Lake Michigan Coastal Dunes
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Introduction to Lake Michigan Coastal Dunes
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Basic Processes - Wind flow around obstacles


When a moving fluid such as wind encounters an obstacle, the fluid deforms to flow around the obstacle. Typical patterns of high and low wind speeds result.

The wind encountering the bottle in the photo is directed around and over the obstacle. Wind energy is stronger on the upwind side of the obstacle as the wind flow is compressed. Wind erosion results, producing the scour that you see around the bottle in the photo.

To the lee of the object, wind energy is lower because the area is protected by the object. Small eddies may bring air into this zone. Wind-blown sand can be deposited in the lee of the object to form shadow dunes.

Further downwind of the object, wind flow regains the characteristics (speed, direction) it had before the object disturbed the wind.


Wind direction is from right to left in this photograph. Scour is visible along sides of bottle and on upwind side of bottle where wind speeds accelerated. Downwind, a deposit of sand forms in the wind shadow of the bottle.
(Hoffmaster State Park in November 2005.)


Basic Processes: previous page / Go on to Sand Movement / Return to Processes home page

 

 

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Last updated 03/23/10.