Aerodynamic Benefits Research Articles

An experimental parametric study on planar sheared wings tip devices for low-to-moderate aspect ratio wings

PurposeThe purpose of this study is to investigate the aerodynamic characteristics of a low-to-moderate-aspect-ratio, tapered, untwisted, unswept wing, equipped of sheared wing tips.Design/methodology/approachIn this work, wind tunnel tests were made to study the influence in aerodynamic characteristics over a typical low-to-moderate-aspect-ratio wing of a general aviation aircraft, equipped with sheared – swept and tapered planar – wing tips. An experimental parametric study of different wing tips was tested. Variations in its leading and trailing edge sweep angle as well as variations in wing tip taper ratio were considered. Sheared wing tips modify the flow pattern in the outboard region of the wing producing a vortex flow at the wing tip leading edge, enhancing lift at high angles of attack.FindingsThe induced drag is responsible for nearly 50% of aircraft total drag and can be reduced through modifications to the wing tip. Some wing tip models present complex geometries and many of them present benefits in particular flight conditions. Results have demonstrated that sweeping the wing tip leading edge between 60 and 65 degrees offers an increment in wing aerodynamic efficiency, especially at high lift conditions. However, results have demonstrated that moderate wing tip taper ratio (0.50) has better aerodynamic benefits than highly tapered wing tips (from 0.25 to 0.15), even with little less wing tip leading edge sweep angle (from 57 to 62 degrees). The moderate wing tip taper ratio (0.50) offers more wing area and wing span than the wings with highly tapered wing tips, for the same aspect ratio wing.Originality/valueAlthough many studies have been reported on the aerodynamics of wing tips, most of them presented complex non-planar geometries and were developed for cruise flight in high subsonic regime (low lift coefficient). In this work, an exploration and parametric study through wind tunnel tests were made, to evaluate the influence in aerodynamic characteristics of a low-to-moderate-aspect-ratio, tapered, untwisted, unswept wing, equipped of sheared wing tips (wing tips highly swept and tapered).

Drag Reduction of TVS Scooty using a Windshield for the Rider Comfort Improvement

Rider comfort and safety has become an essential theme in the design of two-wheeler vehicles. Comfort incorporates wind noise, air pressure on the rider, visibility and the stability of the Scooty handle. Rider comfort and the potential aerodynamics concern have encouraged the current authors to carry out the Computational Fluid Dynamics (CFD) analysis of TVS pep+ Scooty. Numerical computations were carried out using the standard k-ε turbulence model to examine the aerodynamic force coefficients, pressure distribution, velocity vector and streamlines around the Scooty and rider. Simulations were done for a range of speed on an existing and redesigned model of Scooty with a different windshield height. The simulation result shows that there is a reduction in the coefficient of drag (Cd) from 1.58 (baseline model) to 0.95 (model 3) at a speed of 60kmph. The pressure contour reveals the inclusion of the windshield of height 130mm in the baseline model has diminished the pressure drag on the rider. Visual of velocity contour depicts that the velocity of the air decrease above the neck region with in-creasing windshield height at a vehicle speed 120kmph. This study reinforces the need of windshield height of 150mm in the baseline model to avoid unwanted aerodynamic benefits on the rider.

Aerodynamic Analysis of Coning Effects on the DTU 10 MW Wind Turbine Rotor

The size of wind turbine rotors is still rapidly increasing, though many technical challenges emerge. Novel rotor designs emerge to satisfy this up-scale trend, such as downwind load-aligned concepts, which orients the loads along the blade spanwise to greatly decrease the bending moments at the root. As the studies on the aerodynamics of these rotor concepts using 3D body-fitted mesh are very limited, this paper establishes different cone configurations based on the DTU 10 MW reference rotor and conducts a series of simulations. It is found that the cone angle and the distance from the blade section to the tip vortex are two deterministic factors on conning. Upwind rotors have larger power output, less thrust, smaller wake deficit, and smaller influencing area than downwind rotors of the same size, which provides superior aerodynamic priority and benefits wind farm design. The largest upwind cone angle of 14.03°, among the cases studied, leads to the highest torque to thrust ratio which is 3.63% higher than the baseline rotor. The downwind load-aligned rotor, designed to reduce the blade root bending moments at large wind speed, performs worse at the present simulation conditions than an upwind rotor of the same size.

