SPR-555: Atmospheric Effects Associated with Highway Noise Propagation
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CHAPTER 20 Wind Turbine Noise Measurements and Abatement
CHAPTER 20 Wind turbine noise measurements and abatement methods Panagiota Pantazopoulou BRE, Watford, UK. This chapter presents an overview of the types, the measurements and the potential acoustic solutions for the noise emitted from wind turbines. It describes the fre- quency and the acoustic signature of the sound waves generated by the rotating blades and explains how they propagate in the atmosphere. In addition, the avail- able noise measurement techniques are being presented with special focus on the technical challenges that may occur in the measurement process. Finally, a discus- sion on the noise treatment methods from wind turbines referring to a range of the existing abatement methods is being presented. 1 Introduction Wind turbines generate two types of noise: aerodynamic and mechanical. A tur- bine’s sound power is the combined power of both. Aerodynamic noise is gener- ated by the blades passing through the air. The power of aerodynamic noise is related to the ratio of the blade tip speed to wind speed. The mechanical noise is associated with the relevant motion between the various parts inside the nacelle. The compartments move or rotate in order to convert kinetic energy to electricity with the expense of generating sound waves and vibration which is transmitted through the structural parts of the turbine. Depending on the turbine model and the wind speed, the aerodynamic noise may seem like buzzing, whooshing, pulsing, and even sizzling. Downwind tur- bines with their blades downwind of the tower cause impulsive noise which can travel far and become very annoying for people. The low frequency noise gener- ated from a wind turbine is primarily the result of the interaction of the aerody- namic lift on the blades and the atmospheric turbulence in the wind. -
Atmospheric Effects on Traffic Noise Propagation
TRANSPORTATION RESEARCH RECORD 1255 59 Atmospheric Effects on Traffic Noise Propagation ROGER L. WAYSON AND WILLIAM BOWLBY Atmospheric effects on traffic noise propagation have largely L 0 sound level at a reference distance, been ignored during measurements and modeling, even though Ageo attenuation due to geometric spreading, it has generally been accepted that the effects may produce large Ab insertion loss due to diffraction, changes in receiver noise levels. Measurement of traffic noise at L, level increases due to reflection, and multiple locations concurrently with measurement of meteoro Ac attenuation due to ground characteristics and envi logical data is described. Statistical methods were used to evaluate the data. Atmospheric effects on traffic noise levels were shown ronmental effects. to be significant, even at very short distances; parallel components It should be noted that all levels in dB in this paper are of the wind (which are usually ignored) were important at second 2 row receivers; turbulent scattering increased noise levels near the referenced to 2 x 10-s N/m • ground more than refractive ray bending for short-distance prop The last term on the right side of Equation 1, A,, consists agation; and temperature lapse rates were not as important as of three parameters: ground attenuation, attenuation due to wind shear very near the highway. A statistical model was devel atmospheric absorption, and attenuation due to atmospheric oped to predict excess attenuations due to atmospheric effects. refraction. (2) Outdoor noise propagation has been studied since the time of the Greek philosopher Chrysippus (240 B. C.). Modern where prediction models have become accurate, and the advent of computers has increased the capabilities of models. -
Industrial Aerodynamics
