ExcitableBoy wrote:

Yeti wrote:Outrunning AMS sounds interesting, but also dangerous. With something like HACE, you won't know you've hit your wall until you're unable to function, and as good as dead without a significant effort from your mates... or a helicopter pilot.

Pretty much everyone who climbs Rainier on a two or three day schedule is in effect doing this. Pretty much nobody other than the rangers and guides properly acclimate to 14k+, although many climbers spend a lot of time climbing other peaks which certainly helps. I think most people will experience AMS before HACE sets in, although I don't know this for a fact, and will feel crappy enough to head down. I see the real danger in this is getting pinned down by bad weather and being unable to descend.

Pretty much every Colorado peakbagger also does this - daytripping to 14k, or maybe spending one night sleeping at 10k near the trailhead before climbing to 14k. They just don't spend a lot of time on the summit. I assume that the risks of getting trapped at high altitude by weather are significantly higher on Rainier than the average Colorado peak.

There is also evidence from say Mauna Kea or Pikes Peak that you can go straight up to 14k without bursting - but if you hang around up there you'll probably start to experience symptoms of altitude sickness.

From my personal experience, my greatest elevation change over the course of a day was Longs Peak. Waking at 7500ft, scrambling to 14,200 and back down in 1 day. If I spend 5/6 days at 7500, I can do it easily, with only some fatigue. I once tried to do it on day 3 of a week trip, and was hurling up my Gatorade before I broke the treeline.
So, would you be implying that I might have gotten away with it if I'd tried it on day 1? The Cascade Volcanoes are looking more and more appealing.

Yeti wrote:From my personal experience, my greatest elevation change over the course of a day was Longs Peak. Waking at 7500ft, scrambling to 14,200 and back down in 1 day. If I spend 5/6 days at 7500, I can do it easily, with only some fatigue. I once tried to do it on day 3 of a week trip, and was hurling up my Gatorade before I broke the treeline.
So, would you be implying that I might have gotten away with it if I'd tried it on day 1? The Cascade Volcanoes are looking more and more appealing.

The Cascade Volcanoes are pretty great, but it is the other, less known mountains that are the true jewels. I think you misunderstood what I was trying to communicate. It sounds like you take more time than I do to acclimate. If you are having problems climbing to 14k after acclimatizing for three days at 7500 ft, you may have problems climbing Rainier in a two or three day trip since day one typically takes you from sea level to 10k in a matter of hours. A three day itineary gives you an extra day to acclimatize at 10k, but my belief is much of the benefit is from being able to rest and rehydrate. One of the physiological changes that occurs at altitude is the formation of red blood cells, it probably can't hurt to take iron supplements. This has long been suggested to female athletes, whom are often iron deficient, when doing sports at higher altitudes.

coldfoot wrote:Pretty much every Colorado peakbagger also does this - daytripping to 14k, or maybe spending one night sleeping at 10k near the trailhead before climbing to 14k. They just don't spend a lot of time on the summit. I assume that the risks of getting trapped at high altitude by weather are significantly higher on Rainier than the average Colorado peak.

There is also evidence from say Mauna Kea or Pikes Peak that you can go straight up to 14k without bursting - but if you hang around up there you'll probably start to experience symptoms of altitude sickness.

Denver is at 5k, Leadville at 10k. I'm guessing living at those altitudes has a real advantage over living in Seattle (sea level) when it comes to climbing to 14k.

I'm sitting at right around 900ft, which is close enough to sea level.

What of the effect of physical conditioning? When I puked my route, I was about 40lb heavier and relying much more on my natural Vo2 max to carry me. 5 years later; I ran my first Marathon a few weekens ago, and I'm doing much more cardio on a regular basis. I'm taking the physical conditioning side of things more seriously.

I really can't speak much about how this has affected my ability to aclimate. I will say that 2 weeks ago, I spent a weekend in Mexico City, and climbed up and down the Teotihuacan pyramids (7500ft asl) twice each without getting winded. Collectively 700ft of stairs... possibly not comperable to 14,000ft of mountain.

Being aerobically fit helps a lot. I can tell a huge difference on Rainier when I am in top shape vs just good shape.

Let's reiterate that a small pressure difference-- say 1% -- will not be of great significance for someone suffering from HACE or HAPE, but is significant for a wing, be it a car or airplane.

Suppose a formula one car has 80 sq ft that act as a wing. and a mere 1% (lower than normal) air pressure acts over that surface on average. That mean 0.15 lbs per square inch, or over the 80 sq ft surface, 1728 lbs -- a significant fraction of the car weight. Many race cars actually have aerofoils intended to direct force downward, else they will fly off the track on corners.

You can reach huge reynolds numbers on mountains in wind, or over a car, with chaotic recirculation zones and true turbulence; yet those huge effects are associated with fairly small pressure differences. You could generate a significant bernoulli effect by opening your mouth such that your face were perpendicular to a 100mph wind, but I'm pretty sure that other negative effects would take over long before the pressure difference hit you.

