Total drag and its variation with altitude Essay Example

Total drag and its variation with altitude Paper The equation for total drag is: D = CD x S x ? rV2 (Preston, R) where, CD is the coefficient of drag. It must be subdivided into two parts, the Cdi (Coefficient of induced drag) and CDp (Coefficient of parasite drag. ). Therefore it can be written as: D = (Cdi + Cdp) x S x ? rV2 (Preston, R) The airplanes total drag determines the amount of thrust required at a given airspeed. Thrust must equal drag in steady flight. Lift and drag vary directly with the density of the air. As air density increases, lift and drag increase and as air density decreases, lift and drag decrease. Thus, both lift and drag will decrease at higher altitudes. Fig 1 shows the total drag curve which represents drag against velocity of the object. The fuel-flow versus velocity graph for an air graph is derived from this graph, and generally looks as shown in Fig 2 From the above drag it is seen that the total drag is minimum at a certain velocity. This occurs when the parasitic drag is equal to the induced drag. Below this speed induced drag dominates, and above this speed parasite drag dominates. Design engineers are interested in minimizing the total drag. Unfortunately many factors may conflict. We will write a custom essay sample on Total drag and its variation with altitude specifically for you for only $16.38 $13.9/page Order now We will write a custom essay sample on Total drag and its variation with altitude specifically for you FOR ONLY $16.38 $13.9/page Hire Writer We will write a custom essay sample on Total drag and its variation with altitude specifically for you FOR ONLY $16.38 $13.9/page Hire Writer For example, longer wing span reduces induced drag, but the larger frontal area usually means a higher coefficient of parasite drag. Conversely, a high wing loading (i. e. a small wing) with a small aspect ratio produces the lowest possible parasite drag but unfortunately is the produces for a lot of induced drag. In recent time it is seen that jet airliners have longer wings, to reduce induced drag, and then fly at higher altitudes to reduce the parasite drag. This causes no improvement in aerodynamic efficiency, but the higher altitudes do result in more efficient engine operation. (Preston, R) Angle of Attack (AOA), is the angle between the wing and the relative wind. Everything else being costant, an increase in AOA results in an increase in lift. This increase continues until the stall AOA is reached then the trend reverses itself and an increase in AOA results in decreased lift. The pilot uses the elevators to change the angle of attack until the wings produce the lift necessary for the desired maneuver. Besides AOA other factors also contribute to the production of lift, like relative wind velocity and air density i. e. temperature and altitude. Changing the size or shape of the wing (lowering the flaps) will also change the production of lift. Airspeed is absolutely necessary to produce lift. If there is no airflow past the wing, no air can be diverted downward. At low airspeed, the wing must fly at a high AOA to divert enough air downward to produce adequate lift. As airspeed increases, the wing can fly at lower AOAs to produce the needed lift. This is why airplanes flying relatively slow must be nose high (like an airliner just before landing or just as it takes off) but at high airspeeds fly with the fuselage fairly level. The key is that the wings dont have to divert fast moving air down nearly as much as they do to slow moving air. Air density also contributes to the wings ability to produce lift. This is manifested primarily in an increase in altitude, which decreases air density. As the density decreases, the wing must push a greater volume of air downward by flying faster or push it down harder by increasing the angle of attack. This is why aircraft that fly very high must either go very fast e. g. Mach 3, or must have a very large wing for its weight. This is why the large passenger airplanes cruise at higher altitude to reduce drag, and hence save on the furl costs. (â€Å"Aircraft for Amateurs†, 1999) Small sized aircrafts have lower than normal Reynolds number. The drag coefficient attributable to skin friction is hence higher for the small aircraft. For this reason, the maximum lift-drag ratios characteristic of business jet aircraft tend to be lower than those of the large transports. Hence, the smaller flights can fly at relatively lower altitudes. References Books John A. Roberson Clayton T. Crowe, 1997, Engineering fluid Mechanics, 6th ed. , John Weily Sons Inc., ISBN 0-471-14735-4. Clement Klienstreuer, 1997, Engineering Fluid Dynamics, Cambridge University Press, ISBN 0-521-49670-5 Websites â€Å"Aircraft for Amateurs†, 11th Jan. 1999 http://www. fas. org/man/dod-101/sys/ac/intro. htm Benson, T. , â€Å"The Beginner’s guide to Aeronautics†. , 14th March 2006 http://www. grc. nasa. gov/WWW/K-12/////airplane/ Johnston, D. , â€Å"Drag†, http://www. centennialofflight. gov/essay/Theories_of_Flight/drag/TH4. htm â€Å"Parasitic Drag†, http://adg. stanford. edu/aa241/drag/parasitedrag. html Preston, R. , â€Å"Total Drag† and â€Å"Flight Controls†, http://selair. selkirk. bc. ca/aerodynamics1/

