Numerical Investigation of the Effect of Tread Pattern on Rotating Wheel Aerodynamics (original) (raw)
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THE INTERNATIONAL JOURNAL OF COMPUTATIONAL METHODS AND EXPERIMENTAL MEASUREMENTS, 2019
In any racing competitions, the aerodynamic performances of the equipment are determinant. This is true, for example, for cars, where the geometry of the bodywork and of the wings can ensure a lower Cx coefficient and/or a higher down-force and a higher handling. In other competitions, like rowing, the aerodynamics of the hull can reduce the effort done by the athletes. In the cycle and motorcycle racing competitions, other aspects related to aerodynamics become important, such as the manoeuvrability and stability. In the present research, a numerical approach was used in order to compare different front-wheel geometries (of a racing motorbike) in terms of drag, lift and axial forces. Three different wheel designs have been compared. The first one consists in a traditional seven spokes aluminium design, the second wheel is a 6 spokes magnesium solution and the third a solid-disk wheel. Steady state as well as transient simulations was performed with OpenfOaM ® , a free open-source software. This was selected because it allows a higher flexibility with respect to any close-source commercial software. The possibility to customize the solver as well as the boundary conditions allows the analysis of the physical problem of interest. The free license allows a high parallelization of the computations. The steady-state simulations were performed by freezing the wheel position and introducing a rotating reference frame. In this way, the computational time was significantly reduced. for the transient simulations, the computational domain was split into two subdomains. The internal one is cylindrical and contains the wheel. The rotational velocity of the wheel was imposed by applying a rigid rotation to the mesh of the internal subdomain. Mesh interfaces ensures the continuity of the solution across the domains.
The aerodynamic characteristics of an exposed racing car wheel
2004
The aerodynamics of an exposed racing car wheel have been analysed using experimental and computational (CFD) techniques. A 40% full-scale pneumatic tyre/wheel assembly was used for the experimental investigations and the exact geometry was replicated in the CFD model. The wheel had an aspect ratio of 0.53 and the tests were conducted at a Reynolds number, based on the wheel diameter, of 2.5 x 10 5. Both rotating and stationary wheels were tested with moving and fixed groundplanes, respectively. The experiments were conducted using new and existing methods of data acquisition and analysis. A non-intrusive radio telemetry system was successfully designed and developed that enabled surface static pressure data to be transmitted from a rotating wheel to a local PC. Other experimental techniques included the use of particle image velocimetry (PIV) and a pneumatic non-embedded five-hole pressure probe to investigate the flow-field about the wheel. The early flmv separation, which is a characteristic of the rotating wheel, was observed in the surface static pressure distributions allCl PIV velocity fields. Lift and drag forces were found to decrease as a result of wheel rotation, which agreed with the work of other investigators, and the mechanisms responsible for such force reductions are postulated. The wake structures were investigated and showed weaker streamwise vorticity for the rotating wheel compared to the stationary wheel. lll The most important and remarkable aspect of this work was the experimental observation and subsequent CFD prediction of the rear jetting flow mechanism whose existence was previously theoretically predicted by another investigator. The PIV velocity fields clearly show the rear jetting phenomenon and this is further corroborated by a negative pressure peak in the surface pressure distributions on the wheel centreline. The effects the rear jetting phenomenon has on the wake mechanics, and hence the forces acting on the rotating \vheeL are postulated. lV Declaration The work in this thesis is based on research carried out at the Centre for Automotive Research, School of Engineering, University of Durham, England. No part of this thesis has been submitted elsewhere for any other degree or qualification and it is all my own work unless referenced to the contrary in the text.
Fluid Mechanics: Open Access, 2017
A model of Formula One racing car rotating dry wheel in contact with the ground is studied using a computational approach as a validation case. This validation case focuses on the computed surface pressure around the wheel's center line. This computed result is compared to an experimental one obtained from the available literature work and it showed good agreement. Another case study is considered with replacing the dry wheel model with another wetcondition wheel model. The wet-condition wheel's work is mainly concentrated on the developed aerodynamic forces especially the wheel moment values. This moment is translated to an expression of resistive torque developed by the air stream on the wheel and computed in each case study. In addition, general schematic pictures of the flow behavior around the wet wheel are presented. Figure 1: Schematic diagram of a rotating wheel moving against the flow direction.
