AeroLab Topic 1 (Week 1).pdf

Aeronautical Laboratory 1 AeE 650 AeE 650 – Aeronautical Laboratory 1 Course Outline 1. Wind Tunnel Familiarization 2. Air Flow Visualization 3. Calibration of the 3D Balance 4. Test Section Calibration 5. Free Stream Turbulence 6. Drag Measurements 7....

Aeronautical Laboratory 1 AeE 650 AeE 650 – Aeronautical Laboratory 1 Course Outline 1. Wind Tunnel Familiarization 2. Air Flow Visualization 3. Calibration of the 3D Balance 4. Test Section Calibration 5. Free Stream Turbulence 6. Drag Measurements 7. Wing and High Lift Devices Testing Grading System Major Exam: 40% Class Standing: 50% Quizzes: 30% Activities: 20% Character Formation: 10% Introducing Wind Tunnels AeE 650 – Aeronautical Laboratory 1 What is a Wind Tunnel? AeE 650 – Aeronautical Laboratory 1 What is a Wind Tunnel? Wind tunnels are facilities (circular, elliptical or rectangular tunnels) in which the wind is produced by fans or by compressed air to study and measure the action of the air flow around a solid. What is a Wind Tunnel? The method is based on the principle of relativity enunciated by Isaac Newton in 1687: the forces exerted on a solid immersed in a fluid and the fluid are the same either the solid moves with a certain speed through the fluid at rest, or the fluid moves, with the same relative velocity to the solid that it is immobile.  What is a Wind Tunnel? French – wind tunnel is still designated by the term “soufflerie” (correct for the first facilities, since a fan was blowing air upstream) The first evolution was to suck air downstream of the test section. English – wind tunnel German – Windkanal in German, Italian – galleria aerodinamica Russian – aerodinamicheskaya truba What is a Wind Tunnel? Wind tunnels have largely contributed to the development of aviation, reducing the number of accidents, thus saving the lives of pilots and maintaining the equipment. History of Wind Tunnels AeE 650 – Aeronautical Laboratory 1 Benjamin Robins (1707 – 1751) He was the first to make use of the “Whirling arm”. Robins mounted objects of various shapes on the tip of the whirling arm and begin to spin them in different directions. His experiments brought light as to how different shaped objects, when moving through air is affected differently by air resistance, or “drag”. John Smeaton (1724 – 1792), A British engineer, wrote and published in 1759 a paper that addressed the relationship between pressure and velocity for objects moving in water and air. Created the equation 𝐷 = 𝐶𝐷(𝑘)(𝑆)(𝑉^2) Sir George Cayley (1773 – 1857) “Father of Aviation” Also used a whirling arm to measure the drag and lift of various aerofoils. Identified for the first time that lift is generated by a region of low pressure on the upper surface of the wing. Cayley identified two very important factors that are related to flight. 1. Drag vector is parallel to the flow opposite of the aircraft’s motion through the air; and 2. Lift vector is perpendicular to the flow. Otto Lilienthal (1846 – 1896) Also dabbled with the whirling arm and tested various lifting surfaces. His experiments between 1866 and 1889 yielded incorrect results for both flat and cambered aerofoils which led him to believe that “powered” flight was impossible to achieve. Famous as the first man to launch himself into the air, fly, and land safely using a glider. Sir Hiram Stevens Maxim (1840 – 1916) He first tested aerofoils. His version of the whirling arm had a diameter of 64 feet with the arm boasting elaborate instrumentation to measure lift, drag, and relative air velocity. Samuel P. Langley (1834 – 1936) American aviation pioneer, mathematician, astronomer, and Secretary of Smithsonian Institution. Assessed various aerofoils. Built a large whirling arm with 60 feet in diameter and was spun around by 10-horsepower engine. Francis Herbert Wenham (1824 – 1908) A British marine engineer and a member of the Aeronautical Society of Great Britain, is generally credited with designing and operating the first wind tunnel in 1871. Also engaged with whirling arm experiments. In 1871, together with John Browning (1831 – 1925), a colleague in the Aeronautical Society, they built a wind tunnel located in Greenwich at Penn’s Marine Engineering Works.  Horatio Frederick Phillips (1845 – 1926) An English aviation pioneer, reported to be a huge fanatic of aviation even from a young age. Built his own wind tunnel by the early 1880’s. Horatio’s wind tunnel made use of a steam injector to suck air through the apparatus and thus produced more reliable results than any other wind tunnel built of his time.  Osborne Reynolds (1842-1912) Demonstrated that the airflow pattern over a scale model would be the same for the full-scale vehicle if a certain flow parameter were the same in both cases – Reynolds Number. Dr Ludwig Mach (1868 – 1951) An Austrian physician and chemist. The first to use a wind tunnel to photograph the flow of air.  