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Flow Measurement

Flow Measurement

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Flow Measurement

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  1. Flow Measurement • Pitot Tube • Orifice Meter • Venturi Tube • Variable –Area Meters (Rotameter) • Others

  2. Manometer

  3. Measuring static and velocity head in fluid flow

  4. Pitot Tube

  5. Airbus SAS • Airbus SAS is an aircraft manufacturing subsidiary of EADS (European Aeronautic Defence and Space Company), a European aerospace company. • Based in Toulouse, France, and with significant activity across Europe, the company produces around half of the world's jet airliners. • Airbus Industrie was formally established as a Groupement d'Interet Economique (Economic Interest Group or GIE) on 18 December 1970. It had been formed by a government initiative between France, Germany and the UK that originated in 1967. • Airbus Industrie began as a consortium of European aviation firms to compete with American companies such as Boeing, McDonnell Douglas, and Lockheed.

  6. Airbus A380 • The Airbus A380 is a double-deck, wide-body, four-engine airliner manufactured by the European corporation Airbus, a subsidiary of EADS. • The largest passenger airliner in the world, the A380 made its maiden flight on 27 April 2005 from Toulouse, France, and made its first commercial flight on 25 October 2007 from Singapore to Sydney with Singapore Airlines.

  7. Airbus A380

  8. Pitot Tube on A380

  9. The Prototype IDF 10003 • The Air-Data Probe (ADP) is a sensor that measures the primary state parameters of the atmosphere, such as temperature, pressure, humidity and flow velocity. • Temperature, Barometric pressure, Relative humidity, Pitot-static pressure, Angle of attack (flow angle in vertical plane), Sideslip angle (flow angle in horizontal plane), Three-axis acceleration measurement, Three-axis magnetic field measurement.

  10. Mirage III-R

  11. Renault R25

  12. Pitot Tube • 皮式管、畢托管 • Henri Pitot (May 3, 1695 – December 27, 1771) was a French hydraulic engineer and the inventor of the Pitot tube, which measures flow velocity. • The basic instrument consists of two coaxial tubes: the interior tube is open to the flow (i.e. perpendicular), while the exterior tube is open at ninety degrees to the flow (i.e. parallel). A manometer can be used to measure the difference between these two pressures and using Bernoulli's equation the flow rate of the fluid can be calculated.

  13. Pitot Tube • The exterior tube, with an opening parallel to the flow, will register the Static Pressure. • The interior tube, with an opening perpendicular to the flow, will register the Stagnation Pressure. • Stagnation pressure is made up of Static Pressure plus Dynamic Pressure (caused by the force of the fluid flowing into the tube interior). • By measuring the pressure difference between the Static Pressure (exterior tube) and the Stagnation pressure (interior tube) allows the velocity of the fluid flow to be determined.

  14. The Pitot tube has two tubes:  • Static tube (b): The opening of the static tube is parallel to the direction of flow. It measures the static pressure, since there is no velocity component perpendicular to its opening. • Impact tube (a): The opening of the impact tube is perpendicular to the flow direction. The point at the entrance of the impact tube is called as the stagnation point .At this point the kinetic energy of the fluid is converted to the potential energy. Thus, the impact tube measures the total pressure (also referred to as stagnation pressure) i.e. both static pressure and dynamic pressure (also referred to as impact pressure). • The two tubes are connected to the legs of a manometer or equivalent device for measuring pressure.

  15. Daniel Bernoulli • Born in Groningen, in the Netherlands, the son of Johann Bernoulli. Daniel Bernoulli has been described as "by far the ablest of the younger Bernoullis". • He is said to have had a bad relationship with his father. Upon both of them entering and tying for first place in a scientific contest at the University of Paris, Johann, unable to bear the "shame" of being compared to his offspring, banned Daniel from his house. Johann Bernoulli also tried to steal Daniel's book Hydrodynamica and rename it Hydraulica.

  16. Bernoulli's Equation • Daniel Bernoulli (Groningen, 29 January 1700 – 27 July 1782) was a Dutch-Swiss mathematician, who is particularly remembered for his applications of mathematics to mechanics, especially fluid mechanics, and for his pioneering work in probability and statistics. • Bernoulli's principle is equivalent to the principle of conservation of energy. This states that in a steady flow the sum of all forms of mechanical energy in a fluid along a streamline is the same at all points on that streamline. This requires that the sum of kinetic energy and potential energy remain constant.

  17. Bernoulli's Principle • In fluid dynamics, Bernoulli's principle states that for an inviscid flow, an increase in the speed of the fluid occurs simultaneously with a decrease in pressure or a decrease in the fluid's potential energy. • Bernoulli's principle can be applied to various types of fluid flow, resulting in what is loosely denoted as Bernoulli's equation. • There are different forms of the Bernoulli equation for different types of flow. The simple form of Bernoulli's principle is valid for incompressible flows (e.g. most liquid flows) and also for compressible flows (e.g. gases) moving at low Mach numbers.

  18. z1 = z2 V1 = 0 P1 = Pt P2 = Ps This requires the fluid to be inviscid (viscosity = 0).