The concept of progress or the pursuit of the American Dream

The concept of progress or the pursuit of the American Dream The concept of progress or the pursuit of the American Dream since 1930s has been a matter of concern for many immigrants who believe that they can achieve much in the US than in their native countries. Different people have varied perspectives about the concept of progress.Advertising We will write a custom essay sample on The concept of progress or the pursuit of the American Dream specifically for you for only $16.05 $11/page Learn More To immigrants, progress in the US provides opportunities for them to achieve material affluence, advanced education, and general prosperity in life. However, in the process of achieving all these, immigrants experience different challenges but almost of a similar nature, in a strange land. While some of the immigrants are struggling to achieve progress in the US, many of them experience conflicting needs and desires. Most immigrants want to embrace the foreign culture, and at the same time maintain their native cultural or ientation and practices. Immigrants rarely discuss the possibilities of hardships or failure in pursuit of progress in the US. This essay shall present the concept of progress, and historical experiences among immigrants of Chinese and Filipino in the US using Bone by Fae Ng, and America is in the Heart by Carlos Bulosan. Ng tries to look at what happens when hopes of progress in a foreign land fail to come true. Ng looks at the feasibility of achieving progress among Chinese immigrants in the US. To most immigrants, the thought of achieving progress in the US is amazing. However, Ng notes that these hopes and dreams of happiness can fail and lead to disappointments. Ng presents realities immigrants experience in their pursuit of opportunities in the US. The author presents historical experiences of Chinese immigrants as full of challenges in their attempts to achieve freedom, life, success and happiness. Ng gives honest accounts of Chinese immigrants in the US through a family livi ng in Chinatown, in San Francisco. The author presents a father figure who has failed to achieve his hopes of progress through a struggling family of Leon Leong.Advertising Looking for essay on social sciences? Let's see if we can help you! Get your first paper with 15% OFF Learn More Through this, Ng rejects the notion that all immigrants can achieve progress in the US. This is because most of the immigrants remain divided between their heritage orientations and giving it up in order to accommodate the new culture a foreign land presents to them. Scholars insist that not all can achieve progress in America. In fact, a closer look at the concept of progress and the American Dream suggest this fact. Ng presents a lead character who is among Chinese immigrants who can never attain this progress. These immigrants struggle but progress is simply out of reach for them. In order to prove that progress in America is not possible for all immigrants, Ng presents chara cters with limitations and eccentric acts. For instance, Leon shows possibilities of hope in achieving success in the US. However, we can see unavoidable failures in his approaches. Ng enhances this fact by showing that Leon main occupation is making household items from junks. This is after experiencing rejection and discrimination in most employment sectors. Leon says that â€Å"I only had to open the first few to know the story: ‘We Don’t Want You’. A rejection from the army: unfit. A job rejection: unskilled. An apartment: unavailable†¦He had job skills and experience: welding, construction, and electrical work, but no English†. Leon represents the historical experiences of most immigrants in Chinatown. Ng also demonstrates the attitudes and expectations of different immigrant generations. The author shows the conflicts of her characters as painful experiences. Ng notes that earlier immigrants hope to achieve progress through their children. This is because they believed that surviving in a native land and improving their livelihood was in the distance future only possible to their children. Ng also highlights a representative life of constant strain leading to suicide. For instance, Leila has a strained relationship with every character in the novel. Ona’s suicide gives a new experience to Chinese immigrants’ life. These aspects of strained relationships show difficulties immigrants experience, sometimes pushing them to suicide. A family condition in this novel represents the broad picture of Chinese immigrants in San Francisco.Advertising We will write a custom essay sample on The concept of progress or the pursuit