Wind Power Meteorology. Part I: Climate and Turbulence 3
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The Fujita Scale F‐Scale Intensity Wind Type of Damage Done Number Phrase Speed
Weather‐Wind Worksheet 2 L2 MiSP Weather-Wind Speed and Direction Worksheet #2 L2 Name _____________________________ Date_____________ Tornados – Pressure and Wind Speed Introduction (excerpts from http://www.srh.noaa.gov/jetstream/tstorms/tornado.htm ) A tornado is a violently rotating (usually counterclockwise in the northern hemisphere) column of air descending from a thunderstorm and in contact with the ground. The United States experiences more tornadoes by far than any other country. In a typical year about 1000 tornadoes will strike the United States. The peak of the tornado season is April through June and more tornadoes strike the central United States than any other place in the world. This area has been nicknamed "tornado alley." Most tornadoes are spawned from thunderstorms. Tornadoes can last from several seconds to more than an hour but most last less than 10 minutes. The size and/or shape of a tornado are no measure of its strength. Occasionally, small tornadoes do major damage and some very large tornadoes, over a quarter-mile wide, have produced only light damage. The Fujita Scale F‐Scale Intensity Wind Type of Damage Done Number Phrase Speed 40‐72 Some damage to chimneys; breaks branches off trees; F0 Gale tornado mph pushes over shallow‐rooted trees; damages sign boards. The lower limit is the beginning of hurricane wind speed; Moderate 73‐112 peels surface off roofs; mobile homes pushed off F1 tornado mph foundations or overturned; moving autos pushed off the roads; attached garages may be destroyed. Considerable damage. Roofs torn off frame houses; Significant 113‐157 mobile homes demolished; boxcars pushed over; large F2 tornado mph trees snapped or uprooted; light object missiles generated. -
Wind Energy Forecasting: a Collaboration of the National Center for Atmospheric Research (NCAR) and Xcel Energy
Wind Energy Forecasting: A Collaboration of the National Center for Atmospheric Research (NCAR) and Xcel Energy Keith Parks Xcel Energy Denver, Colorado Yih-Huei Wan National Renewable Energy Laboratory Golden, Colorado Gerry Wiener and Yubao Liu University Corporation for Atmospheric Research (UCAR) Boulder, Colorado NREL is a national laboratory of the U.S. Department of Energy, Office of Energy Efficiency & Renewable Energy, operated by the Alliance for Sustainable Energy, LLC. S ubcontract Report NREL/SR-5500-52233 October 2011 Contract No. DE-AC36-08GO28308 Wind Energy Forecasting: A Collaboration of the National Center for Atmospheric Research (NCAR) and Xcel Energy Keith Parks Xcel Energy Denver, Colorado Yih-Huei Wan National Renewable Energy Laboratory Golden, Colorado Gerry Wiener and Yubao Liu University Corporation for Atmospheric Research (UCAR) Boulder, Colorado NREL Technical Monitor: Erik Ela Prepared under Subcontract No. AFW-0-99427-01 NREL is a national laboratory of the U.S. Department of Energy, Office of Energy Efficiency & Renewable Energy, operated by the Alliance for Sustainable Energy, LLC. National Renewable Energy Laboratory Subcontract Report 1617 Cole Boulevard NREL/SR-5500-52233 Golden, Colorado 80401 October 2011 303-275-3000 • www.nrel.gov Contract No. DE-AC36-08GO28308 This publication received minimal editorial review at NREL. NOTICE This report was prepared as an account of work sponsored by an agency of the United States government. Neither the United States government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. -
Wind Characteristics 1 Meteorology of Wind
