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Ever thought what would be the best window setup for you vehicle or uber vehicle to make sure you had ventilation in the vehicle to minimize covid – well opening just the front two windows is not the best choice according to this study. https://advances.sciencemag.org/content/early/2020/11/30/sciadv.abe0166

“As one might expect, all windows open (Config. 6) has the highest ACH – approximately 250, while among the remaining configurations, all windows closed (Config. 1) has the lowest ACH of 62. However, what is somewhat surprising is that the ACH for the configuration with windows adjacent to the driver and the passenger (FL and RR, respectively; Config. 2) are opened is only 89 – barely higher than the all-windows-closed configuration.”

Driver to Passenger

“A well-ventilated space requires the availability of an entrance and an exit, and a favorable pressure gradient between the two (41, 42). Once a cross-ventilation path is established (as in Config. 3 or Fig. 3), opening a third window has little effect on the ACH.”

“The all-windows-closed configuration (Config. 1) relying only on air conditioning fares the worst and results in over 10% of the scalar that leaves the driver reaching the passenger. In contrast, the all-windows-open setting (Config. 6) appears to be the best case, with almost no injected scalar reaching the passenger.”

“A two-windows open situation, wherein the driver and the passenger open their respective windows (Config. 2) might be assumed as the logical thing to do for avoiding infection from the other occupant. Although this configuration does improve over the all-windows closed situation, shown in Fig. 5b, one can see from the concentration field that Config. 2 does not effectively dilute the tracer particles, and the passenger receives a fairly large contaminant load from the driver.”

“With the substantially reduced initial concentration field near the driver, the fraction reaching the passenger is proportionately reduced. Thus, among the configurations with three windows open, Config. 5 might provide the best benefit from the viewpoint of driver-to-passenger transmission.”

Passenger to Driver

“The all-windows closed configuration (Config. 1) shows the highest concentration level at the driver (~8%). This value, however, is lower than the 11% reported for the inverse transport, i.e., from the driver to the passenger (Fig. 5b), a difference that can be attributed to the fact that the air-conditioning creates a front-to-back mean flow.”

“In summary, the flow patterns and the scalar concentration fields obtained from the CFD simulations demonstrate that establishing a dominant cross-ventilation flow within the car cabin is crucial to minimize potentially infectious particle transport between car occupants. With this flow pattern established, the relative positions of the driver and passenger determine the quantity of air transmitted between the occupants.”

“The all-windows-closed scenario (Config. 1) with only air-conditioning providing exchange appears to be the least effective option. Perhaps most surprising is that an intuitive option – of opening the windows adjacent to each occupant (Config. 2) is effective, but not always the best amongst the partial ventilation options. Config. 3, in which the two windows farthest from the occupants (FR and RL, respectively) are open, appears to give better protection to the passenger. The particular airflow patterns that the pressure distributions establish – channeling fresh air across the rear seat, and out the front- right window – help to minimize the interaction with the driver in the front left position.”

Another big reporting day with 2607 deaths in US along with a record 228K confirmation. As an overall the current known infected is 2.6% in the US.