I have not seen this in my city (but maybe there is), but in general in the USSR such an element in architecture was actively used. Looking at this, I did not immediately understand what the functional purpose is. If it was at the bottom of the window, then I would think about some kind of flower boxes (also common) or something for hanging clothes maybe.
Do you know what it was for?
For example, such assumptions can be found on the Internet:
But all this is not that, the sun has nothing to do with it.
These are lamellar visors, which were so constructively installed on administrative buildings, in hospitals and schools.
Promotional video:
The principle of operation is as follows: Warm air in any room is upstairs under the ceiling and wants to be even higher, and cold air spreads below. When you open the window, warm air from above starts to go out of the window onto the street, creating a draft that sucks in colder air from the street. This is with a simple window.
If you put a “wing” at the “exit” of warm air from the window, such as that of an aircraft, then the warm air at the exit from the room will first descend lower along the wing profile, creating a lift like an aircraft wing, and will rush upward even faster at the exit from the edge speeding up. Thus, creating an even stronger draft of cold air at the bottom of the window, which will quickly be sucked into the room.
Now, of course, in the age of air conditioners and forced ventilation, this may no longer be so in demand, but the effectiveness of this structural element is very decent.
Have you seen this in your city?