Chapter 2—Wind Characteristics 2–1 WIND CHARACTERISTICS The wind blows to the south and goes round to the north:, round and round goes the wind, and on its circuits the wind returns. Ecclesiastes 1:6 The earth’s atmosphere can be modeled as a gigantic heat engine. It extracts energy from one reservoir (the sun) and delivers heat to another reservoir at a lower temperature (space). In the process, work is done on the gases in the atmosphere and upon the earth-atmosphere boundary. There will be regions where the air pressure is temporarily higher or lower than average. This difference in air pressure causes atmospheric gases or wind to flow from the region of higher pressure to that of lower pressure. These regions are typically hundreds of kilometers in diameter. Solar radiation, evaporation of water, cloud cover, and surface roughness all play important roles in determining the conditions of the atmosphere. The study of the interactions between these effects is a complex subject called meteorology, which is covered by many excellent textbooks.[4, 8, 20] Therefore only a brief introduction to that part of meteorology concerning the flow of wind will be given in this text. 1 METEOROLOGY OF WIND The basic driving force of air movement is a difference in air pressure between two regions. This air pressure is described by several physical laws. One of these is Boyle’s law, which states that the product of pressure and volume of a gas at a constant temperature must be a constant, or p1V1 = p2V2 (1) Another law is Charles’ law, which states that, for constant pressure, the volume of a gas varies directly with absolute temperature. -
Weather Observations
Operational Weather Analysis … www.wxonline.info Chapter 2 Weather Observations Weather observations are the basic ingredients of weather analysis. These observations define the current state of the atmosphere, serve as the basis for isoline patterns, and provide a means for determining the physical processes that occur in the atmosphere. A working knowledge of the observation process is an important part of weather analysis. Source-Based Observation Classification Weather parameters are determined directly by human observation, by instruments, or by a combination of both. Human-based Parameters : Traditionally the human eye has been the source of various weather parameters. For example, the amount of cloud that covers the sky, the type of precipitation, or horizontal visibility, has been based on human observation. Instrument-based Parameters : Numerous instruments have been developed over the years to sense a variety of weather parameters. Some of these instruments directly observe a particular weather parameter at the location of the instrument. The measurement of air temperature by a thermometer is an excellent example of a direct measurement. Other instruments observe data remotely. These instruments either passively sense radiation coming from a location or actively send radiation into an area and interpret the radiation returned to the instrument. Satellite data for visible and infrared imagery are examples of the former while weather radar is an example of the latter. Hybrid Parameters : Hybrid observations refer to weather parameters that are read by a human observer from an instrument. This approach to collecting weather data has been a big part of the weather observing process for many years. Proper sensing of atmospheric data requires proper siting of the sensors. -
Balanced Flow Natural Coordinates
Balanced Flow • The pressure and velocity distributions in atmospheric systems are related by relatively simple, approximate force balances. • We can gain a qualitative understanding by considering steady-state conditions, in which the fluid flow does not vary with time, and by assuming there are no vertical motions. • To explore these balanced flow conditions, it is useful to define a new coordinate system, known as natural coordinates. Natural Coordinates • Natural coordinates are defined by a set of mutually orthogonal unit vectors whose orientation depends on the direction of the flow. Unit vector tˆ points along the direction of the flow. ˆ k kˆ Unit vector nˆ is perpendicular to ˆ t the flow, with positive to the left. kˆ nˆ ˆ t nˆ Unit vector k ˆ points upward. ˆ ˆ t nˆ tˆ k nˆ ˆ r k kˆ Horizontal velocity: V = Vtˆ tˆ kˆ nˆ ˆ V is the horizontal speed, t nˆ ˆ which is a nonnegative tˆ tˆ k nˆ scalar defined by V ≡ ds dt , nˆ where s ( x , y , t ) is the curve followed by a fluid parcel moving in the horizontal plane. To determine acceleration following the fluid motion, r dV d = ()Vˆt dt dt r dV dV dˆt = ˆt +V dt dt dt δt δs δtˆ δψ = = = δtˆ t+δt R tˆ δψ δψ R radius of curvature (positive in = R δs positive n direction) t n R > 0 if air parcels turn toward left R < 0 if air parcels turn toward right ˆ dtˆ nˆ k kˆ = (taking limit as δs → 0) tˆ R < 0 ds R kˆ nˆ ˆ ˆ ˆ t nˆ dt dt ds nˆ ˆ ˆ = = V t nˆ tˆ k dt ds dt R R > 0 nˆ r dV dV dˆt = ˆt +V dt dt dt r 2 dV dV V vector form of acceleration following = ˆt + nˆ dt dt R fluid motion in natural coordinates r − fkˆ ×V = − fVnˆ Coriolis (always acts normal to flow) ⎛ˆ ∂Φ ∂Φ ⎞ − ∇ pΦ = −⎜t + nˆ ⎟ pressure gradient ⎝ ∂s ∂n ⎠ dV ∂Φ = − dt ∂s component equations of horizontal V 2 ∂Φ momentum equation (isobaric) in + fV = − natural coordinate system R ∂n dV ∂Φ = − Balance of forces parallel to flow. -
