AERONAUTICAL LECTURING NOTES

What is fluid mechanics? It is a science that deals with movement of fluids (Liquids/gas) and its interaction with solid surface. 99% of the practical flow is wall bounded. What is meant by continuum?   All matters are made up of atoms, fluids too. Atoms have some gap in between them.   Now just consider the flow over a circular cylinder of diameter d. The mean distance that an atom travels between two successive collisions is called as Mean free path (λ).   When comparing λ and d, if λ is too small than d, we can assume that the flow over the cylinder as continuum. What is no- slip condition? Consider a fluid flow over a solid surface. The layer of fluid which is attached to the solid surface sticks to the solid surface and so it has zero relative velocity with the solid surface. This is what called as no-slip condition. Due to no slip phenomenon the layer of fluid attached with the surface has zero relative velocity and the next layers are moving with some velocity.

Tamil Nadu Common Entrance Test-2014 Those who took B.E./ B.Tech. Aeronautical Engineering, and willing to join for post graduation in engineering discipline (within Tamilnadu-  Under Anna university, chennai) have to take up Tancet. Eligibilty Stages in getting admission to Post graduation: 1. Apply for Tancet 2. Get Hall ticket for exam 3. Write exam 4. See result 5. Wait for counselling 6. Get admission as per the mark got in Tancet From the following Twenty one discipline, you can choose any one depending upon your performance in upcoming Tancet 2014. M.E. Aeronautical Engineering M.E. Aerospace Technology M.E. Avionics M.E. space science & Engineering M.E. Cryogenic engineering M.E. Computer Aided design M.E. CAD/CAM M.E. Thermal Engineering M.E. Welding technology M.E. Industrial automation and Robotics M.E. Robotics M.E. Industrial Engineering M.E. Industrial safety engineering M.E. Lean manufact

What is the need for inlet in gas turbine engine? When aircraft move with some speed, the inlet has to covert the speed to pressure. That means energy interchanging. Speed is Kinetic energy. Pressure is potential energy. The inlet not only accompanying in energy interchange, it also guides the airflow to the engine. In subsonic airplanes energy interchange may or mayn’t be. Define subsonic inlet? The aircrafts that are operating without exceeding speed of sound is called as subsonic aircrafts. Most of the commercial airplanes are subsonic airplanes.  You might have seen if you made your fight. This inlet is so simple and straight. The most upstream point of inlet is called lip. Subsonic airplanes will have thick lip. Define Supersonic inlet? We know that the main problem in supersonic flow is the formation of shock wave. For supersonic aircrafts shock wave may be advantage or disadvantage, this purely depends on the design. Behind Shock wave there will be dra

What is the velocity of sound? First we will know what sound is. Sound is the resulting effect of molecular collisions. Speed of sound is the speed of transmission of a disturbance (Molecular collision) through a medium air. Mathematically, a= sqrt (ß* R* T)   m/s ß- Ratio of specific heats Cp/Cv R- Gas constant T- Temperature As the altitude increases, the temperature changes hence speed of sound too. What is Mach number? Mach number came into picture of aerodynamics by engineers in order to make their analysis ease. Mach number (M) is defined as the ratio of Speed of aircraft to the speed of sound. It has no unit. M < 1    Subsonic M=1      Sonic M> 1     Supersonic (Upto 5) M>5      Hypersonic What is critical Mach number? Though the free stream Mach number is subsonic, the aerofoil upper surface accelerates it to attain sonic at some point. When sonic speed reaches a shock wave occurs. Shock wave is a one having ability to increase

Elastic Region (Point 1 –2) When we start to apply tensile pull on the specimen, the stress and strain develops,keeps on increasing in a  proportional  manner upto elastic limit. The material will return to its original shape after the material is unloaded (like a rubber band). The stress is linearly proportional to the strain in this region. Point 2: Yield Strength: A point where permanent deformation occurs.  (If it is passed, the material will no longer return to its original length.) Tensile Strength (Point 3) The largest value of stress on the diagram is called  Tensile Strength (TS) or Ultimate Tensile Strength (UTS).  It is the maximum stress which the material can support without breaking. Point 4: Strain Hardening If the material is loaded again from Point 4, the curve will follow back to Point 3 with the same Elastic Modulus (slope). The material now has higher yield strength of Point 4. Raising the yield strength by permanently straining the mate

