說明 
214 p 
附註 
Source: Dissertation Abstracts International, Volume: 6707, Section: B, page: 4055 

Thesis (Ph.D.)University of Ottawa (Canada), 2006 

The unsteady Reynoldsaveraged NavierStokes equations, supplemented by a Reynolds stress model, were solved with relatively high spatial and temporal resolutions to determine the timeaveraged mean velocity and turbulent stresses in isothermal, single phase flows in a rectangular duct containing a single rod and in a 37rod rod bundle. In addition, the timeaveraged mean temperature, temperature fluctuation variance and turbulent heat fluxes were computed in the singlerod duct flow in which the rod was heated passively. The computed values were, in general, in fair agreement with available experimental results. The simulations also resolved the formation of coherent structures in the form of counterrotating vortices with axes alternating on either side of rodrod and rodwall gaps. The contributions of these coherent structures on the turbulent and thermal fields and on crossgap mixing were documented and found to be substantial. The action of coherent structures moderates the mean temperature rise in the gap region but creates substantial local variation of the instantaneous temperature fluctuations at relatively low frequencies. Reduction of the gap size below a critical value resulted in a decrease of the frequency of coherent fluctuations and the crosschannel mixing efficiency, contrary to predictions based on the extrapolation of available empirical correlations. In the case of the 37rod bundle, the coherent velocity fluctuations were found to be strongly correlated in the entire computational domain 

School code: 0918 

DDC 
Host Item 
Dissertation Abstracts International 6707B

主題 
Engineering, Mechanical


0548

Alt Author 
University of Ottawa (Canada)

