A Wind-Tunnel Study of the Effect of Gap Flow and Gap Seals on the Aerodynamic Drag of Tractor-Trailer Trucks

1978 ◽  
Vol 100 (4) ◽  
pp. 434-438 ◽  
Author(s):  
F. T. Buckley ◽  
C. H. Marks
Keyword(s):  
Wind Tunnel ◽  
Drag Coefficient ◽  
Aerodynamic Drag ◽  
Motor Fuel ◽  
Center Line ◽  
Gap Flow ◽  
Yaw Angle ◽  
Wind Tunnel Study ◽  
Gap Width ◽  
Coefficient Reduction

The effect of gap width on the aerodynamic drag of a cab-over-engine tractor-trailer combination has been investigated for full-scale gap widths ranging from 0.61 m (24 in) to 1.83 m (72 in.) over a yaw angle range of 0 to 20 deg. The average drag on the vehicle was found to increase by 16 percent as the gap width increased from 0.61 m to 1.83 m. Drag reductions were found when a vertical seal was placed along the vehicle center line between the tractor and the trailer. Generally, the drag reduction increased as the percentage of gap width that was sealed increased, and as the yaw angle increased. The average drag coefficient reduction provided by a full gap seal increased from 0.02 to 0.05 as the gap width increased from 0.61 m to 1.4 m and then decreased slightly for gap widths up to 1.83 m. The effect of vehicle configuration on gap seal effectiveness was evaluated for a gap width of 1.3 m (51 in.) using models of six different tractors and two different trailers. The average drag coefficient reductions that were found ranged from 0.04 to 0.08 with 83 percent of the data being either 0.04 or 0.05. It is shown that the use of gap seals on the nearly half-million vehicles which comprise the nation’s long-haul trucking fleet can result in the conservation of about 1.4 × 109 liters (0.37 × 109 gal) of motor fuel each year.

scholarly journals A wind-tunnel case study: Increasing road cycling velocity by adopting an aerodynamically improved sprint position

2019 ◽  
pp. 175433711986696
Author(s):  
Timothy Crouch ◽  
Paolo Menaspà ◽  
Nathan Barry ◽  
Nicholas Brown ◽  
Mark C Thompson ◽  
...  
Keyword(s):  
Wind Tunnel ◽  
Drag Coefficient ◽  
Aerodynamic Drag ◽  
Time Trial ◽  
Force Measurements ◽  
Sampling Errors ◽  
Repeated Testing ◽  
Road Cycling ◽  
Wind Tunnel Study

The main aim of this study was to evaluate the potential to reduce the aerodynamic drag by studying road sprint cyclists’ positions. A male and a female professional road cyclist participated in this wind-tunnel study. Aerodynamic drag measurements are presented for a total of five out-of-seat sprinting positions for each of the athletes under representative competition conditions. The largest reduction in aerodynamic drag measured for each athlete relative to their standard sprinting positions varied between 17% and 27%. The majority of this reduction in aerodynamic drag could be accounted for by changes in the athlete’s projected frontal area. The largest variation in repeat drag coefficient area measurements of out-of-seat sprint positions was 5%, significantly higher than the typical <0.5% observed for repeated testing of time-trial cycling positions. The majority of variation in repeated drag coefficient area measurements was attributed to reproducibility of position and sampling errors associated with time-averaged force measurements of large fluctuating forces.

A Study of the Base Drag of Tractor-Trailer Trucks

1978 ◽  
Vol 100 (4) ◽  
pp. 443-448 ◽  
Author(s):  
C. H. Marks ◽  
F. T. Buckley ◽  
W. H. Walston
Keyword(s):  
Wind Tunnel ◽  
Drag Coefficient ◽  
Pressure Distribution ◽  
Aerodynamic Drag ◽  
Base Pressure ◽  
Drag Coefficients ◽  
Vehicle Configuration ◽  
Yaw Angle ◽  
Base Drag

Measurements were made of the base pressure distribution and the aerodynamic drag of a variety of 1/8th-scale tractor-trailer truck models in a wind tunnel at yaw angles ranging from 0° to 20°. Base-drag coefficients and overall aerodynamic-drag coefficients were calculated from this data. The measurements show that the base-drag coefficient of typical tractor-trailer trucks does not vary much with vehicle configuration, and that base drag constitutes approximately 13 to 15 percent of the total aerodynamic drag at zero yaw. The base drag increases in magnitude and also becomes a larger part of the overall aerodynamic drag as yaw angle increases, reaching about 18 to 25 percent of the overall drag at 20° yaw. Streamlining the forebody of the vehicle has little effect on the base-drag coefficient, but increases the fraction of the overall aerodynamic drag due to the base.

