the case of the combustion engine models), electrochemical and combustion reactions where appropriate, along with electrical power output. All of the devices are modelled at levels of detail appropriate for whole-building simulation tools

A design tool for sizing thermosyphon solar water heaters

Today, thermosyphon solar water heaters are the most popular type of solar water heaters for providing households with the required hot water for domestic purposes. However, sizing and designing these systems is still based on experience or on trial and errors methods, which are based more on intuition rather than scientific methods. The present study is aimed at addressing this problem (sizing thermosyphon systems) through the development of a design tool that can be used by engineers and manufacturers to arrive at optimised systems designed according to the weather and operating conditions of particular geographical locations. The design tool developed during the course of this study is based on the TRNSYS simulation programme for evaluating the thermal performance of thermosyphon systems, and on the genetic algorithm approach for the purpose of optimising selected design parameters of thermosyphon systems. A thorough literature review of the available models and software packages that are capable of evaluating the performance of thermosyphon systems has shown that the best available programme is TRNSYS, namely the component Type 45 (thermosyphon collector-storage component). However, the component Type 45 in its current form cannot be used directly for the purpose of optimisation, because this component relies on information that must be determined experimentally. This means that the component is mainly used for evaluating the thermal performance of already-made and tested systems under varying operating and climatic conditions. For this reason, two components developed in this research have been added to the TRNSYS suite to account for information that would otherwise have to be determined experimentally. The new components are: solar collector characteristics component Type 210; and pipes - tank heat loss coefficients Type 211. Furthermore, the component Type 45 is also modified to accept as, inputs, the outputs from the previous two new components. The modified component is named as modified thermosyphon component Type 245. The new components are validated experimentally and by using reports of tests conducted according to the appropriate European standard. The modified component Type 245 does not require any validation, as no changes were made in the main programme, except that of altering the experimentally-determined information from being parameters to instead being inputs in the TRNSYS terminology. The newly validated components were added to the original TRNSYS model so as to constitute a modified TRNSYS model which is used throughout this work. The modified TRNSYS model was· then used to perform a parametric study of the design parameters of thermosyphon systems. A genetic algorithm routine for constrained single objective optimisation problem was used, and the constraints are handled by using the stochastic ranking procedure. The genetic algorithm programme is combined with the modified TRNSYS model to constitute the final design tool. The design tool is used in this study to find the optimum thermosyphon system design that best suits Libyan families (as a case study in this research) according to the weather conditions of Tripoli and a simple, but representative, hot water load pattern. The design tool is shown to have significant potential, and with further development and validation would be capable of commercial application

Automating embedded analysis capabilities and managing software complexity in multiphysics simulation part II: application to partial differential equations

A template-based generic programming approach was presented in a previous paper that separates the development effort of programming a physical model from that of computing additional quantities, such as derivatives, needed for embedded analysis algorithms. In this paper, we describe the implementation details for using the template-based generic programming approach for simulation and analysis of partial differential equations (PDEs). We detail several of the hurdles that we have encountered, and some of the software infrastructure developed to overcome them. We end with a demonstration where we present shape optimization and uncertainty quantification results for a 3D PDE application

Development And Validation Of Trombe Walls In Autodesk Simulation Cfdtm

Computational Fluid Dynamics (CFD), as an architectural tool, has the potential to model the air flow and convective heat transfer that predominates the performance of passive solar building techniques to meet the comfort needs of building occupants; however, there is very little research on the implementation or validation of CFD software for this purpose. This study attempts to validate a verified CFD software program, Autodesk CFD, for the purpose of modeling both unvented and vented Trombe walls. Temperature and air velocity data from two past experimental studies were compared to model results. The results indicate that CFD may be used to simulate and visualize buoyancy driven air flow and mass wall heat transfer closely resembling actual Trombe wall performance

Design and evaluation of fluidized bed heat recovery for diesel engine systems

The potential of utilizing fluidized bed heat exchangers in place of conventional counter-flow heat exchangers for heat recovery from adiabatic diesel engine exhaust gas streams was studied. Fluidized bed heat recovery systems were evaluated in three different heavy duty transport applications: (1) heavy duty diesel truck; (2) diesel locomotives; and (3) diesel marine pushboat. The three applications are characterized by differences in overall power output and annual utilization. For each application, the exhaust gas source is a turbocharged-adiabatic diesel core. Representative subposed exhaust gas heat utilization power cycles were selected for conceptual design efforts including design layouts and performance estimates for the fluidized bed heat recovery heat exchangers. The selected power cycles were: organic rankine with RC-1 working fluid, turbocompound power turbine with steam injection, and stirling engine. Fuel economy improvement predictions are used in conjunction with capital cost estimates and fuel price data to determine payback times for the various cases

Building systems and indoor environment : simulation for design decision support

This paper outlines the state-of-the-art in integrated building simulation for design support. The ESP-r system is used as an example where integrated simulation is a core philosophy behind the development. The paper finishes with indicating a number of barriers, which hinder routine application of simulation for building design

ULTRA-SHARP nonoscillatory convection schemes for high-speed steady multidimensional flow

For convection-dominated flows, classical second-order methods are notoriously oscillatory and often unstable. For this reason, many computational fluid dynamicists have adopted various forms of (inherently stable) first-order upwinding over the past few decades. Although it is now well known that first-order convection schemes suffer from serious inaccuracies attributable to artificial viscosity or numerical diffusion under high convection conditions, these methods continue to enjoy widespread popularity for numerical heat transfer calculations, apparently due to a perceived lack of viable high accuracy alternatives. But alternatives are available. For example, nonoscillatory methods used in gasdynamics, including currently popular TVD schemes, can be easily adapted to multidimensional incompressible flow and convective transport. This, in itself, would be a major advance for numerical convective heat transfer, for example. But, as is shown, second-order TVD schemes form only a small, overly restrictive, subclass of a much more universal, and extremely simple, nonoscillatory flux-limiting strategy which can be applied to convection schemes of arbitrarily high order accuracy, while requiring only a simple tridiagonal ADI line-solver, as used in the majority of general purpose iterative codes for incompressible flow and numerical heat transfer. The new universal limiter and associated solution procedures form the so-called ULTRA-SHARP alternative for high resolution nonoscillatory multidimensional steady state high speed convective modelling

A multi-method approach to radial-velocity measurement for single-object spectra

The derivation of radial velocities from large numbers of spectra that typically result from survey work, requires automation. However, except for the classical cases of slowly rotating late-type spectra, existing methods of measuring Doppler shifts require fine-tuning to avoid a loss of accuracy due to the idiosyncrasies of individual spectra. The radial velocity spectrometer (RVS) on the Gaia mission, which will start operating very soon, prompted a new attempt at creating a measurement pipeline to handle a wide variety of spectral types. The present paper describes the theoretical background on which this software is based. However, apart from the assumption that only synthetic templates are used, we do not rely on any of the characteristics of this instrument, so our results should be relevant for most telescope-detector combinations. We propose an approach based on the simultaneous use of several alternative measurement methods, each having its own merits and drawbacks, and conveying the spectral information in a different way, leading to different values for the measurement. A comparison or a combination of the various results either leads to a "best estimate" or indicates to the user that the observed spectrum is problematic and should be analysed manually. We selected three methods and analysed the relationships and differences between them from a unified point of view; with each method an appropriate estimator for the individual random error is chosen. We also develop a procedure for tackling the problem of template mismatch in a systematic way. Furthermore, we propose several tests for studying and comparing the performance of the various methods as a function of the atmospheric parameters of the observed objects. Finally, we describe a procedure for obtaining a knowledge-based combination of the various Doppler-shift measurements.Comment: 16 pages, 4 figure