Experimental study on thermal characteristics of positive leader discharges using Mach-Zehnder interferometry

Zhou, Xuan; Zeng, Rong; Zhuang, Chijie; Chen, She

doi:10.1063/1.4922660

Cited by 22 publications

(18 citation statements)

References 23 publications

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“…The channel is divided into many small segments each with an equal length. values (1, 1.5 and 2 mm respectively) and that measured in lab, for the point-to-plane gap discharge reported in Zhou et al (2015).…”

Section: Summary and Discussionsupporting

confidence: 50%

A macroscopic physical model for self-initiated upward leaders from tall grounded objects and its application

Chan

Chen

2018

Atmospheric Research

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This paper presents a macroscopic physical model that can simulate an upward leader initiated from a tall grounded object under thunderclouds. Based on a tri-layer leader channel structure and the energy conservation law, a new equation for estimating the upward leader propagation speed is proposed. Equations for modeling other physical parameters, such as the leader line charge density, leader core radius, leader corona sheath radius, leader current, leader electric field and leader conductance, are also proposed.Besides, a set of initiation and survival criteria for a steady self-initiated upward leader from a tall grounded object is suggested. Based on the suggested criteria and the proposed model, the critical corona and charge amount as well as the minimum height for successful initiation of an upward positive leader (UPL) from a tall grounded object are evaluated and discussed. The model is then used to investigate the general properties of UPLs self-initiated from tall grounded objects with and without the effect of corona space charge layer near the ground under different thunderstorm conditions. The modelling results can well explain the leader properties observed in literature. The model is further tested with two set of experiment data and very promising results are obtained.

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Section: Summary and Discussionsupporting

confidence: 50%

A macroscopic physical model for self-initiated upward leaders from tall grounded objects and its application

Chan

Chen

2018

Atmospheric Research

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“…In addition to the above, the leader channel is a partially ionized plasma [36,37] in which the refractive index is dominated by electrons and neutral particles. However, the density of the electrons in the leader channel is far lower than that of the neutral particles so the influence of the electrons can be neglected in this case [38]. Simultaneously, it is also assumed that the composition of the neutral particles does not vary during the leader discharge process.…”

Section: Principles Of M-z Interferometrymentioning

confidence: 99%

Thermal Characteristics of Positive Leaders under Different Electrode Terminals in a Long Air Gap

Tang

et al. 2019

Energies

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The thermal characteristics of the positive leader discharges occurring under the different electrode terminals in a 1 m rod-plate air gap were studied quantitatively using Mach–Zehnder interferometry and a high-speed video camera. When disturbed by the discharge channel, the interference fringes are distorted because of the change in the refractive index of air, which is related to the gas density. Therefore, the gas temperature and gas density distribution in the leader channel can be retrieved from the offset of the interference fringes. Based on these results, the thermal characteristics of the leader channel were studied under different electrode terminals with a radius of curvature of 2.5 mm and 5 mm for cone electrodes and a diameter of 40 mm for a spherical electrode. The results show that the gas temperature in the leader channel increased while the gas density decreased as the radius of curvature of the electrode terminal decreased. Additionally, a smaller radius of curvature leads to a larger thermal diameter, but the difference in the thermal diameter is not obvious; for the terminals used in this paper, the difference is within 2 mm.

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“…In this case, the streamer zone of the leader is probably similar to that of the leader of long spark, although the similarity may not be complete, if the formation of the leader and its streamer zone occurs after the streamers reach the opposite electrode, that is, during the breakthrough phase. Leader discharges in gaps of~1 m length were studied by Kurimoto et al (1978), Domens et al (1988), Reess et al (1995), Zhou et al (2015), and Ma et al (2019), but streamer zone parameters were not measured by those authors.…”

Section: Introductionmentioning

confidence: 99%

Experimental Investigation of the Streamer Zone of Long‐Spark Positive Leader Using High‐Speed Photography and Microwave Probing

et al. 2020

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The streamer zone of positive leader during the breakthrough phase of long sparks was experimentally investigated with two methods. One of the methods is the analysis of streamer‐zone images obtained with a high‐speed framing camera with image enhancement. This method allowed us to estimate the spatial distribution of streamer density and low‐frequency conductivity in the streamer zone. The other method is the microwave probing, which we applied for the first time to long sparks. The attenuation of microwave beam in the streamer zone in our experiments is proportional to the total number of free electrons inside the microwave beam. Experimental data on the microwave attenuation combined with the streamer density found using the first method allowed us to estimate the total number of free electrons in one streamer. The following parameters were obtained. The streamer density in the center of the streamer zone is (0.6–1) · 105 m−3, and the total number of streamers in the streamer zone is 4 · 105–106. The average total number of free electrons in one streamer is about 3 · 1010. Low‐frequency conductivity on the axis of streamer zone was estimated to be typically 2 · 10−5 S/m, which is similar to that estimated for corona sheath in lightning. Both methods are based on the assumption of constancy of electric field and similarity of all streamers inside the streamer zone. The overall results of this study are generally consistent with this assumption.

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Experimental study on thermal characteristics of positive leader discharges using Mach-Zehnder interferometry

Cited by 22 publications

References 23 publications

A macroscopic physical model for self-initiated upward leaders from tall grounded objects and its application

A macroscopic physical model for self-initiated upward leaders from tall grounded objects and its application

Thermal Characteristics of Positive Leaders under Different Electrode Terminals in a Long Air Gap

Experimental Investigation of the Streamer Zone of Long‐Spark Positive Leader Using High‐Speed Photography and Microwave Probing

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