Overdriven Supersonic Heat Waves

Strachan, J.D.; Ahlborn, B.

doi:10.1071/ph750395

Cited by 3 publications

(2 citation statements)

References 2 publications

(3 reference statements)

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“…where the factor q defines the energy per unit mass delivered to the fluid particles in case of considering exothermic effects (q > 0) or the energy per unit mass subtracted to the fluid particles when endothermic effects are considered (q < 0). In general, there exists the possibility of having three different functions for the first adiabatic exponent Γ 1 = (∂lnp)/(∂lnρ) ad , the ratio of the specific heats γ = c p /c v , and the enthalpy coefficient g, as occurs in partially dissociated or ionized gases [67,68]. The definition of the latter g = h/e = h/ (h − p/ρ), where h and e are the specific enthalpy and internal energy, respectively.…”

Section: A Base Flow Equationsmentioning

confidence: 99%

Acoustic stability of nonadiabatic high-energy-density shocks

et al. 2020

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As firstly predicted by D'yakov and Kontorovich (DK), an initially disturbed shock front may exhibit different asymptotic behaviours depending on the slope of the Rankine-Hugoniot curve.Adiabatic and isolated planar shocks traveling steadily through ideal gases are stable, in the sense that any perturbation on the shock front decays in time with the power t −3/2 (or t −1/2 in the strongshock limit). While some gases whose equation of state cannot be modelled as a perfect gas, as those governed by van der Waals forces, may induce constant-amplitude oscillations to the shock front in the long-time regime, fully unstable behaviours are seldom to occur due to the unlikely conditions that the equation of state must meet. In this work, it has been found that unstable conditions are might be found when the gas undergoes an endothermic or exothermic transformation behind the shock. In particular, it is reported that constant-amplitude oscillations can occur when the amount of energy release is positively-correlated to the shock strength and, if this correlation is sufficiently strong, the shock turns to be fully unstable. The opposite highly-damped oscillating regime may occur in negatively-correlated configurations. The mathematical description then adds two independent parameter to the regular adiabatic index γ and shock Mach number M 1 , namely: the total energy added/removed and its sensitivity with the shock strength. The formulation in terms of endothermic or exothermic effects is extended, but not restricted, to include effects associated to ionization, dissociation, thermal radiation, and thermonuclear transformations, so long as the time associated to these effects is much shorter time than the acoustic time.

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Section: A Base Flow Equationsmentioning

confidence: 99%

Acoustic stability of nonadiabatic high-energy-density shocks

et al. 2020

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“…This creates a rearward-facing, i.e. in the opposite direction to the IF, rarefaction wave and a forward-facing shock (Strachan and Ahlborn 1975;Ahlborn and Strachan 1973). Under homogeneous conditions and for an infinite flow stream these waves and shocks will form periodically (Schnerr & Adam 1997).…”

Section: Supersonic Ionization Fronts and Cooling Frontsmentioning

confidence: 99%

IONIZATION-DRIVEN FRAGMENTATION OF GAS OUTFLOWS RESPONSIBLE FOR FeLoBALs IN QUASARS

Bautista¹,

Dunn²

2010

ApJ

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We show that time variations in the UV ionizing continuum of quasars, on scales of ∼1 year, affect the dynamic structure of the plasmas responsible for low ionization broad absorption lines. Variations of the ionizing continuum produce non-equilibrium photoionization conditions over a significant fraction of the absorbing clouds and supersonically moving ionization fronts. When the flux drops the contraction of the ionized region drives a supersonic cooling front towards the radiation source and a rarefaction wave in the opposite direction. The pressure imbalance is compensated by an increased speed of the cool gas relative to the front. When the flux recovers the cool gas is re-ionized and re-heated by a supersonic ionization front traveling away from the radiation source and a forward shock is created. The reheated clouds equilibrate to a temperature of ∼ 10 4 K and are observed to have different radial velocities than the main cloud. Such fragmentation seems consistent with the multicomponent structure of troughs seen in some objects. The velocity differences measured among various components in the quasars QSO 2359-1241 and SDSS J0318-0600 can be reproduced by our model if strong magnetic fields (∼10 mG) are present within the clouds.

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Single and multiple waves induced by power absorption

Armstrong,

Ahlborn,

Liese

1982

The Physics of Fluids

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Sub- and supersonic wave fronts produced by heat input have been generated in a shock tube driven by a step current pulse of variable magnitude (4–50 kA, duration up to 160 μsec). At high current and low fill gas densities, the supersonic mode appears and no substantial compression is possible. The limiting current Ic to reach this supersonic mode is determined as a function of the fill gas pressure. Front velocities, pressures, and electron densities are measured, and the heating characteristic (maximum enthalpy as function of the net absorbed energy flux) is derived. Scaling laws are obtained for the fluid parameters as a function of fill gas density and current. The measurements are interpreted in terms of one-dimensional wave model calculations. Studies with two stepped power pulse reveal that multiple shocks with a region of substantially increased density can be obtained only if the total current It remains below the critical value Ic. For It≳Ic, a supersonic heat wave is created after the transient phase, and multiple shocks with increased density can no longer be achieved.

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Overdriven Supersonic Heat Waves

Cited by 3 publications

References 2 publications

Acoustic stability of nonadiabatic high-energy-density shocks

Acoustic stability of nonadiabatic high-energy-density shocks

IONIZATION-DRIVEN FRAGMENTATION OF GAS OUTFLOWS RESPONSIBLE FOR FeLoBALs IN QUASARS

Single and multiple waves induced by power absorption

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