Numerical simulation of tsunami-scale wave boundary layers

TLDR: In this paper, an existing 1DV boundary layer model, based on the horizontal component of the incompressible Reynolds-averaged Navier-Stokes (RANS) equations, is newly extended to incorporate a transitional variant of the standard two-equation k-ω turbulence closure.

About: This article is published in Coastal Engineering.The article was published on 2016-04-01 and is currently open access. It has received 39 citations till now. The article focuses on the topics: Boundary layer thickness & Boundary layer.

Figures

Figure 12: Maximum computed turbulent kinetic energy density observed during the synthetic tsunami wave cycles for: (a) hydraulically smooth conditions and (b) hydraulically rough conditions (k+s > 30). The solid lines in (a) and (b) respectively denote (25) and (26).

Figure 19: Maximum turbulent kinetic energy density observed during the simulated 2011 Tohoku tsunami under (a) hydraulically smooth and (b) hydraulically rough conditions. Also shown are the corresponding values for the synthetic single wave cases, for comparison.

Figure 5: Comparison of computed (lines) and measured (circles, from Jensen et al., 1989) velocity profiles in an oscillatory boundary layer with Re = 6× 106 and k+s = 84.

Figure 6: Comparison of computed (lines) and measured (circles, from Jensen et al., 1989) turbulent kinetic energy density k profiles in an oscillatory boundary layer with Re = 6 × 106 and k+s = 84. The inset in the right most panel highlights the k = 0 wall boundary condition.

Figure 9: Computed velocity profiles under hydraulically smooth (solid lines) and rough (dashed lines, with fixed d = 3 mm) conditions, beneath (a) oscillatory (sinusoidal), (b) single wave, and (c) N-wave signals. Results with Re = 7.0 × 108 (black) and Re = 2.2 × 107 (red) are depicted. See Table 2 for further details.

Figure 14: Computed wave friction factors for the various synthetic tsunami wave signals considered under (a) hydraulically smooth and (b) hydraulically rough conditions (k+s > 30). On (a) the dotted and full line respectively depict the laminar solutions for single waves and oscillatory signals, whereas the dashed line corresponds to (27). On (b) the full line depicts (28).

Frequently asked questions

Q1. What are the contributions mentioned in the paper "Numerical simulation of tsunami-scale wave boundary layers" ?

This paper presents a numerical study of the boundary layer flow and properties induced by tsunami-scale waves. The validated model is then employed for the study of transient wave boundary layers at full tsunami scales, covering a wide and realistic geophysical range in terms of the flow duration, bottom roughness, and associated Reynolds numbers. The results generally support a notion that the boundary layers induced by ∗Corresponding author Email addresses: i. a. williams @ utwente. nl ( Isaac A. Williams ), drf @ mek. The results likewise suggest that there is a continuum connecting wind-wave and tsunami-wave scales, as existing expressions commonly used for characterising boundary layer properties beneath wind waves maintain reasonable accuracy when extrapolated to full tsunami scales. 

Q2. What are the future works mentioned in the paper "Numerical simulation of tsunami-scale wave boundary layers" ?

Given the wide variety of tsunami wave forms that can be expected in practice, depending on the nature of the generating bottom motions, it is likely that all three of the synthetic wave descriptions considered in the present work can be taken as realistic idealisations, appropriate for use in further numerical or experimental studies.