0.3 m Tunnel

The 0.3m trisonic wind tunnel at NAL was commissioned in 1965 and has been extensively used ever since for various aerospace programs. Compressed air is supplied through the stilling chamber and a sliding-type Isolation valve that controls the flow in the tunnel. A pressure regulating valve (PRV) connected to the other end of isolation valve helps maintain constant pressure in the test section. A wide angle diffuser connects the PRV and the settling chamber. Pressure establishment of the PRV is less than 2 secs with a pressure regulation of ± 0.5% of set value.

The settling chamber consists of a wide-angle diffuser, constant cylindrical region and 3D contraction region. Eight air spreading vanes and a baffle plate with 50% open area are provided in the wide-angle diffuser. The cylindrical region has five anti turbulence screens to reduce the turbulence levels. The 3D contraction is a transition from upstream section of diameter 1.4m to rectangular exit section of 0.457m X 0.3m. The interface mounted between settling chamber and test-section is a box structure having a rectangular duct of 0.457m X 0.3m and 0.34m long.  The purpose of the interface is   to provide quick interchanging of the test-sections. Four hydraulically operated locking pins are provided to lock the test-section to the interface.  A pneumatic inflatable seal  is provided at the downstream end for proper sealing. The flow through this tunnel is two-dimensional, since the area variation along the axial direction of the tunnel is in  top and bottom direction. After passing the test-section, the flow is decelerated in the diffuser region which exhausts into the vertical tower of the concrete muffler.


Overall tunnel features are:

Test section size : 0.3m X 0.3m Supersonic test section

0.381m X 0.3m transonic test section


Mach number range : 0.3 to 4.0

Nozzles available : 1.4, 1.6, 1.8, 2.0, 2.2, 2.5, 2.8, 3.0, 3.5 and 4.0 Reynolds Number range : 8 to 60 million/m



Used Techniques are

Pressure sensitive paint

Particle Image Velocimetry

pressure measurements

oil flow visualization



Last updated on : 01-10-2020 10:54:12pm