Simulation of Turbulent Flows
Simulation of Turbulent Flows • From the Navier-Stokes to the RANS equations • Turbulence modeling • k-ε model(s) • Near-wall turbulence modeling • Examples and guidelines ME469B/3/GI 1 Navier-Stokes equations The Navier-Stokes equations (for an incompressible fluid) in an adimensional form contain one parameter: the Reynolds number: Re = ρ Vref Lref / µ it measures the relative importance of convection and diffusion mechanisms What happens when we increase the Reynolds number? ME469B/3/GI 2 Reynolds Number Effect 350K < Re Turbulent Separation Chaotic 200 < Re < 350K Laminar Separation/Turbulent Wake Periodic 40 < Re < 200 Laminar Separated Periodic 5 < Re < 40 Laminar Separated Steady Re < 5 Laminar Attached Steady Re Experimental ME469B/3/GI Observations 3 Laminar vs. Turbulent Flow Laminar Flow Turbulent Flow The flow is dominated by the The flow is dominated by the object shape and dimension object shape and dimension (large scale) (large scale) and by the motion and evolution of small eddies (small scales) Easy to compute Challenging to compute ME469B/3/GI 4 Why turbulent flows are challenging? Unsteady aperiodic motion Fluid properties exhibit random spatial variations (3D) Strong dependence from initial conditions Contain a wide range of scales (eddies) The implication is that the turbulent simulation MUST be always three-dimensional, time accurate with extremely fine grids ME469B/3/GI 5 Direct Numerical Simulation The objective is to solve the time-dependent NS equations resolving ALL the scale (eddies) for a sufficient time -
A Generalization of the Thermal Wind Equation to Arbitrary Horizontal Flow CAPT
A Generalization of the Thermal Wind Equation to Arbitrary Horizontal Flow CAPT. GEORGE E. FORSYTHE, A.C. Hq., AAF Weather Service, Asheville, N. C. INTRODUCTION N THE COURSE of his European upper-air analysis for the Army Air Forces, Major R. C. I Bundgaard found that the shear of the observed wind field was frequently not parallel to the isotherms, even when allowance was made for errors in measuring the wind and temperature. Deviations of as much as 30 degrees were occasionally found. Since the ther- mal wind relation was found to be very useful on the occasions where it did give the direction and spacing of the isotherms, an attempt was made to give qualitative rules for correcting the observed wind-shear vector, to make it agree more closely with the shear of the geostrophic wind (and hence to make it lie along the isotherms). These rules were only partially correct and could not be made quantitative; no general rules were available. Bellamy, in a recent paper,1 has presented a thermal wind formula for the gradient wind, using for thermodynamic parameters pressure altitude and specific virtual temperature anom- aly. Bellamy's discussion is inadequate, however, in that it fails to demonstrate or account for the difference in direction between the shear of the geostrophic wind and the shear of the gradient wind. The purpose of the present note is to derive a formula for the shear of the actual wind, assuming horizontal flow of the air in the absence of frictional forces, and to show how the direction and spacing of the virtual-temperature isotherms can be obtained from this shear. -
ESSENTIALS of METEOROLOGY (7Th Ed.) GLOSSARY
