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This investigation studied numerically the aerodynamical effects of different modifications in a model of a common sedan. Four car modifications as spoiler, wing profile spoiler, standard diffuser and curved diffuser and their combinations were reported. Using a three-dimensional sedan model created with Computer-Aided Design software, the modifications are applied and assessed their influence on aerodynamics at speeds ranging from 60 to 120 km/h. The spoiler, wing spoiler, standard diffuser and curved diffuser reducing the lift forces experienced by the vehicle. Three cases, spoiler, wing spoiler, and curved diffuser increase the drag forces Combining a curved diffuser and a spoiler significantly decreases lift forces by an average of 77.8%, albeit with a 15.3% increase in drag forces, by 120 km/h The synergy of a curved diffuser and a wing spoiler achieves a substantial 63.3% reduction of net vertical forces, with only a 7.9% increase in drag forces, by 120 km/h, offering improved control with lesser energy consumption in comparison to other combinations. Results show that modifications, greatly influence airflow interaction, with effects varying by speed. Importantly, the impact of using two modifications is not a simple sum of their individual effects; and it must be assessed thoughtfully alongside airflow alterations. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Chongqing University of Technology (Natural Science) is the property of Chongqing University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Based on the LES model, the compressible transient CFD simulation combined with the acoustic finite element method optimizes the effect of the rearview mirror and side window glass on in-vehicle noise from the perspective of sound source and transmission. The primary and secondary orders of the influence of different mirror shape and side window glass geometric parameters on the noise in the car were obtained through the design and analysis of orthogonal experiments, and the results of the flow and sound fields were compared. The following results are presented: acoustic source noise reduction from the rearview mirror is mainly affected by acoustic pressure excitation. The proportion of the mirror body of the rearview mirror, the angle of the lower edge, and the length of the mirror column affect the noise in the car in turn. The noise reduction control with PVB laminated glass as the transmission path is mainly limited by the low frequency turbulent pressure excitation. The inner and outer thicknesses of PVB laminated glass have different influences on the noise in the car under different frequency bands, and the results in the full frequency band are mainly affected by the low frequency band. [ABSTRACT FROM AUTHOR]

The aerodynamic understanding of the automobile has become very significant for the automotive industry to decrease fuel consumption. The aerodynamics of vehicles influences fuel consumption, stability, cooling, safety, and environmental pollution. As the shape of the vehicle plays an important role in automobile aerodynamics, it is desired to optimize it for better performance. For optimization, the simulations are run for the varying parameters of system design. Automobile aerodynamics depends on a large number of parameters. Even if some key parameters are selected, still there are very large numbers of aerodynamic parameters that need to be considered for which a smart optimization tool is required. A Fluent Adjoint solver has been used for aerodynamics optimization in this study. This tool directly identifies the most sensitive parameters and modifies the geometry to achieve desired changes in the observables, i.e., drag and lift. Additionally, it results in optimal design in a minimum number of simulations. In the current study, the aerodynamic investigation was performed for a commercial car, including shape optimization for reducing drag and increasing its stability (negative lift). The drag and lift coefficients of the car were computed using the ANSYS Fluent. After the conventional flow simulation, an Adjoint solver was used to determine its shape sensitivity concerning observables i.e., drag and lift. Based on that sensitivity data, the shape was modified using a mesh morphing operation. The modified car was again analyzed and a significant improvement was observed in its aerodynamics. There was a decrease of 0.02, about 6% in the drag coefficient, and an increase of 0.05, about 24% in the negative lift coefficient. [ABSTRACT FROM AUTHOR]

