Soooo, the 1x90 vs 2x45 one isn't really about number of turns is it... looks like the effective radius of curvature is the real defining difference. The 2x45 corners essentially make a wider radius of curvature in this case, which results in a gentler turn and so less turbulence. You could stick to 1x90 but with a larger radius of curvature and get a similar improvement.
It's about what you can do with the usual off-the-shelf components. Large 90° pieces usually aren't available, but you can make something similar if you put two 45° pieces together.
So, if you're a woodworker and you built a dust extraction system with PVC pipes from the hardware store, you might want to use two 45° pieces instead on one 90° piece where you got the space for that to increase the overall airflow.
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u/lenzflare 2h ago
Soooo, the 1x90 vs 2x45 one isn't really about number of turns is it... looks like the effective radius of curvature is the real defining difference. The 2x45 corners essentially make a wider radius of curvature in this case, which results in a gentler turn and so less turbulence. You could stick to 1x90 but with a larger radius of curvature and get a similar improvement.