INDUSTRIAL AERODYNAMICS Unit I Wind Energy Collectors INTRODUCTION Air Movement Wind Air Current Circulation The horizontal movement of air along the earth’s surface is called a Wind. The vertical movement of the air is known as an air current. Winds and air current together comprise a system of circulation in the atmosphere. TYPES OF WINDS On the earth’s surface, certain winds blow constantly in a particular direction throughout the year. These are known as the ‘Prevailing Winds’. They are also called the Permanent or the Planetary Winds. Certain winds blow in one direction in one season and in the opposite direction in another. They are known as Periodic Winds. Then, there are Local Winds in different parts of the world. 1. Planetary Winds: There are three main planetary winds that constantly blow in the same direction all around the world. They are also called prevailing or permanent winds. 1.Trade Winds: Blow from the subtropical high pressure belt towards the Equator. They are called the north-east trades in the northern hemisphere and south-east trades in the southern hemisphere. 2.Westerly winds: Blow from the same subtropical high pressure belts, towards 60˚ S and 60˚ N latitude. They are called the sought Westerly wind sin the northern hemisphere and North Westerly winds in the southern hemispheres. 3.Polar Winds Blow from the polar high pressure to the sub polar low pressure area. In the northern hemisphere, their direction is from the north-east. In the southern hemisphere, they blow from the south-east. 2. Periodic Winds These winds are known to blow for a certain time in a certain direction - it may be for a part of a day or a particular season of the year. -
Small Lightweight Aircraft Navigation in the Presence of Wind Cornel-Alexandru Brezoescu
Small lightweight aircraft navigation in the presence of wind Cornel-Alexandru Brezoescu To cite this version: Cornel-Alexandru Brezoescu. Small lightweight aircraft navigation in the presence of wind. Other. Université de Technologie de Compiègne, 2013. English. NNT : 2013COMP2105. tel-01060415 HAL Id: tel-01060415 https://tel.archives-ouvertes.fr/tel-01060415 Submitted on 3 Sep 2014 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Par Cornel-Alexandru BREZOESCU Navigation d’un avion miniature de surveillance aérienne en présence de vent Thèse présentée pour l’obtention du grade de Docteur de l’UTC Soutenue le 28 octobre 2013 Spécialité : Laboratoire HEUDIASYC D2105 Navigation d'un avion miniature de surveillance a´erienneen pr´esencede vent Student: BREZOESCU Cornel Alexandru PHD advisors : LOZANO Rogelio CASTILLO Pedro i ii Contents 1 Introduction 1 1.1 Motivation and objectives . .1 1.2 Challenges . .2 1.3 Approach . .3 1.4 Thesis outline . .4 2 Modeling for control 5 2.1 Basic principles of flight . .5 2.1.1 The forces of flight . .6 2.1.2 Parts of an airplane . .7 2.1.3 Misleading lift theories . 10 2.1.4 Lift generated by airflow deflection . -
Unit 11 Sound Speed of Sound Speed of Sound Sound Can Travel Through Any Kind of Matter, but Not Through a Vacuum
Unit 11 Sound Speed of Sound Speed of Sound Sound can travel through any kind of matter, but not through a vacuum. The speed of sound is different in different materials; in general, it is slowest in gases, faster in liquids, and fastest in solids. The speed depends somewhat on temperature, especially for gases. vair = 331.0 + 0.60T T is the temperature in degrees Celsius Example 1: Find the speed of a sound wave in air at a temperature of 20 degrees Celsius. v = 331 + (0.60) (20) v = 331 m/s + 12.0 m/s v = 343 m/s Using Wave Speed to Determine Distances At normal atmospheric pressure and a temperature of 20 degrees Celsius, speed of sound: v = 343m / s = 3.43102 m / s Speed of sound 750 mi/h Speed of light 670 616 629 mi/h c = 300,000,000m / s = 3.00 108 m / s Delay between the thunder and lightning Example 2: The thunder is heard 3 seconds after the lightning seen. Find the distance to storm location. The speed of sound is 345 m/s. distance = v t = (345m/s)(3s) = 1035m Example 3: Another phenomenon related to the perception of time delays between two events is an echo. In a canyon, an echo is heard 1.40 seconds after making the holler. Find the distance to the canyon wall (v=345m/s) distanceround trip = vt = (345 m/s )( 1.40 s) = 483 m d= 484/2=242m Applications: Sonar, Ultrasound, and Medical Imaging • Ultrasound or ultrasonography is a medical imaging technique that uses high frequency sound waves and their echoes. -
