TY - JOUR
T1 - Measurement of unsteady shock standoff distance around spheres flying at Mach numbers near one
AU - Kikuchi, T.
AU - Ohtani, K.
N1 - Funding Information:
The authors thank members of their laboratory for technical support with the experiment and for useful discussions. They also thank T. Ogawa for technical support with the experiment. This work was supported as a Collaborative Research Project in the Institute of Fluid Science of Tohoku University.
Publisher Copyright:
© 2022, The Author(s).
PY - 2022/3
Y1 - 2022/3
N2 - This paper reports the experiments on the shock standoff distance (SSD) around spheres flying at Mach numbers from slightly below 1.0. Spheres of the same diameter but three different densities were launched in a ballistic range by a light-gas gun, and the flow field around each sphere was measured by optical visualization. The purpose of this study is to investigate how projectile deceleration influences the SSD by comparing the results for projectiles of the same shape, size, and Mach number but different densities. The location history of the sphere center is obtained by fitting a formula derived from the equation of motion of a decelerating object, and the history of the instantaneous projectile Mach number is obtained by differentiating this formula.The SSDs of the projectiles with different densities are the same at higher Mach numbers, but different at lower Mach numbers, and the SSD decreases with decreasing projectile density. Seemingly, because projectile deceleration is related to the flow unsteadiness, steady flow cannot be assumed in the present range of Mach number with the different SSDs. At Mach numbers close to one, that of the propagating detached shock wave is higher than that of the flying projectile.
AB - This paper reports the experiments on the shock standoff distance (SSD) around spheres flying at Mach numbers from slightly below 1.0. Spheres of the same diameter but three different densities were launched in a ballistic range by a light-gas gun, and the flow field around each sphere was measured by optical visualization. The purpose of this study is to investigate how projectile deceleration influences the SSD by comparing the results for projectiles of the same shape, size, and Mach number but different densities. The location history of the sphere center is obtained by fitting a formula derived from the equation of motion of a decelerating object, and the history of the instantaneous projectile Mach number is obtained by differentiating this formula.The SSDs of the projectiles with different densities are the same at higher Mach numbers, but different at lower Mach numbers, and the SSD decreases with decreasing projectile density. Seemingly, because projectile deceleration is related to the flow unsteadiness, steady flow cannot be assumed in the present range of Mach number with the different SSDs. At Mach numbers close to one, that of the propagating detached shock wave is higher than that of the flying projectile.
KW - Ballistic range
KW - Near-sonic
KW - Shock standoff distance
KW - Unsteady flow
KW - Visualization
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U2 - 10.1007/s00193-021-01067-x
DO - 10.1007/s00193-021-01067-x
M3 - Article
AN - SCOPUS:85123466037
SN - 0938-1287
VL - 32
SP - 235
EP - 239
JO - Shock Waves
JF - Shock Waves
IS - 2
ER -