Johannes O.V. Irminger (1848 – 1938) & Henrik Christian Vogt (1848 – 1928) They conducted the first wind tunnel measurements of pressure distribution. Charles Renard of France (1847 – 1905) Constructor of the famous war balloon La France Was an inventor in the French military. Poul la Cour (1846 – 1908) A Danish scientist, inventor, and educator. Used wind tunnel technology to further his windmill research. His main contribution to aerodynamics was his experimental investigations using wind tunnels, full scale measurements, control, and storage. Dr Etienne-Jules Marey (1830 – 1904) A French scientist, physiologist and chronophotographer. Marey’s wind tunnel was 7.87 by 11.81 inches in cross-section, with front and sides of plate glass and the back covered with black velvet. The wind tunnel used a small suction fan to draw down the air and straightened by passing through fine silk gauze of very even weave. Dr. Albert Francis Zahm (1862 – 1954) A professor of mathematics and engineering as well as the chief of the Aeronautical Division of the U.S Library of Congress. Devised the first complete Aeronautical Laboratory, equipped for a wide range of experiments in the field of aerodynamics with instruments capable of measuring exact measurements. The Wright brothers, Wilbur (1867 – 1912) and Orville (1871 – 1948) Their first testing machine has a bicycle wheel mounted horizontally on a spar projecting from the front of a bicycle. In 1901 a small wind tunnel was completed with a glass top, and the wind was forced through by a blower fan, and passed through a honeycomb wind-straightener. Components of a Wind Tunnel AeE 650 – Aeronautical Laboratory 1 1. Test Section The test section is the part of the circuit where the solid is studied. It is the part where the model is placed. For low speed tunnel operation, the test section has the smallest cross-sectional area and the highest velocity within the tunnel.  1. Test Section Types of Test Section a. Open Test Section When used in an open circuit wind tunnel requires a form of enclosure around the test section in order to prevent the possibility of the air being drawn from the test section instead of the inlet portion of the Converging tunnel. Difficulties with unsteady flow and noise when running in the open test-section configuration.  1. Test Section Types of Test Section b. Closed Test Section Using closed test sections can lead to a phenomenon called horizontal buoyancy happening. Using a closed test section eliminates the disadvantage of unsteadiness of the flow in open test sections.  1. Test Section Types of Test Section c. Slotted Wall Test Section Slotted wall test sections are becoming more common as are test sections that can be converted among two or more configurations.. 2. Contraction Cone The contraction cone's purpose is to take a large volume of low velocity air and reduce it to a small volume of high velocity air without creating turbulence. It is where the air flow accelerates. Its area converges from a larger cross-sectional area to a smaller one Directly attached to the wind tunnel’s test section. 2. Contraction Cone Its aim is to accelerate the flow from the settling chamber to the test chamber, further reducing flow turbulence and non- uniformities in the test chamber. 3. Diffuser It is a divergent section in between the test section and the suction fan located downstream of the tunnel. A diffuser is necessary to reduce any air turbulence that could lead back into the test section. The main function of diffusers is to recover static pressure in order to increase the wind tunnel efficiency and, of course, to close the circuit. 4. Drive Section (Fan) Drives the flow of air through the wind tunnel by producing an increase in pressure in the flow. It determines how the working fluid is moved through the test section. The fan is turned by a large, electrically-powered drive motor. 5. Settling Chamber The front section of the wind tunnel, and is placed onto the contraction cone. The purpose of the settling chamber is to `straighten' the air flow as the wind tunnel draws air in from the surrounding air, channeling the ambient air. Applications of Wind Tunnel AeE 650 – Aeronautical Laboratory 1 1. For Aircrafts The S1MA wind tunnel in Modane–Avrieux (France) The most impressive Wind Tunnel with a power of 88 megawatts (MW) Located at ONERA in Modane– Avrieux in Savoy, France The air flow is provided by two wheels with a diameter of 15 meters rotating in opposite directions and provided with metal blades (10 for one and 12 for the other). 1. For Aircrafts The icing wind tunnel in Capua (Italy) A test facility dedicated for the experimental study of icing - Italian Aerospace Research Centre (CIRA) in Capua, near Naples, since 1985. Occupies a floor area of approximately 2,500 m^2, and the test section is 11.40 m long. It is equipped with a water spray system that generates various types of clouds, including reproducing the reality of flight for a civil aircraft flying at an altitude of 10 km with an outside temperature of −50◦C. 2. For Spacecrafts The F4 wind tunnel in Le Fauga–Mauzac (France) To reproduce the reality of hypersonic flights, one uses “hot” hypersonic wind tunnels, called hot-shot wind tunnel In the F4 wind tunnel, into operation since 1992, the heating of the flow is obtained by an electric arc heater in a 15-liter chamber, filled with air, nitrogen or other test gases 3. For Ground Vehicles Testing cars in a wind tunnel is not a new idea. In 1914, Peugeot passed a car in the Eiffel wind tunnel located in the rue Boileau, in Paris. To decrease the aerodynamic drag, the back shape of the car has been largely modified. 4. For Buildings Stadiums, bridges or towers, all these works have in common their gigantism. Wind effects on these structures are the subject of extensive studies. End of Presentation AeE 650 – Aeronautical Laboratory 1