ABSTRACT
To design a protection or to judge whether a protection is necessary, detailed information on the velocity field is needed to determine the loads. This can be obtained from measurements, a flow model or a sketch, based on overall discharge data and insight into the flow phenomena. The same is true for turbulence in the velocity field, albeit that the determination of turbulence is much more difficult and uncertain. The turbulent velocity fluctuations are a result of velocity differences, either between a flow and a wall (wall turbulence) or between two fluid bodies (free turbulence). Turbulence is always coupled with loss of kinetic energy, so, especially in deceleration areas, great turbulence can be expected. In accelerating flow, the relative turbulence is less, but the shear stress increases. The turbulent fluctuations cause so-called Reynolds stresses: a normal stress due to the velocity fluctuations in one direction and a shear stress due to the correlation between the fluctuations in two directions.
