Attenuation of pulsation and oscillation using a disk at mid-section of spiked blunt body

Abstract

The two most important modes of flow instability are observed on a flat-faced cylinder fitted with a spike, namely, pulsation and oscillation. A new technique is proposed in this article to attenuate both pressure and aerothermal fluctuations over the cylinder by using a circular disk at the mid-length of the sharp-tipped spike, which splits the separation region in front of the cylinder. Shock tunnel experiments are carried out at a free stream Mach number of M∞ = 5.7 and a Reynolds number of RD = 0.5 × 106 (based on the cylinder diameter, D). Aeroheating is measured using platinum thin film sensors painted over the front face of the cylinder. It is shown that the flow pulsation can be totally mitigated for the ratio of spike length to diameter (L/D = 1.0) by using a disk of diameter d/D = 28% at the mid-section of the spike, and the oscillation flow is suppressed using the same disk diameter with L/D = 1.5. This phenomenon is well evident from the measured heat transfer and schlieren data. Besides, a similar analysis showed that the flow fluctuation over an aerospike mounted on a hemispherical blunt body can be diminished with the use of double-aerospike, which, in turn, decreases the heat flux peak in the proximity of the reattachment. This is an effective means of flow fluctuation mitigation and presents to be a good thermal protection for the fore body.