Experimental investigation of the angle of attack dependence of the flow past a cactus-shaped cylinder with four ribs

The aerodynamic properties of a two-dimensional cactus-shaped cylinder with four ribs are studied experimentally. The cross section of the cylinder corresponds to a modified square cylinder with rounded corners and concave sides inspired by tall succulents with four ribs. The mean aerodynamic coefficients, fluctuating lift coefficient, Strouhal number, and mean surface pressure distribution are measured as a function of the angular orientation for Reynolds numbers ranging from 50,000 to 150,000. Hot-wire measurements are conducted at two locations in the wake for several angles of attack to provide insight into the vortex shedding frequencies. The results show that the studied shape exhibits a strong angle of attack dependence while no Reynolds number dependence is found within the tested range. As for the square cylinder, a critical angle of attack of approximately 13° is observed at which drag and fluctuating lift forces are minimised while mean lift and Strouhal number reach their highest values. Reattachment of the shear layer at and above the critical angle of attack is confirmed using PIV. Overall, succulents with four ribs retain some of the aerodynamic benefits that have been observed for cactus-shaped cylinders with many ribs, albeit over a limited range of angles of attack.

Aerodynamics of electric cars in platoon SAGE publications

The potential aerodynamic benefits of operating full-scale electric vehicles in platoons of 2 and 3 vehicles have been investigated. Since drag reduction has a direct impact on vehicle range, power consumption was measured directly and surface pressure measurements were made to characterise the changes in pressure field that influence the power required to overcome aerodynamic drag. CFD simulations were validated against the track measurements to assess the limitations of using a practical, limited number of pressure tappings to measure drag. The overall power consumption for the whole platoon was found to reduce proportionally with the reduction of vehicle spacing and it was also observed that increasing the number of vehicles in the platoon from 2 to 3 further increased the power savings from 33.4% to 39.1%. These power savings were attributed primarily to changes in surface pressure acting on the base of the leading vehicle and the forebody of the trailing vehicle.

The Effect of Upper-Body Positioning on the Aerodynamic-Physiological Economy of Time-Trial Cycling.

Cycling time trials (TTs) are characterized by riders' adopting aerodynamic positions to lessen the impact of aerodynamic drag on velocity. The optimal performance requirements for TTs likely exist on a continuum of rider aerodynamics versus physiological optimization, yet there is little empirical evidence to inform riders and coaches. The aim of the present study was to investigate the relationship between aerodynamic optimization, energy expenditure, heat production, and performance. Eleven trained cyclists completed 5 submaximal exercise tests followed by a TT. Trials were completed at hip angles of 12° (more horizontal), 16°, 20°, 24° (more vertical), and their self-selected control position. The largest decrease in power output at anaerobic threshold compared with control occurred at 12° (-16 [20]W, P = .03; effect size [ES] = 0.8). There was a linear relationship between upper-body position and heat production (R2 = .414, P = .04) but no change in mean body temperature, suggesting that, as upper-body position and hip angle increase, convective and evaporative cooling also rise. The highest aerodynamic-physiological economy occurred at 12° (384 [53]W·CdA-1·L-1·min-1, ES = 0.4), and the lowest occurred at 24° (338 [28]W·CdA-1·L-1·min-1, ES = 0.7), versus control (367 [41]W·CdA-1·L-1·min-1). These data suggest that the physiological cost of reducing hip angle is outweighed by the aerodynamic benefit and that riders should favor aerodynamic optimization for shorter TT events. The impact on thermoregulation and performance in the field requires further investigation.

Experimental and computational investigation of hybrid formation flight for aerodynamic gain at transonic speed

The influence of the wing-tip vortex of leading aircraft on energy savings, quantified by formation aerodynamic force fraction of the following aircraft, is studied at transonic speed for a matrix of leading aircraft’s vortex locations. The research model adopts the hybrid formation of medium and large aircraft. The leading aircraft is scaled by 2.1%, and the following aircraft is scaled by 1.4%. An aerodynamic benefit “map” is developed to determine the optimum location of the following aircraft relative to the leading aircraft wake and to compare with experimental results, thus validating the use of CFD for the formation flight at cruising speed. The response surface model of aerodynamic gain effect relative to formation parameters is established via numerical calculation and wind tunnel test. The optimal formation parameters and the setting criteria of the study model are optimized. Results show that the wing-tip vortex of large aircraft significantly increases lift and reduces drag on the medium-sized aircraft following it. Reduced drag slightly increases with the flow direction position. With the increase of flow direction distance, the peak area moves from 15% of wing-tip overlap to 20% of overlap. In addition, the maximum drag decreases about 16%, and the maximum lift increases about 12%. The lift drag ratio of the optimal position is increased by 27%, which is twice as large as that of the same scale ratio aircraft formation. Results show that the increase of lift is mainly caused by the increase of suction peak and suction range.

