Last week's question: what are the fluid dynamics of drafting?
Drafting is the practice of staying behind another moving object to reduce the energy needed to move. This is possible because when air moves past an object, there is a small area behind said object where the air cannot reform as rapidly, creating an area of low pressure. This low pressure is filled by pulling nearby particles, including those of the following object, towards it, hence saving energy on the following object's part.
Despite this somewhat technical explanation, I can't see to find fluid flow diagrams of drafting. Maybe someone would be so kind as to provide one?
This week's question: How are the stone arches in Arches National Park and elsewhere formed?
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Seeing as to how 70% of cycling race tactics are drafting-related, I have some experience with this, if not actual fluid flow diagrams.
ReplyDeleteHere are some (more or less obvious) notes about how drafting works for cycling:
If I am riding directly into the wind, I would need to position myself directly behind the rider in front. If there is a crosswind, I would need to angle myself to the side of the rider. If you look at airshots of pro races with crosswinds, you'd see that the pack aligns itself into a slant, which each person's front wheel slightly overlapping the back wheel of the rider in front.
Assuming a straight-on headwind, the "sweet spot" where the draft is felt most strongly is when my front wheel is no more than a 6"-12" behind the back wheel in front of me.
Say there are 5 riders in a line. The third wheel is noticeably the best position. The second wheel still feels a good portion of the wind. Nearer the back, the draft gets diluted significantly.
I save approximately 1% of energy for each mile-per-hour I'm going if I'm drafting correctly.
Also awesome but potentially deadly: drafting cars.