Aerodynamics of Cyclist Posture, Bicycle and Helmet Characteristics in Time Trial Stage

2012 ◽  
Vol 28 (3) ◽  
pp. 317-323 ◽  
Author(s):  
Vincent Chabroux ◽  
Caroline Barelle ◽  
Daniel Favier
Keyword(s):  
Statistical Analysis ◽  
Wind Tunnel ◽  
Drag Coefficient ◽  
Drag Force ◽  
Time Trial ◽  
Frontal Area ◽  
Significant Gain ◽  
Upper Limbs ◽  
Force Coefficient ◽  
Coefficient Reduction

The present work is focused on the aerodynamic study of different parameters, including both the posture of a cyclist’s upper limbs and the saddle position, in time trial (TT) stages. The aerodynamic influence of a TT helmet large visor is also quantified as a function of the helmet inclination. Experiments conducted in a wind tunnel on nine professional cyclists provided drag force and frontal area measurements to determine the drag force coefficient. Data statistical analysis clearly shows that the hands positioning on shifters and the elbows joined together are significantly reducing the cyclist drag force. Concerning the saddle position, the drag force is shown to be significantly increased (about 3%) when the saddle is raised. The usual helmet inclination appears to be the inclination value minimizing the drag force. Moreover, the addition of a large visor on the helmet is shown to provide a drag coefficient reduction as a function of the helmet inclination. Present results indicate that variations in the TT cyclist posture, the saddle position and the helmet visor can produce a significant gain in time (up to 2.2%) during stages.

On the Penetrator Nose Drag Measurements

2010 ◽  
Author(s):  
Joseph P. Holland ◽  
Yesenia Tanner ◽  
Phillip A. Schinetsky ◽  
Semih Olcmen ◽  
Stanley Jones
Keyword(s):  
Wind Tunnel ◽  
Power Series ◽  
Viscous Fluid ◽  
Drag Coefficient ◽  
Aerodynamic Drag ◽  
Terminal Velocity ◽  
Force Balance ◽  
Supersonic Wind Tunnel ◽  
Buoyant Force ◽  
Nose Shape

In the current study, a rigid body penetrator nose shape that is optimized for minimum penetration drag [1] has been tested to determine the aerodynamic drag of such a penetrator in comparison to three additional nose shapes. Other nose shapes tested were an ogive cylinder, a 3/4 power series nose, and a standard cone. Fineness ratio for the studied nose geometries was chosen as l/d = 1 to maximize variation of the aerodynamic drag forces acting on the nose shapes. This paper discusses the measurements carried out in the University of Alabama’s 6″ × 6″ supersonic wind tunnel, using a 4 component force balance system. In separate experiments, drop tests were made in a viscous fluid to determine the skin-friction effects on these nose shapes. Supersonic wind-tunnel experiments were performed on each of the nose shapes at nine different Mach numbers ranging from 2 to 3.65. Results show that the nose shape optimized for penetration has the lowest drag coefficient of all the shapes at each Mach number within an uncertainty of 5.75%. In the viscous flow drop-test experiments, each nose shape was dropped from rest through water and then separately through viscous fluid (Nu-Calgon vacuum pump oil) under freefall conditions. Each drop was recorded via videotape, and the video was then analyzed to find the terminal velocity of each individual nose shape. Using classical dynamics equations, the weight, buoyant force, and experimentally determined terminal velocity are used to determine the drag force applied to each nose cone shape. Results indicate that while the optimal shape has a lesser drag coefficient than tangent ogive and the cone, the 3/4 power series shape is observed to have the least drag coefficient. In addition to the experiments performed, results on further investigation of the optimal nose shape for penetration are presented. The nose shape has been split into a series of line segments, and a program written has been utilized to search through numerical space for the combination of line segment slopes that produces the nose geometry with the lowest nose shape factor. The results of the numerical analysis in this study point to a different nose shape than the “optimal nose” shape tested in the current study.

scholarly journals A drag coefficient for application to the WLTP driving cycle

2017 ◽  
Vol 231 (9) ◽  
pp. 1274-1286 ◽  
Author(s):  
Jeff Howell ◽  
David Forbes ◽  
Martin Passmore
Keyword(s):  
Drag Coefficient ◽  
Fuel Consumption ◽  
Aerodynamic Drag ◽  
Meteorological Data ◽  
Test Procedure ◽  
Driving Cycle ◽  
Alternative Measure ◽  
Speed Distribution ◽  
Road Speed ◽  
Yaw Angle