3Deserts wrote:For anyone interested, "dirty air" is a huge component in racing, and the more aerodynamically tuned a given class of racing, the more a car following in the immediate path of a leading car is negatively affected. The effect in Formula 1 and Le Mans (LMS/ALMS) class racing is huge. Given that wind-storm speeds on mountains sometimes approach those encountered in high-end auto racing--wherein there exist enormous pressure differentials measurable in multiple Gs (so much so that F1 cars since I think the early 80s could theoretically drive upside down at speeds upwards of about 60 mph)--I do wonder if the question has some merit. Granted, F1 aero work is designed to maximize the differential whereas the random accumulation of local topographical features on a mountainside probably wouldn't induce such consistently high differentials, but I'm not convinced the question is without merit.

IMO the issue in car racing is that the shape of the car is designed to produce downforce from laminar flow over the body, spoilers etc in clean air. When the car is in "dirty" turbulent air the downforce will be different, almost certainly less, and probably unpredictable or fluctuating. The actual atmospheric pressure in the dirty air is basically the same as in laminar flow. That is, if you were to drive around with a barometer stuck to the car I think you'd be hard pressed to measure a difference.

3Deserts wrote:Yeti, neat question.

As a fellow mountain fan who also used to partially race air-cooled Porsches (very amateur level), and still follows F1 and endurance racing, I just appreciate the creative speculation in which one pursuit informs the other./car racing

I take it you're looking forward to next weekend? Here, have a nerdgasm:
http://www.mulsannescorner.com/newsmarch12.html


Coldfoot: That is essentially how the cars are tested. The builders who are well funded have the ability to measure and display real-time pressure differentials for a given cross-section of the car. Where there is boundary layer separation (disruptions in laminar flow), there is low pressure. It is these low pressure pockets that make drag such a drag, and lots of money has been spent developing things like vortex generators to alleviate these.

The condition that inspired this discussion isn't meant to pertain to the entire face of a peak, but rather a very small area in the lee of an obstruction to laminar flow. Described by the climbers as an area of total calm, whilst 100mph winds rip by at the edges of the rock. The corollary in motorsport would be the area just behind a gurney tab; a wing feature which purposely creates a small area of low pressure to "suck" the laminar flow up close to the low-pressure side of an aerofoil at high angles of attack. They are very effective.

I sold my trackday toy last winter, had it for 8 years.
.
.
.
.
Bought another with this years tax return. I'm aiming for bonneville this time, I've never done it before so it's really caught my interest.

The condition that inspired this discussion isn't meant to pertain to the entire face of a peak, but rather a very small area in the lee of an obstruction to laminar flow. Described by the climbers as an area of total calm, whilst 100mph winds rip by at the edges of the rock.

Interesting thread, and you have got me wondering again.

Although everyone here is talking about rather simplified models and analogies to aerodynamically designed surfaces, shouldn't this be talked about from the viewpoint of blunt body aerodynamics? e.g. I wonder if anyone could pose this question to someone more familiar with empirical results from wind tunnel testing on buildings, such as the work done at RWDI?

A few factors to consider, which might be insightful as to the nature of the pressure zone we were in:

1. It was completely calm where we were. There wasn't even any noticeable suction.

2. The area of stillness was large. It was not confined to the leeward side of the sub-summit, but extended across the entire summit plateau from Misery Hill to the higher summit and all the way up the higher summit, so the area of reduced pressure was very large, easily covering the size of several football fields (at least until the wind shifted direction at an unknown hour and blew between the two sub-summits. At that point the high winds were encountered lower down and the calm zones were more transverse to the direction the wind was blowing). Since even the area near Misery Hill was calm, we were likely being shielded by the sub-summit above the West Face/Casaval Ridge, which was quite a ways away.

3. The boundary between the still and fast moving air was extreme. I have been in sustained +60 mph winds on mountains where it was difficult to walk, and even when huddling behind bus-sized boulders, the turbulence swirling around was so bad that it was only mildly calmer on the leeward side. On the summit where the high winds were still skimming across the ground, conditions went from completely calm to barely being able to crawl just by stepping out from behind a rocky obstruction.

The critical issue that led to Tom's death was how quickly his HACE developed and the lack of symptoms warning us of him experiencing any altitude related problems. We could and would have taken a higher risk from exposure hazards and descended sooner had Tom developed noticeable AMS, as we had only agreed to stick around if neither of us felt sick from the altitude. Although I could only tell so much from urine output on ascent (frequent & clear), Tom's physical performance on ascent (strong & steady), and Tom's self-reporting from a passive state on the sub-summit, he exhibited no signs of AMS, which is highly unusual to not have before HACE. His first awareness of any symptoms did not occur until he stood up to descend. He didn't even feel nauseous and had a good appetite for breakfast.

