Disputas: Emma My Maria Wingstedt

Siv.Ing. Emma My Maria Wingstedt ved Matematisk institutt vil forsvare sin avhandling for graden ph.d.:

Numerical modelling of dense-gas dispersion in turbulent shear flows

 

Emma My Maria Wingstedt

Tid og sted for prøveforelesning

23. juni 2017 kl. 10.15, Aud. 4, Vilhelm Bjerknes' hus.

Bedømmelseskomité

  • Associate Professor Gianluca Iaccarino, Stanford University
  • Associate Professor Zhengtong Xie, University of Southampton
  • Professor Terje Koren Berntsen, Universitetet i Oslo

Leder av disputas

Professor Hans Brodersen, Matematisk institutt, Universitet i Oslo

Veiledere

Sammendrag

All modern societies use, store, and transport a range of industrial chemicals in large quantities. Many of these chemicals are toxic and may cause harm to humans as well as the environment if they were to be released into the atmosphere. It is therefore important to be able to predict where the toxic gas would be transported and how dangerous, i.e. how concentrated, it would be in order to plan for evacuation as well as decontamination.

In the thesis, a new methodology that enables simulation of dense-gas dispersion in turbulent boundary layers has been developed. Results show that the emission of a dense gas significantly alter the flow field and that the gas even can be transported in the opposite direction of the wind. It is also found that dense-gas dispersion is highly affected by geometrical obstacle, for example houses, which effectively deflect the gas plume.

The density difference between the air and the released gas generates areas with stable stratification, similar to inversion that can be seen on cold winter days, and even Kelvin-Helmholtz instabilities.  

The effect of stable stratification on turbulent shear flow has also been investigated and it has been found that anisotropy on both large and small scales increases. The most commonly used viscous dissipation rate models assume isotropy, which is not appropriate for anisotropic flows. Therefore, a new model for the viscous dissipation rate in stably stratified, shear turbulence has been developed and validated.

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Publisert 9. juni 2017 08:57 - Sist endret 16. juni 2017 17:02