The aerodynamic drag characteristics of a passenger car have, typically, been defined by a single parameter: the drag coefficient at a yaw angle of 0°. Although this has been acceptable in the past, it does not provide an accurate measure of the effect of aerodynamic drag on fuel consumption because the important influence of the wind has been excluded. The result of using drag coefficients at a yaw angle of 0° produces an underprediction of the aerodynamic component of fuel consumption that does not reflect the on-road conditions. An alternative measure of the aerodynamic drag should take into account the effect of non-zero yaw angles, and a variant of wind-averaged drag is suggested as the best option. A wind-averaged drag coefficient is usually derived for a particular vehicle speed using a representative wind speed distribution. In the particular case where the road speed distribution is specified, such as for a driving cycle to determine fuel economy, a relevant drag coefficient can be derived by using a weighted road speed. An effective drag coefficient is determined with this approach for a range of cars using the proposed test cycle for the Worldwide Harmonised Light Vehicle Test Procedure, WLTP. The wind input acting on the car has been updated for this paper using recent meteorological data and an understanding of the effect of a shear flow on the drag loading obtained from a computational fluid dynamics study. In order to determine the different mean wind velocities acting on the car, a terrain-related wind profile has also been applied to the various phases of the driving cycle. An overall drag coefficient is derived from the work done over the full cycle. This cycle-averaged drag coefficient is shown to be significantly higher than the nominal drag coefficient at a yaw angle of 0°.

A Wind-Tunnel Study of the Effect of Turning Vanes on the Aerodynamic Drag of Tractor-Trailer Trucks

1978 ◽  
Vol 100 (4) ◽  
pp. 439-442 ◽  
Author(s):  
C. H. Marks ◽  
F. T. Buckley
Keyword(s):  
Wind Tunnel ◽  
Flow Separation ◽  
Aerodynamic Drag ◽  
Control Flow ◽  
Turning Angle ◽  
Edge Radius ◽  
Wind Tunnel Study

A Wind-Tunnel Study was made of the reduction of the aerodynamic drag of tractor-trailer trucks due to turning vanes used to control flow separation. A variety of vane settings and positions were investigated on the tractor and on the trailer. It was found that substantial drag reductions were obtained by employing vanes on the lower part of the front vertical edges of the tractor. Vanes mounted elsewhere had a smaller effect on the aerodynamic drag. Vane setting, turning angle and edge radius were found to be highly important.

A Wind Tunnel Study of Airflow through Horticultural Crops: Determination of the Drag Coefficient

2006 ◽  
Vol 93 (4) ◽  
pp. 447-457 ◽  
Author(s):  
F.D. Molina-Aiz ◽  
D.L. Valera ◽  
A.J. Álvarez ◽  
A. Madueño
Keyword(s):  
Wind Tunnel ◽  
Drag Coefficient ◽  
Horticultural Crops ◽  
Wind Tunnel Study

Experimental Model of the Aerodynamic Drag Coefficient in Alpine Skiing

2004 ◽  
Vol 20 (2) ◽  
pp. 167-176 ◽  
Author(s):  
Caroline Barelle ◽  
Anne Ruby ◽  
Michel Tavernier
Keyword(s):  
Wind Tunnel ◽  
Drag Coefficient ◽  
Experimental Model ◽  
Aerodynamic Drag ◽  
Aerodynamic Force ◽  
Alpine Skiing ◽  
Aerodynamic Properties ◽  
Speed Performance ◽  
Aerodynamic Drag Coefficient ◽  
The Impact

Aerodynamic properties are one of the factors that determine speed performance in Alpine skiing. Many studies have examined the consequences of this factor in downhill skiing, and the impact of postural modifications on speed is now well established. To date, only wind tunnel tests have enabled one to measure aerodynamic drag values (a major component of the aerodynamic force in Alpine skiing). Yet such tests are incompatible with the constraints of a regular and accurate follow-up of training programs. The present study proposes an experimental model that permits one to determine a skier's aerodynamic drag coefficient (SCx) based on posture. Experimental SCx measurements made in a wind tunnel are matched with the skier's postural parameters. The accuracy of the model was determined by comparing calculated drag values with measurements observed in a wind tunnel for different postures. For postures corresponding to an optimal aerodynamic penetration (speed position), the uncertainty was 13%. Although this model does not permit an accurate comparison between two skiers, it does satisfactorily account for variations observed in the aerodynamic drag of the same skier in different postures. During Alpine ski training sessions and races, this model may help coaches assess the gain or loss in time induced by modifications in aerodynamic drag corresponding to different postures. It may also be used in other sports to help determine whether the aerodynamic force has a significant impact on performance.

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