Explain the stress- strain diagram neatly with relevant fig. To select a material for using it in aircraft, we need to know what its life time is.  How much it performs?  and many more requirements. All these are for having a safe flight. The life time and every required factors will be known once if we know stress strain diagram. In order to attain stress strain diagram, we need to have a specimen of desired standards. A standard specimen of the mild steel material is prepared as per BIS standards is given below. Then we need to fix it properly in the universal testing machine. We can give tensile (widely used) or compressive load to the specimen. Load value has to be adjusted very smoothly. By determining the stress and strain at various magnitudes of the load, we can plot a diagram of stress versus strain. Some common terminologies  Load - The force applied to a material during testing. Strain  Gage  or Extensometer  - A device used for measuring change i

What for aileron is used? How its operation? Aileron is used to make the rolling. To be more specific it creates a force at the fitted place due to aerodynamic effect, and that force causes a moment with respect to c.g.. of the aircraft. Ailerons are fitted at the two ends of the main wing. So that distance is high from center of gravity. Even though if we deflect a small amount of angle of attack to the aileron aerofoil, we will have large amount of moment . See the fig. given inside the next question. Ailerons operate on the differential mechanism. That means if the right aileron goes up, then left aileron goes down. Suppose if pilot wants to have a right turn, he must bring right aileron up. What is adverse yaw? If a pilot wants to have a right turn, then he will apply a control from the cockpit in such a way that the right aileron goes up. Say, for instance, right aileron goes 5 deg upward in AOA. Then you might think left aileron goes 5 deg downwards. If it

What is Magnus effect? The flow over a rotating cylinder can explain the Magnus effect better. The cylinder rotates in one direction. The flow gets high velocity in the upper half and hence less pressure. Bottom half is rotating in opposing fashion to the free stream air flow, hence air molecules going around the region gets less velocity and hence high pressure. The high pressure goes to compensate   the less pressure, then lift gets produced. The theory of production of lift from the rotating cylinder is what known to be Magnus effect. What is fan wing aircraft? Please have a read on Bernoulli’s law  for better understanding of answer. Fan wing aircraft is the one which produces lift primarily from the rotation of cylinder located in the wing span. It works based on the Magnus effect. The fan part rotates. The angular velocity of the fan accelerates the linear velocity of air molecules passing over top surface of the fan wing aerofoil. Thus in the to

What is gas turbine engine? A gas turbine is a machine delivering mechanical power or thrust. It does this using a gaseous working fluid which is continuously flowing. This working fluid is initially compressed in the compressor. It is then heated in the combustion chamber by chemical reaction. Note: lot of energy has been added to working fluid at this stage. Finally, it goes through the turbine. The turbine converts the energy of the gas into mechanical work. Part of this work is used to drive the compressor. What are the types of compressor used in gas turbine engines? Centrifugal Compressor Axial flow compressor Just name any three aircraft power-plant makers? General Electric Rolls Royce Pratt & Whitney

What is meant by I.C. engine? In this type of engine, combustion of fuel takes place within the cylinder. This type of engine includes gas engine, petrol engines and diesel engines. These are generally used for road vehicles, locomotives, and aircraft and for other industrial applications. Write the classification of I.C. engines. Based on ignition: Spark ignition Compression ignition Based on fuel: Petrol engine Diesel engine Based on cooling system: Air cooled   Water cooled  What is reciprocating engine?  An engine in which reciprocating motion of piston creates mechanical    energy, necessary to do a work.    What are the types of fuel ignition in reciprocating engine?    Spark ignition- Uses a spark plug to ignite fuel   Compression ignition- Compression will be done excessively so that when       fuel enters it can automatically ignite.     Note: Whenever we do compression, temperature increases. What is meant by Top dead centre? Th