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Ch. 9 Fluid Mechanics. pgs. 317 - 342. Fluid Flow. When a fluid is in motion, the flow can be described in two ways Laminar (Streamline) – every particle moves along the same smooth path traveled by earlier particles - PowerPoint PPT Presentation
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Ch. 9Fluid
Mechanicspgs. 317 - 342
Examine the motion of a fluid using the continuity equation.
Recognize the effects of Bernoulli’s Principle on fluid motion.
Objectives
When a fluid is in motion, the flow can be described in two ways
◦ Laminar (Streamline) – every particle moves along the same smooth path traveled by earlier particles
◦ Turbulent – the flow of the fluid becomes irregular. These irregular motions are called eddy currents.
Fluid Flow
The ideal fluid model simplifies fluid-flow analysis
Ideal Fluid◦ Incompressible◦ Nonviscous – lose no kinetic energy due to
friction as they flow◦ Steady Flow – velocity, density, and pressure at
each point are constant◦ Nonturbulent – no eddy currents in the moving
liquid
Fluid Flow
The continuity equation results from mass conservation; in other words when a fluid flows,mass is conserved.
Flow rate = Avt
The speed of fluid flow depends on cross-sectional area
The pressure in a fluid is related to the speed of flow
Fluid Flow
The volume per unit time of a liquid flowing in a pipe is constant throughout the pipe.
We can say this because liquids are not compressible, so mass conservation is also volume conservation for a liquid.
Fluid Flow
Bernoulli’s Principle
http://library.thinkquest.org/27948/bernoulli.html
The sum of the pressure, the potential energy per unit volume, and the kinetic energy per unit volume at any one location in the fluid is equal to the sum of the pressure, the potential energy per unit volume, and the kinetic energy per unit volume at any other location in the fluid for a non-viscous incompressible fluid in streamline flow.
All other considerations being equal, when fluid moves faster, the pressure drops.
Bernoulli’s Theorem
Relates pressure to energy in a moving fluid
The expression for the conservation of energy in fluids is called Bernoulli’s Equation
Bernoulli’s Equation
To compare the energy in a given volume of fluid at two different points, Bernoulli’s equation takes the following equivalent form
Bernoulli’s Equation
In a hurricane or tornado, the high winds traveling across the roof of a building can actually lift the roof off the building.
http://video.google.com/videoplay?docid=6649024923387081294&q=Hurricane+Roof&hl=en
Bernoulli’s Principle and Hurricanes
A water tank has a spigot near its bottom. If the top of the tank is open to the atmosphere, determine the speed at which the water leaves the spigot when the water level is 0.500 m above the spigot.
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