Abstract: Wind tunnel having a free jet test section for simulating wind direction fluctuations, principally for the investigation of vehicles, equipped with a nozzle which can be rotated when the wind tunnel is operating, in order to alter the wind flow direction, in which arrangement the nozzle comprises a stationary part and a rotatable front part and the nozzle front part is surrounded by a cylinder surface which is sealed off in the manner of a plug in the end wall of the nozzle prechamber in relation to the test chamber; within the nozzle prechamber, which surrounds the nozzle, a compensating flow can take place upon rotation of the nozzle front part, so that the quality of the jet flow of the wind tunnel is, if at all, only barely noticeably impaired by the rotational movement. In order to investigate flow-acoustic problems with a varying wind direction, the wind tunnel can be equipped with sound deadening and sound attenuating devices as well as an absorbing lining.