Test Facilities and Instrumentation

For the present work, two linear cascade facilities have been used. The description of the low speed passing bar linear cascade facility was previously documented by Banieghbal et. al, (1995). It is the aim of this paper to describe the high speed rotating bar linear cascade facility and to compare it with its low speed counterpart.

1.2 Transonic cascade facility

The high speed experiments were carried out in the transonic cascade facil­ity at the Whittle laboratory. This is a continuous fbw, closed-circuit variable density wind tunnel where Reynolds and Mach number can be fixed indepen­dently. Two vacuum pumps, working in parallel, are used to achieve sub­atmospheric pressures. A compressor is used to control the pressure ratio and thus the Mach number of the flow within the circuit. To control the humidity of the air, some of the air is passed through a dryer. The temperature variation can be limited by adjusting the cooling system. Before entering the cascade, the air passes through a honeycomb and screen in order to filter the air and to break up any large scale structures that may exist in the flow. At the entry to the cascade, the flow is accelerated in a convergent nozzle. At the exit, it is discharged into the large exit plenum that contains the test section.