Bluff Body Drag Reduction Using Passive Flow Control of Jet Boat Tail

Hirst, Trevor; Li, Chuanpeng; Yang, Yunchao; Brands, Eric; Zha, Gecheng

doi:10.4271/2015-01-2891

Cited by 11 publications

(5 citation statements)

References 9 publications

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“…When the width of the slots is increased, the speed of the flow through the slot increases, as shown by a lower static pressure on the slant surfaces ( Figure 22). This promotes the strengthening of the shear layers in the upper sides of the model, similar to that seen by Hirst and Bartow [19,20].…”

Section: Varney Et Al / Sae Int J Passeng Cars -Mech Syst / Volusupporting

confidence: 80%

“…Bartow and Hirst [19,20] carried out similar work on wing mirror geometries. Bartow et al [20] used an automotive mirror with a bell shaped internal geometry to duct the flow to the base of the mirror, this flow was vented circumferentially.…”

Section: Introductionmentioning

confidence: 99%

“…Whilst no experimental force measurements were presented for these geometries, particle image velocimetry (PIV) shows that increasing the intake area increases the mass flow rate and as a result reduces the size of the wake. Hirst et al [19] uses a truck type mirror with an intake placed on the outside of the geometry at the trailing edge , this ventilates the base circumferentially. When the ventilation is introduced the size of the wake decreases at both Reynolds numbers tested with the computational analysis showing a drag reduction of approximately 15%.…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Varney Et Al / Sae Int J Passeng Cars -Mech Syst / Volusupporting

confidence: 80%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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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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“…installing devices in specific locations at specific angles, in order to modify the vortices generated in the wake zone: Synthetic jets [7]; Pulsed jets [8], [9], [10], [11]; Steady blowing micro jets at the top edge of slanted surface [12], [13], [14], [15] ; Suction [16], [17], [18] ; Plasma actuators [19] and fluid oscillators [20]. The passive method consists on the use of discrete obstacles, added around or on the roof of the vehicle to change the vortices that are created in the wake zone: Tail plate [21]; Non-smooth surface [22] ; Rear screen and rear fairing [23] ; Underbody device [24] ; Vortex generators on the roof of the model [25], [26], [27]; Streaks [28] ; Jet boat tail [29] ; Rear linking tunnels [30]; Lateral guide vanes [31] ; Underbody diffusers [32], [33], [34] ; Vertical splitter plate [35] and deflector at the edges of the slanted surface and vertical base [36], [37], [38], [39]. Relative to active control, passive control method does not need any sophisticated actuators and electronic control systems, which insures higher reliability.…”

Section: Introductionmentioning

confidence: 99%

Aerodynamic Drag Reduction Around Vehicles Using a Curved Deflector

Maine,

Oumami,

Bouksour

2023

IJIE

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A passive flow control on a generic car model was numerically studied. The Ahmed model with rear slant angle of 25° was used to study the aerodynamic effects. The concave deflector was tested for the first time in this paper to minimize the drag coefficient. The deflector was fixed between the end of the roof and the top of the rear window. Simulations were firstly performed for different straight deflector’s length rates based on the length of the model, for Reynolds number Re=7.89×105. A significant drag reduction was observed for the high length rate studied. Secondly, the length rate was fixed, and the deflector was investigated for different curvature radius and inclination angles. It was concluded that the Ahmed model with concave deflector gives the best drag reduction, compared to the model with straight deflector and the model without deflector. It was observed that the installation of a concave deflector on the Ahmed model widen the wake zone and remove the vortices from the rear base. For this case, the lift coefficient was reduced, this improves the stability of vehicle on the road at high speed.

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“…A wide variety of research and development studies have been carried out to improve the vehicle aerodynamics of mediumduty to heavy-duty vehicles. [2][3][4][5][6][7][8][9][10] Some of these efforts have led to the use of cab-roof-mounted deflectors, cab forebody fairings, and trailer skirts. Each of these methods has shown to improve the aerodynamics of heavy-duty trucks, but there is an increasing demand for further minimization of the drag on these vehicles.…”

Section: Introductionmentioning

confidence: 99%

Increasing the on-road fuel economy by trailing at a safe distance

Nuszkowski

Smith

McKinney

et al. 2017

Proceedings of the Institution of Mechanical Engineers, Part D:

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Energy is a driving force for automotive applications. Reducing the energy demand of the vehicle is one method of increasing the fuel economy of a vehicle. Heavy-duty commercial vehicles have large frontal areas that provide large amounts of aerodynamic drag at highway speeds. Reducing the aerodynamic drag lowers the engine demand and therefore increases the fuel economy of the vehicle. This study tested the fuel economy and the front air velocity of a 10.7 m box truck trailing another box truck by distances of 3.1 times the truck length, 4.7 times the truck length, and 6.3 times the truck length at a highway speed of 28 m/s. The distance of 6.3 times the vehicle length was considered ‘safe’ for trailing another vehicle, whereas the distances of 3.1 times the truck length and 4.7 times the truck length were not considered safe by the United States Fire Administration. The results showed significant reductions in the air velocity in front of the trailing vehicle of 8.5%, 6.5%, and 3.8% for trailing distances of 3.1 times the vehicle length, 4.7 times the vehicle length, and 6.3 times the vehicle length respectively. The fuel economy of the trailing truck increased significantly by 7.4–8.0%, 8.2–9.0%, and 6.5%–7.7%, for trailing distances of 3.1 times the vehicle length, 4.7 times the vehicle length, and 6.3 times the vehicle length respectively. Based on a road load analysis, these fuel economy improvements indicated a reduction in the drag coefficient of the trailing vehicle of 8–10%. Therefore, a box truck trailing another box truck at a safe distance results in a reduction in the aerodynamics drag and a significant increase in the fuel economy.

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Bluff Body Drag Reduction Using Passive Flow Control of Jet Boat Tail

Cited by 11 publications

References 9 publications

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

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

Aerodynamic Drag Reduction Around Vehicles Using a Curved Deflector

Increasing the on-road fuel economy by trailing at a safe distance

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