MatsNorway wrote: ↑
Sat Nov 16, 2019 11:19 am
strad wrote: ↑
Sat Nov 16, 2019 4:25 am
I sure hate to dispute the aero experts but while watching practice 1 today it sure looked like the barge boards pushed the spray outwards. Some down, some up but mostly out to the sides.?.?
Have people claimed anything else?
Okay this explains more succinctly than I could - maybe you'll believe it as it's from an F1 source - Ogawa et al from Honda, and yes it's from a paper from 2008 but the function of the bargeboard hasn't changed.
5.1 Barge Board Longitudinal Vortex Control
The barge board (Fig. 14) functions to generate a downwash in front of the floor of the vehicle by controlling the longitudinal vortices it produces. The shape of the barge board varies between teams, but its role in each case is generally identical.
The cambered barge board produces upper and lower tip vortices (Fig. 15). Directly behind the barge board, the flow induced between the vortices is directed outboard of the vehicle. As it moves downstream, the upper vortex moves outboard and downwards by the lower vortex, the vanes, the suspension, the side pods, and other parts. The lower vortex proceeds downstream, increasing in intensity as it induced longitudinal vortices at the vertical fence and the WW. Because of this, and also due to ground effects, the lower vortex, shed from the barge board, remains in the same YZ position as was shed from the barge board. In this way, a displacement in the Y direction is produced in the upper and lower vortices, and the flow induced between the vortices is directed downwards. This is a downwash produced by the barge board longitudinal vortices. The downwash increases the angle of attack towards the underfloor, and increases suction at the leading edge of the floor. In addition, while the effect is small, downforce is also increased by the suction of the lower vortex itself that flows under the floor of the vehicle. However, excess suction at the leading edge of the floor and total pressure loss at the center of the lower vortex can promote growth of the boundary layer on the floor and result in a decrease in diffuser performance. Because of this, the sequence of aero parts to be optimized and setting priorities in optimization are important issues.
The barge board does not produce any other effects as significant as the downwash effect produced by the longitudinal vortices, but it does play another role. Figure 16 shows a comparison of streamlines with and without the barge board. The outward flow created by the barge board pushes the separation wake of the leading edge of the inboards lower section of the front tire outwards, helping to prevent a decrease in diffuser performance. However, very little change is observed in the large separation flow at the back of the tires whether or not a barge board is used.
As I said the primary
function of the bargeboard is to create downwash in front of the floor. Not that there are not secondary or tertiary functions like outwash or shedding a vortex which runs streamwise along the underbody.