WIT transactions on engineering sciences, 2018
In motorcycle competitions, aerodynamics play a fundamental role. In order to improve the performance of racing motorbikes, different front-wheel geometries have been studied by means of numerical CFD simulations. Different lean angles were analysed for each geometry and the air motionfield were calculated. The considered geometries range from standard spoked design to solid wheels.. ® source free software OpenFOAM-state and dynamic simulations were run using the open-steady Both This open-source code was selected because, like all the computer programs of this type, it allows a higher flexibility with respect to any close-source commercial software, allowing a customization of the code by implementing specific models for the analysis of the physical problem of interest and also, at the same time, a higher parallelization of the computations. Steady-state simulations were performed using a rotating reference frame (MRF) while, for the transients, a partially-rotating mesh was adopted, thus taking advantage of the internal sliding interfaces (AMI). Drag, lift and force-moments have been calculated with the aim of examining the stability and manoeuvrability of the different configurations.
CFD investigation on wheel rotation modelling
Journal of Wind Engineering and Industrial Aerodynamics, 2018
• Moving Reference Frame-grooves (MRFg) approach for modelling tyre rotation is presented. • It is validated on a freely rotating isolated wheel against the sliding mesh approach. • The prediction of tyre pattern modifications using MRFg shows good agreement with experimental measurements on a full scale vehicle.
Investigation of Wheel Aerodynamic Resistance of Passenger Cars
SAE International journal of passenger cars, 2014
Around the world, constantly growing fuel prices and increasing environmental requirements for road vehicle emissions make it important for vehicle manufactures to address the problem of reducing the fuel consumption. The latter can be achieved by different means and one of the ways to do so is to improve vehicle aerodynamic design. This is one of the most effective ways since at speeds above 60-70 km/h aerodynamic drag force dominates all other resistance forces acting on a vehicle [1]. There are a number of regions of the vehicle that are known to be of particular importance for aerodynamic drag reduction. In this study the area investigated is wheels and wheel-houses. This region accounts for around 30% of vehicle aerodynamic drag [2], [3], [4], [5], [6] moreover there are also other effects in the area that are responsible for additional resistance that are usually left unaccounted for. There is an aerodynamic resistance moment that acts on parts that are rotating in air, in this case the wheels. This moment is sometimes referred to as "ventilation drag" or "ventilation torque" [7]. This aerodynamic resistance moment is rather difficult to measure in the wind tunnel since it is hard to separate it from the rolling resistance. There are different methods described in the literature and all of them require a set of simplifications and geometrical modifications in order for the measurement to be made [8], [9]. CFD on the other hand offers an easier way to predict the ventilation torque since there is no rolling resistance calculation and the deformed shape of the tyre can be used. Of course, one should not forget that CFD has its own limitations and uncertainties, depending on the simulation method and boundary conditions used.
A Numerical Study on the Influences of Non-Pneumatic Tyre Shape on the Wheel Aerodynamics
International Journal for Research in Applied Science & Engineering Technology (IJRASET), 2022
In the present work, the aerodynamic characteristics of two different tyre shapes, Slick Tyre (ST) and Non-Pneumatic Tyre (NPT), fitted to a rotating wheel, has been investigated using a CFD approach. The ST wheel has been primarily utilized to examine the adopted numerical model's validity. The ST wheel pressure coefficient (Cp) profile at its central plane (XY) has directly compared with the robust experimental data experienced from the literature. Further assessments on the computationally obtained outcomes such as drag coefficient, separation and stagnation angular locations are performed. Both wheel cases are compared concerning their aerodynamic coefficients and the flow characteristics around the wheel. Besides, for the NPT wheel case, a shape-optimization study changes the wheel side profile's spokes angle (α) is conducted. The dynamic action of wheel rotation is modelled using the Moving Reference Frame (MRF) technique, and the RNG k-is utilized as the adopted turbulence model for Averaged Reynolds Navier Stokes equations (RANS). All cases run at 30 m/s upstream velocity to be within the fully developed flow regime (supercritical regime). That is equivalent to 6.8 ×105 Reynolds number based on the wheel diameter as the characteristic length. In general, the overall obtained results give a satisfactory agreement to those measured experimentally. In conclusion, The NPT wheel, compared to the ST wheel, has a dramatic increase in drag force by approximately 31%, while a slightly raised lift force is obtained. The minimized spoke angle came with a beneficial drag reduction, while the applied resistive moment remained relatively high.
