fig13

Figure 13. A simple example of the generation of flow acceleration can be shown by observing the draining of water from a household bathtub. Flow acceleration or a localized area of high velocity develops as the large body of water moves toward the “hole” or opening in the bottom of the tub, through which water flows into the drain. Adjacent to this “hole,” the area of flow acceleration becomes smaller and tends to take the shape and size of the circular “hole” (vena contracta). Reproduced with permission from Kapur et al.^[34]