THE AERONAUTICAL JOURNAL 1 Page 1 of 29. c  Royal Aeronautical Society 2019 doi:10.1017/aer.2019.138 Effect of microramps on flare-induced shock – boundary-layer interaction T. Nilavarasan , G. N. Joshi and A. Misra nlvrsnt_phd2015@diat.ac.in Department of Aerospace Engineering Defence Institute of Advanced Technology Pune, 411025, Maharashtra, India ABSTRACT The ability of microramps to control shock - boundary layer interaction at the vicinity of an axisymmetric compression corner was investigated computationally in a Mach 4 flow. A cylinder/flare model with a flare angle of 25 ◦ was chosen for this study. Height (h) of the microramp device was 22% of the undisturbed boundary layer thickness (δ) obtained at the compression corner location. A single array of these microramps with an inter-device spacing of 7.5h was placed at three different streamwise locations viz. 5δ, 10δ and 15δ (22.7h, 45.41h and 68.12h in terms of the device height) upstream of the corner and the variations in the flowfield characteristics were observed. These devices modified the separation bubble struc- ture noticeably by producing alternate upwash and downwash regions in the boundary layer. Variations in the separation bubble’s length and height were observed along the spanwise (circumferential) direction due to these devices. Keywords: Flare; shock-induced separation; microramps; micro-vortex generators; flow control NOMENCLATURE H incompressible shape factor h height of the microramp L upstream influence length M Mach number P static pressure R radius of the body Received 21 February 2019; revised 18 August 2019; accepted 2 October 2019.