The device (2) has a planar element with upstream sides and downstream side edges (5, 6) and fixedly arranged in a swirl orifice (1). The planar element is mounted parallel to extension of a plane of the planar element or extension of a portion of the plane of the planar element in the swirl orifice rotated around an oriented axis. One of the downstream side edges includes an outer contour with protruding projections (7) and intermediate recesses (8), where the projections include a wave-shaped course and width at range of 2-4 mm.
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