Investigation of the Flow behind the Roughness Element on the UAV Surface at a Favorable Pressure Gradient

Read more Abstract
In a wind tunnel of low subsonic speeds, an experimental study was conducted of the windward flow of a trapezoidal model of a flying wing (UAV) with a locally installed perturbation generator in the region of maximum susceptibility on its surface. The generator was a three-dimensional roughness element whose height was comparable to the thickness of the boundary layer. The uniqueness of the work was that the experiments were carried out in a wind tunnel at real flight Reynolds numbers on a UAV model at a scale of 1:1. The results of visualization of the flow near a smooth surface and behind roughness were obtained using the method of liquid crystal thermography. The internal structure and processes of development of the longitudinal perturbation behind the roughness downstream were studied in detail using the thermoanemometry method.

Keywords
streaky structures, laminar-turbulent transition, cross-flow instability, three-dimensional boundary layer, localized three-dimensional roughness, trapezoidal wing
Funding
The reported study was funded by RFBR, project number 19-31-90018. Partially this work was carried out within the framework of the Program of Fundamental Scientific Research of State Academies of Science for 2013-2020 (project АААА-17-117030610128-8). Authors thank G. M. Zharkova and V. N. Kovrizhina for the liquid-crystal films granted for this experiment.
УДК 532.526.3 

Investigation of the Flow behind the Roughness Element on the UAV Surface at a Favorable Pressure Gradient (RUS)