of the American Dream specifically for you for only $16.05 $11/page Learn More The first generation of Chinese immigrants in the US has to contend with the issue of identity crisis. The definition of self has to reflect both what it means to be an American and at the same time a Chinese. Ng shows this through Leila and her sisters. These generations must struggle with the American mainstream culture and culture of their heritage. Carlos Bulason shares the ideas of Fae Ng in relation to experiences of immigrants in the US. Bulosan presents negative aspects, which Filipino immigrants experienced in the US in pursuit of progress. Bulason characterises Filipinos historical experiences as full of historical injustices like racism, violence, severe experiences of poverty, and cultural alienations. At the same time, immigrants also experience inequalities in terms of social, economic and political rights. Bulosan serves the social role of a writer by exposing the unfair social systems in the US that Filipino immigrants had to contend with in a foreign land. Majority sees the US as a land of progress. Consequently, the US has attracted a large number of immigrants. However, multiculturalism has caused a number of problems to the immigrants. Despite the freed om in the US, many immigrants remained tied to their cultural heritages and races. These aspects hinder progress in the US among immigrants who find it hard to fit in the mainstream culture. Bulosan presents the idea that most Filipinos immigrants leave their home country to pursue progress in the US unknowing of the impending difficulties, and unfavourable conditions that await them. These immigrants experience sociological and psychological difficulties that prevent smooth integrations into the mainstream culture of America. America is in the Heart presents economic and assimilation challenges most Filipino immigrants face in the new land. Bulosan expresses the toil most immigrants undergo in the canneries for a mere pay of 13 dollars for the whole job fishing companies offer immigrants. These economic difficulties force many immigrants to become wanderers moving from one city to another in an attempt to secure employment opportunities. It is unfortunate that Filipino immigrants c annot even secure works as farmhands. Immigrants experience career and financial difficulties because the American employers view their education as overseas and of no value.Advertising Looking for essay on social sciences? Let's see if we can help you! Get your first paper with 15% OFF Learn More Employers have noticed the nature of Filipino immigrants as hardworking. Consequently, these employers are ready to exploit cheap, available labour from immigrants. In addition, Bulosan presents several instances of racism and violence against him. For instance, while he was in San Diego, the hotel owner repeatedly assaults him. The drugstore also refuses to provide services to him. In California, the narrator and his friend hear the news that â€Å"local whites are hunting Filipinos at night with shotguns†. However, nasty experiences among Filipino immigrants occur to Filipinos with Native American women as their wives. For instance, in Holtville the narrator observes racial discrimination when a local hotel refuses to serve a Filipino immigrant with his family. In addition, the restaurant owner yells thus, â€Å"You goddam brown monkey have your nerve, marrying our women. Now get out of this town!† Cultural orientations of native Filipinos create conditions that make it difficult for them to assimilate in the mainstream American culture. Racial discrimination has extended to include features of the body, accent and poor English. Filipinos who speak fluent English are still foreigners in the US. The author tries to condemn such violations of immigrants’ rights, and at the same time show immigrants that progress in America can sometimes be elusive, and more often than not remains a dream among the majority of the immigrants. Bulosan highlights the fact that most immigrants lack appreciation of their own country. At the same time, they are also not aware of the difficulties that most immigrants undergo in such of progress in the US. He stresses that progress is not necessarily in the US but may also exists in one’s own native country. In conclusion, both Ng and Bulosan main concerns are the pursuit of elusive progress among immigrants. These authors note that most immigrants experience social injustices, economic hardship, and cultur al strains in their pursuit of happiness and economic prosperity. Once the initial hope has disappeared, most immigrants experience and turn to menial jobs for their upkeeps. In worst cases, some strains may even lead to suicides. Immigrants must understand the impossibilities of achieving success in a foreign land that present barriers of every nature. These authors believe that progress may not necessarily be in a foreign land, but rather in one’s own country.