Aerodynamic characteristics are of great significance to the fuel economy and handling the stability of electric vehicles. The battery pack of electric vehicles has a huge structure and is usually arranged in the chassis area of the vehicle, which inevitably occupies the space at the bottom of the vehicle and affects the aerodynamic characteristics of the vehicle. To study the effect of the power battery pack installed in the chassis on the aerodynamics characteristics of the electric vehicle, the Computational Fluid Dynamics (CFD) method is used to study the flow and pressure fields of the SAE (Society of Automotive Engineers) hierarchical car model with battery packs mounted on chassis. The influence of the structure parameters of the battery pack on the automobile's aerodynamics are also analyzed in detail. Based on the simulation results, it can be seen that the battery pack installed on the chassis has a great impact on the flow and pressure field at the bottom and tail of the vehicle, causing the drag coefficient and lift coefficient to increase. The structural parameters of the battery pack have contradictory effects on the drag and lift coefficients. As the length of the battery pack increases, the drag coefficient decreases, and the lift coefficient increases. As the battery pack width and height increase, the drag coefficient increases, and the lift coefficient decreases. The research results provide a reference for the optimization of the aerodynamic characteristics of electric vehicles with battery packs mounted on chassis. [ABSTRACT FROM AUTHOR]

The purpose of this study was to investigate whether small plates covering the roof and the hood of the DrivAer estate vehicle can be used as airbrakes and increase its drag as well as the downforce. The presented results were obtained with the use of the commercial computational fluid dynamics software ANSYS® Fluent. The main findings of the article are that the aerodynamic devices such as flaps covering surfaces of the vehicle can have a significant impact on drag increase and can be used not only to make the design of the car more striking but also beneficial when utilized as a part of an active aerodynamic setup.

In the case of road cars, road safety is the primary factor. The geometry of high-speed road cars has no regulatory restrictions. In addition to the high engine power and effective shape, they can use various types of additional movable aerodynamic elements to adjust their aerodynamic characteristics to the road conditions. Based on the geometry of a two-seater prototype of such a vehicle, a numerical analysis of the influence of a number of additional movable aerodynamic elements on its aerodynamic characteristics was performed. Several of them were installed on the prototype. An electronic system recording a number of motion parameters of the entire car body and some of its movable elements installed on the body was designed and built. The system has been adapted to program the motion of additional aerodynamic elements according to the set algorithms of their activation, temporarily changing the aerodynamic characteristics of the car. An experimental study of the effect of changes in the aerodynamic characteristics of the prototype on its dynamic properties during a drive through a test road section was carried out. It was shown to what extent an average driver can increase the safe speed of the curve of the road using the possibilities of moving aerodynamic elements installed on it.

In time attack races, aerodynamics plays a vital role in achieving short track times. These races are characterized by frequent braking and acceleration supported by aerodynamic downforce. Usually, typical cars are modified for these races by amateurs. Adjusting the aerodynamic solutions to work with bodies developed for other flow conditions is difficult. This paper presents the results of a numerical analysis of the effects of installing a straight wing in front of or above the body on the modified vehicle system’s aerodynamic characteristics, particularly on the front wheels’ aerodynamic downforce values. The paper presents the methodology and results of calculations of the aerodynamic characteristics of a car with an additional wing placed in various positions in relation to the body. The numerical results are presented (Cd, Cl, Cm, Clf, Clr), as well as exemplary pressure distributions, pathlines, and visualizations of vortex structures. Strong interactions between the wing operation and body streamline structure are shown. An interesting and unexpected result of the analysis is that the possibility of obtaining aerodynamic downforce of the front wheels is identified, without an increase in aerodynamic drag, by means of a wing placed in a proper position in front of the body. A successful attempt to balance the additional downforce coming from the front wing on the front axle is made using a larger spoiler. However, for large angles of attack, periodically unsteady flow is captured with frequency oscillations of ca. 6–12 Hz at a car speed of 40 m/s, which may interfere with the sports car’s natural suspension frequency.

