Environmental wind tunnel

A wind tunnel for producing air flow over a vehicle, said wind tunnel comprising:

• a test chamber for receiving a vehicle, wherein at least a portion of the surfaces of the test chamber include acoustic treatment means;
• a large area fan;
• a low angle diffuser, an upstream end of which is disposed adjacent to a downstream end of the large area fan;
• a first section of large area duct work an upstream end of which is coupled to a downstream end of the low angle diffuser for directing air from the downstream end of the low angle diffuser to a downstream end of the first section of large area duct work, wherein a flow conditioning screen is disposed within a downstream portion of the first section of large area duct work and wherein at least a portion of the surfaces of the first section of large area duct work include acoustic treatment means;
• a large area ratio contraction, an upstream end of which is coupled to the downstream end, of the first section of large area duct work, wherein the surfaces of the large area ratio contraction do not include acoustic treatment means;
• a nozzle, an upstream end of which is coupled to the downstream end of the large area ratio contraction, the downstream end of the nozzle being open into the test chamber;
• a second section of large area duct work for directing air from the testing chamber to an upstream end of the large area fan, wherein at least a portion of the surfaces of the second section of large area duct work include acoustic treatment means;
• a third section of large area duct work extending from the upstream end of the large area fan to the upstream end of the first section of large area duct work, wherein the surfaces of the third section of large area duct work do not include acoustic treatment means;
• and
• at least one large area corner section for directing air within one of the first and second sections of large area duct work around a corner, wherein the at least one large area corner section includes a turning
• vane having acoustic treatment means and wherein at least a portion of the interior surfaces of the large area corner include
• acoustic treatment means.