Implicit LES of turbulent compressible high-speed flows with transverse jet injection

Abstract

Implicit Large Eddy Simulation (ILES) has rapidly emerged as a powerful technique which is utilised to explore the unsteady compressible turbulent flows. Apart from o ering accuracy in numerical simulations, ILES is also computationally e cient compared to Direct Numerical Simulations or conventional Large Eddy Simulations. This report focuses on the validation of the existing high-resolution methods within the framework of ILES and explores its applications to the high-speed compressible turbulent flows such as a typical flow field inside a scramjet engine. The methodology applied in the current work employs a fifth-order MUSCL scheme with a modified variable extrapolation and a three-stage second-order Runge-Kutta scheme for temporal advancement. In order to simulate a realistic and accurate supersonic turbulent boundary layer (STBL) a synthetic turbulent inflow data generation method based upon digital filters has been implemented. This technique has been validated and compared against various other turbulent inflow data generation methods in order to find the most accurate, reliable and computationally e cient technique. The high-speed complex multi-species flow of a transverse sonic jet injection into a supersonic crossflow (JISC), which is typical fuel injection strategy inside a scramjet engine, has been investigated for time-averaged and instantaneous flow. It has been demonstrated that the incoming STBL plays a vital role in establishing the correct flow dynamics in JISC study as it enhances the KH instabilities in the flow field. Thermally perfect gas formulation has been implemented according to the NACA- 1135 report to study the e ects of high temperatures on the ratio of specific heats ( ). Using this, the full geometry of the HyShot-II scramjet engine is investigated to obtain the inflow conditions for the HyShot-II combustion chamber. Although the design of HyShot-II allowed to disgorge the shock and boundary layer which could otherwise enter the combustion chamber, but, it has been demonstrated that the flow field inside the combustion chamber still consists of a weak shock-train. Finally, the hydrogen injection is analysed inside the HyShot-II combustion chamber, with the shock-train travelling inside and the incoming STBL using digital filters based technique, to explore various time-averaged and instantaneous flow structures and parameters with a view to enhance the understanding of the complex flow field inside the combustion chamber. It is demonstrated from the detailed investigations of a complex high-speed flow that ILES methodology has the potential to develop the understandings of the high-speed compressible turbulent flows using comparatively less computational resources.