Summary: Interaction between solid particles and fluid is of fundamental interest to scientists and engineers in many different applications—cardiopulmonary flows, aircraft and automobile aerodynamics, and wind loading on buildings to name a few. In geomechanics, particle shape significantly affects both particle‐particle and particle‐fluid interaction. Herein, we present a generalized method for modeling the interaction of arbitrarily shaped polyhedral particles and particle assemblages with fluid using a coupled discrete element method (DEM) and lattice Boltzmann method (LBM) formulation. The coupling between DEM and LBM is achieved through a new algorithm based on a volume‐fraction approach to consider three‐dimensional convex polyhedral particles moving through fluid. The algorithm establishes the interaction using linear programming and simplex integration and is validated against experimental data. This approach to modeling the interaction between complex polyhedral particles and fluid is shown to be accurate for directly simulating hydrodynamic forces on the particles. [ABSTRACT FROM AUTHOR]

Highlights • Wind tunnel and CFD data of an active aerodynamic device for a sports car. • Flow control around a rear wing with the use of a small plate. • A significant change of downforce with the use of a small aerodynamic element. Abstract In this paper, experimental and numerical results are presented on an active car wing with a moving spoiler placed beneath it. It was shown that movement of a small element, i.e., the spoiler, can result in a significant change of downforce generated by the car body, equivalent to changing the rear wing's angle of attack by several degrees. A 1:2.5 scale car model, equipped with several moving surfaces, was tested in a wind tunnel to establish the aerodynamic coefficients. During wind tunnel tests, all force components were measured for various wing and spoiler configurations. Visualization techniques such as oil and mini-tufts were used. Numerical simulations of wind tunnel configurations were validated with the use of wind tunnel test data. Different turbulence models were considered and a good accuracy with the wind tunnel results was achieved. Graphical abstract Image, graphical abstract [ABSTRACT FROM AUTHOR]

The ground-effect diffuser has become a major aerodynamic device on open-wheel racing and sports cars. Accordingly, it is widely considered to be indispensable to their aerodynamic performance, largely due to its significant downforce contribution. However, the physics and characteristics that determine how it generates downforce and its application in the auto racing industry require an in-depth analysis to develop an understanding. Furthermore, research that could generate further performance improvement of the diffuser has not been defined and presented. For these reasons, this review attempts to create a systematic understanding of the physics that influence the performance of the ground-effect diffuser. As a means of doing this, the review introduces research data and observations from various relevant studies on this subject. It then investigates advanced diffuser concepts mainly drawn from the race car industry and also proposes a further research direction that would advance the aerodynamic performance of the diffuser. It is concluded that although the diffuser will continue to be paramount in the aerodynamic performance of racing cars, research is needed to identify means to further enhance its performance. [ABSTRACT FROM AUTHOR]

In this study, the effects of grilles in a vehicle on the aerodynamic drag coefficient and energy loss have been investigated. For this purpose, grilles have been placed horizontally to the front of the vehicle. Firstly, the aerodynamic drag coefficient and aerodynamic energy loss of the vehicle model without grilles have been determined numerically. Then, the aerodynamic loss coefficient and the aerodynamic energy loss of the vehicle model with grilles have been determined. Thus, the effect of the grilles placed in the front of vehicle on aerodynamic resistance and energy loss is compared to the vehicle model without grilles. For all estimates, the vehicle models have been modeled in SolidWorks software. ANSYS-Fluent software has been used for numerical analysis for the modeled vehicles. It has been determined that the grilles placed in the front of vehicle increased the aerodynamic drag coefficient of the vehicle and thus the aerodynamic energy loss of the vehicle increased. Thus, it has been shown that it is possible to reduce a certain extent the additional aerodynamic losses in the vehicle by approaching the grilles designs closer to the vehicle model without grilles. [ABSTRACT FROM AUTHOR]

Race car performance is strongly affected by aerodynamics. Due to downforce generated by the vehicle floor (i.e. diffuser), vehicle ride heights are key parameters to improve performance, and the coupling of aerodynamics and suspension is one of the key points of race car setting. This work focuses on the suspension and aerodynamic coupling from the vertical dynamics point of view. Besides road holding performance, for race cars, aerodynamic performance and stability are major factors. Downforce decreases laptime (the main performance target) but pitch instability is a non-desired effect that can happen in high downforce race cars. A new vertical dynamic performance index is proposed through the use of simulation to improve aerodynamic performance and understand the pitch instability phenomenon. This new index uses all relevant vehicle nonlinearities related to vertical dynamics and can handle a specific track profile and vehicle speed range, allowing the analysis be conducted according to a circuit specification. A previously validated Formula 3 car model was used as an example. [ABSTRACT FROM AUTHOR]

Abstract: We consider an autonomous vehicle platoon system consisting of N+1 vehicles in the presence of modeling uncertainty. The uncertainty may be due to parameter variations, aerodynamics, external disturbances, etc., which is nonlinear and time‐varying. Subject to the collision avoidance consideration, the original state is one‐sided restricted. To resolve this restriction, we propose a state transformation to convert the bounded state into a globally unbounded state. Furthermore, motivated by the properties of artificial swarm systems, we incorporate the swarm system performance into the platoon system by treating it as a d'Alembert's constraint. By the Udwadia and Kalaba's approach, we obtain the analytic (closed‐form) expression of the constraint force. Based on this, a class of robust controls for each vehicle (except the leading vehicle) is proposed to drive the platoon system to follow the ideal swarm model. Four major system performances are accomplished: (i) compact vehicle formation, (ii) collision avoidance, (iii) stable platoon system formation, (iv) global behavior. [ABSTRACT FROM AUTHOR]

Current development of modern vehicles reqidres rigorous aerodynamic study due to the complexity of the flow field around a car which is influenced by geometric design of vehicles. That makes research on the aerodynamic drag force on vehicles very important. This study aimed to analyze the effect of active flow control by suction and variations on front geometry towards the reduction of aerodynamic drag as well as pressure coefficients on vehicle models. The research was conducted in computational and experimental approaches. Frontal slant angle variations (6) of 25 ° 30 °and 35° were applied in the study. Computational approach used k-epsilon standard turbulence model. Upstream and suction velocity values used were 16.7 m/sand 0.5 m/s, respectively. Load cells were used in the experimental approach to validate the reduction of aerodynamic drag obtained from computational approach. Results indicate that active flow control by suction and variations on front geometry give significant impact to the increasing on pressure coefficients and the reduction of aerodynamic drag on vehicle models. While the largest increasing on pressure coefficients occurred on the vehicle model with 9=35° at 26.50%, the largest reduction of aerodynamic drag occurred on the same model with the value of 14.74 for computational approach and 13.57 for experimental approach, while the reductions of aerodynamic drag coefficients of the two approaches differ about 1.17%. [ABSTRACT FROM AUTHOR]

This paper describes the effect of different testing parameters (configuration of infrastructure and truck position on road) on truck aerodynamic coefficients under cross wind conditions, by means of a numerical approach known as Large Eddy Simulation (LES). In order to estimate the air flow behaviour around both the infrastructure and the truck, the filtered continuity and momentum equations along with the Smagorinsky-Lilly model were solved. A solution for these non-linear equations was approached through the finite volume method (FVM) and using temporal and spatial discretization schemes. As for the results, the aerodynamic coefficients acting on the truck model exhibited nearly constant values regardless of the Reynolds number. The flat ground is the infrastructure where the rollover coefficient acting on the truck model showed lowest values under cross wind conditions (yaw angle of 90°), while the worst infrastructure studied for vehicle stability was an embankment with downward-slope on the leeward side. The position of the truck on the road and the value of embankment slope angle that minimizes the rollover coefficient were determined by successfully applying the Response Surface Methodology. [ABSTRACT FROM AUTHOR]

In order to improve the limitation of steady-state automobile aerodynamic lift characteristics in finite volume method, the Lattice Boltzmann Method (LBM) was conducted on transient simulation of automobile aerodynamic lift. This proposed method utilized adaptive wake refinement feature to obtain a series of regular fluid particles for macroscopic fluid and combined large eddy simulation (LES) with wale-viscosity model to study the transient characteristics of automobile aerodynamic lift. In this numerical investigation, using the international standard automobile MIRA model, the temporal and spatial characteristics of rear velocity field and vorticity field were analyzed, whose results had agreement with the wind tunnel test data. It was showed that the elaborate information of flow field around the car-body and the aerodynamic lift could be more accurately described. A pair of asymmetric non-periodical and inward twisting rear vortexes in the car rear flow field was found, while it squeezed and dragged each other in different eddy scales. This result also indicated the aerodynamic lift to oscillate in a certain amplitude scope, markedly different from the simulated result of steady state automobile aerodynamic lift, which is more close to real driving conditions. [ABSTRACT FROM AUTHOR]

High pressure acting on the vehicle's body plays an important role in deciding the aerodynamic drag. An idea has been suggested to enhance the aerodynamic performance for small passenger car by relieving the high pressure in the engine room. The high pressure inside the engine room can be released to the outside of the vehicle through a hole perforated on the wheel house liner. About 1 % of the drag coefficient can be improved with the 1.88 % of the radiator air mass flow rate increment by installing the top hole with slots on the wheel house liner. Flow simulations are performed at the driving velocity of 110 km/h with the moving wall condition of the same velocity. The tire is rotating to catch more precise flow physics around a tire and wheelhouse liner. [ABSTRACT FROM AUTHOR]

The paper presents an optimization of car aerodynamic properties using the simulation software STAR-CCM+. For real simulation was used tested car Fiat 127 which was modified on the performance car. The basic objective of this work is using computer simulations to obtain knowledge about the impact of individual body parts on the results of aerodynamic drag, downforce or lift. Based on the results, bodywork modifications will be designed to improve the aerodynamic characteristics of the body, but would not disrupt the basic shape and appearance of the vehicle. The modifications will be again subjected to tests in simulation software. On the modified body was significantly reduced torque of the front axle, while increased of rear axle (cca 1250 N.m). This caused a significant stabilizing effect on the rear axle. The results of simulation tests before and after use bodywork modifications are processed in graphical and numerical form. [ABSTRACT FROM AUTHOR]

By optimizing the aerodynamic shape parameters, the aerodynamic performance of the vehicle becomes better as the aerodynamic drag decreases. The driving stability also becomes better as the aerodynamic lift decreases. This research presents aerodynamic shape optimization which employs the multi-variable parametric model and the iterative optimal approach to reduce the aerodynamic drag and the aerodynamic lift. For aerodynamic studies with computational fluid dynamics simulations, a parametric surface grid model was used to morph and enhance the mesh quality by linear deformation of the exterior surfaces. This method employed the radial basis function model, and integrated optimization with multi-software provides excellent morphing ability and reasonable optimal designs. In this paper, the process of aerodynamic optimization for a vehicle body is divided into two phases. The first phase is two-dimensional body optimization aimed at a global search, and the second phase aims at a local approximation by running three-dimensional body optimization. The iterative optimal approach can optimize efficiently the aerodynamic characteristics with a reduction in the aerodynamic drag of 13.23% and a marked improvement in the aerodynamic lift. Sensitivity analysis of the design parameters demonstrated that the hood angle is the major factor in the aerodynamic drag coefficient CD. For the aerodynamic lift coefficient CL, the trunk lid angle is the major factor. In addition, the angle of the windshield and the angle of the side window have small influences on CL. The results obtained are accurate reference values for application in automotive engineering. [ABSTRACT FROM AUTHOR]

More accurate information about the basic vehicle parameters can improve the dynamic control functions of a vehicle. Methods for online estimation of the mass, the rolling resistance, the aerodynamic drag coefficient, the yaw inertia and the longitudinal position of the centre of gravity of an electric hybrid vehicle is therefore proposed. The estimators use the standard vehicle sensor set and the estimate of the electric motor torque. No additional sensors are hence required and no assumptions are made regarding the tyre or the vehicle characteristics. Consequently, all information about the vehicle is available to the estimator. The estimators are evaluated using both simulations and experiments. Estimations of the mass, the rolling resistance and the aerodynamic drag coefficient are based on a recursive least-squares method with multiple forgetting factors. The mass estimate converged to within 3% of the measured vehicle mass for the test cases with sufficient excitation that were evaluated. Two methods to estimate the longitudinal position of the centre of gravity and the yaw inertia are also proposed. The first method is based on the equations of motion and was found to be sensitive to the measurement and parameter errors. The second method is based on the estimated mass and seat-belt indicators. This estimator is more robust and reduces the estimation error in comparison with that obtained by assuming static parameters. The results show that the proposed method improves the estimations of the inertial parameters. Hence, it enables online non-linear tyre force estimators and tyre-model-based tyre–road friction estimators to be used in production vehicles. [ABSTRACT FROM AUTHOR]

