Effect of Riblets on Pressure Recovery in a Straight-Walled Diffuser.

摘要

The objective of this thesis was to investigate the effect of riblets on the pressure recovery in a straight-walled diffuser. Previous work has shown that riblets were effective in reducing the viscous drag over surfaces subjected to a turbulent boundary layer. More recently, riblets were shown to delay the flow separation within a subsonic, straight-walled diffuser by as much as 200%. The purpose of this investigation was to determine the effect on the pressure distribution within a diffuser that has had the flow separation point favorably altered by the application of riblets. Investigation results revealed that riblets not only delayed flow separation in a diffuser, but also altered the pressure distribution in a manner that allowed for improved recovery. This improvement was realized by an increase in the pressure coefficient of between 30-38% the larger increases occurring for those diffuser geometrics most likely leading to stall (high aspect ratio). Additionally, it was discovered that the introduction of static ports into the riblet surface did not significantly alter the flowfield over that of a geometrically similar riblet surface.