TY - JOUR
T1 - A numerical study of swash flows generated by bores
AU - Zhang, Qinghai
AU - Liu, Philip L.F.
N1 - Funding Information:
This research has been supported by grants from the National Science Foundation (Fluid Dynamics Program, Physical Oceanography Program and ITR program) and from the Office of Naval Research (Geoscience Program) to Cornell University. We would also like to thank Dr. Harry Yeh for providing the pictures shown in the paper.
PY - 2008/12
Y1 - 2008/12
N2 - The dynamic processes of bore propagation over a uniform slope are studied numerically using a 2-D Reynolds Averaged Navier-Stokes (RANS) solver, coupled to a non-linear k - ε{lunate} turbulence closure and a volume of fluid (VOF) method. The dam-break mechanism is used to generate bores in a constant depth region. Present numerical results for the ensemble-averaged flow field are compared with existing experimental data as well as theoretical and numerical results based on non-linear shallow water (NSW) equations. Reasonable agreement between the present numerical solutions and experimental data is observed. Using the numerical results, small-scale bore behaviors and flow features, such as the bore collapse process near the still-water shoreline, the 'mini-collapse' during the runup phase and the 'back-wash bore' in the down-rush phase, are described. In the case of a strong bore, the evolution of the averaged turbulence kinetic energy (TKE) over the swash zone consists of two phases: in the region near the still-water shoreline, the production and the dissipation of TKE are roughly in balance; in the region farther landwards of the still-water shoreline, the TKE decay rate is very close to that of homogeneous grid turbulence. On the other hand, in the case of a weak bore, the bore collapse generated turbulence is confined near the bottom boundary layer and the TKE decays at a much slower rate.
AB - The dynamic processes of bore propagation over a uniform slope are studied numerically using a 2-D Reynolds Averaged Navier-Stokes (RANS) solver, coupled to a non-linear k - ε{lunate} turbulence closure and a volume of fluid (VOF) method. The dam-break mechanism is used to generate bores in a constant depth region. Present numerical results for the ensemble-averaged flow field are compared with existing experimental data as well as theoretical and numerical results based on non-linear shallow water (NSW) equations. Reasonable agreement between the present numerical solutions and experimental data is observed. Using the numerical results, small-scale bore behaviors and flow features, such as the bore collapse process near the still-water shoreline, the 'mini-collapse' during the runup phase and the 'back-wash bore' in the down-rush phase, are described. In the case of a strong bore, the evolution of the averaged turbulence kinetic energy (TKE) over the swash zone consists of two phases: in the region near the still-water shoreline, the production and the dissipation of TKE are roughly in balance; in the region farther landwards of the still-water shoreline, the TKE decay rate is very close to that of homogeneous grid turbulence. On the other hand, in the case of a weak bore, the bore collapse generated turbulence is confined near the bottom boundary layer and the TKE decays at a much slower rate.
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U2 - 10.1016/j.coastaleng.2008.04.010
DO - 10.1016/j.coastaleng.2008.04.010
M3 - Article
AN - SCOPUS:56349123036
SN - 0378-3839
VL - 55
SP - 1113
EP - 1134
JO - Coastal Engineering
JF - Coastal Engineering
IS - 12
ER -