Modelling the calmed region behind a spot

Brown, S. N.; Smith, F. T.

doi:10.1098/rsta.2005.1550

Cited by 2 publications

(2 citation statements)

References 9 publications

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“…The trailing or calmed region of the spot is characterized by a velocity profile much fuller than the laminar profile, indicating the presence of higher momentum fluid near the wall (Antonia et al 1981;Wygnanski, Zilberman & Haritonidis 1982;Gostelow et al 1997;Chong & Zhong 2006). This key characteristic has been captured by a theoretical model proposed by Brown & Smith (2005). Additionally, the visualizations of Cantwell et al (1978) reveal streamwise streak patterns within the calmed region that are more regular and have a higher aspect ratio than those found within the turbulent body of the spot.…”

Section: Introductionmentioning

confidence: 91%

Turbulent spot flow topology and mechanisms for surface heat transfer

Sabatino

Smith

2008

J. Fluid Mech.

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The properties of artificially initiated turbulent spots over a heated plate were investigated in a water channel. The instantaneous velocity field and surface Stanton number were simultaneously established using a technique that combines particle image velocimetry and thermochromic liquid crystal thermography. Several characteristics of a spot are found to be similar to those of a turbulent boundary layer. The spacing of the surface heat transfer streak patterns within the middle or ‘body’ of a turbulent spot are comparable to the low-speed streak spacing within a turbulent boundary layer. Additionally, the surface shear stress in the same region of a spot is also found to be comparable to a turbulent boundary layer. However, despite these similarities, the heat transfer within the spot body is found to be markedly less than the heat transfer for a turbulent boundary layer. In fact, the highest surface heat transfer occurs at the trailing or calmed region of a turbulent spot, regardless of maturity. Using a modified set of similarity coordinates, instantaneous two-dimensional streamlines suggest that turbulent spots entrain and subsequently recirculate warm surface fluid, thereby reducing the effective heat transfer within the majority of the spot. It is proposed that energetic vortices next to the wall, near the trailing edge of the spot body, are able to generate the highest surface heat transfer because they have the nearest access to cooler free-stream fluid.

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Section: Introductionmentioning

confidence: 91%

Turbulent spot flow topology and mechanisms for surface heat transfer

Sabatino

Smith

2008

J. Fluid Mech.

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“…Antonia et al (10) , Gostelow et al (11) , and Chong et al (12) ). In addition, this characteristic was captured by a theoretical model that was proposed by Brown et al (13) . In related studies, Schröder et al (14) investigated the trailing edge of a turbulent spot by using multi-plane stereo particle image velocimetry.…”

Section: Introductionmentioning

confidence: 99%

Streamwise Interfaces of an Isolated Turbulent Region in a Laminar Boundary Layer

Terashima

Izawa

Inasawa

et al. 2012

JFST

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The streamwise interfaces of an isolated turbulent region in a flat plate boundary layer are investigated by performing a wind tunnel experiment. A bimorph-type piezoceramic actuator is used to generate a trapezoidal turbulent region whose spanwise width is larger than those of a typical turbulent spot. The experimental results show that the traveling speeds of the leading and trailing ends of the turbulent region are almost same as those of the turbulent spots with an arrow-head shape. This result indicate that the spanwise width have little influence to the streamwise growth of an isolated turbulent region. It is also found that the traveling speed of the trailing end of the turbulent region exceeds that of local flow velocity in the near-wall region, which is η < 1.3, and vice versa. This result shows that a relaminarization is in progress in the near-wall region, where the turbulent fluid is moving across the trailing end turning laminar. The critical wall-normal distance of η = 1.3 corresponds to about 10 in the wall unit (y + ), suggesting that the relaminarization process is taking place in the viscous sublayer.

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Modelling the calmed region behind a spot

Cited by 2 publications

References 9 publications

Turbulent spot flow topology and mechanisms for surface heat transfer

Turbulent spot flow topology and mechanisms for surface heat transfer

Streamwise Interfaces of an Isolated Turbulent Region in a Laminar Boundary Layer

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