The first opeIation in this method of tunneling is to dig two small pilot-tunnels-or ... The surface of the hill, over the line ot the tunnel, is thickly covered with brick buildings from th ...

The small wind tunnel with a 16-by-16 inch test section is a low speed, open return tunnel, as shown in Figure 1. It is mainly used for airfoil section tests and teaching. he velocity is up to 50 m/s.