ESSENTIALS OF METEOROLOGY (7th ed.) GLOSSARY Chapter 1 Aerosols Tiny suspended solid particles (dust, smoke, etc.) or liquid droplets that enter the atmosphere from either natural or human (anthropogenic) sources, such as the burning of fossil fuels. Sulfur-containing fossil fuels, such as coal, produce sulfate aerosols. Air density The ratio of the mass of a substance to the volume occupied by it. Air density is usually expressed as g/cm3 or kg/m3. Also See Density. Air pressure The pressure exerted by the mass of air above a given point, usually expressed in millibars (mb), inches of (atmospheric mercury (Hg) or in hectopascals (hPa). pressure) Atmosphere The envelope of gases that surround a planet and are held to it by the planet's gravitational attraction. The earth's atmosphere is mainly nitrogen and oxygen. Carbon dioxide (CO2) A colorless, odorless gas whose concentration is about 0.039 percent (390 ppm) in a volume of air near sea level. It is a selective absorber of infrared radiation and, consequently, it is important in the earth's atmospheric greenhouse effect. Solid CO2 is called dry ice. Climate The accumulation of daily and seasonal weather events over a long period of time. Front The transition zone between two distinct air masses. Hurricane A tropical cyclone having winds in excess of 64 knots (74 mi/hr). Ionosphere An electrified region of the upper atmosphere where fairly large concentrations of ions and free electrons exist. Lapse rate The rate at which an atmospheric variable (usually temperature) decreases with height. (See Environmental lapse rate.) Mesosphere The atmospheric layer between the stratosphere and the thermosphere. -
Hydraulics Manual Glossary G - 3
Glossary G - 1 GLOSSARY OF HIGHWAY-RELATED DRAINAGE TERMS (Reprinted from the 1999 edition of the American Association of State Highway and Transportation Officials Model Drainage Manual) G.1 Introduction This Glossary is divided into three parts: · Introduction, · Glossary, and · References. It is not intended that all the terms in this Glossary be rigorously accurate or complete. Realistically, this is impossible. Depending on the circumstance, a particular term may have several meanings; this can never change. The primary purpose of this Glossary is to define the terms found in the Highway Drainage Guidelines and Model Drainage Manual in a manner that makes them easier to interpret and understand. A lesser purpose is to provide a compendium of terms that will be useful for both the novice as well as the more experienced hydraulics engineer. This Glossary may also help those who are unfamiliar with highway drainage design to become more understanding and appreciative of this complex science as well as facilitate communication between the highway hydraulics engineer and others. Where readily available, the source of a definition has been referenced. For clarity or format purposes, cited definitions may have some additional verbiage contained in double brackets [ ]. Conversely, three “dots” (...) are used to indicate where some parts of a cited definition were eliminated. Also, as might be expected, different sources were found to use different hyphenation and terminology practices for the same words. Insignificant changes in this regard were made to some cited references and elsewhere to gain uniformity for the terms contained in this Glossary: as an example, “groundwater” vice “ground-water” or “ground water,” and “cross section area” vice “cross-sectional area.” Cited definitions were taken primarily from two sources: W.B. -
Meteorological Monitoring Guidance for Regulatory Modeling Applications
United States Office of Air Quality EPA-454/R-99-005 Environmental Protection Planning and Standards Agency Research Triangle Park, NC 27711 February 2000 Air EPA Meteorological Monitoring Guidance for Regulatory Modeling Applications Air Q of ua ice li ff ty O Clean Air Pla s nn ard in nd g and Sta EPA-454/R-99-005 Meteorological Monitoring Guidance for Regulatory Modeling Applications U.S. ENVIRONMENTAL PROTECTION AGENCY Office of Air and Radiation Office of Air Quality Planning and Standards Research Triangle Park, NC 27711 February 2000 DISCLAIMER This report has been reviewed by the U.S. Environmental Protection Agency (EPA) and has been approved for publication as an EPA document. Any mention of trade names or commercial products does not constitute endorsement or recommendation for use. ii PREFACE This document