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A KIA Soul was instrumented to measure the relative velocity (magnitude and yaw angle) at the front of the vehicle and in-cabin sound at a location close to the side glass near the A-pillar vortex impingement. Tests were conducted at a proving ground under a range of conditions from low wind conditions (~3 m/s) to moderate (7-8 m/s) wind speeds. For any given set of atmospheric conditions the velocity and sound data at any given position on the proving ground were noted to be very repeatable, indicating that the local wakes dominated the "turbulent" velocity field. Testing was also conducted in an aeroacoustic wind tunnel in smooth flow and with a number of novel turbulence generating methods. The resulting sounds were analyzed to study the modulation at frequencies likely to result in fluctuation strength type noise.

Wind tunnels provide a convenient, repeatable method of assessing vehicle engine cooling, yet important draw-backs are the lack of a moving ground and rotating wheels, blockage constraints and, in some tunnels, the inability to simulate ambient temperatures. A series of on-road and wind-tunnel experiments has been conducted to validate a process for evaluating vehicle cooling system performance in a high blockage aerodynamic wind tunnel with a fixed ground simulation. Airflow through the vehicle front air intake was measured via a series of pressure taps and the wind-tunnel velocity was adjusted to match the corresponding pressures found during the road tests. In order to cope with the inability to simulate ambient temperatures, the technique of Specific Dissipation (SD) was used (which has previously been shown to overcome this problem).

A pressure-based technique has been developed for the purpose of radiator cooling airflow measurement. The technique was effectively utilised to quantify the local time-averaged air velocity through radiator cores in a small wind tunnel. The pressure difference indicated by the technique was found to be a function of the normal component of the air velocity. This paper describes the development and use of the technique which is compact, robust and non-intrusive. By applying this technique, the airflow distribution across the radiator face has been measured for a complete vehicle in an aerodynamic wind tunnel and in an environmental chamber. Results are compared for the different test environments. The influence of airflow distribution on the Specific Dissipation (a parameter used for evaluating radiator cooling performance) is examined and results for propeller-based methods and pressure-based methods are compared.

Two domains of aerodynamic testing of vehicles are identified; one representing typical driving conditions, where the average atmospheric wind is less than about 10 m/s; the other representing driving under extreme wind conditions for safety considerations. The first domain influences fuel consumption and other parameters related to driving comfort (e.g. aerodynamic noise, transient forces and transient moments experienced during general driving), whereas the second needs to be assessed for stability considerations. The purpose of this paper is to document turbulence commonly encountered by vehicles moving at highway speeds under typical driving conditions. In order to document this, data obtained from hot-wire anemometers fitted above a moving vehicle are presented. It was found that longitudinal and lateral turbulence intensities ranged between 2.5% to 5% and 2.0% to 10% respectively.

This paper summarises the effects of turbulence on the aerodynamics of road vehicles, including effects on forces and aero-acoustics. Data are presented showing that a different design of some vehicles may result when turbulent flow is employed. Methods for generating turbulence, focusing on physical testing in full-size wind tunnels, are discussed. The paper is Part Two of a review of turbulence and road vehicles. Part One (Cooper and Watkins, 2007) summarised the sources and nature of the turbulence experienced by surface vehicles.

This paper is the first of two papers that address the simulation and effects of turbulence on surface vehicle aerodynamics. This, the first paper, focuses on the characteristics of the turbulent flow field encountered by a road vehicle. The natural wind environment is usually unsteady but is almost universally replaced by a smooth flow in both wind tunnel and computational domains. In this paper, the characteristics of turbulence in the relative-velocity co-ordinate system of a moving ground vehicle are reviewed, drawing on work from Wind Engineering experience. Data are provided on typical turbulence levels, probability density functions and velocity spectra to which vehicles are exposed. The focus is on atmospheric turbulence, however the transient flow field from the wakes of other road vehicles and roadside objects are also considered.

In this study, flow measurements were taken in the wake of a 3/10 scale model of a passenger vehicle using a high frequency, four-hole pressure probe (Dynamic Cobra Probe). The purposes of this study were to further the understanding of the wake development of a passenger vehicle in isolation (in order to provide representative input boundary conditions for CFD and EFD simulations of vehicles traveling in traffic) and to also investigate the wake properties under the influence of upstream turbulence (i.e. with a turbulence generator upstream). The results from several downstream planes are presented and include the time-averaged contour plots of turbulence intensity, velocity deficit and vorticity and cross-flow velocity fields. The presence of increased levels of upstream turbulence mostly affected the upper region of the vehicle wake. In this region, the A-pillar vortex was reduced in size and strength, while the C-pillar vortex had increased in both respects.

