IISc Bangalore

Investigations on Interacting and Isolated Swirl Flows

MSc (Engg.) Thesis Defense Notice

Student: Paidipati Mallikarjuna Tilak
Department of Aerospace Engineering
Indian Institute of Science

Date: April 05, 2019
Time: 4 pm
Venue: AE 006
Research Supervisor: Prof. Swetaprovo Chaudhuri

This work investigates (from the experimental data) the flow structures emerging from the mutual interaction between adjacent swirling flows at variable degrees of swirl, issued into a semi-confined chamber, as it could happen in a three-cup sector of an annular premixed combustor of a modern gas turbine engine. A central swirling flow with a fixed swirl vane angle is allowed to interact with its neighboring flows of varied swirl levels, with constant inlet bulk flow velocity through the central port. It is found that the presence of straight jets with zero swirl or co-rotating swirling jets with increasing swirl on both sides of the central swirling jet, significantly alters its structures. As such, an increase in the amount of swirl in the neighboring flows increases the recirculation levels in central swirling flow leading to a bubble type vortex breakdown, not formed otherwise. It is shown with the aid of Helmholtz decomposition that the transition from conical to bubble type breakdown is captured well by the radial momentum induced by the azimuthal vorticity. It is attempted to gain a deeper understanding of vortex breakdown as a general feature of swirling flows by subjecting an available computational data to the theoretical model that was based on flow criticality (Benjamin,1962). A slight confusion in the literature that prevails about the choice of boundary conditions of criticality equation is clarified. At increasing swirl, it is found that the occurrence of vortex breakdown and transition of flow from supercritical to subcritical state are very closely related. Given its limitations, it is shown that the Benjamin’s model is able to explain the phenomenon partially.

All are Welcome.

Date(s) - 05/04/2019
4:00 pm - 5:00 pm

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