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Contents

1. What it is
2. What it does
3. References

1. What it is

Origins

PISA is a CFD code for piston-engine analysis derived by CHAM from the widely-used public-domain KIVA 2 code created by the Los Alamos Laboratory.

PISA generates numerical solutions of the Reynolds-averaged Navier-Stokesfor equations for multi-component chemically-reactive fluid-flow problems.

However, the program was developed with applications to internal-combustion engines in mind, and therefore contains a several especially-appropriate features. In particular, the diesel and direct-injection stratified-charge engines are analysed, with the capability to represent an evaporating fuel spray.

The formulation is fully three-dimensional; but it also has two-dimensional (planar or axi-symmetrical) options.

Numerics

PISA is a time-marching finite-difference program that uses an acoustic sub-cycling method for efficiency at low Mach number.

Spatial differences are formed with respect to a generalised three-dimensional mesh of arbitrary hexahedrons whose corner locations are specified functions of time. This feature allows a Lagrangian, Eulerian, or mixed description, and is particularly useful for representing curved or moving boundaries.

Physics

The program can be applied to flows which are:-

• laminar or turbulent,
• subsonic or supersonic, and
• single-phase or dispersed two-phase flows.

• a subgrid-scale model, including transport of turbulent energy,
• and a law-of-the-wall boundary-layer turbulence model.

A discrete-particle technique is used to represent an evaporating liquid spray, including the effects of droplet collisions and coalescence.

2. How it does it

Hardware platforms

The KIVA 2 program released by Los Alamos was designed in the first instance use on Cray machines. In creating PISA, CHAM has:

• adapted the code for use on UNIX workstations and Personal Computers;

• simplified and otherwise improved the coding;

• modified KIVA 2 in a manner which allows it:
  1. to accept problem-defining input data from the PHOENICS SATELLITE;
  2. to display its output by means of the PHOTON post-processor; and
  3. thus to act as an alternative to the EARTH flow-simulation module of PHOENICS.

On the PC, the code can be operated under either the Windows or DOS operating Systems.

PISA can be supplied either with or without the source code.

The library of input files

A Library of input files is provided with the PISA package, specifically :

1. Engine With A Bowl And Cone Injector.
   ( Mesh NX=20, NY=22, NZ=1 )
2. Engine With An Offset Chamferrd Bowl And Tilted Injector.
   (Coarse Mesh NX=6, NY=8, NZ=10)
3. Engine With An Offset Chamferred Bowl And Tilted Injector.
   (Mesh NX=13, NY=16, NZ=16)
4. Model Engine With A Bowl
   From J.H. Whitelaw ... Report December 1981 (Piston Shape No.2).
   (Mesh NX=13, NY=16, NZ=1)
5. Engine With An Offset Domed Head And Tilted Injector.
   (Coarse Mesh NX=6, NY=8, NZ=10)
6. Engine With An Offset Domed Head And Tilted Injector.
   ( Mesh NX=10, NY=16, NZ=16)
7. Engine With A Square Bowl And Tilted Injector.
   ( Mesh NX=13, NY=20, NZ=12)

3. References