Pulsed Jet Characteristics of Circulation Control Airfoil

Compared with the steady jet, the mass flow consumed by the pulsed jet is lower, which is of great significance for solving the jet source in the circulation control technology. In order to further study the effects of different parameters on energy consumption and aerodynamic coefficient pulse in pulsed jet, based on the Reynolds average N-S equation, the aerodynamic characteristic calculation and flow field analysis of the circulation control airfoil under the action of pulsed jet are carried out, and the aerodynamic benefit is evaluated with the combination of energy consumption and aerodynamic coefficient fluctuation. The results show that: Pulsed jet is more suitable for use at high angle of attack. By using the combination of pulsed jet and steady jet, good results can be obtained in three aspects: time-averaged lift coefficient, lift coefficient fluctuation and energy consumption. The research results can be used as a reference for guiding the use of pulsed jet in circulation control technology.

Aerodynamic benefits for a cyclist by drafting behind a motorcycle

Motorcycles are present in cycling races for reasons including television broadcasting. During parts of the race, these motorcycles ride in front of individual or groups of cyclists. Concerns have been expressed in the professional cycling community that these motorcycles can provide aerodynamic benefits in terms of drag reduction for the cyclists drafting behind them. However, to the best of our knowledge, no information about the extent of these benefits is present in the scientific literature. Therefore, this paper analyses the potential drag reduction for a cyclist by drafting behind a motorcycle. Wind tunnel measurements and numerical simulations with computational fluid dynamics were performed. It was shown that drafting at separation distances d = 2.64, 10, 30 and 50 m can reduce the drag of the cyclist down to 52, 77, 88 and 93% of that of an isolated cyclist, respectively. A cyclist power model is used to convert these drag reductions into potential time gains. For a non-drafting cyclist at a speed of 54 km/h on level road in calm weather, the time gains by drafting at d = 2.64, 10, 30 and 50 m are 12.7, 5.4, 2.7 and 1.6 s per km, respectively. These time differences can influence the outcome of cycling races. The current rules of the International Cycling Union do not prevent these aerodynamic benefits from occurring in races.

Large eddy simulation of dynamic stall flow control for wind turbine airfoil using plasma actuator

To solve aerodynamic performance deterioration caused by dynamic stall, a large eddy simulation numerical calculation based on dynamic grid and sliding grid technology was conducted and the dynamic flow control mechanism of unsteady pulsed plasma was explored. The results showed that plasma aerodynamic actuators can effectively control the airfoil’s dynamic stall, improve the mean and transient aerodynamic forces, and reduce the negative peak value of the pitch moment and hysteresis loop area. A negative pressure “bulge” appears in the plasma application areas, and the peak suction of the airfoil’s upper surface obviously increases. Two unsteady control parameters, the pulsed frequency and duty cycle, significantly influence the flow control. When the dimensionless pulsed frequency is 1.5, plasma control improves, and when the duty cycle is 0.8, it is close to the aerodynamic benefits under the continuous working mode. In the deep stall state, plasma impels the flow separation position to obviously move backward, resisting large-scale dynamic stall vortices. The structure of the separation vortices is broken, dissipated, and reattached to the airfoil by the plasma, and the influence area of the vortices is reduced. In the light stall state, the plasma actuator easily controls the shear layer, inducing the transition of the airfoil’s boundary layer and promoting the momentum mixing with the main flow. “Vortex clusters” near the airfoil’s leading edge induced by plasma actuation play a role in the virtual aerodynamic shape. The harmonic oscillation of aerodynamic force/moment is caused by the nonlinear and strong coupling effect between dynamic vortex structures with different scales and frequencies and plasma aerodynamic actuation. The amplitude of low-order mode energy concentration is relatively large, which is mainly caused by the pitching motion. The high-order fluctuation energy concentration is caused by the evolution process of starting vortices and derived secondary vortices with different frequencies induced by plasma.

