Physics of drafting - if someone drafts on you, does it slow you down?

In fact (apart from any mental barriers that may arise from having someone right on your heels) they are helping you, by pushing the air in front of them towards you. It's why in the individual time trials in the tour de france no support vehicles are allowed to ride right behind the athletes.

noakes says that if you want to slow someone down, run alongside them to increase drag on both of you.

Like you said, it depends on the bodies involved, but in general, it will actually make it easier for you to have someone draft off of you. The second person fills in the eddy behind you, thus improving your own aerodynamics.

jjjjjjj wrote:

noakes says that if you want to slow someone down, run alongside them to increase drag on both of you.

? Really?

They bump draft in NASCAR where the car behind boosts the car in front.

actually wrote:

In fact (apart from any mental barriers that may arise from having someone right on your heels) they are helping you, by pushing the air in front of them towards you. It's why in the individual time trials in the tour de france no support vehicles are allowed to ride right behind the athletes.

Might make a bit more of a difference when you're traveling 30+ mph versus 12-13 mph...

see Noakes, Lore of Running, p.59 (you can get this quote by searching noakes, lore of running, drafting on google books.

Citing Brownlie, he writes that running to the side of a runner increases the effective frontal area, increasing drag on both, and thus the strategy to slow down a frontrunner might be to run alongside him.

metrododger wrote:

Might make a bit more of a difference when you're traveling 30+ mph versus 12-13 mph...

This would help to push you forward, at a much greater speed.

jjjjjjj wrote:

see Noakes, Lore of Running, p.59 (you can get this quote by searching noakes, lore of running, drafting on google books.

Citing Brownlie, he writes that running to the side of a runner increases the effective frontal area, increasing drag on both, and thus the strategy to slow down a frontrunner might be to run alongside him.

While that's true (the cross-section has doubled assuming same size runners), you also have 2 runners, instead of one, pushing thru the air. So I don't see it slow down anybody except the one who could have tag behind the front runner but now running along side him. (I do have a degree in aerodynamics related field).

It definitely slows down both runners, since neither of them are receiving an aerodynamic benefit. It also increases the turbulence behind the runners more than two runners running single file.

comparison wrote:

jjjjjjj wrote:

see Noakes, Lore of Running, p.59 (you can get this quote by searching noakes, lore of running, drafting on google books.

Citing Brownlie, he writes that running to the side of a runner increases the effective frontal area, increasing drag on both, and thus the strategy to slow down a frontrunner might be to run alongside him.

While that's true (the cross-section has doubled assuming same size runners), you also have 2 runners, instead of one, pushing thru the air. So I don't see it slow down anybody except the one who could have tag behind the front runner but now running along side him. (I do have a degree in aerodynamics related field).

In cycling, drafting at speeds of 10 mph is almost inperceptible. the benefits do not really come into play until 25mph. So drafting at under 10mph is ridiculous. In addition as a cyclist you have much more mass. the bike and rider and for the full benefit of the draft you need to be within inches. Once you are three feet behind(your front wheel to their rear wheel) you are essentially no longer in the draft unless you are above 30mph.

Now with back kick you cannot run closer than about 2 to 3 feet.No draft at that distance at running speed.

drafting in running is purely psychological.

also in cycling drafting does not slow down the leading cyclist. Studies have shown that if the following rider stays in the draft the "dirty air" coming off the back of the leading rider becomes less turbulent so he is more efficient.

At higher speeds, such as in auto racing, two cars move faster than a lone car for this reason.

I think you are talking about still conditions only. Any wind disadvantages the leader over a single 100m ad advantages the trailer on the opposite. Double benefit.

What I was trying to imply with my quip about 30+ mph vs. 12-15.

At running speeds, drafting is in your head only.

Drag increases exponentially with velocity. Also, drafting becomes noticeable around 15 mph, not 25.

You guys are pretending we all run in a vacuum. With any headwind at all, the speed at which drafting becomes useful drops by the speed of the wind. Also, with a tail wind, someone drafting off you decreases the the benefit you receive from that wind.

Th Real World wrote:

You guys are pretending we all run in a vacuum. With any headwind at all, the speed at which drafting becomes useful drops by the speed of the wind. Also, with a tail wind, someone drafting off you decreases the the benefit you receive from that wind.

This is true, velocity when drafting is concerned is all relative to wind velocity.

Also, as far as what speeds drafting becomes effective at: It's 2012 guys, it isn't hard to research anything anymore.

Nice find, although it looks like they didn't test someone leading without drafting.

No Way wrote:

This is true, velocity when drafting is concerned is all relative to wind velocity.

Also, as far as what speeds drafting becomes effective at: It's 2012 guys, it isn't hard to research anything anymore.

https://circle.ubc.ca/bitstream/handle/2429/4043/ubc_1995-0589.pdf?sequence=1

Having a trailing runner slightly reduces wake turbulence and drag, but the effect is tiny for the lead runner.

As for the suggestion that drafting doesn't matter in running, try running 5 minute miles into a 15 mph wind, then follow someone.

No Way wrote:

Also, as far as what speeds drafting becomes effective at: It's 2012 guys, it isn't hard to research anything anymore.

https://circle.ubc.ca/bitstream/handle/2429/4043/ubc_1995-0589.pdf?sequence=1

Mehhhh

I'm not convinced. Not the best experimental design. What else do you have?