Measurement of the flow field induced by a spark plasma using particle image velocimetry

Experimental study of energy delivered to the filaments in high pressure nanosecond surface discharge

“…These jets are assumed to be generated due to the baroclinic torque present near the end of the heat release zone. Similar structures were obtained during the cavern decay of the volumetric electrode and laser sparks [11,12]. Another typical feature is the jet propagating along the surface in the crossflow planes.…”

Two regime cooling in flow induced by a spark discharge

“…All results were non-dimensionalized using the induced velocity (𝑢 𝑠ℎ𝑜𝑐𝑘 ) and density (𝜌 𝑠ℎ𝑜𝑐𝑘 ) behind the compression wave produced by the spark and the characteristic length (𝑑) taken to be the electrode gap distance (5 mm) [9], [11]. The velocity and length scales were used to define a characteristic time scale, 𝜏, as 𝑑/𝑢 𝑠ℎ𝑜𝑐𝑘 .…”

“…Results were non-dimensionalized similar to prior work [17] using the velocity induced behind the shock wave produced by the spark expansion. The shock was assumed to be weak [50], [51] and the weak shock solution for the pressure jump across a shock, developed by Jones et al [52], was used:…”

“…Experimental results of the late stages of the flow induced by sparks have been restricted to qualitative descriptions of the flow field [15], primarily due to difficulties associated with measuring such a transient and highly complex flow field with sufficient spatiotemporal resolution. Some of the first experimental results presenting quantitative information on the flow induced by microsecond-duration sparks [17] have shown the presence of a pair of vortex rings around the hot gas kernel for 5 mm and 8 mm electrode gap distances. In addition, these experiments revealed, jets of surrounding gas entrained into the electrode gap, and the circulation of the vortex rings as well as the rate of entrainment was found to decay over time.…”

“…Recently, we performed measurements using stereoscopic particle image velocimetry (S-PIV) and background oriented schlieren (BOS) to measure the velocity and density fields, respectively, during the kernel cooling process [9], [10]. The velocity measurements showed the presence of vortex rings near each electrode and significant entrainment of ambient gas into the electrode gap [9], [11]. The density measurements showed that the cooling of the hot gas kernel occurs in two distinct regimes: an initially fast, convective cooling regime, followed by a slower cooling regime, with the fast regime contributing approximately 50% of the overall cooling in less than 1 ms after the spark discharge.…”