The cylinder in crossflow

In boundary layers with a pressure increase in the direction of flow, the flow can become detached. This can be seen in the momentum equation (3.109), which due to wv u = 0 is transformed into 

In turbulent flow, momentum is constantly fed into the layer adjacent to the wall because of the momentum transfer between layers at different velocities. The kinetic energy of the fluid elements close to the wall does not decrease as rapidly as in laminar flow. This means that turbulent boundary layers do not become detached as quickly as laminar boundary layers. Heat and mass transfer close to the wall is not only promoted by turbulence, the fluid also flows over a larger surface area without detachment. At the same time the pressure resistance is lower because the fluid flow does not separate from the surface for a longer flow path. 

The flow pattern around a cylinder in crossflow is heavily dependent on the Reynolds number, as Fig. 3.23 clearly shows for a circular cylinder. At low Reynolds numbers Re = w djv 5, Fig. 3.23a, the flow surrounds the cylin- 

3 Convective heat and mass transfer. Single phase flow 

In practice, the mean heat transfer coefficient is of greatest interest. It can be described by empirical correlations of the form 

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