Vortices formed around the A-pillar region dictates the pressure distribution on the side panels of a passenger vehicle and also can lead to aerodynamic noise generation. This paper compares the suitability of various turbulence models in simulating the flow behind a vehicle A-pillar region under laboratory operating conditions. Commercial software's (FLUENT and SWIFT) were used to compare the performance of various turbulence models. In FLUENT, a simplified vehicle model with slanted A-pillar geometry was generated using GAMBIT and in SWIFT, the simplified vehicle model was generated using Fame Hybrid. Computational Fluid Dynamics (CFD) simulations were carried out using FLUENT under steady state conditions using various turbulence models (k-, k- Realize, k- RNG, k- and Spalart Allamaras). In SWIFT, k-, A-RSM and HTM2 turbulence models were used for the steady state simulations. Investigations were carried out at velocities of 60, 100 and 140km/h and at 0-degree yaw angle.

Engine cooling systems are usually designed to meet two rare and extreme conditions; driving at maximum speed and driving up a specified gradient at full throttle while towing a trailer of maximum permitted mass. At all other times, the cooling system operates below its maximum capacity with an incurred drag penalty. In this work it is being suggested to design the system using the existing methods and then vary the area of the cooling air intakes to permit the minimum amount of cooling air for adequate engine cooling. A full-size, Australian made Ford Falcon car (a large modern 'family' saloon) was tested at the Monash University Aero-acoustic Wind Tunnel. The cooling air intakes of the vehicle were shielded progressively until fully blocked. Four different possibilities of shielding were investigated with the aim of determining the variation of drag reduction with the shielding method employed.

The function of a rear view mirror is a determining factor in its shape - resulting in a flat rear mirrored face. The resulting bluff body generates unsteady base pressures which generate unsteady forces, leading to movement of the mirror surface and potential image blurring. The objective of this paper was to experimentally determine the fluctuating base pressure on a standard and modified mirror. Half a full-size vehicle was utilised, fixed to the side wall of a wind tunnel. A dynamically responsive multi channel pressure system was used to record the pressures. The modification to the mirror consisted of a series of extensions to the mirror rim, to see if this method would attenuate the fluctuating base pressures. It was found that increasing the length of the extension changed the pressure pattern across the face, and the over all magnitude of the fluctuations reduced with increasing length of extension. It was recommended to further the work via phase measurements.

Water tow-tank tests were performed for the Ahmed model at a range of “high-drag” backlight angles at Reynolds numbers of up to 1.3 × 105. Dye was injected just upstream of the c-pillars and visualizations were recorded with a submerged CCD camera moving with the model. Discrete sub-vortices were found to be shed periodically along the length of the c-pillar at Strouhal numbers (based on square root of frontal area) between 8 and 12. These sub-vortices were observed to undergo vortex pairing and then to roll up into the familiar c-pillar vortices. These observations are consistent with previously published observations for delta wings. Wind tunnel tests were performed in order to provide Reynolds numbers of up to 1.6 × 106. These revealed some spectral features which could be due to the shedding and pairing of discrete vortices from the c-pillar but the evidence was much less conclusive than at low Reynolds number.

This paper presents an experimental comparison between two factors used for evaluating engine cooling in motor cars, Air-to-Boil (ATB) and Specific Dissipation (SD). It is shown that Specific Dissipation can increase the experimental productivity for evaluating cooling system by giving more reliable results than Air-to-Boil. Results from road tests and experiments conducted in three different wind tunnels are presented. All experimental results indicate that Specific Dissipation gives more repeatable results and can be used in both stable and slowly-varying test conditions.

Green racing technologies are described with a focus on two categories of sustainable racing; solar racing, including an overview of the World Solar Challenge (WSC) held in Australia, and Formula SAE-E (Society of Automotive Engineers-Electric). Both types of cars utilise sustainably generated electricity, the former uses solar arrays integrated into the vehicle body and the latter electricity generated from a renewable energy park and stored onboard in lithium polymer cells. The design considerations of both vehicles are contrasted with a focus on energy usage minimisation. The Aurora team (which has broken many records, including winning the World Solar Challenge across Australia) is used to illustrate the importance of minimizing the power requirements by having a low aerodynamic drag, frontal area, a highly efficient powertrain and low rolling resistance. To illustrate the technology behind FSAE Electric the R10E car from RMIT is described.

