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Let's say we place an immovable rectangular object of an area X perpendicularly to a constant wind flow. The wind will now affect it with some force F.
Now we split that rectangular object into 4 smaller rectangles. Their total area is still equal to X and we mount them with a small spacing in form of a 2 x 2 grid.
Front view
Front view

Will the total force F of the wind affecting 4 smaller rectangles with a spacing be different than the force affecting the big solid rectangle?
Please explain why or why not.

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If small rectangles were sufficiently separated from each other, the total drag (force) for the four small rectangles would be smaller than the drag for the large rectangle, since the total exposed area is the same, while the drag coefficient for the small rectangles would be lower due to a different form-factor (small rectangles will be relatively longer).

As the gaps between the small rectangles decreases, the structure will look more like one large rectangle with slots, which makes it more difficult to figure, but, at some point, the total drag is likely to increase in comparison with the original rectangle.

This article and the study it refers to gives an idea how slots and holes affect the drag in square plates. Perhaps similar studies have been done on slotted rectangles. Anyway, unless you are already an expert, it could give you an idea how to solve your problem.

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  • $\begingroup$ Thank you for your answer and the idea where to look for answers. $\endgroup$ – o_petriv Apr 7 '18 at 8:34

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