Abstract: A magnetohydrodynamic device having a duct for a conducting gas to flow at an angle with the direction of the magnetic field induction vector. The duct is situated in the magnetic system and is provided with a plurality of electrodes adapted to interact electrically with the gas, whereas the cross-sectional shape of the duct working space is bounded by a closed contour formed by a curve inscribed into a rectangle having its sides a.gtoreq.b, while the minimum radius R of curvature of said curve is related to the distance x from the entry to the duct for the conducting gas to flow, to the cross-section under consideration by the following formula: ##EQU1## where P.sub.o and S.sub.o stand, respectively, for the perimeter and cross-sectional area of the duct 1 at the entry thereof, and 0.5.ltoreq..alpha..ltoreq.1.

Abstract: The wind tunnel for testing a transport vehicle comprises rotary drums mounted on a base with their bearing surfaces located in the working chamber of the wind tunnel, essentially level with its floor, and a wind tunnel balance located in the zone of the rotary drums and comprising a frame which is linked mechanically with dynamometers secured to the base and a supporting platform. The frame is located at the outer sides of the rotary drums, somewhat below their bearing surfaces so that said rotary drums are inside said frame, and is connected with at least three horizontal links whose ends are articulated with the base via vertical links of which one is directed up and the other down. The supporting platform is located in the working chamber of the wind tunnel and mounted on the frame so that it can turn around a vertical axis during the test of the transport vehicle on the wind tunnel balance and be removed during the test of the transport vehicle on the rotary drums.