TY - JOUR
T1 - A RANS numerical study of experimental swash flows and its bed shear stress estimation
AU - Hu, By Peng
AU - Xie, Jiafeng
AU - Li, Wei
AU - He, Zhiguo
AU - Marsooli, Reza
AU - Wu, Weiming
N1 - Publisher Copyright:
© 2020 Elsevier Ltd
PY - 2020/7
Y1 - 2020/7
N2 - Quantification of the bed shear stress in the swash zone is subject to much uncertainty due to the very shallow water, complex flow structure and the strong unsteadiness in this zone. This study presents a RANS modeling of experimental dam-break flow generated swash processes, giving numerical reproduction of vertical flow structure of swash flows and thus an opportunity to study the magnitude and features of the bed shear stress. Firstly, numerical solutions (i.e., temporal or spatial variation of the depth-averaged velocity and water surface elevation, the time variations of the swash front, the vorticity structure and the boundary layer thickness) are compared with existing laboratory data and the previous knowledges on swash hydrodynamics. Secondly, using the computed vertical flow structure as input data, performances of four methods (the Reynolds stress method, and the three variants of the log-law method: the depth-averaged variant, the one-position variant, the two-position variant) for estimating the bed shear stress are evaluated. It is shown that the Reynolds stress method produces non-zero bed shear stress during the reversal time, during which the swash flows may be partly stagnant. Among the three variants of the log-law method, the depth-averaged method appears to agree with the measured data much better than the other two variants: those by the two-point log-law method is very sensitive to the selected near-bed positions, and those by the empirical value variant may underestimate (overestimate) the bed shear stress in the early uprush stage (in the initial stage of the backwash).
AB - Quantification of the bed shear stress in the swash zone is subject to much uncertainty due to the very shallow water, complex flow structure and the strong unsteadiness in this zone. This study presents a RANS modeling of experimental dam-break flow generated swash processes, giving numerical reproduction of vertical flow structure of swash flows and thus an opportunity to study the magnitude and features of the bed shear stress. Firstly, numerical solutions (i.e., temporal or spatial variation of the depth-averaged velocity and water surface elevation, the time variations of the swash front, the vorticity structure and the boundary layer thickness) are compared with existing laboratory data and the previous knowledges on swash hydrodynamics. Secondly, using the computed vertical flow structure as input data, performances of four methods (the Reynolds stress method, and the three variants of the log-law method: the depth-averaged variant, the one-position variant, the two-position variant) for estimating the bed shear stress are evaluated. It is shown that the Reynolds stress method produces non-zero bed shear stress during the reversal time, during which the swash flows may be partly stagnant. Among the three variants of the log-law method, the depth-averaged method appears to agree with the measured data much better than the other two variants: those by the two-point log-law method is very sensitive to the selected near-bed positions, and those by the empirical value variant may underestimate (overestimate) the bed shear stress in the early uprush stage (in the initial stage of the backwash).
KW - Bed shear stress
KW - RANS modeling
KW - Swash flow
UR - http://www.scopus.com/inward/record.url?scp=85084649740&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85084649740&partnerID=8YFLogxK
U2 - 10.1016/j.apor.2020.102145
DO - 10.1016/j.apor.2020.102145
M3 - Article
AN - SCOPUS:85084649740
SN - 0141-1187
VL - 100
JO - Applied Ocean Research
JF - Applied Ocean Research
M1 - 102145
ER -