Garden Watering 1 Garden Watering. Garden Watering 2 Question: Water pours weakly from an open hose...
-
Upload
alan-reynolds -
Category
Documents
-
view
238 -
download
0
Transcript of Garden Watering 1 Garden Watering. Garden Watering 2 Question: Water pours weakly from an open hose...
![Page 1: Garden Watering 1 Garden Watering. Garden Watering 2 Question: Water pours weakly from an open hose but sprays hard when you cover most of the end with.](https://reader036.fdocuments.net/reader036/viewer/2022081504/56649f2a5503460f94c440fb/html5/thumbnails/1.jpg)
Garden Watering 1
Garden Watering
![Page 2: Garden Watering 1 Garden Watering. Garden Watering 2 Question: Water pours weakly from an open hose but sprays hard when you cover most of the end with.](https://reader036.fdocuments.net/reader036/viewer/2022081504/56649f2a5503460f94c440fb/html5/thumbnails/2.jpg)
Garden Watering 2
Question:
Water pours weakly from an open hose but sprays hard when you cover most of the end with your thumb. When is more water coming out of the hose?
• When the hose end is uncovered
• When your thumb covers most of the end
![Page 3: Garden Watering 1 Garden Watering. Garden Watering 2 Question: Water pours weakly from an open hose but sprays hard when you cover most of the end with.](https://reader036.fdocuments.net/reader036/viewer/2022081504/56649f2a5503460f94c440fb/html5/thumbnails/3.jpg)
Garden Watering 3
Observations AboutGarden Watering
• Faucets allow you to control water flow
• Faucets make noise when open
• Longer, thinner hoses deliver less water
• Water sprays faster from a nozzle
• Water only sprays so high
• A jet of water can push things over
![Page 4: Garden Watering 1 Garden Watering. Garden Watering 2 Question: Water pours weakly from an open hose but sprays hard when you cover most of the end with.](https://reader036.fdocuments.net/reader036/viewer/2022081504/56649f2a5503460f94c440fb/html5/thumbnails/4.jpg)
Garden Watering 4
Faucets:Limiting Flow
• Pressure limits water’s total energy– Total energy limits maximum kinetic energy– Kinetic energy limits maximum speed
• Water has viscosity (friction in the fluid)– Water at the walls is stationary– All water slows due to viscous forces
![Page 5: Garden Watering 1 Garden Watering. Garden Watering 2 Question: Water pours weakly from an open hose but sprays hard when you cover most of the end with.](https://reader036.fdocuments.net/reader036/viewer/2022081504/56649f2a5503460f94c440fb/html5/thumbnails/5.jpg)
Garden Watering 5
Viscous Forces
• Oppose relative motion within a fluid
• Similar to sliding friction – waste energy
• Fluids are characterized by viscosities
![Page 6: Garden Watering 1 Garden Watering. Garden Watering 2 Question: Water pours weakly from an open hose but sprays hard when you cover most of the end with.](https://reader036.fdocuments.net/reader036/viewer/2022081504/56649f2a5503460f94c440fb/html5/thumbnails/6.jpg)
Garden Watering 6
Hoses: Limiting Flow
• Water flow through a hose:– Increases as 1/viscosity– Increases as 1/hose length– Increases as pressure difference– Increases as (pipe diameter)4
• Poiseuille’s law:4Pressure difference Pipe diameter
Flow 128 Pipe length Viscosity
![Page 7: Garden Watering 1 Garden Watering. Garden Watering 2 Question: Water pours weakly from an open hose but sprays hard when you cover most of the end with.](https://reader036.fdocuments.net/reader036/viewer/2022081504/56649f2a5503460f94c440fb/html5/thumbnails/7.jpg)
Garden Watering 7
Water Flow in a Hose
• Viscous drag wastes water’s energy
• Viscous drag increases with flow speed– Faster flow leads to more viscous energy loss– Faster flow causes quicker drop in pressure
![Page 8: Garden Watering 1 Garden Watering. Garden Watering 2 Question: Water pours weakly from an open hose but sprays hard when you cover most of the end with.](https://reader036.fdocuments.net/reader036/viewer/2022081504/56649f2a5503460f94c440fb/html5/thumbnails/8.jpg)
Garden Watering 8
Question:
Water pours weakly from an open hose but sprays hard when you cover most of the end with your thumb. When is more water coming out of the hose?
