Unsteady staggered DPM injections

Unsteady DPM injection will release particles at the beginning of every timestep.
If the timestep size is very small and the elapsed time of the simulation is long, this
will result in a large number of particle packets which are tracked in the domain.
This is expensive in CPU time.

A workaround is to write a UDF which will stagger the particle injection. Instead
of releasing the particles at the beginning of every timestep, the injections will be
staggered at every user specifed time-interval. This can be done by moving the
unsteady-starting-time of the injection forward by this user specified time after an
injection has just been performed.

During the non-injection timestep, the UDF will also accumulate the mass of the
particles and will release the accumulated mass all together at the next injection
event. In this way, the total mass of the particles in the domain is preserved.

As a sample problem, an unsteady silo launch is used. The particles are injected
at the moving nozzle exhaust boundary.

The UDF, sample problem, presentation, and animations are provided. The files
are attached to this solution.

<a target=_blank href="http://www.fluentusers.com/support/solutions/1017/dpm-inject.zip">http://www.fluentusers.com/support/solutions/1017/dpm-inject.zip</a>http://www.fluentusers.com/support/solutions/1017/dpm-inject.zip

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