|MadSci Network: Physics|
Hi Tim, The Bernoulli Equation is basically a statement of the conservation of energy principle for flowing fluids. The "Bernoulli effect" is the lowering of fluid pressure in regions where the flow velocity is increased. This lowering of pressure in a constriction of a flow path may seem counterintuitive but seems less so when you consider pressure to be energy density. In the high velocity flow through the constriction, kinetic energy must increase at the expense of pressure energy. Now there is also an effect linked to Poiseuille's Law which means that there is going to be a pressure difference between the start and the end of the tube (a bit like a potential difference across a wire in an electric circuit) caused by the viscous resistance between the fluid and the wall. So the pressure at the end of the tube would be slightly less than at the start but in the middle, where the tube is wider, the pressure will increase slightly due to the slower speed of the fluid (and hence less kinetic energy, giving more pressure energy). Hope this helps! Keith Wales United Kingdom
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