Influence of Boundary-Layer Thickness on Base Pressure and Vortex Shedding Frequency

Rowe, Anthony; Fry, A. L. A.; Motallebi, F.

doi:10.2514/2.1377

Cited by 31 publications

(14 citation statements)

References 5 publications

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“…The boundary layer thickness does further decrease with increasing suction, see Eqs. (3) and (4). Hence, the shape factor seems to play a significant role in the fact that the Strouhal number is constant.…”

Section: A Energy Spectramentioning

confidence: 98%

“…A first comprehensive study on the influence of the boundary layer thickness on the base pressure and the vortex shedding frequency was carried out by Rowe, Fry, and Motallebi. 4 The increase in the effective distance between the shear layers for an increasing boundary layer thickness can explain the decreasing vortex shedding frequency. Furthermore, the effect on the base pressure is partially attributed to a change in the boundary layer shape factor as well.…”

Section: Introductionmentioning

confidence: 99%

“…6 A laminar boundary is found to have a higher vortex shedding frequency and, due to a lower rate of entrainment of fluid crossing the wake, a lower base drag compared to its turbulent counterpart. 4 The influence of the boundary layer state further complicates the study on the relation between the wake inlet conditions and the wake characteristics. 5 In previous studies, the boundary layer has been modified by adding some kind of surface roughness to the forebody.…”

Section: Introductionmentioning

confidence: 99%

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Boundary layer modification by means of wall suction and the effect on the wake behind a rectangular forebody

Trip

Fransson

2014

Physics of Fluids

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The wake characteristics of a two-dimensional rectangular forebody with a smooth leading edge and a blunt trailing edge are investigated. Wall suction is applied along the forebody in order to modify the developing boundary layer. An initially laminar boundary layer subject to suction yields an asymptotic suction boundary layer at the trailing edge of the body, whereas a high enough suction coefficient relaminarizes an initially turbulent boundary layer. The critical suction velocity required to achieve this significant modification of the boundary layer properties is typically in the order of 1% of the free-stream velocity, where the critical suction coefficient depends on the Reynolds number. We show that a thinner boundary layer induces a higher vortex shedding frequency and a lower base pressure. Furthermore, the boundary layer state, laminar or turbulent, has a significant influence on the wake. For example, the Strouhal number based on the effective body thickness is being reduced by 25% from laminar to turbulent inlet conditions. C 2014 AIP Publishing LLC. [http://dx.

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Section: A Energy Spectramentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Boundary layer modification by means of wall suction and the effect on the wake behind a rectangular forebody

Trip

Fransson

2014

Physics of Fluids

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“…At this point of this research project, we are focused upon the low Reynolds number range, for which the boundary layers and, most of the time also the shear layers, are laminar. One can find in the literature some studies related to the influence of the turbulent boundary layers upon the characteristics of the wake - Sieverding and Heinemann (1990); Rowe et al (2001) -, but in general the Reynolds numbers are much larger (the works are mostly experimental) and the emphasis lies on the analysis of "macro" parameters, for example, the influence of the boundary layer shape factor upon the shedding frequency, and studies alike. In Fig.…”

Section: The Influence Of the Boundary Layersmentioning

confidence: 99%

Direct Numerical Simulation of the Onset of Vortex Shedding for Blunt Elongated Bodies

Ortega

Girardi

Silvestrini

2014

J.Aerosp. Technol. Manag.

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This research project focuses upon the wake behind a two-dimensional blunt-trailing-edged body. Data are obtained numerically by means of a Direct Numerical Simulation code. The body has an elliptical nose followed by a straight section that ends in a blunt base. The present paper is dedicated to the analysis of the onset of the shedding process. The effort is certainly worthwhile, because, in contrast to the case of the circular cylinder, the boundary layers's separation points are defined and fixed. This allows a better assessment of the vital influence of the boundary layers upon the wake, in a controlled way. This is not the case for the circular cylinder, because, in this instance, the separation points oscillate in relation to a mean position. In the present analysis, the relationship between the onset of shedding Reynolds number, Re h K , and the aspect ratio, AR, is obtained. To this end, a wide range of aspect ratios, between 3 and 25, was investigated. The result represented by this relationship is a novelty in the literature. Values of Re h K are strongly influenced by the aspect ratio for the case of the short cylinders-for which AR is low. After AR about 9, the curve flattens and the influence of the aspect ratio upon the shedding Reynolds number is very mild. Besides, the paper discusses another very important aspect; the overall stability of the pre-shedding laminar bubble at the base of the body. It is important to stress that the latter study relies on the fact that the boundary layers separation points are fixed.

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“…The characteristics of the vortex shedding in turbine bladings were investigated by several authors. Rowe et al 6 underlined that a thick boundary layer upstream of the trailing edge had the effect of reducing the frequency of the vortex shedding, resulting in decreased base pressure loss. The influence of the boundary layer state on both pressure and suction side on the vortex shedding demonstrated by Sieverding and Heinemann 7 .…”

Section: Introductionmentioning

confidence: 98%

Heat Transfer Investigation on a Transonic Turbine Cascade with Pulsating Trailing Edge Cooling

Saracoglu

Paniagua²

2012

48th AIAA/ASME/SAE/ASEE Joint Propulsion Conference &Amp;amp; Exhibit

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Increasing efficiency while reducing specific fuel consumption of aero-engines results in extensively cooled single stage transonic and supersonic high pressure turbine designs. Vane trailing edge shocks are inevitable in such architectures. Steady and unsteady interactions of the shock waves with adjacent and downstream blading results in severe efficiency abadement and high cycle fatigue problems. Pulsating trailing edge cooling is proposed to control shock waves and reduce their detrimental effects. A series of experiments were performed on a transonic turbine cascade at four Mach (0.8, 0.95, 1.1 and 1.2) and two Reynolds numbers (4x10 6 and 6x10 6 ) with presence of continuous and pulsating cooling on an isentropic compression tube facility. Pressure and heat transfer measurements were performed to quantify the consequences of different coolant blowing schemes. Shock angle variation and intensity reduction has been quantified at different cooling rates. Shock induced boundary layer transition has been identified with both continuous and pulsating coolant ejection. The most significant improvents were attained by the pulsating cooling. Nomenclature f = Frequency M = Mach number Nu = Nusselt number P = Pressure Re = Reynolds number S = Curvilinear abscissa along wall surface T = Temperature t = Time NGV = Nozzle guide vane RMS = Root mean square Subscripts cool = coolant properties is = Isentropic max = Maximum s = Static w = Wall 0 = Total quantities 1 = Inlet conditions 2 = Downstream plane (at 25% of chord)

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Influence of Boundary-Layer Thickness on Base Pressure and Vortex Shedding Frequency

Cited by 31 publications

References 5 publications

Boundary layer modification by means of wall suction and the effect on the wake behind a rectangular forebody

Boundary layer modification by means of wall suction and the effect on the wake behind a rectangular forebody

Direct Numerical Simulation of the Onset of Vortex Shedding for Blunt Elongated Bodies

Heat Transfer Investigation on a Transonic Turbine Cascade with Pulsating Trailing Edge Cooling

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