by : CHAM Consultancy Team

Date: 1997 - PHOENICS Version: 3.0

- This project focused on the flow simulation of a particular type of
fire-fighting equipment, which has an inlet manifold including
six water inlets, one foam inlet and one outlet at the top of the
domain.
- The case was three-dimensional, and the simulation was for steady,
incompressible, turbulent and isothermal flow. A Cartesian grid was
used to discretise the domain.
- The geometry within the domain was created using PHOENICS-VR. As the
manifold was symmetrical, only half of the domain was simulated.
- As the problem required a simplified simulation, the foam flow was
represented by the transport of a concentration source. Thus a single
constant fluid density is fixed throughout the computational domain.
- The LVEL turbulence model, which is a standard model found in PHOENICS,
was implemented to close the Reynolds-averaged Navier-Stokes equations.
- The computational domain was 2.4m long by 0.75m wide by 0.35m high.
The grid comprised 40*40*15 cells, and was generated automatically
by PHOENICS-VR.
- The water inlets were represented by 150mm-diameter plate cylinder
shapes. The velocity of each one was set to 14m/s, giving an inflow
rate of about 15,000 litres/min.
- The foam inlet was made of a 125mm diametre plate cylinder shape,
extended by a 600mm long pipe shape. As the foam velocity was fixed
to 10m/s, it gave an inflow rate of about 7,000 litres/min.
- The outlet was a 250mm diameter plate cylinder shape and its pressure
was set to atmospheric.
- To increase the outlet foam rate and improve the mixing, vertical
baffles were designed within the manifold extending from the floor
to the roof.
- A pyramid shape was placed at the bottom of the tank, under the outlet, to drive the flow vertically faster to the outlet.

The following illustrates the geometry and results.

1. PHOENICS-VR model of half the manifold

2. Velocity field in horizontal plane centrally located

3. Foam concentration (SMOK) at the top of the domain

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