Bypass Transition in Turbomachinery Flows: Turbulent Spots and the Calming Effect
Abstract
Direct numerical simulations (DNS) were carried out of bypass transition in favorable, zero, and adverse pressure gradient boundary layers in the presence of free-stream turbulence. A time sequence from the ZPG simulations was stored in order to obtain a number of spots for the study of the calming effect. Since the previous report on the research, additional spots have been obtained, in order to increase the number of available events to forty two (42) spots. Various flow visualization techniques were used to analyze the evolution of the spots. It was observed that the location of spot inception is difficult to identify. In the previous report, the investigator analyzed the instability of the streaky boundary layer. The investigator herein report the use of the Lyapunov Exponent in order to determine the Lagrangian Coherent Structures (LCS), which form the spot. Additionally, work was done to determine the average spot inception location, spreading rate, and speed of propagation.
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 04, 2010
- Accession Number
- ADA531085
Entities
People
- D. Kyriazis
- Tamer A. Zaki
Organizations
- Imperial College London