ESDU Engineer
Issue 18
ESDU CFD GUIDES
Computer-aided engineering (CAE) software is used extensively in a wide range of industries. Usage is being driven by the increasing speed and lower costs of computer hardware, coupled with improvements in both software technology and ease of use.
CAE programs based on numerical methods, such as finite element analysis (FEA) and computational fluid dynamics (CFD), were originally developed as analysis tools. Today an increasing number of critical design decisions are made on the basis of numerical simulations. For example, CFD calculations now underpin the design of a wide range of components within gas turbine engines, Formula 1 racing cars and chemical processing plants.
CAE can also be used to improve existing engineering knowledge. An article in Issue 17 of the ESDU Engineer highlighted the use of FEA by the ESDU Strength Analysis Group to improve design methods for lugs to reduce aircraft weight.
Of prime concern to industrial users of CAE software, especially in safety-critical situations, is the validation of the results of simulations. Another concern is the level of understanding of the underlying fundamentals by users, who increasingly frequently are not experienced engineering specialists. The extensive data, guidance and software in the IHS ESDU Fluid Mechanics, Internal Flow Series have long been held up as ideal tools to help address those concerns. They include industry-standard methods for calculating pressure losses in internal flow systems, developed using CFD to supplement and support experimental data. Today, the methods are increasingly used for training engineers in fluid mechanics and providing validated, experimentally-based tools for CFD validation.
The technical committee that guides this work, the IHS ESDU Internal Flow Panel, is now guiding the development of unique ‘CFD Best Practice Guidelines’ and ‘CFD Benchmarks’ to assist better the CFD user modelling flows and pressure losses in pipes, ducts and other enclosed equipment. CFD Best Practice Guidelines provide detailed modelling guidance and CFD Benchmarks provide reliable validation data against which engineers can test their CFD models and assess parameter sensitivity.
Dr John Eaton, Director of the Aerospace Research Centre at the National University of Ireland, Galway, and Chair of the IHS ESDU Internal Flow Panel, explained that “Pressure losses are particularly difficult to predict for internal flow applications. The ESDU CFD Guides capture ESDU’s extensive experience in rigorous CFD analysis of internal flows, and make recommendations on crucial features such as turbulence modelling. Combined with ESDU’s unique coverage of pressure losses in internal flows, they will cover an increasingly wide range of geometrical configurations and flows, underpinned by experimental data and, where appropriate, CFD predictions”.
The industrial value of ESDU CFD Guides is recognised by Dr Ian Jones, Head of Technical Services at ANSYS Europe and a member of the Internal Flow Panel. Dr Jones noted that “ESDU CFD Guides can help users by providing reliable CFD benchmarks for the validation of their CFD predictions, allowing them to have greater confidence in the accuracy of their simulations and the use of the methodology, and reduce the need for time-consuming sensitivity studies”.
ESDU CFD Best Practice Guidelines and CFD Benchmarks include recommendations made by ESDU for CFD modelling of pressure and flow characteristics in internal flow components. The Guidelines are concise but informative and are based on extensive and rigorous CFD validation studies performed by expert CFD engineers at ESDU. They may be used with any finite volume Reynolds-averaged Navier-Stokes (RANS) CFD code with low-Reynolds-number turbulence modelling capabilities.
Within the CFD Best Practice Guidelines, advice is given on mesh size and distribution, setting of boundary conditions, turbulence modelling, advection algorithm and convergence criterion for a wide range of geometrical configurations and Reynolds number.
ESDU CFD Benchmarks provide reliable benchmark data for the validation of CFD predictions. These are from a critical analysis of published and unpublished experimental data. Within the CFD Guide, comparisons with validated ESDU CFD predictions performed using ESDU’s rigorous validation procedure are discussed in detail. Input geometrical and flow parameters in laminar to turbulent flow are provided for defining a number of CFD Benchmarks.
Guidance on CFD modelling of the flow in straight pipes will provide critical information on setting of boundary conditions. For the flow through orifice plates, CFD modelling guidance is important when, for example, using CFD for designing film cooling holes in turbo-engines and oil flow-metering devices.
| Benchmark 1: Comparison of ESDU CFD predictions with LDA measurements |
Benchmark 2: Comparison of ESDU CFD predictions with Bullen’s measurements and Crane, Miller, Idel’chik correlations |
Now available:
| ESDU CFD-BPG 07008 |
CFD Best Practice Guidelines for modelling pressure loss and flow characteristics. Incompressible flow in sudden contractions. IHS ESDU, London, 2007. |
| ESDU CFD-BMK 07009 |
CFD Benchmarks for predicting pressure loss and flow characteristics. Incompressible flow in sudden contractions. IHS ESDU, London, 2007. |
| ESDU TN 06023 |
CFD validation studies for pressure loss and flow characteristics in sudden contractions. IHS ESDU, London, 2006. |
Queries regarding this article should be directed to Dr Francesca Iudicello, Head of the Fluid Mechanics Group: francesca.iudicello@ihs.com
For more information visit www.esdu.com.