Nose Design
BLOODHOUND Design Engine Intake Design Wheel Design Nose Design Base Drag Winglet Design Vehicle Sensitivity Analysis
To achieve a slender nose shape, the initial concept placed the steered front wheels in a staggered configuration. This resulted in the challenge of designing fairings for these wheels that allowed a geometrically asymmetric vehicle to dynamically respond symmetrically in yaw and steering. After much CFD analysis, it was deemed that this was an extremely difficult proposition. In fact, it was found to be impossible to remove the lateral force generated by the interaction of the trailing wheel with the wake of the leading wheel, even at zero yaw and zero steering angle. In another major deviation from the inital BLOODHOUND SSC design configuration, it was, therefore, decided to revert to a more standard parallel front wheel configuration, that would behave better aerodynamically at the expense of slightly widening the nose.
From a roll stability perspective, narrow front wheels are not a good option. Even though BLOODHOUND SSC is not designed to travel around corners at high speed, achieving a satisfactory roll stability index is still crucial for safety. A widened front wheel option was considered and the drag penalty, associated with this configuration, was calculated. The design team agreed a compromise front wheel spacing of 1m, thus achieving a suitable balance between drag reduction and stability, within the geometric constraints imposed by the proposed suspension system.
An extensive analysis of the nose of the vehicle was undertaken in an attempt to understand how the front of the vehicle would respond to changes in yaw angle and steer angle, throughout the proposed speed range. This CFD data is fed directly to the group responsible for the study of the vehicle dynamics.
Finally, the precise shape of the nose, from the tip to the wheels, was developed with three considerations in mind. Firstly, the nose should generate a small downward force at all speeds. This would help in achieving the fundamental requirement of keeping the front wheels firmly planted on the desert surface, while minimising the design requirements placed on the front winglets. Secondly, and more subtly, as Ron Ayers hypothesised that destruction of the desert surface occurs when the pressure at the surface falls below atmospheric, the underside was shaped so as to remove negative values of the pressure coefficient at the desert surface as the front wheels are approached. This should ensure that the surface remains intact, at least until the front wheels have passed over it, thus maximising traction and steerability. Finally, the nose shape was influenced by the requirement to deliver an acceptable airflow quality at the engine intake.