|dc.contributor.author||Mallone, Kevin Charles||
|dc.description.abstract||The applicability of computational fluid dynamics (CFD) modelling schemes to
turbulent wall-bounded flows is a matter of concern. In the near-wall region of bounded
flows, the standard high Reynolds number k-e model is not valid and requires the use of
empirical wall models to mimic the behaviour of this region.
A theoretical study of the physics of prevalent wall modelling techniques showed
that the velocity distribution took no account of the pressure gradient. To determine the
effect of this shortcoming, a typical transient three-dimensional flow was analysed using
current CFD methods and the results compared with experimental flow measurements.
Consideration of these results showed that the 'traditional' wall model was unable to
replicate observed flow features in the near-wall region: further analysis of the
computational results confirmed that these poor flow predictions arose from the inability
of the model to consider local pressure gradient effects.
Consequently, a strong case was made for a more robust wall model for use in
conjunction with the standard high Reynolds number k-e model. A number of boundary
layer analyses were reviewed and Coles' law of the wake (1956) presented as a viable
candidate for the development of a new wall modelling scheme. In theory, Coles' law
(1956) provides a description of bounded flows under arbitrary pressure gradients up to
the point of near-separation and may be extended to the study of reversed flows.
A generic algorithm for Coles' law was prepared and used to study the fundamental
test cases of U-bend and backward facing step flows. In a comparison between
documented experimentation, 'conventional' CFD modelling and Coles' law models of
these flows, the Coles' law model was shown to provide a viable alternative to
'traditional' schemes. Consequently, the Coles' law model of the near-wall region, being
valid for pressure-driven flows, offers an extension to the range of flows for which the
standard high Reynolds number k-e model may be used.||en_US
|dc.publisher||University of Hertfordshire||en_US
|dc.subject||Computational fluid mechanics, Fluid mechanics||en_US
|dc.title||A more robust wall model for use with the two-equation turbulence model||en_US