Atmospheric Cold Front-Generated Waves in the Coastal Louisiana
Journal of Marine Science and Engineering Article Atmospheric Cold Front-Generated Waves in the Coastal Louisiana Yuhan Cao 1 , Chunyan Li 2,* and Changming Dong 1,3,* 1 School of Marine Sciences, Nanjing University of Information Science and Technology, Nanjing 210044, China; [email protected] 2 Department of Oceanography and Coastal Sciences, College of the Coast and Environment, Louisiana State University, Baton Rouge, LA 70803, USA 3 Southern Laboratory of Ocean Science and Engineering (Zhuhai), Zhuhai 519000, China * Correspondence: [email protected] (C.L.); [email protected] (C.D.); Tel.: +1-225-578-2520 (C.L.); +86-025-58695733 (C.D.) Received: 15 October 2020; Accepted: 9 November 2020; Published: 11 November 2020 Abstract: Atmospheric cold front-generated waves play an important role in the air–sea interaction and coastal water and sediment transports. In-situ observations from two offshore stations are used to investigate variations of directional waves in the coastal Louisiana. Hourly time series of significant wave height and peak wave period are examined for data from 2004, except for the summer time between May and August, when cold fronts are infrequent and weak. The intra-seasonal scale variations in the wavefield are significantly affected by the atmospheric cold frontal events. The wave fields and directional wave spectra induced by four selected cold front passages over the coastal Louisiana are discussed. It is found that significant wave height generated by cold fronts coming from the west change more quickly than that by other passing cold fronts. The peak wave direction rotates clockwise during the cold front events. -
A Review of Ocean/Sea Subsurface Water Temperature Studies from Remote Sensing and Non-Remote Sensing Methods
water Review A Review of Ocean/Sea Subsurface Water Temperature Studies from Remote Sensing and Non-Remote Sensing Methods Elahe Akbari 1,2, Seyed Kazem Alavipanah 1,*, Mehrdad Jeihouni 1, Mohammad Hajeb 1,3, Dagmar Haase 4,5 and Sadroddin Alavipanah 4 1 Department of Remote Sensing and GIS, Faculty of Geography, University of Tehran, Tehran 1417853933, Iran; [email protected] (E.A.); [email protected] (M.J.); [email protected] (M.H.) 2 Department of Climatology and Geomorphology, Faculty of Geography and Environmental Sciences, Hakim Sabzevari University, Sabzevar 9617976487, Iran 3 Department of Remote Sensing and GIS, Shahid Beheshti University, Tehran 1983963113, Iran 4 Department of Geography, Humboldt University of Berlin, Unter den Linden 6, 10099 Berlin, Germany; [email protected] (D.H.); [email protected] (S.A.) 5 Department of Computational Landscape Ecology, Helmholtz Centre for Environmental Research UFZ, 04318 Leipzig, Germany * Correspondence: [email protected]; Tel.: +98-21-6111-3536 Received: 3 October 2017; Accepted: 16 November 2017; Published: 14 December 2017 Abstract: Oceans/Seas are important components of Earth that are affected by global warming and climate change. Recent studies have indicated that the deeper oceans are responsible for climate variability by changing the Earth’s ecosystem; therefore, assessing them has become more important. Remote sensing can provide sea surface data at high spatial/temporal resolution and with large spatial coverage, which allows for remarkable discoveries in the ocean sciences. The deep layers of the ocean/sea, however, cannot be directly detected by satellite remote sensors. -
Physical Geography Chapter 5: Atmospheric Pressure, Winds, Circulation Patterns
