FIZIKALNO NUMERIČNI MODEL POZITIVNE, NAVZDOL USMERJENE ATMOSFERSKE RAZELEKTRITVE

Gaber, Matjaž

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Title:	FIZIKALNO NUMERIČNI MODEL POZITIVNE, NAVZDOL USMERJENE ATMOSFERSKE RAZELEKTRITVE
Authors:	ID Gaber, Matjaž (Author) ID Trlep, Mladen (Mentor) More about this mentor... ID Pihler, Jože (Comentor)
Files:	DR_Gaber_Matjaz_2009.pdf (14,74 MB) MD5: 0E650BEEA0FF0545B1E6DE2E4D593706 PID: 20.500.12556/dkum/03676756-7c6e-451f-8397-03e8039eb94e
Language:	Slovenian
Work type:	Dissertation
Organization:	FERI - Faculty of Electrical Engineering and Computer Science
Abstract:	Približno 10 % vseh udarov strele je pozitivnih udarov. Čeprav ta vrsta atmosferskega udara ni najbolj pogosta, povzroči največ škode. Zaradi tega je dobro razumevanje omenjenega pojava nujno za zmanjševanje škode, ki zaradi teh udarov nastane. Vendar pa samo opazovanje teh pojavov ni dovolj, potrebno je še več. Relativno dobre podatke imamo o laboratorijskih razelektritvah, ki izvirajo iz različnih raziskovanj. Tako obstajajo podatki o razelektritvah pri nizkem tlaku, o dolgih in kratkih razelektritvah v laboratoriju, podatki o razelektritvah med elektrodami iz različnih materialov itd. Vendar pa o razelektritvah v zraku ni veliko podatkov; obstaja jih le nekaj. V zadnjem času so se pojavili numerični modeli cepljenja pozitivnega vodilnega kanala. Ti modeli se uporabljajo za simulacijo razelektritev v laboratorijskih prototipih iskril. Omenjeni modeli pa ne omogočajo simulacije prečkanja celotne poti med glavnima elektrodama. Težava je v uporabljeni metodi končnih elementov (MKE), za katero se je izkazalo, da ni najbolj primerna. Zaradi tega je v tej disertaciji uporabljena metoda simulacije elektrine (MSE). Sprememba metode za izračun električnega polja omogoča prečkanje celotne razdalje med obema elektrodama. Zaradi menjave metode je bilo potrebno vpeljati še nekaj drugih modifikacij, ki omogočajo numerično stabilnost simulacije. Isti numerični model je bil kasneje uporabljen kot temelj numeričnega modela pozitivne, navzdol usmerjene atmosferske razelektritve, ki je predstavljal glavni cilj disertacije. V atmosferskem modelu je poleg drugih odvisnosti zajeta tudi odvisnost efektivne ionizacije od zračnega tlaka. V disertaciji so predstavljeni rezultati testiranja laboratorijskega in atmosferskega modela, predstavljeni in razloženi pa so tudi predlogi za v prihodnosti potrebne spremembe na modelu.
Keywords:	numerični model, fizikalni model, pozitivna navzdol usmerjena strela, atmosferska razelektritev
Place of publishing:	Maribor
Publisher:	[M. Gaber]
Year of publishing:	2009
PID:	20.500.12556/DKUM-11795
UDC:	621.316.98(043.2)
COBISS.SI-ID:	247640832
NUK URN:	URN:SI:UM:DK:K8TPXRJF
Publication date in DKUM:	21.09.2009
Views:	3408
Downloads:	254
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Categories:	KTFMB - FERI
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Secondary language

Language:	English
Title:	Physically numerical model of downward positive lightning
Abstract:	Only about 10% of all lightning incidents are due to downward positive lightning. Although this kind of atmospheric discharge is not the most frequent one it causes the most damage. Because of that, a good understanding of this phenomenon is critical for minimizing the damage it causes. Observation of lightning strikes alone is not enough; much more is needed in order to understand their behavior. On the other hand, we have relatively good data on discharges in laboratory setting. This information comes from observations of different types of discharge; there is data on low pressure discharges, about short and long spark discharges, discharges between electrodes of different materials, and so on. Unfortunately, there is not much data in discharges in the air, but nevertheless some data is available. Lately some numerical models have been developed that use this data to simulate positive streamers branching in the air. These models are used to simulate conditions in laboratory prototypes of spark gaps. These models are not able to simulate streamers to bridge the gap between the main electrodes. The problem lies in the finite elements method (FEM) computation for which there are clear indications that is not suited to the purpose. So charge simulation method (CSM) is used instead in this dissertation. Such modification of the numerical model of the positive streamer branching in the air enables streamers to bridge the path between electrodes. With regard to that, some other modifications to ensure numerical stability were introduced to the model. Lately, the same model was used as a foundation for a numerical model of a downward positive lightning, which was the main goal of this dissertation. Among other dependencies in the atmospheric model, altitude dependency of an effective ionization is taken into account. Test results of both, laboratory and atmospheric model, are presented and suggestions for future modifications are described.
Keywords:	numerical model, physical model, downward positive lightning, atmospheric discharge

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