Numerical modeling of turbulent oscillatory boundary layers using two-equation turbulence models
The coastal bottom boundary layers undergo transition
from laminar to turbulent or vice versa in response to the changing field
conditions. Due to the importance of the transitional characteristics of bottom
boundary layer in relation to the sediment movement, a lot of research has been
done in the past. Although many experimental and analytical studies have been
carried out, the idea of using turbulence models to tackle this phenomenon is
relatively new. With the availability of excellent computing facilities at
affordable costs, this option is gaining more popularity among the hydraulic
and coastal engineers. The benefit of using a good turbulence model is that it produces detailed boundary layer
properties to facilitate precise estimation of sediment movement under a
variety of hydraulic conditions. For a turbulence model to be good, an essential requirement is its computational economy with reasonable
accuracy. With a large number of available turbulence models, it is very
difficult for practicing engineers to choose the most suitable one.
This study deals with the application of a low
Reynolds number k-e
model to a transitional oscillatory boundary layer. The term low Reynolds number implies that this
model is applicable over the whole cross-stream dimension including the low
Reynolds number region (viscous sublayer). A total of approximately 15 versions
of k-e models have been tested
against the available data for oscillatory boundary layers on smooth bottom.
Three versions of k-w model have also been tested. Recently the work has been
started to test some of the two-equation models against the data on rough bed.
Moreover, the research is being carried out to propose a new version of two or
one equation turbulence model capable of tackling the whole range of boundary
layer problems.