in your latest post, is that bug mounted with a yaw angle or what? because the bugs antenna and its head are not disturbing the flow. and the flow perfectly follows the surface of the bug’s aft body. how does this happen? is it something about low reynolds number?
The locust in that post is fully immersed in the flow and its antenna and head are disturbing the air, just not the smoke. The smoke generator is placed in a single vertical plane that’s offset from the bug’s midsection. According to the published paper, the smoke visualization corresponds to:
“[…] the vertical plane that intercepts the hindwing at the mid-wing position when the wing is horizontal.”
That’s why you can see perfectly smooth lines of smoke between the camera and the locust’s head.