DES vs RANS: The flatback airfoil case

Using flatback airfoils at the root of wind turbine (WT) blades is becoming more popular as the WTs increase in size. The reason is that they provide significant aerodynamic, aeroelastic and structural benefits. However, due to the blunt trailing edge (TE), the wake of such airfoils is highly unsteady and rich in three-dimensional vortical structures. This poses significant challenges on the numerical simulation of the flow around them, given the highly unsteady, three-dimensional turbulent character of their wake. In this work, computational predictions for a flatback airfoil employing both RANS and DES approaches on three successively refined grids up to 25 million cells are compared with available experimental data. Results suggest that even though URANS and DDES are in good agreement in terms of lift and drag, RANS simulations fail to accurately capture the turbulent wake unsteady characteristics.

On the effect of changing handgrip position on joint specific power and cycling kinematics in recreational and professional cyclists.

IntroductionIn cycling, the utilization of the drops position (i.e. the lowest handlebar position relative to the ground) allows for reduced frontal area, likely improved aerodynamics and thus performance compared to the tops (i.e. the position producing the most upright trunk). The reduced trunk angle during seated submaximal cycling has been shown to influence cardiorespiratory factors but the effects on pedalling forces and joint specific power are unclear. The purpose of this study was to investigate the effect of changing handgrip position on joint specific power and cycling kinematics at different external work rates in recreational and professional cyclists.MethodNine professional and nine recreational cyclists performed cycling bouts using three different handgrip positions and three external work rates (i.e. 100W, 200W and external work rate corresponding to the lactate threshold (WRlt)). Joint specific power was calculated from kinematic measurements and pedal forces using 2D inverse dynamics.ResultsWe found increased hip joint power, decreased knee joint power and increased peak crank torque for the professional cyclist compared to the recreational cyclists, but only at WRlt where the professional cyclists were working at a higher external work rate. There was no main effect of changing handgrip position on any joint, but there was a small interaction effect of external work rate and handgrip position on hip joint power contribution (Generalized eta squared (ηg2) = 0.012). At 100W, changing handgrip position from the tops to the drops decreased the hip joint contribution (-2.0 ± 3.9 percentage points (pct)) and at the WRlt, changing handgrip position increased the hip joint power (1.6 ± 3.1 pct). There was a small effect of handgrip position with the drops leading to increased peak crank torque (ηg2 = 0.02), increased mean dorsiflexion (ηg2 = 0.05) and increased hip flexion (ηg2 = 0.31) compared to the tops.DiscussionThe present study demonstrates that there is no main effect of changing handgrip position on joint power. Although there seems to be a small effect on hip joint power when comparing across large ranges in external work rate, any potential negative performance effect would be outweighed by the aerodynamic benefit of the drops position.

Geliştirilmiş Ticari Uçak Performansı için Uyarlanabilen Kanatçıkların Aerodinamik Analizi

This article describes the performance benefits of variable winglet configurations. The primary variables investigated involved varying the winglet twist and dihedral angle of a comparable Airbus A330-300 wing structure. Numerical studies have been carried out in AVL (Athena Vortex Lattice Method). In order to illustrate the aerodynamic benefits of morphing winglet concepts for different flight regimes, values of twist (-10°< θ <10°, in steps of ±2.5°) and values of dihedral (-90°< θ <90°, in steps of ±15°) were designed and numerically investigated. The results obtained from this work indicate that by carefully adjusting morphing winglets on air vehicles (Airbus A330-300), the aerodynamic performance benefits could be achieved.

The water-hopping kinematics of the tree-climbing fish, Periophthalmus variabilis

In this communication, we describe the water-hopping kinematics of the dusky-gilled mudskipper (Periophthalmus variabilis), and by doing so elucidate an entirely new form of fish locomotion that has yet to be reported in the public domain. Water-hopping is defined herein as an ability to hop once, or in succession, on the surface of water without full submergence and without a fin-guided glide. We find that taxiing on the water surface is the predominating kinematic movement used for the execution of successful water-hops. We observe that an initial concentric ripple forms as the mudskipper impacts the water, and that subsequent taxiing on the water surface generates a sinusoid-like ripple pattern in the water prior to take off. Interestingly whilst airborne, the pectoral fins of P. variabilis appear to remain stationary, only to be deployed upon contact with the water. When landing back onto the surface of the water, P. variabilis makes the initial contact via its pelvic region, occasionally extending its pectoral fins during its descent. The reasons for pectoral and pelvic fin extension are unclear, however, there may be either aerodynamic or hydrodynamic benefits in its doing so. This motion furthermore prepares the mudskipper for either, a follow-on water-hop, or a discontinuation of movement altogether, as the body of the mudskipper becomes aligned in a way conducive to either. P. variabilis will launch and land using both, horizontal surfaces such as littorals, and inclined-to-vertical surfaces such as rocks and trees.

