49 / 2019-08-27 16:31:00

NUMERICAL INVESTIGATION IN STABILITY ANALYSIS OF STREAMWISE CORNER FLOW

Streamwise Corner flow, self-similar solution, linear stability analysis

Righted-angled streamwise corner formed by two vertically assembled parts exists on the surface of aircrafts. The stream-wise corner flow is three-dimensional wall bounded shear flow which exhibits instable feature so that a limited length of local stream-wise corner flow may induce flow transition downstream. The present work conducted stability investigation in incompressible streamwise corner flow. The laminar base flow was obtained by self-similar solution of two-dimensional corner layer equation with Chebyshev spectral method. Based on two-dimensional flow field slice perpendicular to streamwise direction, the stability characteristics was examined.
The three-dimensional structure of streamwise corner flow was investigated. The velocity profile perpendicular to the wall, away from the corner, approaches to the theoretical self-similar velocity profile of two-dimensional plate boundary layer with cross flow. The three-dimensional effect of the streamwise corner produces flow structures which is not contained in two-dimensional boundary layer. The thickening effect of streamwise corner induces secondary flow which is also self-similar. And the secondary flow forms two streamwise vortexes with same strength and opposite directions, which are believed to be unstable in transition process and are of interest in the present research. Not only the secondary flow but also the main stream-wise velocity exhibits three-dimensional effect--its profile along the corner bisector possess inflection point which does not appear in the two-dimensional plate boundary layer velocity profile and is considered as a necessary condition for instability in the one-dimensional velocity profile cases.
The one-dimensional bisector velocity profile, which is featured by its turning point, was studied by linear stability method. The linear stability analysis of streamwise corner flow field slice was conducted with bi-global method. The influence of laminar streamwise vortex in the corner zone to stability was analyzed. The corner modes and T-S like modes were detected and the eigenfilds exhibited even/odd characteristics along the bisector.