An overview of hydraulic systems and transient Flows

Arturo S. Leon, Oregon State University (Fall 2011)

1 © Arturo S. Leon, OSU, Fall 2011

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Types of Channel SystemsSingle Channel

River & Tributaries

Canal & Distributaries

River Delta

Network

Dendritic (tree-type) System

Braided rivers

Source: http://www.flickr.com/photos/deadlyphoto/2457635320/

Braided river, Denali National Park, Alaska

3 © Arturo S. Leon, OSU, Fall 2011

Meandering rivers

Source: http://www.scienceclarified.com/landforms/Ocean-Basins-to-Volcanoes/Stream-and-River.html

The meandering Tigre River, Argentina)

4 © Arturo S. Leon, OSU, Fall 2011

Terminology Compressible vs incompressible flow (Wiki

definition)

All fluids are compressible to some extent, that is changes in pressure or temperature will result in changes in density. However, in many situations the changes in pressure and temperature are sufficiently small that the changes in density are negligible

For liquids, whether the incompressible assumption is valid depends on the fluid properties and the flow conditions. Acoustic problems always require allowing compressibility, since sound waves are compression waves involving changes in pressure and density of the medium through which they propagate.

5 © Arturo S. Leon, OSU, Fall 2011

Examples of compressible flows (gas and liquid)

6 © Arturo S. Leon, OSU, Fall 2011

Photos1. Bow shock wave in front of a bluff body 2. Fighter at transonic speed 3. SR-71 Blackbird with diamond shaped wave pattern in the exhaust (NASA) 4. Transient flow in closed-conduit system

Terminology (Cont) Steady vs unsteady flow (Wiki)

When all the time derivatives of a flow field vanish, the flow is considered to be a steady flow. Whether a particular flow is steady or unsteady, can depend on the chosen frame of reference.

Turbulent flows are unsteady by definition. A turbulent flow can, however, be statistically stationary. The random field U(x,t) is statistically stationary if all statistics are invariant under a shift in time. This means that all statistical properties are constant in time. Often, the mean field is the object of interest, and this is constant too in a statistically stationary flow.

7 © Arturo S. Leon, OSU, Fall 2011

Flood Waves and Channels (Taken from NWS FLDWAV Model)

Types of Flood Waves

Floods – Rainfall/ Snowmelt RunoffDam-Break WaveReservoir Releases for Power, Flood ControlTidal-Generated WavesEarthquake-Generated Tsunami (tidal waves)Irrigation Releases, Diversions, etc.Wind-Generated Seiches in LakesLandslide-Generated Reservoir WaveMud-Debris FloodsHurricane-Generated Storm SurgesVolcanic Mud FlowsGlacier Dam Outbreaks

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Types of Channels

Rivers Réservoirs Lakes Estuaries Canals Ditches Sewers/Drains

Animations of unsteady Flows

Dam removal with explosives http://www.youtube.com/watch?

v=Sm7xgPjCxXI&NR=1&feature=fvwp

 

Dam break collapse: http://www.youtube.com/watch?

v=kIeNM8cm6J8&feature=PlayList&p=480AFA3CB0803808&index=0

Deep tunnel Geyser (Minnessota): http://www.youtube.com/watch?v=NDy3fBLfhYQ9 © Arturo S. Leon, OSU, Fall 2011

Animations of unsteady Flows (Cont.)

Urban Flooding

http://www.youtube.com/watch?v=kYUpkPTcqPY

 

Extreme street flooding

http://www.youtube.com/watch?NR=1&v=u5sYhNFNjls

Another extreme flooding

http://www.youtube.com/watch?v=s6XAeP15Slo&feature=related

10 © Arturo S. Leon, OSU, Fall 2011