The baroclinic effect in combustion

Premixed flame response to oscillatory pressure waves

“…The authors [13] attributed the early stage of turbulence development to interaction of the flame front with an acoustic wave, with associated acceleration (or deceleration) of the gas flow normal to it. Modelling studies [14,16] showed that the enhancement of the wrinkling a flame front in a changing pressure field is associated with the generation of vorticity through baroclinic effects. In our earlier papers [14,15], we mainly considered the influence of a pressure ramp function with only one example of a sinusoidal input of pressure to a two-dimensional flame front.…”

A mechanism of vortex generation in a supersonic flow behind a gas-plasma interface

“…It is well known that a shock wave interaction with plasma results in significant changes in the shock wave structure and the plasma flow. Such phenomena are particularly observed in the shock-flame interactions [1], in the front separation regions control experiments [2], in combustion [3,4], and in the electric discharge [5], RF- [6], or laser-induced [7,8] energy deposition experiments. Dynamic instability and turbulence in impulsively loaded flows is also of considerable interest in astrophysics plasmas [9] and fusion research [10,11].…”

“…It is well known that a shock wave interaction with plasma results in significant changes in the shock wave structure and the plasma flow. Such phenomena are particularly observed in the shock-flame interactions (Batley et al 1996a), in the front separation region control experiments (Georgievskii 2005), in combustion (Thomas et al 2001, Bret andDeutsch 2005) The complex nature and a number of co-processes often involved in this type of the interaction can be seen from the images of the initially simply structured planar, bow, or oblique shock evolving into a complicated system of distorted and secondary shocks with flow separation regions and formation of vortices (Adelgren et al 2003). Among the most remarkable changes are: the shock wave acceleration and its strong front distortion increasing with time followed with remarkable weakening of the shock until it appears less and less identifiable (Kuo and Bivolaru 2001, Adelgren et al 2003, Markhotok et al 2008, Markhotok and Popovic 2014; motion of the shock away from the body in the presence of heating (Marconi 1998); substantial changes in the gas/plasma parameter distribution behind the shock, particularly sharp reduction of pressure (Erdem et al 2013); remarkable, up to 40% reduction in the wave drag experienced by a body when the plasma is created up-stream (Jones 1959, Jones 1991; the time-delays in the effects on the flow relative to the discharge on-off times and a finite pressure rise time (Sasoh et al 2006); and a vortex system formation in the flow behind the shock often followed with strong distortion or collapse of the plasma region (Thomas et al 2001, Sasoh et al 2006.…”

“…The effect of baroclinity in the spherical/cylindrical geometry of the flame front was also studied in (Batley et al 1996a) where the vorticity field rapidly distorted the laminar flame front and the induced vorticity eventually lead to the turbulent break-up of a laminar flame. Similar interaction of a flat shock wave with a cylindrical flame/hot region was studied in (Picone et al 1985, Kim et al 2010.…”

Wave Drag Modification in the Presence of Discharges

“…The baroclinic effect is one of the mechanisms that can be responsible for vorticity generation on an interface when there is nonalignment of pressure and density gradients in the hot gas region [32]. Richtmyer-Meshkov instability (RMI) takes place when two gases of different densities are accelerated by a passage of a shock wave.…”