Aerodynamic benefits of boundary layer ingestion for distributed propulsion configuration

Purpose Boundary layer ingestion (BLI) is one of the probable noteworthy features of distributed propulsion configuration (DPC). Because of BLI, strong coupling effects are generated between the aerodynamics and propulsion system of aircraft, leading to the specific lift and drag aerodynamic characteristics. This paper aims to propose a model-based comprehensive analysis method to investigate this unique aerodynamic. Design/methodology/approach To investigate this unique aerodynamics, a model-based comprehensive analysis method is proposed. This method uses a detailed mathematical model of the distributed propulsion system to provide the essential boundary conditions and guarantee the accuracy of calculation results. Then a synthetic three-dimensional computational model is developed to analyze the effects of BLI on the lift and drag aerodynamic characteristics. Findings Subsequently, detailed computational analyses are conducted at different flight states, and the regularities under various flight altitudes and velocities are revealed. Computational results demonstrate that BLI can improve the lift to drag ratio evidently and enable a great performance potentiality. Practical implications The general analysis method and useful regularities have reference value to DPC aircraft and other similar aircrafts. Originality/value This paper proposed a DPS model-based comprehensive analysis method of BLI benefit on aerodynamics for DPC aircraft, and the unique aerodynamics of this new configuration under various flight altitudes and velocities was revealed.

The use of hybrid intuitive class shape transformation curves in aerodynamic design

The inherent mathematical smoothness of intuitive class shape transformation (iCST) curves has been shown to be suitable for the design of aerodynamic shapes. However, this property means that any changes to a constraint are not local but will result in a modification to the whole curve. This poses a problem to the aerodynamic designer when different parts of the curve are required to fulfil particular design requirements. A Hybrid iCST (HiCST) parameterisation approach is proposed which allows two sections of a single aero-line curve to be decoupled, without geometric discontinuity, whilst maintaining the dimensionality of a design problem. The HiCST approach has been tested on two key aerodynamic components of an aero-engine. Firstly, a design space exploration and optimisation were carried out for an aero-engine fan cowl. A comparison of Pareto fronts showed a 3.9% reduction in the minimum achievable nacelle drag from the iCST to the HiCST parameterisation. Secondly, aero-engine intakes were designed with both the iCST and HiCST parameterisations. The HiCST intake showed improved aerodynamic performance in terms of DC60 and IPR and proved more insensitive to changes in massflow and incidence. This development of the method for an aero-engine fan cowl and intake highlights the potential aerodynamic benefit from the proposed HiCST method.

Aerodynamic Interaction Effects of wingtip-Mounted Propellers

The study presents an aerodynamic analysis of the propeller–wing interaction effects for the wingtip-mounted propeller configuration. The influence of the initial parameters of the propellers, such as the radius, the pitch angle as well as the direction of rotation on the models aerodynamic characteristics, in particular, on the wing span-efficiency factor and the induced drag was determined. In this research a computational simulation of the wingtip flow field was implemented using two different computational models with two different Reynolds numbers.Flow field simulations over computational models with different combinations of initial parameters were performed by means of the computational aerodynamic methods (the panel-vortex method of symmetric peculiarities). The simulation showed a significant positive effect on the aerodynamic characteristics of the computational models due to wingtip-vortex attenuation and swirl recovery by the propeller slipstreams. Analysis of the wing performance pointed out that the aerodynamic benefit of the wingtip-mounted propeller was due to an increase of the effective span-efficiency parameter of the wing.The induced drag coefficients and wing span-efficiency factors of the computational models for different combinations of given initial parameters, such as propellers radius and pitch angles, as well as the direction of rotation are obtained. The dependences between the given initial parameters and the studied aerodynamic characteristics of the computational models are determined. It is established that the character of these dependencies is identical for both computational models with two different Reynolds numbers. The analysis of the obtained dependencies indicates that when the propellers pitch angle φ changes, the highest efficiency zone is observed, that is characterized by the maximum value of the derivative dλef/dφ. The range of expedient change of the propellers pitch angle is determined, as a consequence.The most of the results are presented by diagrams for both computational models. The results obtained are of practical significance and will be useful for the aircraft design, performed according to the studied aerodynamic scheme.

