CUED Publications database

LARGE EDDY SIMULATION OF BOUNDARY LAYER TRANSITION MECHANISMS IN A GAS-TURBINE COMPRESSOR CASCADE

Scillitoe, AD and Tucker, PG and Adami, P and ASME, (2018) LARGE EDDY SIMULATION OF BOUNDARY LAYER TRANSITION MECHANISMS IN A GAS-TURBINE COMPRESSOR CASCADE. In: ASME Turbo Expo 2018: Turbomachinery Technical Conference and Exposition, -- to -- V02AT45A009-..

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Abstract

Large Eddy Simulation (LES) is used to explore the boundary layer transition mechanisms in two rectilinear compressor cascades. To reduce numerical dissipation, a novel locally adaptive smoothing scheme is added to an unstructured finite-volume solver. The performance of a number of Sub-Grid Scale (SGS) models is explored.With the first cascade, numerical results at two different freestream turbulence intensities (Ti’s), 3.25% and 10%, are compared. At both Ti’s, time-averaged skin-friction and pressure coefficient distributions agree well with previous Direct Numerical Simulations (DNS). At Ti = 3.25%, separation induced transition occurs on the suction surface, whilst it is bypassed on the pressure surface. The pressure surface transition is dominated by modes originating from the convection of Tollmien-Schlichting waves by Klebanoff streaks. However, they do not resembled a classical bypass transition. Instead, they display characteristics of the “overlap” and “inner” transition modes observed in the previous DNS. At Ti = 10%, classical bypass transition occurs, with Klebanoff streaks incepting turbulent spots.With the second cascade, the influence of unsteady wakes on transition is examined. Wake-amplified Klebanoff streaks were found to instigate turbulent spots, which periodically shorten the suction surface separation bubble. The celerity line corresponding to 70% of the free-stream velocity, which is associated with the convection speed of the amplified Klebanoff streaks, was found to be important.

Item Type: Conference or Workshop Item (UNSPECIFIED)
Subjects: UNSPECIFIED
Divisions: Div A > Fluid Mechanics
Depositing User: Cron Job
Date Deposited: 24 Sep 2018 20:06
Last Modified: 09 Sep 2021 01:29
DOI: