On the Aerodynamics of an Enclosed-Wheel Racing Car: An Assessment and Proposal of Add-On Devices for a Fourth, High-Performance Configuration of the DrivAer Model

Abstract

A modern benchmark for passenger cars-DrivAer modelhas provided significant contributions to aerodynamics-related topics in automotive engineering, where three categories of passenger cars have been successfully represented. However, a reference model for highperformance car configurations has not been considered appropriately yet. Technical knowledge in motorsport is also restricted due to competitiveness in performance, reputation and commercial gains. The consequence is a shortage of open-access material to be used as technical references for either motorsport community or academic research purposes. In this paper, a parametric assessment of race car aerodynamic devices are presented into four groups of studies. These are: (i) forebody strakes (dive planes), (ii) front bumper splitter, (iii) rear-end spoiler, and (iv) underbody diffuser. The simplified design of these add-ons focuses on the main parameters (such as length, position, or incidence), leading to easier manufacturing for experiments and implementation in computational studies. Consequently, a proposed model aims to address enclosed-wheel racing car categories, adapting a simplified, 35% scaled-model DrivAer Fastback shape (i.e. smooth underbody, no wheels, and with side mirrors). Experimental data were obtained at the 8ft x 6ft Cranfield Wind Tunnel using an internal balance for force and moment measurements. The aerodynamic performance of each group of add-on was assessed individually in a range of ride heights over a moving belt. All cases represent the vehicle at a zero-yaw condition, Reynolds number (car length-based) of 4.2 × 10 6 and Mach number equal to 0.12. The proposed high-performance configuration (DrivAer hp-F) was tested and a respective Reynolds number dependency study is also provided. In line with the open-access concept of the DrivAer model, the CAD geometry and experimental data will be made available online to the international community to support independent studies.

Experimental Data for the Validation of Numerical Methods: DrivAer Model

“…Since its creation in 2012 [7,8], the DrivAer model has become a popular test case for studies where a realistic vehicle is preferred to a simplified geometry, as commonly used for studies of the underlying aerodynamic fundamentals. The DrivAer has therefore found applications in CFD particularly for the validation of commercial code, and increasingly by Original Equipment Manufacturers (OEM's) for more generic experimental work [7,8,[32][33][34][35][36][37][38][39][40][41][42][43][44][45][46]. However, because the model has a large number of variations, with three main rear end geometries, three cooling flow options, three under-body, two tyre and two wheel configurations, it is difficult to find two studies that use the same geometry.…”

Cost-effective numerical analysis of the DrivAer fastback model aerodynamics

“…Another way of visualizing turbulent structures is by using the Q-Criterion (9), where for Q . 0 the vorticity magnitude, O ij (10), overcomes the strain rate, S ij (11), forming eddies. Q = 250 (Figure 9) was found to give a representative image of the turbulence, specifically in the wake, around the wheels, at the A-pillar and the conjunction of the hood and the windshield.…”

“…Such studies have been carried out for the DrivAer model as well, focusing in either drag reducing geometry changes for a more cost-efficient, economic and eco-friendly operation 8,9 or high performance racing applications. 10 The DrivAer model came to bridge the gap between oversimplified models, like the Ahmed and SAE bodies, which could not be used to study the complex flow phenomena around real cars, and the actual designs and data of the manufacturing companies, which are kept secret. 11 On the contrary, many experimental studies in wind tunnels such as the WTA of the TUM, 1,2,[12][13][14] AWT of the Ford Motor Company, 15 AAWK of Audi AG, 14 MWK of TU Berlin, 16,17 MWK of the University of Stuttgart (Research Institute of Automotive Engineering and Vehicle Engines Stuttgart-FKFS), 3 Large Wind Tunnel of the Loughborough University, 18 and others, can validate the numerical modeling and contribute a base for comparison of the different approaches.…”

Use of an Aerodynamic Wake Emulator to Assess the Impact on a High-Performance Ground Vehicle in Close Proximity

“…The properties of a generic high-performance ground vehicle wake are measured, using a 35% sub-scale model of the DrivAer configuration in Ref. [2], by Soares and colleagues. An example of the total pressure distribution in a plane within the wake is reproduced in Ref.…”

“…The base geometry of a high-performance car is obtained from a DrivAer model adapted with other devices to turn it into a racing specification setup from Ref. [2] (Fig. 1).…”