Control of edney IV interaction by pulsed laser energy deposition

An experimental investigation was conducted to examine the effect of a pulsed Nd:YAG laser energy addition on the shock structures and surface pressure in a Mach 3.45 flow past a sphere. Two configurations were considered: 1) a sphere in a uniform freestream and 2) an Edney IV interaction generated by impingement of an oblique shock on the bow shock of the sphere. For laser energy addition upstream of the sphere in a uniform freestream, schlieren images show that the interaction of the blast wave and thermal spot cause the bow shock to move upstream while creating an expansion wave that propagates to the sphere surface. This results in a momentary 40% decrease of centerline surface pressure. The effect of the energy deposition was relatively consistent for laser energies ranging from 13 to 283 mJ/pulse. For laser energy addition upstream of an oblique shock interacting with the sphere's bow shock (Edney IV interaction), a similar thermal lensing evolution is observed, but is asymmetric due to the presence of the oblique shock. The embedded jet characteristic of the Edney IV type interaction is also perturbed as the thermal spot first interacts with the oblique shock and then the bow shock, momentarily decreasing the peak surface pressure caused by the jet by 30%.