航空發(fā)動(dòng)機(jī)專業(yè)英語之空氣動(dòng)力學(xué).ppt

CHAPTER 1 Introduction to Aeronautics,What is Aeronautics? Aeronautics Versus Aerospace Before there can be a discussion about aeronautics, it must be defined a bit better. Aeronautics is the science of designing an airplane or other flying machine, There are four basic subjects that aeronautical engineers must understand.,Aeronautic 航空 Aerospace 航天 Versus 比較，對(duì)抗 Tail 尾翼 Aerodynamic 空氣動(dòng)力學(xué) Spin旋轉(zhuǎn) Propeller 螺旋槳 Fall apart 分離，分解，崩潰 Aircraft carrier 航空母艦,1.How to shape the airplane and its wing and tail so that it slips easily through the air and can lift itself off the ground. This is called aerodynamics. 2. How to control the airplane so that it will be able to turn but not spin out of control. This is called stability and control. 3. How to build an engine (be it jet or propeller) so that the airplane can push its way through the air. This is called propulsion.,How to build the airplane so that it wont fall apart when it hits a gust of wind or slams down on an aircraft carrier. This is called structures. Aeronautical engineering should not be confused with aerospace engineering, which deals with things such as rockets and satellites. While rockets must ascend through the atmosphere, they must also navigate through space where there is no air. Their designs and engines have very different requirements than those of airplanes.,How Air Moves-AerodynamicsHow Air and other Gases Move-Aerodynamics,Aerodynamics is the study of forces (more pushes and pulls) acting on an object because air or another gas is moving around it. These forces are important for the design of airplanes, sailboats, cars, and other objects moving quickly through the air. Buildings, bridges, and windmills are also affected by the wind moving past them, and they also experience aerodynamic forces.,The bulk of the sections in this chapter are devoted to understanding the motions of air around objects. When these motions are defined and measured, they contribute to the calculation of the forces on the object. With the aerodynamic forces known, the flight possibilities of the object can be discussed!,Measurements,In order to determine if the aerodynamic forces on an object are sufficient to allow flight, the forces must be measured. The different contributions of the air moving around the object must be categorized and defined, and they must be quantified. There are specific qualities that are used to categorize and define these contributions. In addition, these qualities need a guideline to measure them by. The guidelines are called units, and the qualities are mass, time, length, and temperature.,Unit,Units are used to define measurements so that everyone knows exactly how much. They sound very technical, but they are used all over the world in every day examples. It is important to always include the units when talking about measuring a quality. If a bridge designer develops a bridge across a river that is supposed to be 1000 meters long (a measure of length), and one of the builders tells him or her that the bridge is short by 1, what does that mean?,If it is 1 centimeter short (1/100 of a meter), it wont be a problem it cant even be seen. If it is 1 meter short, it may cause a problem years later if the river bank erodes away. If it is short by 1% (10 meters), the bridge may not reach the other side of the river! So units are very important! A measurement should always include 2 things: a number and a unit. Some examples everyone may know include things like:,there are 20 minutes until recess; it takes 10 days to drive across the country: a desk top is 20 inches wide and 25 inches long; a recipe uses 2 cups of flour; it is 85 degrees outside today. Each of these measurements includes a number and a unit. Recess 休息，休會(huì)，切口，凹口，凹槽，退刀槽，環(huán)槽 Recipe處方，配方，訣竅，秘訣,Mass,Everything, whether it is a solid, liquid, or gas has mass. It is a measure of how much of the substance is involved-how many molecules. Mass is sometimes used interchangeably with weight (more on that in the properties section), even though they are not the same. In the metric system, the units for mass are grams, kilograms (1000grams) or milligrams (1/1000 grams). In the American units (called the English system), the weight of the substance is used, in pounds or ounces. A pound is 16 ounces. Often, abbreviations are used for the units: a gram is g. a kilogram is kg, a milligram is mg, a pound is lb, and an ounce is oz.,substance物質(zhì)，物體，實(shí)體 molecules分子 interchangeably交替的，可拆卸的，可交換的 metric度規(guī)，度量標(biāo)準(zhǔn)，量度 ounce盎司（1盎司28.349克） abbreviation縮短，縮寫,Time,The easiest