Bluff-body drag reduction by passive ventilation

Suryanarayana, GK; Pauer, H.; Meier, G. E. A.

doi:10.1007/bf00944909

Cited by 34 publications

(17 citation statements)

References 10 publications

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“…Because of the practical importance of bluff bodies in uniform flow, a large number of numerical and experimental investigations have been performed for a wide range of Reynolds numbers (Griffin, 1995;Hoerner, 1957;Kim and Lee, 2001;Roshko, 1955;Suryanarayana et al, 1993). Details on the subject of a circular cylinder in uniform flow can also be found in the book of Zdravkovich (1997).…”

Section: Introductionmentioning

confidence: 98%

“…For the former, acoustics excitations (Blevins, 1985), heating the cylinder (Lecordier et al, 1991), oscillating the cylinder at an appropriate frequency or frequency-modulation (Berger, 1967;Nakano and Rockwell, 1991;Tokumaru and Dimotakis, 1991;Suryanarayana et al, 1993), blowing and suction (Bearman, 1965), and recently electromagnetic force control (Kim and Lee, 2001) are typical examples. For the latter, typical examples are surface protrusions (Nigim and Batill, 1997) to change the flow separation location, shrouds to affect the fluid entrainment (Zdravkovich, 1997), the rear-wake stabilizer to minimize the mutual interactions of separated shear layers (Bearman, 1965;Eisenlohr and Eckelmann, 1989), and recently use of a very small control cylinder to efficiently suppress the wake behind the main cylinder (Strykowski and Sreenivasan, 1990).…”

Section: Introductionmentioning

confidence: 99%

“…Although the Reynolds number is usually high in most practical situations, wake flows are also important at low Reynolds numbers for microsystem applications. Three important goals to modify the wake flows at low Reynolds numbers are: (i) reducing the form drag (Huner and Hussey, 1977;Suryanarayana et al, 1993), (ii) suppressing the vortex shedding (Bearman, 1965;Berger, 1967;Blevins, 1985;Strykowski and Sreenivasan, 1990), and (iii) changing the heat transfer characteristics (Lange et al, 1998).…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Wake flow pattern modified by small control cylinders at low Reynolds number

Kuo

Chiou

Chen

2007

Journal of Fluids and Structures

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Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Wake flow pattern modified by small control cylinders at low Reynolds number

Kuo

Chiou

Chen

2007

Journal of Fluids and Structures

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“…Suryanarayana [17] carried out passive ventilation on a sphere by ducting air from the front of the sphere to the base with a duct that was 15% of the diameter of the sphere, producing drag reductions of up to 60%. The ventilation resulted in a ring shaped stagnation at the front of sphere and a toroidal recirculating region, due to an additional shear layer, at the base of the model.…”

Section: Introductionmentioning

confidence: 99%

The Effect of Passive Base Ventilation on the Aerodynamic Drag of a Generic SUV Vehicle

Varney¹,

Passmore²,

Gaylard³

2017

SAE Int. J. Passeng. Cars - Mech. Syst.

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INTRODUCTIONAerodynamic drag is an increasing concern for vehicle manufacturers due to its impact on CO 2 emissions and fuel economy. For instance, the European Union will phase in significant penalties for CO 2 emissions above a mass-dependent limit curve from 2020 [1]. As Sport Utility Vehicles (SUVs) are the most popular body type [2], the methods of reducing their drag come under closer scrutiny, specifically when the success of these vehicles owes much to elements of design and utility.The blunt nature of SUV rear geometries arises from their historical use as working vehicles, with a need for maximal access to a large rear load space, whilst maintaining off-road capability. For squareback geometries, such as these, more than one-third of the aerodynamic drag is attributable to the rear surfaces [3], resulting from separation at the trailing edges leading to low pressure on the base.In order to combat the depressed static pressure on the base of vehicles a number of studies have been done to investigate base pressure recovery. Typical passive methods such as side tapering [4,5], roof tapering [4,6,7,8,9], roughness strips [10] and underbody tapering [11,12] have all been shown to result in base drag reductions.Active methods have also been tested with drag reductions being reported but little shown in terms of net energy reduction (as the systems require energy input); these include rolling trailing and leading edges [13], blowing [14] and thermal riblets [15].Both passive and active methods alter the shear layers bounding the wake of the vehicle and, as a result change the base pressure and reduce drag. Typically the reduction in drag is shown to be due to the increase in base pressure [4,5,7,8] Adrian Gaylard Jaguar Land Rover ABSTRACT Sports Utility Vehicles (SUVs) typically have a blunt rear end shape (for design and practicality), however this is not beneficial for aerodynamic drag. Drag can be reduced by a number of passive and active methods such as tapering and blowing into the base. In an effort to combine these effects and to reduce the drag of a visually square geometry slots have been introduced in the upper side and roof trailing edges of a squareback geometry, to take air from the freestream and passively injects it into the base of the vehicle to effectively create a tapered body.This investigation has been conducted in the Loughborough University's Large Wind Tunnel with the ¼ scale generic SUV model. The basic aerodynamic effect of a range of body tapers and straight slots have been assessed for 0° yaw. This includes force and pressure measurements for most configurations. The slots generate useful, but small, drag reductions with the best configurations giving reductions in drag coefficient (C d ) of approximately 0.01, whereas the best taper configurations reduce C d by close to 0.035. The slots also have a tendency to modify the lift.

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“…Control of flow structure around a sphere for various active and passive methods was studied by Suryanarayana and Prabhu (2000), Suryanarayana and Meier (1995), Suryanarayana et al (1993), Ozgoren et al(2011bOzgoren et al( , 2011c, Kim and Durbin (1988), Kiya (1988), Owen and Bearman (1988), Mehta (1985) and further investigations cited therein [19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36].…”

Section: Introductionmentioning

confidence: 99%

Comparison of Flow Characteristics of Different Sphere Geometries Under the Free Surface Effect

Özgören

Doğan

Okbaz

et al. 2013

EPJ Web of Conferences

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Abstract.Comparison of the experimental results of turbulent flow structures between a smooth sphere and a sphere with a vent hole, roughened, and o-ring is presented in the presence of a free-surface. Dye visualization and particle image velocimetry (PIV) techniques were performed to examine effects of passive control methods on the sphere wake for Reynolds number Re = 5000 based on the sphere diameter with a 42.5mm in an open water channel. Instantaneous and time-averaged flow patterns in the wake region of the sphere were examined from point of flow physics for the different sphere locations in the range of 0≤h/D ≤2.0 where h was the space between the top point of the sphere and the free surface. The ratio of ventilation hole to sphere diameter was 0.15, o-ring was located at 55 o with a 2 mm from front stagnation point of the sphere and roughened surface was formed by means of totally 410 circular holes with a 3 mm diameter and around 2 mm depth in an equilateral triangle arrangement. The flow characteristics of instantaneous velocity vectors, vorticity contours, time-averaged streamline patterns, Reynolds stress correlations and streamwise and cross-stream velocity fluctuations for both the smooth and passively controlled sphere were interpreted.

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Bluff-body drag reduction by passive ventilation

Cited by 34 publications

References 10 publications

Wake flow pattern modified by small control cylinders at low Reynolds number

Wake flow pattern modified by small control cylinders at low Reynolds number

The Effect of Passive Base Ventilation on the Aerodynamic Drag of a Generic SUV Vehicle

Comparison of Flow Characteristics of Different Sphere Geometries Under the Free Surface Effect

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