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See also GENTRA library case g722 and applications album example track

The particle-tracking procedure is attached to the GENTRA option of PHOENICS. It computes the volume fractions of the fluids in each cell, based on particle locations, and then calculates the densities which are to be employed in the momentum equations.

Limitations: 2-D X-Y plane; single-track line (no break up)

How to use:

1. Users need to specify data in the following files:

The Q1 file Apart from the conventional settings required for the problem in question, the following settings are specific to the particle-tracking procedure:

STORE(C1) and RHO1=GRND -- for density calculation
LG(30)=T -- to activate particle tracking procedure 
RG(30) -- to define the face from which the first particle will enter the calculation
RG(30)=1 - from West; north 
RG(30)=2 - from East;
RG(30)=3 - from South
RG(30)=4 - from North; 
RG(1) -- density of the fluid on the left side of the track 
RHO2 -- density of the fluid on the right side of the track

|--> left side |/ / ---> | right / --> | / / / / / --> |-----------------

There are two parts in the Q1 file; the first part from Group 1 to Group 23 is for standard Q1 settings and the second part after Group 23 is for GENTRA settings.

The most convenient way for users to set a problem is to load GENTRA library case g722 and then modify the first part according to the problem description and then modify only Group 2 of the GENTRA settings, that is Boundary conditions for particles.

Users should specify the initial particle positions there. The program will automatically perform a linear interpolation between particles in order to adjust the distance between two adjacent particles.
Therefore only two particles need to be specified for a straight line of the initial distribution as described in case 722. For other shapes of the initial distribution, users have to specify a sufficient number of particles to produce the desired result.

Sub-routine trkden.htm in phoenics/d_earth/d_opt/d_gentra

This is the routine for the density calculation. Users must re-dimension local variable array to be consistant with NX,NY specified in Q1.

gentra.htm in phoenics/d_earth/d_opt/d_gentra
group 9 -- To calculate density (no users' action is needed)
group 11 -- Users must set initial density distribution; note that RG(6) is used only for library case g722
group 19 -- To call tracking routine (no user action is needed)

2. compile trkden.htm and gentra.htm

3. re-build EARTH executable

How to view tracks:

1. use upkexe to unpack particles

type: upkexe
followed by t <return> and then by T1-T2 <return>
where T1 and T2 are integer numbers defining
the first time step and the last time step;

2. run PHOTON and use command 'use genuse' to draw particle tracks.