Time-accurate CFD simulation of transonic flow over a hammerhead nose cone configuration

Abstract

Hammerhead nose cone configurations are essential in accommodating larger payloads. However, during transonic flight regime, they experience high-level of pressure fluctuations due to flow-induced turbulence, wake effects, flow separation and shock oscillations which can lead to severe buffet phenomenon. Buffet loads can cause severe structural damage to the payload; and can ultimately destroy the whole mission. Therefore, it is extremely necessary to determine unsteady pressure fluctuations on a hammerhead configuration and consider them in the overall design load analysis to ensure that the configuration is safe from the severity of buffet loads. In the present work, time-accurate CFD simulation of flow over a hammerhead nose cone configuration (NASA Model IV) has been performed for a Mach number of 0.79. The objectives of the present work are to compute the unsteady surface pressure fluctuations, analyze the time-accurate aerodynamic behaviour of the flow, and determine the validity and accuracy of the computational methodology using ANSYS Fluent®. For validation, the rms (root mean square) value of the computed instantaneous pressure is compared with the experimental results and the time-average solution is compared with the steady state solution. In the present work, the separated shear layer off the boat-tail edge is successfully captured and the turbulence region downstream is found responsible for unsteady loadings.