Transitions in the vortex wake behind the plunging profile

Abstract

In this study we investigate numerically the vortex wake formation behind the profile performing simple harmonic motion known in the literature as plunging. This research was inspired by the flapping motion which is appropriate for birds, insects and fishes. We assume the two dimensional model of flow. Depending on the parameters such as plunging amplitude, frequency and the Reynolds number, we demonstrate many different types of vortex street behind the profile. It is well known that the type of vortex wake determines the hydrodynamic forces acting on the profile. Dependences of the plunging amplitude, the Strouhal number and various topology vortices are established by constructing the phase transition diagram. The areas in the diagram related to the drag, thrust, and lift force generation are captured. We notice also the areas where the vorticity field is disordered. The disordered vorticity field does not allow maintenance of the periodic forces on the profile. An increase in the Reynolds number leads to the transition of the vortex wake behind the profile. The transition is caused by the phenomenon of boundary layer eruption. Further increase of the Reynolds number causes the vortex street related to the generation of the lift force to vanish.

Deflected wake interaction of tandem flapping foils

“…The resultant wakes (see figure 3) maintain the basic features and deflection mechanism of asymmetric jets reported in the literature for pure pitch (Godoy-Diana et al 2008He et al 2012) and pure heave (Cleaver et al 2012;Kozłowski & Kudela 2014). Vortex circulation Γ is proportional to the flapping frequency while the opposite is true for the distance between consecutive vortices.…”

“…2012) and pure heave (Cleaver et al. 2012; Kozłowski & Kudela 2014). Vortex circulation is proportional to the flapping frequency while the opposite is true for the distance between consecutive vortices.…”

Three-dimensional numerical study of acoustic streaming phenomenon in rectangular resonator

“…In memory of my colleague Dr Tomasz Kozłowski, with whom I discussed many issues in the field of fluid mechanics and more (Kozłowski and Kudela 2014).…”

Collapse of n Point Vortices, Formation of the Vortex Sheets and Transport of Passive Markers

“…Good introductory reference material to the subject can be found in [2][3][4][5][6][7][8]. The concept of replacing the continuous field of vorticity by the distribution of δ-Dirac functions, called point vortices, constitutes the foundation of the vortex methods and provides a very useful numerical methodology to study the inviscid or viscous flow problems [9][10][11]. The set of point vortices that was obtained by replacing the continuous vorticity led to the generation of a velocity field that approximates the solution of the Euler equation [12] (refer to Appendix A).…”

“…The set of point vortices that was obtained by replacing the continuous vorticity led to the generation of a velocity field that approximates the solution of the Euler equation [12] (refer to Appendix A). Essential ingredients of modern modeling of any fluid flow are studies of evolution of vorticity using the point vortices [6,10,13,14]. Sometimes mathematical analysis of a collection of a few point vortices' dynamics can shed light on interesting features of fluid motion, which is the reason why scientists remain highly interested in the point vortex system's dynamics.…”