Changing Settling Velocity

Topics about the HYSPLIT dispersion model.
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kjmohr
Posts: 23
Joined: June 22nd, 2020, 3:05 pm
Registered HYSPLIT User: Yes

Changing Settling Velocity

Post by kjmohr »

Hi,

I understand how HySPLIT calculates settling velocity for the simulations, but I was wondering how do you change the velocity of a particular particle size within a command script, can you have different settling velocities for different particle sizes? Or is there a way to change the drag coefficient?

Also, where does the shape factor come into play when doing the settling velocity calculations? And why do the shape factors for HySPLIT range from 1-2 instead of 0-1?

I am asking for volcanic eruptions, as eruptions have varying particle sizes and it has been noted that different size particles follow different Reynold flow regimes. So I am wondering if there is a way to set the Reynolds Regime, from laminar, intermediate or turbulent for different particle sizes on the same run?

Thanks in advance,

Kyle
barbara.stunder
Posts: 421
Joined: November 9th, 2012, 4:23 pm
Registered HYSPLIT User: Yes

Re: Changing Settling Velocity

Post by barbara.stunder »

For information on gravitational settling, see section 5.1 of
https://www.arl.noaa.gov/documents/reports/arl-224.pdf
and
https://ready.arl.noaa.gov/hysplitusersguide/S314.htm
The settling velocity can be forced by entering it as the dry deposition velocity.
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