TY - JOUR

T1 - Hydrodynamics and Associated Scour around a Free-Standing Structure Due to Turbulent Bores

AU - April-LeQuéré, Philippe

AU - Nistor, Ioan

AU - Mohammadian, Abdolmajid

AU - Schimmels, Stefan

AU - Schendel, Alexander

AU - Goseberg, Nils

AU - Welzel, Kim Mario

AU - Krautwald, Clemens

AU - Stolle, Jacob

N1 - Funding information: The authors would like to acknowledge the contributions of: (1) Flow Science for generously helping the authors by providing a full access license to the program FLOW-3D through their research program; (2) the Coastal Research Center, jointly operated by the Leibniz University Hannover and Technische Universität Braunschweig and its team of staff for the experimental work done in their Large Wave Flume; (3) the support of the Natural Science and Engineering Research Council (NSERC) is acknowledged through the Discovery Grants held by Ioan Nistor and Abdolmajid Mohammadian; and (4) the support of Volkswagen Foundation (Grant Number 93826, “Beyond Rigidity”) held by Nils Goseberg.

PY - 2022/9

Y1 - 2022/9

N2 - Forensic engineering field surveys conducted in the aftermath of large-scale tsunamis documented the presence of deep local scour holes around structures caused by extreme inundation occurring during such events. The mechanisms leading to scour in extreme flows are still not well understood, as several physical phenomena influencing the spatiotemporal extent of scour have not been adequately investigated. The authors have conducted an experimental test program that has employed a large square column in the Large Wave Flume ofthe Coastal Research Center, Germany, while they also used a state-of-the-art numerical model (FLOW-3D) to numerically reproduce the experimental results. An investigation of the turbulent flow structures observed around the impacted structure showed that these flow structures are largely responsible for the sediment transport during the runup phase, but the turbulent energy was far less intense during the draw-down phase. The weakness of the turbulent structures observed during drawdown indicates that a different physical phenomenon than the one corresponding to the inflow phase is responsible for the sediment transport experienced during inundation drawdown. Due to the rapid low-ering of the flow depth during the drawdown phase of tsunami inundations, a loss of excess pressure occurs because of the upward pressure gradient forming within the soil. However, the pore pressure measurements taken inside the soil in the physical experiment indicate no sign of upward pressure gradient on the inshore side of the column, which is an observation that is incongruent with previous similar studies and previous theoretical concepts. This difference was explained by a layer of soil that remained with a low water content throughout the testbecause the column was installed on dry sand with low permeability, a condition never tested before for pore pressure change caused by tsunami-like waves

AB - Forensic engineering field surveys conducted in the aftermath of large-scale tsunamis documented the presence of deep local scour holes around structures caused by extreme inundation occurring during such events. The mechanisms leading to scour in extreme flows are still not well understood, as several physical phenomena influencing the spatiotemporal extent of scour have not been adequately investigated. The authors have conducted an experimental test program that has employed a large square column in the Large Wave Flume ofthe Coastal Research Center, Germany, while they also used a state-of-the-art numerical model (FLOW-3D) to numerically reproduce the experimental results. An investigation of the turbulent flow structures observed around the impacted structure showed that these flow structures are largely responsible for the sediment transport during the runup phase, but the turbulent energy was far less intense during the draw-down phase. The weakness of the turbulent structures observed during drawdown indicates that a different physical phenomenon than the one corresponding to the inflow phase is responsible for the sediment transport experienced during inundation drawdown. Due to the rapid low-ering of the flow depth during the drawdown phase of tsunami inundations, a loss of excess pressure occurs because of the upward pressure gradient forming within the soil. However, the pore pressure measurements taken inside the soil in the physical experiment indicate no sign of upward pressure gradient on the inshore side of the column, which is an observation that is incongruent with previous similar studies and previous theoretical concepts. This difference was explained by a layer of soil that remained with a low water content throughout the testbecause the column was installed on dry sand with low permeability, a condition never tested before for pore pressure change caused by tsunami-like waves

KW - Tsunami

KW - Laboratory

KW - Wave flume

KW - Scour

UR - http://www.scopus.com/inward/record.url?scp=85133371991&partnerID=8YFLogxK

U2 - 10.1061/(ASCE)WW.1943-5460.0000717

DO - 10.1061/(ASCE)WW.1943-5460.0000717

M3 - Article

VL - 148

JO - Journal of Waterway, Port, Coastal and Ocean Engineering

JF - Journal of Waterway, Port, Coastal and Ocean Engineering

SN - 0733-950X

IS - 5

M1 - 04022013

ER -