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Developments of PHOENICS as CFD engine for WindSim

Tomasz STELMACH CHAM Ltd, UK

ts@cham.co.uk

WindSim Annual User Meeting

16 June 2011

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Topics of presentation

1. CHAM - who we are, what we do

2. PHOENICS

3. GCV - GENERAL COLOCATED VELOCITY METHOD

4. USP – unstructured version of PHOENICS

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CHAM - Concentration Heat And Momentum

CHAM is a world leading consultancy and software house specialising

in computer simulation of fluid-flow, fluid-structure-interaction and heat-

transfer

• Founded by Professor Brian Spalding in 1974

• Independent CFD company run by its founder

• PHOENICS general purpose package

• Specialized, PHOENICS based,

stand alone CFD programs

• CFD engine behind WindSim

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CHAM - Concentration Heat And Momentum

• Software development

• Model-building and applied consultancy

• Software sales

• Introductory/advanced training courses

• Technical support

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PHOENICS

• Aerospace

• Automotive

• Chemical

• Combustion

• Electronics Cooling

• Metallurgical

• Power Generation

• Turbomachinery

• Atmospheric flows

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PHOENICS

Noteworthy Special Features

• RDI: Relational data input allows

parameterization of model scenarios

• In-Form: Input of data via formulae removes

the need for user programming.

• PARSOL: ‘cut-cell’ technique to fit curved

bodies in structured Cartesian grids

eliminates grid-generation problem.

• USP: Unstructured grids are created

automatically

• Parallelisation: domain decomposition

allows simulation of very large scenarios

• PRELUDE: provides user-friendly

application-specific Gateways

• DFW: Distance from wall calculator used in

turbulence and radiation models

• PARAB: Parabolic mode simplifies flows in

ducts, jets and boundary layers

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PHOENICS Usual features

Plus all the usual features:

• 1-,2- and 3-D geometries

• Cartesian, Polar and BFC

• Conjugate Heat Transfer

• Multi-Phase; Particle Tracking

• Chemical reaction; Radiation

• Turbulence

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PHOENICS – terrain related simulations

• flows in rivers and adjacent flood plains;

• flow over and air pollution in urban landscapes;

• the spread of forest fires;

• air and smoke movement in underground passages;

• gas-releases into the atmosphere and consequent explosions;

• thermal and fluid-flow interactions between adjacent equipment items in chemical-industry scenarios

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PHOENICS – stand alone programs

• Virtual Wind tunnel

• FLAIR

• Terrain

• Shell and Tube Heat Exchangers

• Gas release

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GCV - GENERAL COLOCATED

VELOCITY METHOD

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GCV - GENERAL COLOCATED

VELOCITY METHOD

The GCV - alternative algorithm for solving the N-S equations in BFC

geometries.

The main features of the GCV method are:

• A block-structured multi-block implementation, with a capability to tackle

highly non-orthogonal grids. Convergence can be obtained with included

angles as small as 10 degrees.

• A sliding-grid option enables the simulation of problems where a

computational grid is divided into two parts, namely a part which rotates

around the Z axis and a part which is at rest.

•The method uses a segregated pressure-based solver strategy with an

additional correction of cell-centre momentum velocity components, which

converges faster in comparison with the standard one-step face velocity

correction.

• The solver works in a block-by-block manner, but takes the links between

blocks into account implicitly, thus providing fast convergence.

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GCV - GENERAL COLOCATED

VELOCITY METHOD

Key benefits:

• Faster convergence,

• Shorter computational time,

• Better convergence (results) with complex terrain cases.

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GCV - GENERAL COLOCATED

VELOCITY METHOD

Comparison with standard method

STANDARD GCV

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GCV - GENERAL COLOCATED

VELOCITY METHOD

Computational time: 10 min

STANDARD GCV

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GCV - GENERAL COLOCATED

VELOCITY METHOD

Terrain simulation example using with GCV=T

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GCV - GENERAL COLOCATED

VELOCITY METHOD

Terrain simulation example using with GCV=T

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GCV - GENERAL COLOCATED

VELOCITY METHOD

Terrain simulation example using with GCV=T

STANDARD GCV

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GCV - GENERAL COLOCATED

VELOCITY METHOD

Terrain simulation examples using with GCV=T

Conclusions

• Obtain convergence with cases which before it was very

difficult or even impossible,

• Lower computational time,

• Only ~3% increase of memory requirements,

• More reliable results.

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USP – UNSTRUCTURED PHOENICS

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USP – UNSTRUCTURED PHOENICS

• USP is a part of the standard

PHOENICS package, which can

therefore working structured or

unstructured modes at user’s choice.

• All USP grids consist of Cartesian (i.e.) brick-shaped cells.

• USP mesh can be generated automatically via special utility called Automatic Grid Generator (AGG)

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USP – UNSTRUCTURED PHOENICS

Advantages of using USP grids in flow over terrains modelling:

High quality (density) numerical grid is required only in the near ground layer

• For given fineness near the ground, USP uses fewer cells than SP.

• For the same number of cells, USP’s grid is finer near the ground

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USP – UNSTRUCTURED PHOENICS

Example of USP grid

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USP – UNSTRUCTURED PHOENICS

COMPARISON SP and USP

SP USP

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USP – UNSTRUCTURED PHOENICS

COMPARISON SP and USP

SP USP

USP case converged 6 times faster.

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USP – UNSTRUCTURED PHOENICS

USP terrain case example:

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USP – UNSTRUCTURED PHOENICS

USP example - results

Contours of velocity Contours of pressure

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USP – UNSTRUCTURED PHOENICS

USP example – convergence plot

Converge just after 774 iterations

Computational time: aprox. – 7min

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USP – UNSTRUCTURED PHOENICS

CONCLUSIONS

Conclusions:

• Reduced computation time and memory requirements

• Results are very similar to standard gird cases

• Useful for terrain simulation problems

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PHOENICS – near future R&D

• Further development and validation of USP and GCV

solvers

• PARSOL – optimizing for UPS solver

• Optimization for terrain cases

• Introducing parallel processing for USP and GCV

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PHOENICS

Thank you for attentions!

Questions?