• When the hose end is uncovered
• When your thumb covers most of the end
![Page 9: Garden Watering 1 Garden Watering. Garden Watering 2 Question: Water pours weakly from an open hose but sprays hard when you cover most of the end with.](https://reader036.fdocuments.net/reader036/viewer/2022081504/56649f2a5503460f94c440fb/html5/thumbnails/9.jpg)
Garden Watering 9
Accelerating Flows
• Water in steady-state flow can accelerate• Acceleration must be partly to the side
– Forward acceleration would expand water– Backward acceleration would compress water
• Sideways acceleration– requires obstacles– causes pressure imbalances– causes speed changes
![Page 10: Garden Watering 1 Garden Watering. Garden Watering 2 Question: Water pours weakly from an open hose but sprays hard when you cover most of the end with.](https://reader036.fdocuments.net/reader036/viewer/2022081504/56649f2a5503460f94c440fb/html5/thumbnails/10.jpg)
Garden Watering 10
Outward Bend
• Deflecting water away from a surface– involves acceleration away from the surface– is caused by an outward pressure gradient
• higher pressure near surface• lower pressure away from surface
– causes water to travelslower near the surface
![Page 11: Garden Watering 1 Garden Watering. Garden Watering 2 Question: Water pours weakly from an open hose but sprays hard when you cover most of the end with.](https://reader036.fdocuments.net/reader036/viewer/2022081504/56649f2a5503460f94c440fb/html5/thumbnails/11.jpg)
Garden Watering 11
Outward Bend
![Page 12: Garden Watering 1 Garden Watering. Garden Watering 2 Question: Water pours weakly from an open hose but sprays hard when you cover most of the end with.](https://reader036.fdocuments.net/reader036/viewer/2022081504/56649f2a5503460f94c440fb/html5/thumbnails/12.jpg)
Garden Watering 12
Inward Bend
• Deflecting water toward a surface– involves acceleration toward surface– is caused by inward pressure gradient
• lower pressure near surface• higher pressure away from surface
– causes water to travelfaster near the surface
![Page 13: Garden Watering 1 Garden Watering. Garden Watering 2 Question: Water pours weakly from an open hose but sprays hard when you cover most of the end with.](https://reader036.fdocuments.net/reader036/viewer/2022081504/56649f2a5503460f94c440fb/html5/thumbnails/13.jpg)
Garden Watering 13
Inward Bend
![Page 14: Garden Watering 1 Garden Watering. Garden Watering 2 Question: Water pours weakly from an open hose but sprays hard when you cover most of the end with.](https://reader036.fdocuments.net/reader036/viewer/2022081504/56649f2a5503460f94c440fb/html5/thumbnails/14.jpg)
Garden Watering 14
Nozzles: Speeding Water Up
• Water passing through a narrowing– speeds up– experiences pressure drop
• Water passing througha widening– slows down– experiences a rise in pressure
![Page 15: Garden Watering 1 Garden Watering. Garden Watering 2 Question: Water pours weakly from an open hose but sprays hard when you cover most of the end with.](https://reader036.fdocuments.net/reader036/viewer/2022081504/56649f2a5503460f94c440fb/html5/thumbnails/15.jpg)
Garden Watering 15
Nozzles
![Page 16: Garden Watering 1 Garden Watering. Garden Watering 2 Question: Water pours weakly from an open hose but sprays hard when you cover most of the end with.](https://reader036.fdocuments.net/reader036/viewer/2022081504/56649f2a5503460f94c440fb/html5/thumbnails/16.jpg)
Garden Watering 16
Types of Flow
• Laminar Flow– Nearby regions of water remain nearby– Viscosity dominates flow
• Turbulent Flow– Nearby regions of water become separated– Inertia dominates flow
![Page 17: Garden Watering 1 Garden Watering. Garden Watering 2 Question: Water pours weakly from an open hose but sprays hard when you cover most of the end with.](https://reader036.fdocuments.net/reader036/viewer/2022081504/56649f2a5503460f94c440fb/html5/thumbnails/17.jpg)
Garden Watering 17
Reynolds Number
• Reynolds number controls type of flow
• Below about 2300 : Laminar flow– Viscosity dominates
• Above about 2300 : Turbulent flow– Inertia dominates
Density Obstacle length Flow speedReynolds number
Viscosity
![Page 18: Garden Watering 1 Garden Watering. Garden Watering 2 Question: Water pours weakly from an open hose but sprays hard when you cover most of the end with.](https://reader036.fdocuments.net/reader036/viewer/2022081504/56649f2a5503460f94c440fb/html5/thumbnails/18.jpg)
Garden Watering 18
Water and Momentum
• Water carries momentum• Momentum is transferred by impulses:
impulse = pressure imbalance · surface area · time
• Large transfers: long times, large surface areas, or large pressure imbalances
• Moving water can be hard to stop
![Page 19: Garden Watering 1 Garden Watering. Garden Watering 2 Question: Water pours weakly from an open hose but sprays hard when you cover most of the end with.](https://reader036.fdocuments.net/reader036/viewer/2022081504/56649f2a5503460f94c440fb/html5/thumbnails/19.jpg)
Garden Watering 19
Summary AboutGarden Watering
• Total energy limits speed, height, pressure
• Nozzles exchange pressure for speed
• Viscosity wastes energy of water
• Turbulence wastes energy of water
• Moving water has momentum, too