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Sphere Legendas PortuguГЄs (pt)

Portuguese (português or, in full, língua portuguesa) is a western Romance language of the Indo-European language family, originating in the Iberian Peninsula of Europe. It is an official language of Portugal, Brazil, Cape Verde, Angola, Mozambique, Guinea-Bissau and São Tomé and Príncipe,[6] while having co-official language status in East Timor, Equatorial Guinea, and Macau. A Portuguese-speaking person or nation is referred to as "Lusophone" (lusófono). As the result of expansion during colonial times, a cultural presence of Portuguese speakers is also found around the world. Portuguese is part of the Ibero-Romance group that evolved from several dialects of Vulgar Latin in the medieval Kingdom of Galicia and the County of Portugal, and has kept some Celtic phonology in its lexicon.[7][8]

Sphere Legendas PortuguГЄs (pt)

With approximately 230 million native speakers and 25-30 million second language speakers, Portuguese has approximately 260 million total speakers. It is usually listed as the sixth-most spoken language, the third-most spoken European language in the world in terms of native speakers[9] and the second-most spoken Romance language in the world, surpassed only by Spanish. Being the most widely spoken language in South America[10][11] and all of the Southern Hemisphere,[12] it is also the second-most spoken language, after Spanish, in Latin America, one of the 10 most spoken languages in Africa,[13] and an official language of the European Union, Mercosur, the Organization of American States, the Economic Community of West African States, the African Union, and the Community of Portuguese Language Countries, an international organization made up of all of the world's officially Lusophone nations. In 1997, a comprehensive academic study ranked Portuguese as one of the 10 most influential languages in the world.[14][15]

Modern Standard European Portuguese (português padrão[88] or português continental) is based on the Portuguese spoken in the area including and surrounding the cities of Coimbra and Lisbon, in central Portugal. Standard European Portuguese is also the preferred standard by the Portuguese-speaking African countries. As such, and despite the fact that its speakers are dispersed around the world, Portuguese has only two dialects used for learning: the European and the Brazilian. Some aspects and sounds found in many dialects of Brazil are exclusive to South America, and cannot be found in Europe. The same occur with the Santomean, Mozambican, Bissau-Guinean, Angolan and Cape Verdean dialects, being exclusive to Africa. See Portuguese in Africa.

The closest relative of Portuguese is Galician, which is spoken in the autonomous community (region) and historical nationality of Galicia (northwestern Spain). The two were at one time a single language, known today as Galician-Portuguese, but they have diverged especially in pronunciation and vocabulary due to the political separation of Portugal from Galicia. There is, however, still a linguistic continuity consisting of the variant of Galician referred to as galego-português baixo-limiao, which is spoken in several Galician and Portuguese villages within the transboundary biosphere reserve of Gerês-Xurés. It is "considered a rarity, a living vestige of the medieval language that ranged from Cantabria to Mondego [...]".[116]As reported by UNESCO, due to the pressure of Spanish on the standard official version of Galician and centuries-old Hispanization, the Galician language was on the verge of disappearing.[116] According to the UNESCO philologist Tapani Salminen, the proximity to Portuguese protects Galician.[117] The core vocabulary and grammar of Galician are noticeably closer to Portuguese than to those of Spanish and within the EU context, Galician is often considered the same language as Portuguese.[118] Galician like Portuguese, uses the future subjunctive, the personal infinitive, and the synthetic pluperfect. Mutual intelligibility estimated at 85% is excellent between Galicians and Portuguese.[119] Despite political efforts in Spain to define them as separate languages, many linguists consider Galician to be a co-dialect of the Portuguese language with regional variations.[120][118]

We can estimate the intensity of the free-stream turbulence in the wind tunnel using a well-defined object with known flow behavior, like a sphere. This method is called the turbulence sphere method. The turbulence sphere method relies on the well-studied condition called the sphere drag crisis.

The sphere drag crisis describes the phenomenon where the drag coefficient of a sphere suddenly drops as the Reynolds number reaches a critical value. When the flow reaches the critical Reynolds number, the boundary layer transitions from laminar to turbulent very close to the leading edge of the sphere. This transition, as compared to flow at a low Reynolds number, causes delayed flow separation and a thinner turbulent wake and thus decreased drag.

Therefore, we can measure the drag coefficient of a sphere at a range of test Reynolds numbers to determine the critical Reynolds number. This enables us to determine the turbulence factor, which correlates the test Reynolds number to the effective of Reynolds number.

This experiment utilizes an aerodynamic wind tunnel as well as several turbulence spheres with varying diameter to determine the turbulence level of the free-stream flow in the tunnel test section. The turbulence spheres, each with a pressure tap at the leading edge as well as 4 pressure taps located 22.5 from the trailing edge, have well-defined flow characteristics, which help us analyze turbulence in the wind tunnel.

To set up the experiment, first connect the wind tunnel pitot tube to pressure scanner port number 1. Then, connect the wind tunnel static pressure port to port number 2. Now, lock the external balance. Fix the sphere strut in the balance support inside the wind tunnel.

Then, install the 6 in sphere. Connect the leading edge pressure tap to the pressure scanner port number 3 and connect the four aft pressure taps to port 4. Connect the air supply line to the pressure regulator, and set the pressure to 65 psi. Then, connect the manifold of the pressure scanner to the pressure line regulated at 65 psi.

Start up the data acquisition system and pressure scanner. While the system equilibrates, estimate the maximum dynamic pressure, q max, necessary for the test based on the free-air critical Reynolds number for a smooth sphere.

Here, we list the recommended test parameters for the first and second test of each sphere. Now, using these parameters, define the dynamic pressure test range from zero to q max, and then define the test points by dividing the range into 15 intervals.

With the wind speed equal to zero, start recording data on the data acquisition system, then type the command scan to start pressure measurement. Then, record the wind tunnel temperature. Since wind speed is directly related to the dynamic pressure, increase the wind speed until you reach the next dynamic pressure test point. Then, wait until the air speed stabilizes and commence the pressure scan again. Be sure to record the wind tunnel temperature. Continue the experiment by conducting a pressure scan at each of the dynamic pressure points, recording the wind tunnel temperature each time. When all points have been measured for the 6-inch sphere, repeat the stabilization and pressure scan experiment for the 4.987 inch and 4-inch turbulence spheres.

For each sphere, we measured the stagnation pressure at pressure port 3 and the pressure at the aft ports via pressure port 4, which are subtracted to give the pressure difference, delta P. We also measured the test section total pressure, Pt, from pressure port one and the static pressure, Ps, from pressure port two, which are used to determine the test dynamic pressure, q.

Using this plot, we can determine the critical Reynolds number for each sphere, since the critical Reynolds number corresponds to a normalized pressure value 1.22. With each critical Reynolds number, we can evaluate the turbulence factor and the effective Reynolds number. The turbulence factor is correlated to the intensity of the turbulence in the wind tunnel.

In summary, we learned how the free-stream turbulence affects testing in a wind tunnel. We then used several smooth spheres to determine the turbulence factor and intensity of the wind tunnel flow and evaluate its quality. 041b061a72

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