Novel morphing wing actuator control-based Particle Swarm Optimisation

AbstractThe paper presents the design and experimental testing of the control system used in a new morphing wing application with a full-scaled portion of a real wing. The morphing actuation system uses four similar miniature brushless DC (BLDC) motors placed inside the wing, which execute a direct actuation of the flexible upper surface of the wing made from composite materials. The control system of each actuator uses three control loops (current, speed and position) characterised by five control gains. To tune the control gains, the Particle Swarm Optimisation (PSO) method is used. The application of the PSO method supposed the development of a MATLAB/Simulink® software model for the controlled actuator, which worked together with a software sub-routine implementing the PSO algorithm to find the best values for the five control gains that minimise the cost function. Once the best values of the control gains are established, the software model of the controlled actuator is numerically simulated in order to evaluate the quality of the obtained control system. Finally, the designed control system is experimentally validated in bench tests and wind-tunnel tests for all four miniature actuators integrated in the morphing wing experimental model. The wind-tunnel testing treats the system as a whole and includes, besides the evaluation of the controlled actuation system, the testing of the integrated morphing wing experimental model and the evaluation of the aerodynamic benefits brought by the morphing technology on this project. From this last perspective, the airflow on the morphing upper surface of the experimental model is monitored by using various techniques based on pressure data collection with Kulite pressure sensors or on infrared thermography camera visualisations.

Experimental study of a passive control of airfoil lift using bioinspired feather flap

Birds are known for their extraordinary agility, maneuverability, flexibility and endurance during their flight, even under some adverse flying conditions. Bird wings have been the most inspirational element, attracting the attention of researchers to reveal the underlying physical mechanism of lift production as well as to apply the results into the artificial flying vehicles. This paper presents a systematic experimental investigation on a passive flow control of a NACA0012 airfoil using real feather flap which is installed on the suction or pressure surface. The focus of the present study is to determine the major role of a real feather flap in the aerodynamic performance of a NACA0012 airfoil at small attack angles (α). The feather flap width w and its installation position xin are varied from 0.27c to 0.8c and from 0.0 to 0.2c, respectively, where xin is measured from the leading edge of the airfoil, and c is the chord length of the airfoil. Detailed particle image velocimetry (PIV) measurements are conducted to understand the origin of the aerodynamic benefits introduced by the feather flap. The flap mounted on the suction side may have a positive impact only at large α, beyond the stall. On the other hand, when mounted on the pressure side, the feather flap is proved to be beneficial to improve the aerodynamic performance of the airfoil at small α (= −4° to 8°). The lift CL and lift-to-drag ratio CL/CD are enhanced by 186% and 72%, respectively, for w = 0.53c, xin = 0.2c at α = 2°. Time-averaged and instantaneous vorticities, time-averaged streamwise velocity, and lateral velocity around the flapped airfoil weaken, decrease and increase, respectively, compared with those around the plain airfoil, which are attributed to the increased CL and CL/CD.

An experimental investigation of the aerodynamic flows created by lorries travelling in a long platoon

The concept of autonomous road vehicles has recently gained a great deal of technical respectability. Expected advantages over normal driver-controlled vehicles are through increased safety, reliability and fuel efficiency. This paper presents a novel experimental study enabling for the first time a full understanding of the aerodynamic flow development of a long vehicle platoon. Moving model experiments were carried out at the University of Birmingham Transient Aerodynamic Investigation (TRAIN) rig facility on a 1/20th scale eight lorry platoon with three constant vehicle spacings. Slipstream velocity and pressures, as well as simultaneous on-board vehicle surface pressure measurements were made. Results indicated a highly turbulent boundary layer development, with slipstream pulse peaks near the front of each lorry; similar to previous findings on flows around container freight trains. The drag coefficient of an isolated lorry was in agreement with previous studies. There are substantial reductions in aerodynamic drag for the non-leading platoon vehicles. Drag results plateaued towards a constant value within the platoon. Vehicle spacing affected drag values, with decreases of 57% observed for the closest spacing of half a vehicle length, demonstrating the aerodynamic benefits of platooning.