1. 1. Supervised By Md. Amzad Hossain Lecturer Department of Mechanical Engineering Khulna University of Engineering & Technology Khulna-9203. Submitted By Md. Abrar Amin Md. Asif Uddin Md. Hasan Ikbal Md. Tanver Ahmed Md. Shahjahan Mahmud Department of Mechanical Engineering , KHULNA UNIVERSITY OF ENGINEERING & TECHNOLOGY, KHULNA 9203 . Course No: ME 3113
2. 2. To define shock wave phenomena. To study the properties of shock wave. To discuss about different types of shock wave & their properties. To discuss about the formation of shock wave. To discuss about over expanded flow & under expanded flow. To know the application of different types of shock wave.
3. 3. A shock wave is a type of propagating disturbance. An alternative name for the shock wave is shock front. Like an ordinary wave, it carries energy and can propagate through a medium (solid, liquid, gas or plasma) or in some cases in the absence of a material medium, through a field such as the electromagnetic field. Shock wave is a very thin region in a flow where supersonic flow is decelerated to subsonic flow. The process is adiabatic but non-isentropic.
4. 4. Across the shock there is always an extremely rapid rise in pressure, temperature and density of the flow. Shock wave are characterized by an abrupt nearly discontinuous change in the characteristics of the medium. Continued
5. 5. Shock wave is a very thin region in a flow where supersonic flow is decelerated to subsonic flow. The process is adiabatic but non-isentropic. Figure: Shock Wave
6. 6. Shock wave is not a conventional sound wave. A Shock wave travels through most media at a higher speed than an ordinary wave. When a shock wave passes through matter the total energy is preserved. Shock wave is a large amplitude compressibility wave . A shock wave takes the form of a very sharp change in the gas properties.
7. 7. Shock wave form when the speed of a fluid changes by more than the speed of sound. Over larger distances a shock wave can change from a non linear wave into a linear wave. Shock wave is a strong wave, i.e. property changes across it are finite. Shock waves can be stationary or moving. Shock waves are very thin, in the order of 107 m. In a shock wave the properties of the fluid (density, pressure, temperature, velocity, Mach number) changes almost instantaneous.
8. 8. Case- 1: Mach Number is less than 1 that means subsonic flow. Case- 2: Mach Number is equal to 1 that means sonic flow. Case- 3: Mach Number is greater than 1 that means supersonic flow. Ma= V/C where, Ma= Mach Number V= Velocity of fluid or body moving in fluid C= Velocity of sound in fluid
9. 9. Figure : Wave Front of a Shock Wave
10. 10. There are three types of shock wave. These are: 4.1 Normal Shock Wave 4.2 Oblique Shock Wave 4.3 Curved Shock Wave
11. 11. 6.0 Normal Shock Wave If the shock wave is perpendicular to the flow direction it is called a normal shock. A normal shock occurs in front of a supersonic object if the flow is turned by a large amount and the shock cannot remain attached to the body. Figure: Normal Shock Wave
12. 12. Perpendicular to the flow. Always decelerate flow to subsonic flow.
13. 13. Video Clip: Normal Shock Wave Formation of Normal Shock Wave
14. 14. An oblique shock wave is one that is not perpendicular to the direction of fluid flow. Such a shock wave arises when a fluid stream flowing at a supersonic speed moves along a convergent or divergent boundary. Properties The oblique shock wave is not perpendicular to the direction of flow. Oblique shock wave always decreases Mach number. Properties of oblique shock wave can be obtained by modification & manipulation of the normal shock wave.
15. 15. From the figure, it is clear that the original horizontal streamlines ahead of the shock wave are uniformly deflected by the wave (Deflection angle is ) Formation of Oblique Shock Wave
16. 16. Oblique shock waves are used predominantly in engineering applications. This can be attributed to the fact that using one or a combination of oblique shock waves results in more favorable post-shock conditions when compared to utilizing a single normal shock. One example is that many supersonic aircraft wings are designed around a thin diamond shape. Placing a diamond-shaped object at an angle of attack relative to the supersonic flow streamlines will result in two oblique shocks which could generate lift. Application of Oblique Shock Wave:
17. 17. For non-isentropic chocked flows through convergence-divergence duct if the pressure rises downstream of the duct exit, the flow is considered as over expanded. Properties This type of flow occurs for non-isentropic chocked flow. Pressure must be rises downstream of the duct exit.
18. 18. Figure: Over-expanded Flow
19. 19. For non-isentropic chocked flows through convergence-divergence duct if the pressure drops downstream of the duct exit, the flow is considered as under expanded. Properties This type of flow occurs for non-isentropic chocked flow. Pressure must be dropped downstream of the duct exit.
20. 20. Figure: Under-expanded Flow
21. 21. PROBLEM 11.39 : The stagnation pressure indicated by a pitot tube mounted on an airplane in flight is 45 kPa (abs). If the aircraft is crushing in standard atmosphere at an altitude of 10,000 m. Determine the speed & Mach number involved. From table C.1(Fundamental of Fluid Mechanics page-717 sixth edition) for standard atmosphere , P = 2.65 10 Pa = 26.50 kPa (abs) T = (273-49.9) K = 223.10 K SOLUTION : Thus we get, P/P0 = 26.50/45 = 0.59 From figure D.1 we get , Ma = 0.90 Thus, v = (Ma)c =Ma (kRT) = 0.9 (286.4 223.1 1.4) =269.18 m/sec