I am trying to run a series of CFD simulations for a (advanced) middle school science fair project. I am simulating airflow in small classrooms in order to test various interventions and layouts for aid in reducing Covid-19 spread. I have been trying to use a Passive Scalar Source as a proxy for virus particles by originating it on the “mouth” of one of the students. The simulation is run for 1000ms.
I have tried various values for the Passive Scalar “flux” such as 0,1, 100, and 1000. The resulting spread of values during post processing doesn’t make sense. I was hoping to see a “cloud” drifting from the initial point toward the outflow and to be able to visualize how the dense part moves through the room and to measure the density at the locations where the other people are. The instructions at Passive Scalar Sources | Advanced Concepts | SimScale suggest a flux of 0. At this value, the scalar field seems to fill the room and using the range filter to try to look at it, many values are negative or (with a larger flux) gigantic. In either case they have large exponents (it would be more convenient to have a range like 0-1 or 0-100).
Is this an appropriate technique? Any tips for getting a more sane output? I was trying to use as an example Smoke Propagation From a Chimney | Tutorial | SimScale as the scalar there seemed to track the outflow of the chimneys fairly closely. I’m not seeing the same results at all.
Also, is there any kind of guide as to how to balance the inflow and outflow vents so approximate a room? A simple small room with simulated air-conditioning “supply” and “return” vents would be sufficient.
After simulating, is there a way to measure the average (or total?) density of the scalar in a certain area?
The link is here: https://www.simscale.com/projects/NobleLizard/test2/. Incompressible 5 is intended is to be very simple. It has a person spewing out air and two vent, an in and an out, on the ceiling and wall.
There is a single passive scalar here which is intended to represent the possible infectious particles emitting from one of the rectangular solid “people”. We are having an incredibly hard time understanding and visualizing the scalar. First of all, there is a bug in the Iso Volume panel where when you select the passive scalar the interface usually hides the mix/max sliders. It’s blind luck for us to get them to reappear. But even when it does we don’t see what we would expect (which is the higher density of scalar flowing from its source) and the range of values seems nonsensical.
Hi,
Really interesting concept!
I’m no expert at this, but I saw the project and found the following about your latest simulation “Semi-simple New Model”-
Inlet velocity of air through ceiling ducts is set to 100 m/s which is extremely high for an indoor simulation. A realistic value would be 0.5 m/s.
Inlet velocity of Scalar species is not properly oriented ( x = 1, y = 1, z = 0). You may want to properly orient velocity vector(normal to inlet face) to get good results.
In this simulation, you haven’t set the scalar species input correctly. Passive Scalars Value was never set to 1.
Still, Iso volume works. You’ll see some results with the following settings
In your other simulation, “Super Complex - Old Model”, passive scalar was assigned the value 1, but the direction of velocity (1, 1, 0) sets the velocity vector in the opposite direction of what it should be. So probably that’s the problem.
