In the present work the zonal flow (ZF) growth rate in toroidal ion-temperature-gradient (ITG) mode turbulence including the effects of elongation is studied analytically. The scaling of the ZF growth with plasma parameters is examined for typical tokamak parameter values. The physical model used for the toroidal ITG driven mode is based on the ion continuity and ion temperature equations whereas the ZF evolution is described by the vorticity equation. The results indicate that a large ZF growth is found close to marginal stability and for peaked density profiles and these effects may be enhanced by elongation.Comment: 20 pages, 5 figure

A general statistical theory of the intermittency in turbulence based on short-lived coherent structures (instantons) is presented. The probability density functions (PDFs) of the flux R are shown to have an exponential scaling P(R)∝exp(−cRs) in the tails, with the exponent s=(n+1)∕m. Here, n and m are the order of the highest nonlinear interaction term and moments for which the PDFs are computed, respectively; c is constant depending on spatial profile of the coherent structure. The results can have important implications for understanding the universality often observed in simulations and experiments.

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The probability distribution function (PDF) tails of the zonal flow structure formation and the PDF tails of momentum flux by incorporating effect of a shear flow in ion-temperature-gradient (ITG) turbulence are computed in the present paper. The bipolar vortex soliton (modon) is assumed to be the coherent structure responsible for bursty and intermittent events driving the PDF tails. It is found that stronger zonal flows are generated in ITG turbulence than Hasegawa-Mima (HM) turbulence as well as further from marginal stability. This suggests that although ITG turbulence has a higher level of heat flux, it also more likely generates stronger zonal flows, leading to a selfregulating system. It is also shown that shear flows can significantly

A model is presented for predicting the cell-to-cell propagation of a thermal runaway/fire in a lithium-ion battery cell to neighboring cells by simulating the temperature development in neighboring cells. The modelling work comprises of two major steps; setting up a model of the cells including the thermal properties of the cells, and then validating the model through experiments where the boundary conditions in the validation test must be determined carefully. The model is developed to allow a fast evaluation of several different preventive means of thermal insulation, it is not modelling the pack and cells to a great detail. Still the experimental validation indicates that the model is good enough to fulfil its purpose of the model. A feasibility study using the model is conducted assessing two different types of fire walls between battery modules of 10 cells. The results show that there is a substantial risk for a cascading of thermal events in a battery pack, although cooling systems and fire walls may mitigate these risks.