Alpynisto wrote:All of this ignores altitude...the wind at 20,000 feet has significantly force than the same speed at sea level.

That is captured in the dependence on air density (rho). The plot is for sea level, but the derivation is general.

tigerlilly wrote:Geeks!

Flattery will get you .. everywhere

nickels wrote:A related question:

"How many beans must one eat to effectively propel themselves up the mountain?"

In that situation, a climber must be vigilant of other's breaking wind that might prevent them from standing up.

Alpynisto wrote:All of this ignores altitude...the wind at 20,000 feet has significantly force than the same speed at sea level.

I think cause of the more air density, a wind at sea level forces more than a same wind at summit. but due to lack of Oxygen, a man is more vulnerable than feel more power! at summit

bump

Man, good choice on the bump topics. Just got home and your handiwork today has been entertaining. Treasure hunting are we?

Walking in high winds. One of my little eccentricities!

Well, I am English. We are allowed to be eccentric!



Report at Storm in Folkestone Warren

I recall that the original thread was called "What wind speed will knock you down?". Then some wag then started "What wind speed will knock you up?".

I was on the Palisade Glacier one winter -- the wind gusts were so strong that they actually lifted you off the ground.

You could see the gust coming at you, a wall of spindrift. If you didn't drop to the ground, the wind would lift you off your feet and blow you a couple of feet. We barely made it to the top of the U-Notch and called the climb for high winds.

On the way home we heard on the news that semi trucks had been blown off the freeway during the weekend.

What speed of wind will lift you off the ground like that?

Great thread. I've always wondered about these things!

When I was trying to get off of Mt Shasta last March, on the lower mountain I was having to lean 45 degrees sideways (across the fall line) into the wind to avoid burning out my abdominals (estimate based on how close the ground looked to my face). It was harder leaning further than than even though I didn't quite feel in equilibrium, and I guess that was the lift effect beginning to take hold? Those weren't the strongest or most sustained winds that I felt - just the ones light enough to be walking upright!

For those who are wondering, the winds were sustained for about a minute or two at a time and would die down to something were I would only be leaning ca. 20-25 degrees into the wind for the next minute or so.

By the way, how about a calculation for what angle will the plane of the rope catenary between two climbers take for a given wind speed? I'm sure a couple of factors to consider are rope diameter and length between climbers. Would rope stiffness affect this significantly?

I'm wondering because the summit winds that caused Tom and I to rethink our plans of descending the Bolam-Whitney Ridge were strong enough that the plane of the rope between us was nearly horizontal in the sustained winds and you could feel a significant pull coming from the rope. We had a single 8mm double rope with about 20 ft of slack between us.

daw37 wrote:But all this assumes the wind remains constant in strength - which it very rarely does. Last time I tried this on a summit the wind suddenly died down and I ended up on my hands and knees on the ground!

And direction too!

Not only this, but unless I missed it, thus far the problem of vertical wind shear (dv/dz) and its effect have been assumed constant, which should factor into the calculation of the moment due to wind (as if the wind moment is a function of shear since shear will change the value of q). Would be interesting to see how low shear v. high shear environments change the application of Bernoulli's equation in the generation of lift due to leaning...though I'm no expert in aerodynamics!

I think a wind has to be around 120mph or more to be able to pick you up and push you above the ground vertically (so it has to be an updraft or at a steep upward angle). It takes much less to knock you off balance or to allow you to lean into it. Your shape does have something to do with it so if you change your shape to a more aero shape while you are balanced against the wind you might fall quickly.

I find it easy to walk in 40-50mph wind if its pretty consistent. Much above that things get much harded and it isnt a linear difference!