Kareem Ahmed, PhD, Associate Professor, Mechanical and Aerospace Engineering at the University of Central Florida talks about the fluid properties that effect the way spread viruses.
So briefly, could you just explain what’s the study about and how did you conduct it?
AHMED: So, the study is essentially about the super spreader – trying to understand the topology that comes out of the transmission of droplets and aerosols for different age, gender and body size.
And how did you conduct this?
AHMED: So, it’s numerically conducted with some experiments that help validate the numerical simulations.
So how do people’s fluid dynamics vary and how does that make you more susceptible to spread or catch COVID?
AHMED: So it comes down to your saliva, your mouth and nasal passage, which essentially is a liquid form, so it’s a fluid. And that liquid form has a specific density, viscosity, and surface tension that is different from one person to another. The jet plume that comes out of our mouth when we speak, when we cough, when we sneeze drives the droplets that form. So, it’s a fluid-based, it changes depending on this property, and that change would actually result in a different atomization process.
So what were the major factors you were studying in this?
AHMED: So we were trying to understand how a nasal passage would affect the speaking or sneezing or coughing behavior and primarily how it varies from one person to another, depending on their age, their gender and their size. And what we found is essentially a younger male would have a tendency to spread the virus more than a female, for example.
Well, in the article it was mentioning teeth and congestion. Those sound like blockages, could you explain how that makes you more spreadable?
AHMED: Yeah, that was another key finding is teeth has a blockage effect. However, when you think about the blockage of the teeth, it produces these, high speed jets and that induces a larger velocity and that transmits to the next person easier. So, a person without teeth obviously would transmit the virus less to the next person compared to a person with teeth.
And what were the differences you measured in – among the models in your study?
AHMED: So the fluid property difference and the presence of blockages – how it alters the spreading mechanism.
And what was your most dramatic rate of difference?
AHMED: It’s on the order of a factor of two to three.
And is this just distance or could you explain a little bit about the lingering in the air?
AHMED: So, there are different mechanisms, and that’s what’s outlined in the paper – that you could have an interaction with the teeth. It could be a straight jet, and that has its propagation distance. But when there’s other factors that introduce vortices that could potentially induce a turbulent cloud that would propagate further. So that would give you a larger distance. So, it depends on different scenarios that are occurring. But it also comes down to the properties of the saliva itself because that controls the droplets and aerosols that do form.
So, we were saying congestion makes you more likely to spread. Are there things that anybody could do? Like, precautions people could take if they notice they’re congested to not spread?
AHMED: So obviously, wear your face mask is critical.
And are these factors exclusive to spreading it or any of these factors going to make you more susceptible to getting it?
AHMED: Spreading it is more critical, yes.
And you were saying wearing your mask is critical. Is this effective in blocking even the most distanced of sneezes?
AHMED: Yes, absolutely, the facemask blocks the jet that you’re producing there and reduces the droplets and aerosols. It doesn’t 100 percent effectively mitigate transmissibility, but it does help reduce a significant factor of the aerosols and droplets. Think of it as: you’re producing this high-speed jet. If you could slow it down with the facemask, that is effectively what the facemask is doing, is reducing that velocity that would come out. And then with social distancing, then you would prevent transmitting the virus to the next person.
Yeah, I was asking Mike about this. I thought it was going to make it so we need more distance, the results of this, but he was saying four and a half feet might be enough. How distanced do you think we should be when we’re sneezing, I guess?
AHMED: I mean, so sneezing is the extreme case. But technically, when we’re in a sneezing phase which is an extreme case. I think transmissibility happens when we’re speaking like I’m speaking right now. What we’re finding is that the distance is about four feet distance without a facemask. And that is with speaking very loudly. With a face mask, you probably reducing that distance significantly.
Could you just outline your next steps. Where do you plan to go with this research?
AHMED: So, the next step is that we’re working with the research office to formulate a clinical study where we can actually get a group of people to exercise this experimentally and make the measurements and evaluate that effective distance. That is besides, engineered solution to tailoring the saliva production. So, these are the two critical areas that we’re working on next. So, one is including a group of people, different gender, size, and do this effective distance study measurement and documenting it with and without facemask. And then the second thing is actually tailoring and engineering a confection or candy to alter the saliva itself. Now that we know how the saliva behaves with different gender and age and so forth, can we tailor it for these variations.
And you mentioned gender and size. Does age also make a factor?
AHMED: Yes.
Would that make it thicker, thinner?
AHMED: An older person has a thicker saliva than a younger person. A younger person would tend to spread the virus easier than an older person. And that is the essence of the finding from the paper. When you’re stressed, when you’re younger versus older, females tend to spread less than male.
Is this exclusive to sneezes? Or are you also studying, like, coughing and talking and…
AHMED: Speaking, coughing and sneezing. But we focus on the sneeze because that is the extreme event, meaning the sneeze is the strongest transmissibility mechanism of our respiratory function. Because your jet velocity that comes out of your mouth is the highest.
And is there anything I didn’t ask you about that you’d like people to know?
AHMED: No, I think these are mostly the key ones, emphasizing that we’re doing this study primarily so that we could engineer this this saliva alteration mechanism. So, this is sort of a side study that came about the main one, because we believe that we have a solution for coupled in with the facemask, you could bring in a distance to about one to two feet from each other, which is more effective in that way. Because the mask prevents the high velocity. Altering the saliva would actually prevent the aerosols and droplets from coming out of the mask that we would have. So now you would have something that would prevent transmissibility significantly.
Interview conducted by Ivanhoe Broadcast News.
END OF INTERVIEW
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