High-rise aerodynamics

[freebeard]

Chicago’s Newest Towers Are Invisible to Wind

The lead building employs vortex generators, although they talk about 'confusing the wind' and compare with golf ball dimples. What follows are contemporary examples and a history of wind tunnels and CFD. ....followed by an ad.

[aerohead]

Perhaps an unfortunate use of the word.
* A skyscraper would never experience a sub-critical Reynolds number, and a laminar boundary layer, so introducing the notion of a golf ball dimple parallel would be inappropriate.
* Every 'face' of the tower would have to be considered within the context of the particular type of flow it experiences.
* With increasing height, the moment arm is lengthening, and the 'narrowing' reduces the local frontal area proportionately, mitigating the torque introduced by the aerodynamic drag from wind speeds which are no doubt, also increasing with elevation.
* At times, edge vortices might induce torsional loads.
* Natural frequencies of the structure would vary with location. These frequencies, and their harmonics would need to be dampened or eliminated, in order to avoid flutter.
* The staggered 'stepping' would work towards that end.
* The edge flow separation may not reattach at all near the top of the tower at times, imparting a very low base pressure in the turbulent wake, and amplifying the overturning torque; putting part of the structure and foundation in compression on the leeward side, while inducing an opposing tension on the windward face.
* The staggering of the steps 'flow confusion' might be an analogue to tuning downwash and up-wash on the rear of a car in order to 'burst', otherwise strong longitudinally-attached vortices.
* I'll bet that the load cell data is invaluable.

[freebeard]

It must experience a prevailing wind, the whole design seems directional.

The specific example was less important for me, than the discussion that followed.

[aerohead]

Originally Posted by freebeard

It must experience a prevailing wind, the whole design seems directional.

The specific example was less important for me, than the discussion that followed.

They do talk about the wind coming off the lake from the south, but they'd be tasked with analyzing the structure from every conceivable orientation.
We're seeing large, onshore wind circulations now, not necessarily ' Day After Tomorrow' inland hurricanes, but Derechos and significant supercell cyclonic circulations, and it's not going to do anything but increase with time. If they're doing a 100-year building, or more, they need to look at the model trends, and cover future worst-case-scenarios.

[j-c-c]

Being from So Fla, I am to assume those are not dwellings, and have no balcony access nor window openings?
With the potential aero interaction possible between the buildings at the higher elevations/wind speeds, humans and pets and other moveable objects would need a restraint/safety harness if near an open window when someone would open their front door.

Assuming "directionally" with today's changing weather with a structure with a many decade lifespan IMO seems rather foolish/shortsighted if safety is a consideration

[freebeard]

humans and pets and other moveable objects would need a restraint/safety harness if near an open window...

A fool's errand, driven by densely spaced city streets. An omni-directional solution would tend toward quasi-spherical. Fuller's Old Man River's City project:

Old Man River's City project

The Old Man River's City project was an architectural design created by Buckminster Fuller in 1971. Fuller was asked to design the structure by the city of East St. Louis. Old Man River's City would have been a truly massive housing project for the city's 70,000 residents. The total capacity of the building, a circular multi-terraced dome, would be 125,000 occupants. Each family would have approximately 2,500 square feet (230 m2) of living space.Wikipedia

Even if it turned into a dystopia, it would be a clean, well-lighted dystopia.