Tyre aerodynamics of passenger vehicles ERIK JOSEFSSON
To decelerate climate change and limit global warming, there is a need for reducing the environmental impact of vehicles, which can be achieved by increasing their energy efficiency. For a passenger vehicle, one of the largest resistive forces is aerodynamic drag. A significant contribution to the total drag originates from the wheels, making the understanding of their flows essential for creating efficient vehicles. However, wheel flows are complex and challenging to comprehend due to factors such as the rotation, high level of geometrical details and tyre deformation, all of which have been shown to affect drag. For a better understanding, numerical simulations can be used. However, to determine the accuracy of the simulations, these must be correlated to experiments. In this work, both the correlation between experiments and simulations as well as the flow field effect of varying the tyre tread pattern are investigated. Wind tunnel tests using a full-scale DrivAer model have been performed for four tyre tread patterns and two rim designs. First, the numerical simulations are compared to the experiments, where the interference of the wind tunnel on wheel flows is investigated. By performing simulations using both an open road domain and a domain containing a detailed model of the wind tunnel, it was found that the inclusion of the wind tunnel improves predictions of both absolute drag values as well as the drag deltas between configurations. Then, the effects of the different tyre tread patterns are analysed in more detail. Results showed that adding rain grooves typically reduces drag compared to a slick tyre, whereas the effect of lateral grooves is dependent on the rim configuration. In addition to the drag, lift variations were considered. There, the largest effects were obtained at the front axle and, in general, the lift is reduced by the rain grooves and increased by the lateral grooves, most clearly for the closed rim. Also, the influence of the parasitic lift forces acting on the wheel drive units was demonstrated.
Comparison of the Aerodynamic Performance of Four Racing Bicycle Wheels by Means of CFD Calculations
Procedia Engineering, 2015
Aerodynamic drag is the main source of losses in cycling so improving the bicycle aerodynamic is a fundamental key factor to increase the performance. The aim of this work is to assess the capability of CFD RANS simulations to predict the aerodynamic performance of modern racing bicycle wheels. This paper describes the design and development of a numerical model for the resolution of the airflow field surrounding four different racing wheels. Drag and side forces are resolved and compare to experimental data (and other simulation results) taken from the literature.
The impact of the wheel's rim on the aerodynamics of passenger vehicles
Proceedings of the 4th International Congress of Automotive and Transport Engineering (AMMA 2018), 2018
The purpose of this Paper is to investigate the amount of aerodynamic energy consumed by the wheels and the impact on the overall drag of a passenger vehicle. The wheel parts (rim, tire and cap) were modeled and aerodynamically analyzed using a finite element Computational Fluid Dynamics (CFD) software. To highlight the wheel's potential in the overall aerodynamic drag the rim's useful area is modified by decreasing the porosity in a progressive manner. The CFD simulation results are presented using Iso-Lambda and Iso-Cpi, parameters together with coefficients like total pressure deficit, skin friction and vorticity magnitude. An important conclusion of the study was the fact that by blocking the flow thru the rim, an aerodynamic potential can be achieved. Careful design of wheels may lead to significant reduction in drag and improvements of vehicle drag coefficient. This would generate lower fuel consumption and important CO 2 reduction, leading to a more environmentally friendly vehicle. The work will be continued by extending the analysis towards commercial vehicles like heavy trucks that have a significant number of wheels and are more exposed to air flow. Improvements in this area may lead to a significant reduction in fuel consumption. It should be pointed out that CFD is a good method for developing and optimizing solutions but has to be reinforced by physical tests performed on road or in wind tunnels.