I Why Do My Umbrella Keep Flipping in One-Direction Wind?

[Trying2Learn]

TL;DR Summary

Why do umbrellas flip?

Today, I was walking during a heavy rain with winds.

But I swear to you, the wind kept blowing in one direction.

Despite this, the umbrella kept inverting.

I understand if the wind was turbulent, but it was not.

So is there a boundary layer on the umbrella that makes the wind (again, when the wind is blowing one way), curl around and under?

Or is the presence of my own physical body enough to induce a vortext that causes the flip?

I understand if the wind was turbulent, but this happens when there is no turbulent wind (I think -- or am I just not "aware" that a turbulent vortex is passing by me")

And if there is a cause of the flip (during what "appears" to me to be a lanimar flow), is there any preventative action I can take to stop the flip?

 

[BvU]

There is spring energy when the wind is heavy. If the wind speed isn't constant the spring energy may be enough to let the thing flop. It should flip back again when the wind picks up. This calls for an experiment with more controlled circumstances: wind tunnel and umbrella fixed to a stand.

 

[Trying2Learn]

There is spring energy when the wind is heavy. If the wind speed isn't constant the spring energy may be enough to let the thing flop. It should flip back again when the wind picks up. This calls for an experiment with more controlled circumstances: wind tunnel and umbrella fixed to a stand.

Absolutely fascinating. So you are suggesting that when the "laminar" wind pushes down on the umbrella, but then "lets up" the spring energy can flip it?

OK, so now I must wait for the next storm.

 

[BvU]

In all modesty: it's just a guess. Experiment decides !

 

[russ_watters]

Spring energy? No, this really is simple: umbrellas are aerodynamically unstable, and people tend to hold them in their most unstable position; perpendicular to the wind (vertical in a horizontal wind). With one hand on the handle, you can generate very little torque to keep the wind from rotating the support rod backwards. and then from perpendicular it only takes a small rotation before the wind force is "under" the umbrella, flipping it inside out.

For better stability, lower risk of losing control/flipping inside out and also better coverage from the rain, angle/lean the umbrella into the wind. Don't hold it vertical.

 

[BvU]

angle/lean the umbrella into the wind

Did you, @Trying2Learn ? ( I assumed so )

 

[russ_watters]

Did you, @Trying2Learn ? ( I assumed so )

Er...while I see it a lot, I will say this isn't entirely an issue of operator error. There's also the issue that an umbrella is unstable in balance against gravity. So, holding it in a way that minimizes wrist strain means balancing the aerodynamic torque against the gravitational torque. This means you aren't completely eliminating the aerodynamic instability and a gust will create a significant net torque and rotation.

 

[Lnewqban]

Why do you believe that the turbulent wind had better chance to flip the umbrella than a more laminar flow?

 

[kuruman]

Spring energy? No, this really is simple: umbrellas are aerodynamically unstable, and people tend to hold them in their most unstable position; perpendicular to the wind (vertical in a horizontal wind). With one hand on the handle, you can generate very little torque to keep the wind from rotating the support rod backwards. and then from perpendicular it only takes a small rotation before the wind force is "under" the umbrella, flipping it inside out.

For better stability, lower risk of losing control/flipping inside out and also better coverage from the rain, angle/lean the umbrella into the wind. Don't hold it vertical.

I disagree, judging from myself and others, that people tend to hold their umbrellas perpendicular to the wind. See this video in which umbrellas are oriented into the wind, held with both hands (if possible) and higher up from the handle to minimize random torques due to turbulence.

I wouldn't underestimate aeroelastic effects. As @BvU suggested, experiment is needed.

 

[256bits]

Umbrellas are used to try to keep you dry, and not to keep your hair from flying all over ( but in some cases... )

Anyways, they are not held directly into the wind, but at an angle supposedly the angle from the vertical at which the rain impacts upon you. The rain droplets fall at terminal velocity and are blown sideways by the wind. Smaller droplets having less terminal velocity would be taking up more of the wind speed and direction than larger droplets. Which angle one holds the umbrella would be a function of droplet size, and of course the wind speed.

So the front edge of the umbrella receives the full force of the strong wind and bends inward.
The rearward edge due to the curve of the umbrella frame receives less wind force, and maybe if the wind is strong enough could be horizontal. Air pressure within the umbrella envelope would push the rear-er part of the umbrella upwards flipping it inside out so to speak.

 

[A.T.]

This calls for an experiment with more controlled circumstances: wind tunnel and umbrella fixed to a stand.

Unfortunately not a good test of pure flipping over, because the shaft bends here too.

 

[Trying2Learn]

All fascinating!

Thank you, everyone