Instabilities of Decelerating Flow

This paper numerically investigates the instability characteristics of decelerating flows. The flow dynamics and temporal evolution of coherent structures in a diverging section with mild spatial pressure gradient are analyzed using numerical experiments with Incompact3d code. The unsteady nature of flow and adverse pressure gradient is the reason for inflectional velocity profiles, results into boundary layer separation and instability with reverse flow and later on it leads to vortex formation. Vortex formation time is found by vortex Reynold's number. Time of first vortex formation, non-dimensional vortex formation times with Reynold's number etc. are validated with an experimental results.Comment: Proceedings of the 25th National and 3rd International ISHMT-ASTFE Heat and Mass Transfer Conference (IHMTC-2019

Assessment of Pressure Based Solver in Resolving Complex Shock Wave Phenomenon

This study presents a critical assessment of a pressure-based solver (PBS) in resolving complex interactions of shocks, turbulent structures etc.. The canonical problem chosen to be resolved in this study is of mode staging in axisymmetric supersonic jet screech. The screech phenomenon exhibits staging behavior characterized by frequency and azimuthal structure changes at specific frequencies. The PBS simulations in the popular ANSYS Fluent software-suite were validated against numerical work and experimental measurements, and results were analyzed. Simulations are performed on supersonic jets which emits dual high frequency screech tones at particular Mach numbers. At lower end of these supersonic Mach numbers, the flow can involve vanishingly weak shock strengths which is routinely captured in experiments and by density based solvers in literature. The limitations of the pressure-based solver in resolving complex shock flow phenomena and predicting mode staging are highlighted at vanishingly weak Mach numbers, emphasizing the need for further investigation given the recent popularity of such solvers for all Mach numbers including in high-speed flow.Comment: 14th Asian Computational Fluid Dynamics Conference, 30th October - 02nd November, 2023, Bengalur