  19. Tube Coefficient, C • This equation may be modified for real fluids by introducing a tube coefficient, C. • In most cases, C ≦ 1.0.

  20. The Orifice Meter

  21. The Venturi Meter

  22. Rotameter • A rotameter is a device that measures the flow rate of liquid or gas in a closed tube. • A rotameter consists of a tapered tube, typically made of glass, with a float inside that is pushed up by flow and pulled down by gravity. • At a higher flow rate more area (between the float and the tube) is needed to accommodate the flow, so the float rises. • Floats are made in many different shapes, with spheres and ellipsoids being the most common. The float is shaped so that it rotates axially as the fluid passes. This allows you to tell if the float is stuck since it will only rotate if it is free. Readings are usually taken from the top of the float.

  23. Variable-Area Meters

  24. Anemometer • An anemometer is a device that is used for measuring wind speed, and is one instrument used in a weather station. The term is derived from the Greek word anemos, meaning wind. The first known description of an anemometer was given by Leon Battista Alberti in around 1450. • Anemometers can be divided into two classes: those that measure the wind's velocity, and those that measure the wind's pressure; but as there is a close connection between the pressure and the velocity, an anemometer designed for one will give information about both.

  25. Anemometer Velocity anemometers • Cup anemometers • Windmill anemometers • Hot-wire anemometers • Laser Doppler anemometers • Sonic anemometers • Ping-pong ball anemometers Pressure anemometers • Plate anemometers • Tube anemometers • Effect of density on measurements

  26. A hemispherical cup anemometer of the type invented in 1846 by John Thomas Romney Robinson

  27. A windmill style of anemometer

  28. TSI's VELOCICALCAir Velocity Meters

  29. Turbo Meter, Davis Instruments

  30. Hot Wire Anemometer • Hot wire anemometers use a very fine wire (on the order of several micrometers) electrically heated up to some temperature above the ambient. • Air flowing past the wire has a cooling effect on the wire. As the electrical resistance of most metals is dependent upon the temperature of the metal (tungsten is a popular choice for hot-wires), a relationship can be obtained between the resistance of the wire and the flow velocity.

  31. Hot-wire sensor • Several ways of implementing this exist, and hot-wire devices can be further classified as CCA (Constant-Current Anemometer), CVA (Constant-Voltage Anemometer) and CTA (Constant-Temperature Anemometer). • The voltage output from these anemometers is thus the result of some sort of circuit within the device trying to maintain the specific variable (current, voltage or temperature) constant.

  32. Wind Chill • Wind chill is the apparent temperature felt on exposed skin due to wind. The degree of this phenomenon depends on both air temperature and wind speed. • The wind chill temperature (often popularly called the wind chill factor) is always lower than the air temperature for values where the wind chill formula is valid. • In cases where the apparent temperature is higher than the air temperature, the heat index is used instead.

  33. Theory for Wind Chill • The human body loses heat largely by evaporative cooling and convection. The rate of heat loss by a surface depends on the wind speed above that surface: the faster the wind speed, the more readily the surface cools. • For inanimate objects, the effect of wind chill is to reduce any warmer objects to the ambient temperature more quickly. • For most biological organisms, the physiological response is to maintain surface temperature in an acceptable range so as to avoid adverse effects. Thus, the attempt to maintain a given surface temperature in an environment of faster heat loss results in both the perception of lower temperatures and an actual greater heat loss increasing the risk to adverse effects such as frostbite and death.

  34. A chart of wind chill temperatures for given air temperatures and wind speeds.

  35. Celsius Wind Chill Chart w/Frostbite information

  36. Original Model for Wind Chill Index Where WCI = Wind chill index, kcal/m2/h V = Wind velocity, m/sec T = Air temperature, ℃

  37. New Model for Wind Chill Index where is the wind chill index based on the Celsius scale, is the air temperature in ℃ and is the air speed in km/h measured at 10 metres (33 ft), standard anemometer height).

  38. Comparison of old and new values of Wind Chill at −15 °C (5.0 °F)

  39. Beaufort Scale • The Beaufort scale is an empirical measure for describing wind speed based mainly on observed sea conditions. • Its full name is the Beaufort wind force scale. • The scale was created in 1805 by Sir Francis Beaufort, an Irish-born British admiral and hydrographer. • This scale is also widely used in China, Taiwan, Hong Kong and Macau, however with some differences between them. Taiwan uses the Beaufort scale with the extension to 17 noted above.

  40. Beaufort Number → Wind Speed where V = Wind speed, m/sec B = Beaufort number

  41. Beaufort Wind Force Scale

  42. Beaufort Wind Force Scale

  43. Beaufort Wind Force Scale (Taiwan)

  44. 蒲福風級

  45. 蒲福風級

  46. 翼梢小翼 • B747-400型: 300型的改進型,翼尖加裝翼梢小翼,減少阻力,可增大航程3%,翼梢小翼也是其外形上與300型的一個明顯區別。 • 最大油箱容量:216,840升