So I wonder if the pressure differential had something to do with this possible skipping over AMS, perhaps by causing other mechanisms of HACE to take hold before the usual ones of AMS became evident? If pressure differentials from blunt body aerodynamics could have a noticeable effect, I would wonder whether the morning arrangement of pressures would have had a greater or lesser effect than the evening arrangement, as the wind did change by 90 degrees when we were on the summit, resulting in a very different morning wind pattern, with us essentially in a calm zone transverse to and within a trough with a large venturi effect occuring (wind speeds increased as I descended the sub-summit and approached the lowpoint between the two summits).

If there is any significant pressure difference between open areas, there will be wind between. Really, it doesn't take much pressure difference. Look at the Navier-Stokes equation and the reasons become obvious. If there was no wind, there wasn't a significant pressure drop on the scale of meters and much larger.

"Blunt" objects generally require numerical models; but for the scale we are describing, a R=0.1m wall end looks pretty blunt. It is instructive to look at something as simple as the backward-facing step, or flow over a wall; these are very common benchmarks for numerical codes. I used them. Even at the Reynolds numbers of formula one cars, with complex recirculation zones, the pressure drop is simply not that great, in terms of a percent of the average wind speed. This might be a fun exercise for a student with FIDAP, but the results would probably be regarded as fairly trivial by the fluid-flow community.

There are measurements of the pressure difference caused by wind blowing over a house; the inside-outside difference for a 20 mph wind is something like 50 Pa, or 0.00005 atmospheres. That's not a lot, and that's a fairly extreme case. There's that crude speed-squared dependence, and indeed, hurricane-force winds can cause homes to explode; but as with the formula one racer, the problems is that integrating a very small fractional pressure difference, over a huge area, generates big forces.

I'm still puzzling over what you folks are picturing; but for the fine scale, you can't get much blunter than a pitot tube, for which the Bernoulli equation will reduce to ~ delta pressure ~ rho* V^2/2. Again lets take the air density at that altitude as ~1 kg/m^3. Let's up the air velocity to 20m/s, giving us about 200 Pa. Again, that's not much when it comes to physiology.

Yeti wrote:Coldfoot: That is essentially how the cars are tested. The builders who are well funded have the ability to measure and display real-time pressure differentials for a given cross-section of the car. Where there is boundary layer separation (disruptions in laminar flow), there is low pressure. It is these low pressure pockets that make drag such a drag, and lots of money has been spent developing things like vortex generators to alleviate these.

The condition that inspired this discussion isn't meant to pertain to the entire face of a peak, but rather a very small area in the lee of an obstruction to laminar flow. Described by the climbers as an area of total calm, whilst 100mph winds rip by at the edges of the rock. The corollary in motorsport would be the area just behind a gurney tab; a wing feature which purposely creates a small area of low pressure to "suck" the laminar flow up close to the low-pressure side of an aerofoil at high angles of attack. They are very effective.

The local pressure on a surface can vary with a properly shaped surface - this is also why airfoils generate lift (OK, I know the lift mechanism is actually complicated, but it is a pressure differential). But the time and spatially averaged pressure in the dirty air itself is essentially the same as in the clean air before it encounters the object. By essentially I meant on scales that would be important to human physiology. One percent of 1 atmosphere is a pressure of 1000 N/m^2, which is a lot of lift (or downforce in the car example) but negligible physiologically.

From energy considerations, delta-P ~ rho v^2 as MoapaPk said (both quantities are energy densities). If you have two areas at a differential of 1 ambient pressure (1 atm at sea level), air will rush from one to the other at roughly the speed of sound. If they are at a differential of 0.1 atm, the speed is about sqrt(0.1) or 0.3 x the speed of sound. This makes me think you'd need a 200 mph wind to generate fluctuations of 0.1 atm, which still is not very large from the physiology point of view.

ExcitableBoy wrote:

Yeti wrote:From my personal experience, my greatest elevation change over the course of a day was Longs Peak. Waking at 7500ft, scrambling to 14,200 and back down in 1 day. If I spend 5/6 days at 7500, I can do it easily, with only some fatigue. I once tried to do it on day 3 of a week trip, and was hurling up my Gatorade before I broke the treeline.
So, would you be implying that I might have gotten away with it if I'd tried it on day 1? The Cascade Volcanoes are looking more and more appealing.

The Cascade Volcanoes are pretty great, but it is the other, less known mountains that are the true jewels.

Bingo! You nailed it right there! I like to think of the Cascade Volcanoes as the "Colorado 14ers" of Washington. All the crowds gather on Rainier or Adams or Saint Helens leaving all the real mountains in complete solitude.

Yeti...did you read the disaster TR from Mount Shasta? I was wondering the EXACT same thing as you when I read it.

Matt Lemke wrote:Yeti...did you read the disaster TR from Mount Shasta? I was wondering the EXACT same thing as you when I read it.

Read the analytical parts of this thread. The pressure differences "caused" by local winds are trivial compared to the differences caused by altitude.