AX

The relationship between X and the breaking mechanism is an ongoing area of active research. Laboratory experiments show that for small X (Figure 13(a)),

Figure 12 False color images showing types of internal wave breakers: (a) spilling breakers, (b) plunging and (c) collapsing breakers, (d) mixed plunging and Kelvin-Helmholtz breaking. Note the steepening of the rear face of the incident wave of depression, the transformation to a wave of elevation and subsequent breaking. Small numbered figures denote different stages of the breaking process. Adapted from Boegman L, Ivey GN, and Imberger J (2005) The degeneration of internal waves in lakes with sloping topography. Limnology and Oceanography 50: 1620-1637.

Figure 12 False color images showing types of internal wave breakers: (a) spilling breakers, (b) plunging and (c) collapsing breakers, (d) mixed plunging and Kelvin-Helmholtz breaking. Note the steepening of the rear face of the incident wave of depression, the transformation to a wave of elevation and subsequent breaking. Small numbered figures denote different stages of the breaking process. Adapted from Boegman L, Ivey GN, and Imberger J (2005) The degeneration of internal waves in lakes with sloping topography. Limnology and Oceanography 50: 1620-1637.

spilling breakers occur when small-scale shear instabilities form on the wave crests prior to breaking, causing mixing to be suppressed by viscosity. The mixing efficiency Rf = b/(b + e), where b is the energy lost irreversibly to mixing and e the energy dissipated by viscosity as heat, is less than 15%. As X increases, plunging (Figure 12(b)) then collapsing (Figure 12(c)) breakers occur. In the plunging region, wave inertia dominates and the most energetic overturns approach the Ozmidov scale (the largest scale where inertia can overcome buoyancy); the potential energy available for mixing is maximized and Rf > 15%. For collapsing breakers, the wave breaking processes is not sufficiently energetic to overcome the stratification, mixing is suppressed by buoyancy and <Rf 15%. For X ! 1 surging breakers occur, Rf ! 0 and the wave energy is reflected from the slope. Mixed-mode convective and shear-driven breaking is also possible when the wave shoals through a strong background flow field (Figure 12(d)).

Was this article helpful?

0 0
Project Earth Conservation

Project Earth Conservation

Get All The Support And Guidance You Need To Be A Success At Helping Save The Earth. This Book Is One Of The Most Valuable Resources In The World When It Comes To How To Recycle to Create a Better Future for Our Children.

Get My Free Ebook


Post a comment