TY - JOUR
T1 - COMPRESSIBLE FLOW in front of AN AXISYMMETRIC BLUNT OBJECT
T2 - ANALYTIC APPROXIMATION and ASTROPHYSICAL IMPLICATIONS
AU - Keshet, Uri
AU - Naor, Yossi
N1 - Funding Information:
This research has received funding from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement no 293975, from an IAEC-UPBC joint research foundation grant, from an ISF-UGC grant, and from an individual ISF grant.
Publisher Copyright:
� 2016. The American Astronomical Society. All rights reserved.
PY - 2016/10/20
Y1 - 2016/10/20
N2 - Compressible flows around blunt objects have diverse applications, but current analytic treatments are inaccurate and limited to narrow parameter regimes. We show that the gas-dynamic flow in front of an axisymmetric blunt body is accurately derived analytically using a low order expansion of the perpendicular gradients in terms of the parallel velocity. This reproduces both subsonic and supersonic flows measured and simulated for a sphere, including the transonic regime and the bow shock properties. Some astrophysical implications are outlined, in particular for planets in the solar wind and for clumps and bubbles in the intergalactic medium. The bow shock standoff distance normalized by the obstacle curvature is ∼2/(3g) in the strong shock limit, where g is the compression ratio. For a subsonic Mach number M approaching unity, the thickness δ of an initially weak, draped magnetic layer is a few times larger than in the incompressible limit, with amplification ∼(1 + 1.3M2.6)/ (3σ).
AB - Compressible flows around blunt objects have diverse applications, but current analytic treatments are inaccurate and limited to narrow parameter regimes. We show that the gas-dynamic flow in front of an axisymmetric blunt body is accurately derived analytically using a low order expansion of the perpendicular gradients in terms of the parallel velocity. This reproduces both subsonic and supersonic flows measured and simulated for a sphere, including the transonic regime and the bow shock properties. Some astrophysical implications are outlined, in particular for planets in the solar wind and for clumps and bubbles in the intergalactic medium. The bow shock standoff distance normalized by the obstacle curvature is ∼2/(3g) in the strong shock limit, where g is the compression ratio. For a subsonic Mach number M approaching unity, the thickness δ of an initially weak, draped magnetic layer is a few times larger than in the incompressible limit, with amplification ∼(1 + 1.3M2.6)/ (3σ).
KW - hydrodynamics
KW - intergalactic medium
KW - interplanetary medium
KW - methods: analytical
KW - shock waves
UR - http://www.scopus.com/inward/record.url?scp=84993939748&partnerID=8YFLogxK
U2 - 10.3847/0004-637X/830/2/147
DO - 10.3847/0004-637X/830/2/147
M3 - Article
AN - SCOPUS:84993939748
SN - 0004-637X
VL - 830
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 2
M1 - 147
ER -