way to think of time is how long it takes something to happen. It may take 10 minutes to drive to school; it may take an hour to eat dinner. The units for time are the same around the world: seconds, hours, days, years. In aerodynamics, a common time measurement is how long it takes an object to go from one point to another, or from point A to point B.,Length,How long is it? How far is it? These are questions heard every day. Length is a quality used by many people to define an object. A pencil is 7 inches long. A student is 4 feet tall. A swimming pool is 2 meters deep. The most common units for the metric system are a centimeter, a meter (100 centimeters), and a kilometer (1000 meters). In the English system that most Americans use, common units are the inch, a foot (12 inches), or a mile (5280 feet). These units may be abbreviated: centimeter as cm, meter as m, kilometer as km, inch as in, foot or feet as ft, and a mile as mi.,quality 性質(zhì)，性能，屬性 multiply復(fù)合地，多樣地，并聯(lián)，復(fù)雜，增殖 acre英畝 mile英里 dimension尺寸，線度，量綱 cabin座艙 cube立方，立方體 inch英寸 cubic立方體的，三次的 gallon加侖,In addition to the length of an object, it often useful to know the area or volume of the object in question. The area is how much room is on a surface like the floor of the classroom or the surface of a wing. It is found by multiplying one length by another (one side of the room by the front for example), and the units are length squared. So common measurements for area in science and engineering would include square feet or square meters. Other common measurements include an acre (approximately 40,000 square feet) or square miles.,The volume of an object can be illustrated by how much there is in a container like a fuel tank or an airplane cabin. Volume is in all three dimensions, so it is calculated by multiplying a length by a length by a length, The units are length cubed. A 12 inch long section of a 2 by 4 board (2 inches by 4 inches) would have a volume of 72 cubic inches, or 72 in3. Cubic feet, cubic meters, gallons, liters, and cubic centimeters (cc for short) are all common units for volume.,Temperature,The quality of temperature is a measure of how hot or cold something is. A thermometer is commonly used to determine the temperature of an object, Everything has a temperature-the rocks, trees, people, air. The weather report in the newspaper usually gives the high and low temperatures of the air each day. The common units for temperature are degrees Fahrenheit or degrees Celsius (what used to be centigrade).,In America, almost everyone uses the Fahrenheit scale, so temperatures are reported just as degrees. In science and engineering, however, temperatures can be reported using either scale, so a temperature will always be properly defined as 85 degrees F or 85 degrees C.,1.4 Properties,In order to determine if the aerodynamic forces on an object are sufficient to allow flight, the forces must be measured, The different contributions of the fluid moving around the object must be categorized and defined, and they must be quantified. There are specific qualities that are used to categorize and define these contributions. In the Measurements section, units were introduced to help quantify these qualities. In this section, these qualities, or properties, of a fluid are defined, These definitions will use the units defined in the previous section.,Before the aerodynamic forces on an object can be computed, the properties of the fluid must be defined. These properties include the temperature, pressure, density and viscosity of the fluid. The values of the aerodynamic forces are dependent on defining the conditions of the problem. In addition, several other quantities are defined to help further understanding of aerodynamics. These include weight and gravity, velocity, and acceleration.,viscosity 黏性，黏度 quantity數(shù)量，數(shù)目 gravity重力 velocity速度 acceleration加速度，促進(jìn)作用,Temperature,The temperature of the fluid is an important part of how the fluid behavior. Hot oil, for example, flows faster than cold oil. Warm air rises and cold air drops in a room; house designers often place heat vents at the floor level because of this. Very cold water is lighter than cool water, so it rides to the top of a lake. Thats why lakes freeze from the surface down. Sound travels farther on cold days than hot days.,It Is crucial then, to know the temperature of the fluid when computing aerodynamic quantities. As mentioned in the Measurements section, temperature has units of degrees Fahrenheit or degrees Celsius. behavior 行為，狀態(tài) vent通風(fēng)，通氣 lighter更輕 crucial 有決定性的，極重要的，嚴(yán)重的 Fahrenheit華氏溫標(biāo) Celsius攝氏溫標(biāo),