Vortex Interactions Subjected to Deformation Flows: A Review

Deformation flows are the flows incorporating shear, strain and rotational components. These flows are ubiquitous in the geophysical flows, such as the ocean and atmosphere. They appear near almost any salience, such as isolated coherent structures (vortices and jets) and various fixed obstacles (submerged obstacles and continental boundaries). Fluid structures subject to such deformation flows may exhibit drastic changes in motion. In this review paper, we focus on the motion of a small number of coherent vortices embedded in deformation flows. Problems involving isolated one and two vortices are addressed. When considering a single-vortex problem, the main focus is on the evolution of the vortex boundary and its influence on the passive scalar motion. Two vortex problems are addressed with the use of point vortex models, and the resulting stirring patterns of neighbouring scalars are studied by a combination of numerical and analytical methods from the dynamical system theory. Many dynamical effects are reviewed with emphasis on the emergence of chaotic motion of the vortex phase trajectories and the scalars in their immediate vicinity.

Vortex Interactions Subjected to Deformation Flows: A Review

Deformation flows are flows incorporating shear, strain and rotational components. These flows are ubiquitous in the geophysical flows, such as the ocean and atmosphere. They appear near almost any salience, such as isolated coherent structures (vortices and jets), various fixed obstacles (submerged obstacles, continental boundaries). Fluid structures subject to such deformation flows may exhibit drastic changes in motion. In this review paper, we focus on the motion of a small number of coherent vortices embedded in deformation flows. Problems involving isolated one and two vortices are addressed. When considering a single-vortex problem, the main focus is on the evolution of the vortex boundary and its influence on the passive scalar motion. Two vortex problems are addressed with the use of point vortex models, and the resulting stirring patterns of neighbouring scalars are studied by a combination of numerical and analytical methods from the dynamical system theory. Many dynamical effects are reviewed with emphasis on the emergence of chaotic motion of the vortex phase trajectories and the scalars in their immediate vicinity.

Obstacle marks as palaeohydraulic indicators of Pleistocene megafloods

Pleistocene megafloods generated several large-scale obstacle marks that could not be interpreted hydraulically with the present knowledge of submerged obstacles. Thus, flume and field data of classical obstacle marks, characterised by a frontal scour hole and an adjacent depositional ridge, are analysed to estimate flow velocities from obstacle mark geometry, especially scour depths, length, width and ridge width. These data reveal a consistency of correlations between obstacle mark morphometries across a wide spatial scale. Two existing analytical models, basically integrating obstacle size, flow velocity as well as sediment size and grading, are transformed so that the magnitude of individual geometric parameters can be used as variables for the estimation of mean and tip flow velocities. These reconstructed velocities have to be regarded as minimum velocities during the rising limb of the hydrograph, as peak discharge might not last long enough to significantly influence the obstacle mark dimensions. A universally applicable practical outline is developed for palaeohydraulic reconstruction. This framework is applied on three examples of obstacle marks generated by Pleistocene megafloods. The reliability and scale-invariance of these reconstructions is confirmed by similar results of velocity estimations by other independent approaches at the same locations.