Multiple bins for varying particle diameters

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Christopher
Posts: 4
Joined: June 15th, 2021, 9:13 am
Registered HYSPLIT User: Yes

Multiple bins for varying particle diameters

In the HYSPLIT 2021 workshop, there was talk of automatically adding particle diameter bins.

I'm working with spray drift where a spray nozzle is defined as a mostly gaussian distribution with three parameters: D1, D5 and D9 which are the particle diameter where 10%, 50%, and 90% of the mass lie below, respectively.

Currently, I'm doing five HYSPLIT runs: three with evenly split mass in the D1 range adding up to 10% of mass, one for D5 with 80% of the mass, and one for D9 with 10% of the mass. It's really the small diameter particles that are interesting, hence the three runs for 10% of the mass.

Is there a better way to do this?

Ideally, it would be nice to tell HYSPLIT to use a gaussian distribution with specified mean and std-dev (or even better a curve fitted to three points) then automatically distribute the mass amongst the particle diameters. But without touching any HYSPLIT source code, is there a better way to kludge this? Maybe doing all the mass/diameter splits in one run with multiple bin levels specified through HYSPLIT input files?
alicec
Posts: 328
Joined: February 8th, 2016, 12:56 pm
Registered HYSPLIT User: Yes

Re: Multiple bins for varying particle diameters

You can define multiple species within the same HYSPLIT run.
So for instance suppose you have total emission of 1 kg/hr.
You want 3 particle sizes with 10%, 50% and 40% of mass respectively.
Emission rates for the 3 particle sizes would then be defined as
0.10
0.50
0.40

So you can create your Gaussian distribution similar to what you are doing now, but have all the particles simulated
in the same run.

In the tutorial the NBPTYP namelist parameter was discussed. more info here.
NBPTYP=1 number of redistributed particle size bins per pollutant type

This is probably similar to what you are looking for, but the distribution is not Gaussian.
"NBPTYP (1) - defines the number of bins assigned to each particle size as defined in the pollutant section of the CONTROL file. The default value of one uses the input parameters. A value larger than one will create that number of particle size bins centered about each value in the CONTROL file. The program creates the mass distribution for a range of particle sizes given just a few points within the distribution. We assume that dV/d(log R) is linear between the defined points for an increasing cumulative mass distribution with respect to particle diameter. The input points in the CONTROL file should be sorted by increasing particle size within the array. For instance, if the CONTROL file defines 3 particle sizes (5, 20, and 50), and NBPTYP=10, then for the 5 micron particle generates sizes from 2.3 to 8.1 microns while the 50 micron input particle generates sizes from 30.2 to 68.9 microns."
Sometimes it can be advantageous to have the different particles sizes in different runs to have better control over how many computational particles are assigned to each particle size and how much mass is on each computational particle.