Quote:
Originally Posted by orange4boy
I've been thinking about this for a while. It occurred to me that being beside a car or truck is a bad thing therefore being beside a wall or divider must also cause additional drag. The aero penalty of tunnels is well known.
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Depends on the relative tunnel and vehicle size - and on it being uni- or bi-directional.
Biking in a tunnel (4m / 13' wide) is a dream, even on the gentle uphill part.
Tunnels, walls, and dividers shield you from the prevailing wind, which can be very beneficial.
For the walls to have such a huge impact as the "ground effect", it'd have to be a narrow tunnel compared to the vehicle.
There a thread on moving the vehicle's body out of ground effect, that suggests a relative height where the ground effect greatly diminishes.
A uni-directional tunnel will have an air flow through it going in the direction of traffic, so you'll get free tailwind
A tunnel with bi-directional traffic will clearly illustrate the effects of a bow wave.
Even at a modest 50kph / 30mph for both vehicles, the bow wave of a truck can really be felt when going the other way, as it's got nowhere to go but into the opposite lane.