Physical Geography Chapter 5: Atmospheric Pressure, Winds, Circulation Patterns Torricelli – 1643- first Mercury barometer (76 cm, 29.92 in) – measures response to pressure Pressure – millibars- 1013.2 mb, will cause Hg to rise in tube Unequal heating of Earth’s surface is responsible for differences in pressure to! Variations in Atmospheric Pressure 1. Vertical Variations – increase in elevation, less air pressure Mt. Everest – 8848 m (or 29, 028 ft) – 1/3 pressure 2. Horizontal Variations a. Thermal (determined by T) Warm air is less dense – it rises away from the surface at the equator b. Dynamic: Air from the tropics moves northward and then to the east due to the Coryolis Effect. It collects at this latitude, increasing pressure at the surface. Basic Pressure Systems 1. Low – cyclone – converging air pressure decreases 2. High – anticyclone – Divergins air pressure increases Wind Isobars- line of equal pressure Pressure Gradient - significant difference in pressure Wind- horizontal movement of air in response to differences in pressure ¾ Responsible for moving heat toward poles ¾ 38° Lat and lower: radiation surplus If Earth did not rotate, and if there wasno friction between moving air and the Earth’s surface, the air would flow in a straight line from areas of higher pressure to areas of low pressure. Of course, this is not true, the Earth rotates and friction exists: and wind is controlled by three major factors: 1) PGF- Pressure is measured by barometer 2) Coriolis Effect 3) Friction 1) Pressure Gradient Force (PGF) Pressure differences create wind, and the greater these differences, the greater the wind speed. -
Diving Air Compressor - Wikipedia, the Free Encyclopedia Diving Air Compressor from Wikipedia, the Free Encyclopedia
2/8/2014 Diving air compressor - Wikipedia, the free encyclopedia Diving air compressor From Wikipedia, the free encyclopedia A diving air compressor is a gas compressor that can provide breathing air directly to a surface-supplied diver, or fill diving cylinders with high-pressure air pure enough to be used as a breathing gas. A low pressure diving air compressor usually has a delivery pressure of up to 30 bar, which is regulated to suit the depth of the dive. A high pressure diving compressor has a delivery pressure which is usually over 150 bar, and is commonly between 200 and 300 bar. The pressure is limited by an overpressure valve which may be adjustable. A small stationary high pressure diving air compressor installation Contents 1 Machinery 2 Air purity 3 Pressure 4 Filling heat 5 The bank 6 Gas blending 7 References 8 External links A small scuba filling and blending station supplied by a compressor and Machinery storage bank Diving compressors are generally three- or four-stage-reciprocating air compressors that are lubricated with a high-grade mineral or synthetic compressor oil free of toxic additives (a few use ceramic-lined cylinders with O-rings, not piston rings, requiring no lubrication). Oil-lubricated compressors must only use lubricants specified by the compressor's manufacturer. Special filters are used to clean the air of any residual oil and water(see "Air purity"). Smaller compressors are often splash lubricated - the oil is splashed around in the crankcase by the impact of the crankshaft and connecting A low pressure breathing air rods - but larger compressors are likely to have a pressurized lubrication compressor used for surface supplied using an oil pump which supplies the oil to critical areas through pipes diving at the surface control point and passages in the castings. -
In Wind and Ocean Currents
PAPERS IN PHYSICAL OCEANOGRAPHY AND METEOROLOGY PUBLISHED BY MASSACHUSETTS INSTITUTE OF TECHNOLOGY AND WOODS HOLE OCEANOGRAPHIC INSTITUTION (In continuation of Massachusetts Institute of Technology Meteorological Papers) VOL. III, NO.3 THE LAYER OF FRICTIONAL INFLUENCE IN WIND AND OCEAN CURRENTS BY c.-G. ROSSBY AND R. B. MONTGOMERY Contribution No. 71 from the Woods Hole Oceanographic Institution .~ J~\ CAMBRIDGE, MASSACHUSETTS Ap~il, 1935 CONTENTS i. INTRODUCTION 3 II. ADIABATIC ATMOSPHERE. 4 1. Completion of Solution for Adiabatic Atmosphere 4 2. Light Winds and Residual Turbulence 22 3. A Study of the Homogeneous Layer at Boston 25 4. Second Approximation 4° III. INFLUENCE OF STABILITY 44 I. Review 44 2. Stability in the Boundary Layer 47 3. Stability within Entire Frictional Layer 56 IV. ApPLICATION TO DRIFT CURRENTS. 64 I. General Commen ts . 64 2. The Homogeneous Layer 66 3. Analysis of Material 67 4. Results of Analysis . 69 5. Scattering of the Observations and Advection 72 6. Oceanograph Observations 73 7. Wind Drift of the Ice 75 V. LENGTHRELATION BETWEEN THE VELOCITY PROFILE AND THE VALUE OF THE85 MIXING ApPENDIX2.1. StirringTheoretical in Shallow Comments . Water 92. 8885 REFERENCESSUMMARYModified Computation of the Boundary Layer in Drift Currents 9899 92 1. INTRODUCTION The purpose of the present paper is to analyze, in a reasonably comprehensive fash- ion, the principal factors controlling the mean state of turbulence and hence the mean velocity distribution in wind and ocean currents near the surface. The plan of the in- vestigation is theoretical but efforts have been made to check each major step or result through an analysis of available measurements. -
