A pipe for carrying a fluid, having a longitudinal axis and defining a radial aperture for release of a jet of fluid having a radial direction component α, the aperture having an aspect ratio greater than 2 and arranged with its elongate axis within 30 degrees of the longitudinal axis and having area greater than 0.2 the cross-sectional area of the pipe, the fluid jet having an angle α between 30 and 80 degrees from the longitudinal axis.