Separated flow is the main generator of aerodynamic noise in passenger vehicles. The flow around the A-pillar is central to the wind noise as many modern vehicles still have high fluctuating pressures due to flow separations in this region. Current production vehicle geometry is restricted due to the amount of three dimensionality possible in laminated windscreen glass (and door opening etc). New materials (e.g., polycarbonate) offer the possibility of more streamlined shapes which allow less or no flow separation. Therefore, a series of experimental investigations have been conducted to study the effects of the A-pillar and windshield geometry and yaw angles on the local flow and noise using a group of idealised road vehicle models. Surface mean and fluctuating pressures were measured on the side window in the A-pillar regions of all models at different Reynolds numbers and yaw angles.

For high-speed driving conditions, the air flow around a car creates wind noise that is transmitted into the cabin, which can dominate other noises. If an atmospheric wind is present, it will create a turbulent cross wind, which not only changes the air flow velocity and direction as experienced by the vehicle, but leads to continuously varying wind noise, as heard inside the car. The purpose of this paper is to look at how the on-road wind environment affects wind noise, and to evaluate the need to simulate real on-road conditions such as fluctuating yaw angles and velocities in vehicle wind tunnels.

The sensitivity of cross-winds in reducing the engine cooling ability in motor cars is highlighted. Tests on three different motor cars were conducted in the Monash University full-scale wind tunnel at different yaw angles under different wind velocities. The test results show that motor car engine cooling capability decreases with an increase in yaw angles. For a wind velocity of 14 m/s, a 13% decrease in radiator cooling capability was found at a yaw angle of 20° compared to a zero yaw angle. The effect of yaw angles on the engine cooling also depends on the motor car front-end configuration, but this becomes less important with increasing wind velocity. The effect of cross-winds on car engine cooling was also evaluated by on-road engine cooling tests. A convenient experimental method to measure wind velocity and yaw angle relative to a moving car is also described.

A small-scale aeroacoustic wind tunnel has been designed and built to investigate tonal cavity noise in the frequency range applicable to passenger vehicles; 1 - 16 kHz. The tunnel is required for testing associated with an investigation into tonal cavity noise on passenger-vehicle wing mirrors. It was designed to operate in the low subsonic speed range (60 - 140 km/h) with a nozzle exit cross-sectional area of 0.02 m2 and a 4:1 aspect ratio. The design was intended to achieve a smooth, quiet flow facility. In this paper the design process is summarised and the factors leading to particular design decisions are detailed. An initial evaluation has shown that only minimal changes are required to achieve very smooth, even flow at the nozzle exit at all required test speeds. The acoustic design needs further work as there is a significant amount of flow noise at the nozzle exit between 1 and 13 kHz.

The design of the exterior body shape and structure of a solar-electric sports car which competed in the 2019 Bridgestone World Solar Challenge (BWSC) Cruiser Class is explored. A low-drag and low-lift aerodynamic shape with a coefficient of lift near zero and drag area of 0.16 m2 is developed as a primary focus around the constraints of a solar array, occupant space, and aesthetics. The maximally sized 5 m2 rearward tilted solar array capable of generating an expected event average power of 885 W influences the size and shape of the roof. The space for which two occupants are seated in the vehicle is developed to achieve a reclined occupant position that minimizes the vehicle frontal area. A carbon fiber-reinforced polymer (CFRP) and foam composite sandwich monocoque make up the structure of the vehicle at a mass of 59.53 kg. Factors of practicality and their compromises are also explored.

A morphing ram-air intake, capable of deploying from a flat, closed surface to an open state is investigated. Via geometric and material optimisation, an origami-inspired folding structure is developed to exhibit bi-stable behaviour. An iterative finite element design process was conducted, noting the effects of the critical design properties of geometry, bending stiffness and material strain limits on bi-stability and the achievable geometric shape change. As a first step, thermoplastic polyurethane elastomer materials are proposed while increased stiffness by fibre reinforcements are considered at a later design stage and evaluated under aerodynamic loading. The bi-stable structure is capable of remaining in either open or closed stable configurations without sustained actuation. The ability to retract the intake when not required has the potential to reduce drag. It is envisioned that such a concept may be readily adopted within automotive and aerospace applications.

Noise in passenger cars is dependent upon the fluctuating surface pressures on the exterior, particularly in the region of the A-pillar and the front side glass. The purpose of this work was to investigate whether the fluctuating surface pressure profile obtained in a typical full-size automotive wind tunnel can be duplicated within the limitations of high blockage tunnel. A further aim was to compare the data from both wind tunnels with road data. In order to investigate the spatial resolution of fluctuating pressures on the side window of a car, flush mounted microphones were used as fluctuating pressure transducers. Mean pressure coefficients were obtained from flush-mounted pressure taps in the same locations. Frequency based (spectral) analysis was carried out on the fluctuating pressure signal. It was found that the regions of flow separation coincide with the regions of maximum fluctuating pressure.