Computational model is developed to analyze aerodynamic loads and flow characteristics for an automobile, when the rear wing is placed above the trunk of the vehicle. The focus is on effects of the rear wing height that is investigated in four different positions. The relative wind incidence angle of the rear wing is equal in all configurations. Hence, the discrepancies in the results are only due to an influence of the rear wing position. Computations are performed by using the Reynolds-averaged Navier-Stokes equations along with the standard k- ε turbulence model and standard wall functions assuming the steady viscous fluid flow. While the lift force is positive (upforce) for the automobile without the rear wing, negative lift force (downforce) is obtained for all configurations with the rear wing in place. At the same time, the rear wing increases the automobile drag that is not favorable with respect to the automobile fuel consumption. However, this drawback is not that significant, as the rear wing considerably benefits the automobile traction and stability. An optimal automobile downforce-to-drag ratio is obtained for the rear wing placed at 39 % of the height between the upper surface of the automobile trunk and the automobile roof. Two characteristic large vortices develop in the automobile wake in configuration without the rear wing. They vanish with the rear wing placed close to the trunk, while they gradually restore with an increase in the wing mounting height. [ABSTRACT FROM AUTHOR]

Evaluation of the safety and performance of road vehicles in windy conditions requires accurate descriptions of wind loads on vehicles. However, the research in this area has been far from comprehensive. In the present study, wind tunnel tests were carried out on various vehicle models under different flow conditions, including smooth flow, turbulent flow, and boundary layer flow. The lift, drag, and side forces, and the pitching, rolling, and yawing moments for these vehicle models were measured and analyzed to interpret the effects of flow conditions on these forces. The results were also compared with other wind tunnel tests results published in the literature. The experimental results reveal that the flow conditions did have effects on the variation of wind loads; the smooth flow case is a conservative estimation in general. The height of the center of gravity of the vehicle will significantly affect the results of the aerodynamic moment coefficients, which causes the significant difference between different studies. The results under the boundary layer flow also provide a good reference guide for the context of applications such as stability problem of still vehicles under extreme wind events. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Middle European Construction & Design of Cars is the property of Sciendo and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Current diesel engines commonly employ a variable geometry turbocharger (VGT) to improve drivability and fuel efficiency, and this paper addresses model-based feedforward control of the VGT based on empirical models of compressor and turbine efficiencies to improve transient response. Though compressor and turbine efficiencies affect compressor air flow and turbine power, respectively, it is challenging to understand exactly the compressor and turbine efficiencies in real engines. In order to cope with this problem, we propose empirical models of compressor and turbine efficiencies. The input states are proposed based on maps of the compressor and turbine efficiencies, which are provided by turbocharger manufacturers. Parameters of the efficiency models are identified with 225 data of steady-state engine experiments to reflect engine operating conditions. The proposed compressor and turbine efficiency models were applied to the model-based VGT feedforward control algorithm to verify the effectiveness of the efficiency models. The proposed modelbased VGT feedforward control algorithm based on the compressor and turbine efficiency models was experimentally verified with 2.2 L common-rail-direct-injection diesel engines. [ABSTRACT FROM AUTHOR]

Large eddy simulations (LES) are used to study passive flow control for drag reduction in a simplified ground vehicle. Add-on devices in the form of short cylinders are used for the formation of streaks in the streamwise direction that lead to the separation delay. The results of the present numerical simulations are compared with the experimental data and show good agreement. The two-stage flow control mechanism is analyzed from the LES results. It was found to be in agreement with the previous experimental observations that the counter-rotating vortices behind the impinging devices influence the separation only indirectly through the longitudinal vortices further downstream. [ABSTRACT FROM AUTHOR]