In this example, FLUENT 5 is used to study the flow around a model of the Red Bull Sauber C-20 Formula One (F-1) racing car in high speed, high downforce conditions. Pressure coefficients, computed at two locations on the rear wing and flap, are in very good agreement with experimental measurements. Other results are helpful in understanding the interaction between the many complex components of the car.
A P P L I C A T I O N B R I E F S F R O M F L U E N T EX166 Formula 1 External Aerodynamics In this example, FLUENT 5 is used to study the flow around a model of the Red Bull Sauber C-20 Formula One (F-1) racing car in high speed, high downforce conditions. Pressure coefficients, computed at two locations on the rear wing and flap, are in very good agreement with experimental measurements. Other results are helpful in understanding the interaction between the many complex components of the car. The flow around a model of the Development of the CFD model Red Bull Sauber C-20 Formula began with a geometry file, One (F-1) racing car (Figure 1) is created by the CAD package studied in this example. Modern CATIA. ANSA was then used to F-1 cars are capable of reaching create a triangular surface mesh. speeds in excess of 350 km/hr. This mesh was imported into Cornering in these conditions is TGrid, where a hybrid mesh of possible because of the large approximately 20 million negative lift, or downforce, gener- Figure 1: A model of the prismatic and tetrahedral elements Red Bull Sauber C-20 ated primarily by wing structures Formula One racing car was created. The surface mesh on at the front and rear of the vehicle. the driver's helmet and cockpit When combined with wind tunnel typical of those in the vicinity of area is shown in Figure 2. The tests, CFD can be used to under- the front and rear wings of the car. lower rear mainplane (wing) mesh stand the effect that these wings The model is also capable of is shown in gray in Figure 3. In have on the vehicle aerodynamics. resolving the salient features of this figure, a planar surface with a the exterior and interior flow quadrilateral mesh, used to To explore the complex flow fields. To complete the simulation generate layers of prismatic around the F-1, a half-car model of the car motion, the ground elements, is shown in red. of the Red Bull Sauber C-20 was plane was given a velocity equal simulated. An unstructured to the free stream velocity, and the Pressure contours on the surface hybrid mesh was used for the tires were assigned a corres- of the car in Figure 4 show high turbulent, 3D, steady-state ponding rotational speed. pressure regions (red) at the upper simulation. A free stream velocity surfaces of the front and rear of 69.44 m/s (250 km/hr) was set at the inlet boundary of the solution domain, as were turbulence quantities based on local turbulence intensity and length scale. The Spalart- Allmaras turbulence model was used to facilitate closure of the Navier-Stokes equations. This one-equation turbulence model performs well in the prediction of Figure 3: The surface mesh in the rear wing area, Figure 2: The surface mesh in the cockpit area showing a planar surface of quadrilateral faces, attached and separated flows, used to create prism layers Copyright © 2002 Fluent Inc. EX166 • Page 1 of 2 laminar flow in the experiment (that are not in the CFD model), and the presence of the main wind tunnel strut which is absent from the geometry used in the numerical solution. In addition, the difference between the Figure 5: Path lines around the vehicle results in Figures 6 and effectiveness of these compo- 7 suggest that 2D simulations of nents, the pressure coefficient, C p, wing components will fail to ade- is plotted against the normalized quately capture the full three- chordwise position, x/c in Figures dimensional nature of the flow. 6 and 7. In both cases, the Figure 4: Contours of static pressure on the surface components FLUENT predictions are The results presented in this wings, indicative of the strong compared to wind tunnel test data. example demonstrate that it is downforce generated by these In Figure 6, the results correspond possible to use CFD to analyze the components. Low pressure to a position that is 100 m to the complex flow field about a regions (green) indicate areas side of the vehicle centerline. realistic contemporary Formula where the air velocity is highest. There is very good agreement One car model. The pressure between the predicted pressures distribution and surface flow Path lines around the car body are and the experimental visualization compare well with shown in Figure 5. Of interest is measurements for both the experimental results, showing that the interaction between the front mainplane and flap. there is significant merit in using a wing and wheels. The degree of one-equation turbulence model for upwash generated by the front In Figure 7, Cp is again plotted this type of application, despite wing is also important. The up- against the normalized chordwise the anisotropic nature of the wash can have a deleterious effect position, only the results corres- highly turbulent, separated flow. on the cooling system and can pond to a position that is 400 mm The results derived from the compromise the aerodynamic from the vehicle centerline. numerical solutions have behavior of some components Experimental measurements are complemented the experimental immediately downstream of the again in good agreement with program at Sauber Petronas wing. At the rear of the car, a FLUENT predictions. The small Engineering AG, allowing for a strong upward motion of air is in differences that do exist can be more rigorous approach to finding evidence, along with a pair of attributed to differences in the improvements in car performance. large, counter-rotating vortices. free stream conditions used in the These effects are the result of the experiment and simulation, Courtesy of Sauber Petronas downforce produced by the car possible localized regions of Engineering AG, Hinwil, Switzerland underbody and rear wing, respectively. The upper rear wing of the vehicle consists of two compo- nents: the mainplane wing, and a flap. These are designed to generate a strong downforce at Figure 6: Pressure coefficient 100 mm from the Figure 7: Pressure coefficient 400 mm from the high speeds. To illustrate the centerline of the rear wing mainplane and flap centerline of the rear wing mainplane and flap Copyright © 2002 Fluent Inc. EX166 • Page 2 of 2
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