Tap the suit. Adjust tolerance until the silhouette is clean, then Use.
Enter your tunnel's airspeed at 100% and the wind is shown as tunnel % as well. Every tunnel is different, so there is no default, and % is worked out in a straight line from 0, which is close but not exact.
Wind 4.0 on the slider = 320 km/h. Forces are reported per metre of depth (this is a 2-D section), using air at 1.225 kg/m³.