Ground Effect Simulation System "G.E.S.S."

The Ground Effect Simulation System (GESS) installed in the Pininfarina Wind Tunnel allows both the simulation of ground motion under a car and the wheels rotation. In this way, it reproduces, up to 200 Km/h conditions very close to those existing when a car is running on the road.

This is important in order to achieve a correct aerodynamic development of a car's underbody, fairings and aerodynamic add-on parts (front dams and rear spoilers), as well as of wheel housings and (rotating) wheels. Furthermore, it allows a correct optimization of the cooling flows through the radiator and the engine compartment.

The Boundary Layer Control along the test section floor is performed by:

• A first Suction System, upstream of the test section (Basic Suction System);
• a Blowing System to 'fill' the remaining boundary layer, for a width of 4 m (Tangential Blowing);
• A distributed suction system, for a width of xxx m and a length of yyy m;
• a Moving Ground of reduced width (1 m), flush with the floor, between the car’s wheels (Moving Belt).

The combined work of the three systems gives, at V = 140 Km/h, a δ* = 0.3 mm at the balance center instead of the δ* = 7.1 mm existing in the case of a conventional fixed ground.

The boundary layer velocity profiles in the two conditions of 'Gess-On' and 'Gess-Off' are shown in the following diagram.

Wheel rotation is obtained  by 4 rollers, flush with the floor, integrated into the Balance and capable of spinning the wheels up to 200 Km/h. Further information are reported in the references.

The car standing heights are remotely controlled by computer through 4 supports acting on the car rockers.
Any combination of pitch, roll (and yaw, by turning the turn-table) can be achieved in continuous without stopping the wind.
This is very important to speed up the tests.