updates the June 1987 EPA document, "On-Site Meteorological Program Guidance for Regulatory Modeling Applications", EPA-450/4-87-013. The most significant change is the replacement of Section 9 with more comprehensive guidance on remote sensing and conventional radiosonde technologies for use in upper-air meteorological monitoring; previously this section provided guidance on the use of sodar technology. The other significant change is the addition to Section 8 (Quality Assurance) of material covering data validation for upper-air meteorological measurements. These changes incorporate guidance developed during the workshop on upper-air meteorological monitoring in July 1998. Editorial changes include the deletion of the “on-site” qualifier from the title and its selective replacement in the text with “site specific”; this provides consistency with recent changes in Appendix W to 40 CFR Part 51. -
Computational Turbulent Incompressible Flow
This is page i Printer: Opaque this Computational Turbulent Incompressible Flow Applied Mathematics: Body & Soul Vol 4 Johan Hoffman and Claes Johnson 24th February 2006 ii This is page iii Printer: Opaque this Contents I Overview 4 1 Main Objective 5 2 Mysteries and Secrets 7 2.1 Mysteries . 7 2.2 Secrets . 8 3 Turbulent flow and History of Aviation 13 3.1 Leonardo da Vinci, Newton and d'Alembert . 13 3.2 Cayley and Lilienthal . 14 3.3 Kutta, Zhukovsky and the Wright Brothers . 14 4 The Navier{Stokes and Euler Equations 19 4.1 The Navier{Stokes Equations . 19 4.2 What is Viscosity? . 20 4.3 The Euler Equations . 22 4.4 Friction Boundary Condition . 22 4.5 Euler Equations as Einstein's Ideal Model . 22 4.6 Euler and NS as Dynamical Systems . 23 5 Triumph and Failure of Mathematics 25 5.1 Triumph: Celestial Mechanics . 25 iv Contents 5.2 Failure: Potential Flow . 26 6 Laminar and Turbulent Flow 27 6.1 Reynolds . 27 6.2 Applications and Reynolds Numbers . 29 7 Computational Turbulence 33 7.1 Are Turbulent Flows Computable? . 33 7.2 Typical Outputs: Drag and Lift . 35 7.3 Approximate Weak Solutions: G2 . 35 7.4 G2 Error Control and Stability . 36 7.5 What about Mathematics of NS and Euler? . 36 7.6 When is a Flow Turbulent? . 37 7.7 G2 vs Physics . 37 7.8 Computability and Predictability . 38 7.9 G2 in Dolfin in FEniCS . 39 8 A First Study of Stability 41 8.1 The linearized Euler Equations . -
Chapter 7 Balanced Flow
Chapter 7 Balanced flow In Chapter 6 we derived the equations that govern the evolution of the at- mosphere and ocean, setting our discussion on a sound theoretical footing. However, these equations describe myriad phenomena, many of which are not central to our discussion of the large-scale circulation of the atmosphere and ocean. In this chapter, therefore, we focus on a subset of possible motions known as ‘balanced flows’ which are relevant to the general circulation. We have already seen that large-scale flow in the atmosphere and ocean is hydrostatically balanced in the vertical in the sense that gravitational and pressure gradient forces balance one another, rather than inducing accelera- tions. It turns out that the atmosphere and ocean are also close to balance in the horizontal, in the sense that Coriolis forces are balanced by horizon- tal pressure gradients in what is known as ‘geostrophic motion’ – from the Greek: ‘geo’ for ‘earth’, ‘strophe’ for ‘turning’. In this Chapter we describe how the rather peculiar and counter-intuitive properties of the geostrophic motion of a homogeneous fluid are encapsulated in the ‘Taylor-Proudman theorem’ which expresses in mathematical form the ‘stiffness’ imparted to a fluid by rotation. This stiffness property will be repeatedly applied in later chapters to come to some understanding of the large-scale circulation of the atmosphere and ocean. We go on to discuss how the Taylor-Proudman theo- rem is modified in a fluid in which the density is not homogeneous but varies from place to place, deriving the ‘thermal wind equation’. Finally we dis- cuss so-called ‘ageostrophic flow’ motion, which is not in geostrophic balance but is modified by friction in regions where the atmosphere and ocean rubs against solid boundaries or at the atmosphere-ocean interface.