Entropy Analysis of the Flat Tip Leakage Flow with Delayed Detached Eddy Simulation

Area of Science:

• Aerospace Engineering
• Turbomachinery Flow Physics

Background:

• Tip leakage vortices in unshrouded turbine rotors are a primary source of aerodynamic loss.
• Reynolds Averaged Navier-Stokes (RANS) limitations in predicting complex turbulent tip leakage flow necessitate advanced simulation methods.

Purpose of the Study:

• To investigate the loss mechanisms in the tip leakage flow of a high-pressure turbine using advanced simulation techniques.
• To compare the predictive capabilities of Delayed Detached Eddy Simulation (DDES) against RANS for detailed flow structure analysis.

Main Methods:

• Delayed Detached Eddy Simulation (DDES) was employed to model the flow in a high-pressure turbine blade tip region.
• Snapshot Proper Orthogonal Decomposition (POD) was utilized to identify dominant flow structures and energy distribution.
• Entropy generation rates were analyzed to quantify aerodynamic losses.

Main Results:

• DDES accurately captured detailed flow structures and turbulence characteristics, outperforming RANS.
• Strong interactions between the tip leakage vortex (TLV) and up passage vortex (UPV) were identified as key drivers of unsteady effects and turbulence enhancement.
• Viscous dissipation was found to be the dominant loss mechanism, with peak losses occurring in the tip clearance due to TLV-UPV interactions.

Conclusions:

• DDES provides superior insights into tip leakage flow physics and loss generation compared to RANS.
• Unsteady flow effects significantly influence loss distribution and are critical for accurate aerodynamic analysis.
• Understanding these loss mechanisms can guide the design of more efficient, low-loss turbine blade tips.