Air Pressure and Wind
Air Pressure We know that standard atmospheric pressure is 14.7 pounds per square inch. We also know that air pressure decreases as we rise in the atmosphere. 1013.25 mb = 101.325 kPa = 29.92 inches Hg = 14.7 pounds per in 2 = 760 mm of Hg = 34 feet of water Air pressure can simply be measured with a barometer by measuring how the level of a liquid changes due to different weather conditions. In order that we don't have columns of liquid many feet tall, it is best to use a column of mercury, a dense liquid. The aneroid barometer measures air pressure without the use of liquid by using a partially evacuated chamber. This bellows-like chamber responds to air pressure so it can be used to measure atmospheric pressure. Air pressure records: 1084 mb in Siberia (1968) 870 mb in a Pacific Typhoon An Ideal Ga s behaves in such a way that the relationship between pressure (P), temperature (T), and volume (V) are well characterized. The equation that relates the three variables, the Ideal Gas Law , is PV = nRT with n being the number of moles of gas, and R being a constant. If we keep the mass of the gas constant, then we can simplify the equation to (PV)/T = constant. That means that: For a constant P, T increases, V increases. For a constant V, T increases, P increases. For a constant T, P increases, V decreases. Since air is a gas, it responds to changes in temperature, elevation, and latitude (owing to a non-spherical Earth). -
Aircraft Performance: Atmospheric Pressure
Aircraft Performance: Atmospheric Pressure FAA Handbook of Aeronautical Knowledge Chap 10 Atmosphere • Envelope surrounds earth • Air has mass, weight, indefinite shape • Atmosphere – 78% Nitrogen – 21% Oxygen – 1% other gases (argon, helium, etc) • Most oxygen < 35,000 ft Atmospheric Pressure • Factors in: – Weather – Aerodynamic Lift – Flight Instrument • Altimeter • Vertical Speed Indicator • Airspeed Indicator • Manifold Pressure Guage Pressure • Air has mass – Affected by gravity • Air has weight Force • Under Standard Atmospheric conditions – at Sea Level weight of atmosphere = 14.7 psi • As air become less dense: – Reduces engine power (engine takes in less air) – Reduces thrust (propeller is less efficient in thin air) – Reduces Lift (thin air exerts less force on the airfoils) International Standard Atmosphere (ISA) • Standard atmosphere at Sea level: – Temperature 59 degrees F (15 degrees C) – Pressure 29.92 in Hg (1013.2 mb) • Standard Temp Lapse Rate – -3.5 degrees F (or 2 degrees C) per 1000 ft altitude gain • Upto 36,000 ft (then constant) • Standard Pressure Lapse Rate – -1 in Hg per 1000 ft altitude gain Non-standard Conditions • Correction factors must be applied • Note: aircraft performance is compared and evaluated with respect to standard conditions • Note: instruments calibrated for standard conditions Pressure Altitude • Height above Standard Datum Plane (SDP) • If the Barometric Reference Setting on the Altimeter is set to 29.92 in Hg, then the altitude is defined by the ISA standard pressure readings (see Figure 10-2, pg 10-3) Density Altitude • Used for correlating aerodynamic performance • Density altitude = pressure altitude corrected for non-standard temperature • Density Altitude is vertical distance above sea- level (in standard conditions) at which a given density is to be found • Aircraft performance increases as Density of air increases (lower density altitude) • Aircraft performance decreases as Density of air decreases (higher density altitude) Density Altitude 1.