Journal ArticleDOI
Drag reduction by a rotationally oscillating cylinder with a flexible filament
Reads0
Chats0
TLDR
In this article , the hydrodynamic mechanism of drag reduction by a rotationally oscillating cylinder with a flexible filament was explored using the penalty immersed boundary method, and the effects of the filament length, bending rigidity, oscillatory frequency, and oscillatory amplitude on drag reduction were systematically examined.Abstract:
The hydrodynamic mechanism of drag reduction by a rotationally oscillating cylinder with a flexible filament was explored using the penalty immersed boundary method. A simulation of a stationary cylinder without a filament was also performed for comparison. The effects of the filament length, bending rigidity, oscillatory frequency, and oscillatory amplitude on drag reduction were systematically examined. The underlying mechanism of drag reduction was characterized in terms of the shape deformation of the filament, wake pattern, pressure distribution, and flapping dynamics. Two dominant flapping modes were observed: an oscillation mode with less than half a wave on the filament, and an undulation mode with more than one wave on the filament. In the oscillation mode, drag reduction is mainly achieved by the thrust generated by the filament, accompanied by an increase of lift fluctuations. The pressure difference caused by the flapping motion between the upper and lower sides of the filament is the main cause of the thrust. In the undulation mode, drag reduction is realized by both the thrust generated by the filament and the decreased form drag of the cylinder. A filament flapping in the oscillation mode can generate greater thrust than a filament flapping in the undulation mode. A long undulatory filament with relatively low oscillatory amplitude effectively stabilizes the wake, resulting in a decrease of the lift fluctuations.read more
Citations
More filters
Journal ArticleDOI
Receptivity-orientated drag reduction of twin cylinders by steady leading-edge suction control based on adjoint method
TL;DR: In this paper , the position where the suction flow should be placed is determined by using a receptivity analysis based on the adjoint method, and the authors investigate how control affects the fluid force and flow structures.
Journal ArticleDOI
Drag reduction by flapping a flexible filament behind a stationary cylinder
TL;DR: In this paper , the authors explored the hydrodynamic mechanism of drag reduction by flapping a flexible filament behind a stationary cylinder using the penalty immersed boundary method, and the effects of the filament length, bending rigidity, pitching amplitude and frequency on drag reduction were systematically examined.
Journal ArticleDOI
Flexible Polymeric Tail for Micro Robot Drag Reduction Bioinspired by the Nature Microorganisms
TL;DR: In this paper , a dissipative particle dynamics (DPD) method is used to study the flexible tails' influences on drag reduction. And the results show that long polymer tails strongly affect pressure drag, such that the longer polymeric tails (single/multi), the more drag reduction, particularly the pressure drag.
Journal ArticleDOI
Flow Control of an Elastically Mounted Square Cylinder by using an Attached Flexible Plate
TL;DR: In this article , the influence of plate length and flexibility on VIV suppression for an elastically mounted square cylinder at Reynolds number 150 was investigated, and the authors concluded that a maximum 96% reduction in the vibration amplitude can be achieved with a long flexible plate with optimal flexibility.
Journal ArticleDOI
Control of thermal and fluid flow characteristics of an oscillating cylinder by porous media
TL;DR: In this article , the effect of variables including permeability and thickness of porous media on the thermal and hydrodynamic behavior of an oscillating cylinder at a constant temperature was studied, where the authors employed finite volume technique to model the flow field for various thicknesses of the porous layer and Darcy numbers at low Reynolds numbers.
References
More filters
Journal ArticleDOI
The immersed boundary method
TL;DR: This paper is concerned with the mathematical structure of the immersed boundary (IB) method, which is intended for the computer simulation of fluid–structure interaction, especially in biological fluid dynamics.
Journal ArticleDOI
Modeling a no-slip flow boundary with an external force field
TL;DR: In this paper, the Navier-Stokes equations permit the presence of an externally imposed body force that may vary in space and time, and the velocity is used to iteratively determine the desired value.
Journal ArticleDOI
On the Wake and Drag of Bluff Bodies
TL;DR: In this article, a modification to Kirchhoff's free streamline introduces the parameter k = √(1-C_ps), which allows arbitrary base pressure and which must depend on the dynamics of the wake.
Journal ArticleDOI
Simulation of flexible filaments in a uniform flow by the immersed boundary method
TL;DR: An improved version of the immersed boundary (IB) method is developed for simulating flexible filaments in a uniform flow and a repulsive force was included in the formulation to handle collisions between the free ends of side-by-side filaments undergoing out-of-phase flapping.
Journal ArticleDOI
A computational fluid dynamics study of tadpole swimming
TL;DR: The CFD analysis shows that the kinematics of tadpoles is specifically matched to their special shape and produces a jet-stream propulsion with high propulsive efficiency, as high as that achieved by teleost fishes.