wake flow


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Wake flow

The flow downstream of a body immersed in a stream or the flow behind a body propagating through a fluid. Wakes are narrow elongated regions, filled with large and small eddies. The wake eddies of a bridge pier immersed in a river stream, or of a ship propelled through the water, are often visible on the surface. On windy days, similar wakes form downstream of smoke stacks or other structures, but the eddies in the air are not visible unless some smoke or dust is entrained in them.

Turbulence in the wake of bluff bodies consists of all sizes of eddies, which interact with each other in their unruly motion. Yet, out of this chaos emerges some organization, whereby large groups of eddies form a well-ordered sequence of vortices. The sense of rotation of these vortices alternates, and their spacing is quite regular. As a result, they can drive a structure that they encounter, or they can exert on the body that created them a force alternating in sign with the same frequency as that of the formation of the vortices. Such forces can impose on structures unwanted vibrations which often lead to serious damage. Flow-induced forces can be catastrophic if they are in tune with the frequency of vibration of the structure. See Fluid flow, Turbulent flow

Wakes are sustained for very large distances downstream of a body. Ship wakes retain their turbulent character for miles behind a vessel and can be detected by special satellites hours after their generation. Similarly, condensation in the wake of aircraft sometimes makes it look like a narrow braided cloud, traversing the sky.

wake flow

[′wāk ‚flō]
(fluid mechanics)
Turbulent eddying flow that occurs downstream from bluff bodies.
References in periodicals archive ?
PILF Images of Wake Flow Field Depend on Laser Sheet Position.
In this paper, a new active control method called the leading edge rotating cylinder method is used to optimize the wake flow of a vehicle.
The efficiency of our approach was demonstrated for a two-dimensional cylinder wake flow by comparing it with the Tikhonov-based calibration method introduced in [8].
As shown in Figures 2 through 4, winds can create recirculation regions and wake flows around a building.
This causes highly complicated rear flow patterns such as vortices, eddies, downwash, upwash and mixed wake flows [1].
They also noted that the variation of Re was contributed much to the transformation of flow pattern and the characteristics of wake flow when spacing ratio is small (L/D = 2.0).
Vortex structures were also observed by Theissen [5] on a more realistic vehicle and were considered responsible for a delay in the aerodynamics of the wake flow. Figure 21 shows the difference between the steady-state situation and a transient situation.
Researchers experimentally investigated the wake flow structure around an external rear view mirror which is mounted on a production car [5].
First of all, the velocity detection part has a heat insulation sub covered by the wake flow of the temperature detection part.
It is shown in [17-21] (in contrast to [29]) that, for shallow water flows, the Landau constant in (25) has the "right sign" so that (25) can be used (and is successfully used in [17-21]) in order to describe some important features of shallow wake flows.