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Implicit Large Eddy Simulation (ILES) has rapidly emerged as a powerful techniquewhich is utilised to explore the unsteady compressible turbulent flows. Apart from o ering accuracy in numerical simulations, ILES is also computationallye cient compared to Direct Numerical Simulations or conventional Large Eddy Simulations. This report focuses on the validation of the existing high-resolution methodswithin the framework of ILES and explores its applications to the high-speed compressibleturbulent flows such as a typical flow field inside a scramjet engine. Themethodology applied in the current work employs a fifth-order MUSCL scheme witha modified variable extrapolation and a three-stage second-order Runge-Kutta schemefor 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 beenimplemented. This technique has been validated and compared against various otherturbulent inflow data generation methods in order to find the most accurate, reliableand computationally e cient technique. The high-speed complex multi-species flowof a transverse sonic jet injection into a supersonic crossflow (JISC), which is typicalfuel injection strategy inside a scramjet engine, has been investigated for time-averagedand instantaneous flow. It has been demonstrated that the incoming STBL plays a vitalrole in establishing the correct flow dynamics in JISC study as it enhances the KHinstabilities 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 obtainthe inflow conditions for the HyShot-II combustion chamber. Although the design ofHyShot-II allowed to disgorge the shock and boundary layer which could otherwiseenter the combustion chamber, but, it has been demonstrated that the flow field insidethe combustion chamber still consists of a weak shock-train. Finally, the hydrogeninjection is analysed inside the HyShot-II combustion chamber, with the shock-traintravelling inside and the incoming STBL using digital filters based technique, to explorevarious time-averaged and instantaneous flow structures and parameters with aview to enhance the understanding of the complex flow field inside the combustionchamber. It is demonstrated from the detailed investigations of a complex high-speedflow that ILES methodology has the potential to develop the understandings of thehigh-speed compressible turbulent flows using comparatively less computational resources.