[L2]_PROPERTIES OF WIND Flashcards
ENGY-688
What is the Weibull density function formula?
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What is the Weibull density function formula?
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What is the Coriolis Force?
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Inertial force in rotating frames
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How does the Coriolis Force affect the northern hemisphere?
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Positive Acceleration
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What are ocean Gyres?
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Large currents in warm areas
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What is a Cyclone?
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Large scale rotating air mass
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How high above Earth’s surface does solar-heated air rise towards the poles?
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10 to 15 km
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How many Convection Cells are in each hemisphere?
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Three (3)
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Name the three (3) convection cells in each hemisphere
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Polar, Mid-Latitude, Hadley
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What is meso scale wind?
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Local topographic or thermally induced circulations (10-100km)
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What are jet streams?
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Type of wind streams
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What are geostrophic winds?
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Straight line flow winds
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What characterizes gradient winds?
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Non-geostrophic, parallel
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What is a key characteristic of the Normal Distribution?
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Symmetrical Function
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Why is Normal Distribution rarely used for wind modeling?
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Inaccurate Reflection
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What is the Rayleigh Distribution?
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A one parameter distribution
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What is easily computed from the Rayleigh Distribution?
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Mean Wind Speed
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What number of parameters does Weibull Distribution use?
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Two Parameters
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What does ‘k’ represent in Weibull distribution?
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Shape Factor
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What is the purpose and parameters does Weibull utilize?
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Site assessment of wind speed & Scale (c), shape (k)
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What effect does a higher k value have on a distribution curve?
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Narrower Shape, Lower Energy
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What is the common wind speed measurement interval?
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10-Min Average
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What is the typical value for k or alpha (shape factor)?
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2
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ENGY-688
What is the formula for Power Density?
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PD = ½ * p * V³
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What affects Power Density?
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Air Density and Wind Speed
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What is the air density at 15°C?
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1.225 kg/m³
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ENGY-688
Who created the first wind scale?
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Admiral Sir Francis Beaufort
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What is the purpose of the Beaufort wind scale?
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Estimate wind speeds via visual identifiers
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What determines NREL Wind Power Class?
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Power Density, Velocity, Hub Height
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What class is suitable for utility power applications?
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Class 4 or Greater
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What is wind shear?
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Change in wind speed in regards to altitude
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What generates microburst of wind shear typically?
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Thunderstorms
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What are the stages of a microburst life cycle?
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Formation, Impact, Dissipation
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What occurs during the formation stage of a microburst?
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Evaporation and Precipitation Drag
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What is Low-level Wind Shear (LLWS)?
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Longer Time-Frame of Velocity Changes
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How is LLWS quantified?
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10-knots per 200-ft change
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What is the formula for the Power Law Profile?
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v₂/v₁ = (h₂/h₁)γ
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How is z₀ related to the height of average roughness element?
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1/30 of height
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What is the elevation range of the troposphere?
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0 to 11 km
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What is the density difference at ground level vs 100m?
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< 1% difference
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What does pd represent?
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Partial pressure of dry air
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