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Title: Numerical simulations of shock cloud interactions
Author: Aluzas, Robertas
ISNI:       0000 0004 5362 866X
Awarding Body: University of Leeds
Current Institution: University of Leeds
Date of Award: 2014
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This Thesis presents numerical simulations of shocks interacting with regions containing multiple individual clouds. Firstly, the hydrodynamic interaction is presented. It is the first study to include 100s of clouds in a clumpy region which `mass-load' the flow. The 'mass-loading' reduces the Mach number of the shock and leads to the formation of a dense shell. In cases in which the `mass-loading' is sufficient the flow slows enough that the shock degenerates into a wave. The shock does not decelerate below a minimum velocity determined by properties of the region. Despite the turbulence generated behind the shock, the initial mass loss from the clouds is weaker. Nevertheless, the shell is found to regulate the cloud lifetimes such that all clouds are destroyed in similar time. The one exception occurs when a few high density clouds are distributed among lower density ones. Secondly, 2D adiabatic magnetohydrodynamic simulations of a shock interacting with groups of two or three cylindrical clouds are presented. We find (i) some clouds are stretched along their field lines, whereas others are confined by their field lines; (ii) upstream clouds may accelerate past downstream clouds; (iii) clouds may also change their relative positions transverse to the direction of shock propagation as they `slingshot' past each other; (iv) downstream clouds may be offered some protection from the oncoming flow as a result of being in the lee of an upstream cloud; (v) the cycle of cloud compression and re-expansion is generally weaker when there are nearby neighbouring clouds. This small-scale study helps to interpret the behaviour of systems with 100s of clouds. Infinitely wide regions can be interpreted via interactions between individual clouds, but in regions of finite width shocks driven from the sides of the region have different field-flow orientations - individual clouds can experience evolving field morphology.
Supervisor: Pittard, Julian M. Sponsor: STFC
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available