Technology & Engineering
Supersonic Flow
Supersonic flow refers to the movement of a fluid at a speed greater than the speed of sound. In this type of flow, shock waves are formed due to the abrupt changes in pressure and density. Supersonic flow is a key concept in aerodynamics and is relevant to the design and performance of supersonic aircraft and high-speed projectiles.
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9 Key excerpts on "Supersonic Flow"
eBook - PDFScramjet Propulsion
A Practical Introduction
- Dora Musielak, Peter Belobaba, Jonathan Cooper, Allan Seabridge(Authors)
- 2022(Publication Date)
- Wiley(Publisher)
From aerodynamics perspective, we define hypersonic flow when the following flow phe- nomena become progressively more important as Mach number increases: • High Temperature Effects aerodynamic heating increases proportionally with M 2 0 • Low Density Flow aerodynamic equations (Euler and Navier–Stokes equations) break down. • Thin Shock Layers shock layer is composed of the flowfield between the oblique shock wave and the vehicle. As the Mach number increases, the shock wave gets closer to the vehicle. 4 1 Introduction to Hypersonic Air-Breathing Propulsion • Entropy Layer entropy increase becomes greater as shock strength increases. • Viscous Interaction increased flow temperature (due to friction heat) near body surface causes boundary layer to become thicker as speed increases, resulting in high drag. Each factor plays a huge role in the design and operation of practical hypersonic vehicles. Hypersonic flight regime is characterized by flow velocities that exceed five times the local speed of sound (M 0 > 5) and where shock layers are thin and viscous drag and heat- ing loads are very high. Inside the air-breathing engine flowpath, the term hypersonic refers to regions of high stagnation temperatures at which chemical reactions become important and simple models of gas behavior break down. 1.2 Chemical Propulsion Systems A propulsion system is a sophisticated engineering device capable of generating a thrust force to propel a vehicle in a particular direction or to accelerate it in flight. All methods to produce a thrust force for propelling a vehicle are based on one principle: the time rate of change of momentum of a fluid accelerated by the system under consideration. The fluid may be a propellant stored in the vehicle and carried along during its flight, as in the case of rocket propulsion, or it can be a mixture of a fuel and an oxidizer that is taken from the surrounding environment, such as in the air-breathing propulsion systems we study herein.
eBook - PDF- Pijush K. Kundu, Ira M. Cohen(Authors)
- 2001(Publication Date)
- Academic Press(Publisher)
664 Compressible Flow von Karman (1954, p. 116) stated that I first introduced the term in a report to the U.S. Air Force. I am not sure whether the general who read the word knew what it meant, but his answer contained the word, so it seemed to be officially accepted.) (iv) Supersonic Flow. M lies in the range 1-3. Shock waves are generally present. In many ways analysis of a flow that is supersonic everywhere is easier than an analysis of a subsonic or incompressible flow as we shall see. This is because information propagates along certain directions, called characteristics, and a determination of these directions greatly facilitates the computation of the flow field. (v) Hypersonic flow. M > 3. The very high flow speeds cause severe heating in boundary layers, resulting in dissociation of molecules and other chemical effects. Useful Thermodynamic Relations As density changes are accompanied by temperature changes, thermodynamic prin-ciples will be constantly used here. Most of the necessary concepts and relations have been summarized in Sections 8 and 9 of Chapter 1, which may be reviewed before proceeding further. Some of the most frequently used relations, valid for a perfect gas with constant specific heats, are listed here for quick reference: Equation of state Internal energy Enthalpy Specific heats Speed of sound Entropy change P = pRT, e = C V T, h = C P T, vR r — — ã - 1 y -i C p — C v = R, C = ^RT, T 2 S 2 - Si = C p In — i l = C v In — -J l l n ^ Pi -RVL —. Pi (16.4) (16.5) An isentropic process of a perfect gas between states 1 and 2 obeys the following relations: (5)' · El 2. Speed of Sound 665 Some important properties of air at ordinary temperatures and pressures are # = 287m 2 /(s 2 K), C p = 1005m 2 /(s 2 K), C,=718m7(s 2 K), y = 1.4. These values will be useful for solution of the exercises.
Available until 30 Nov |Learn moreFlight Theory and Aerodynamics
A Practical Guide for Operational Safety
- Charles E. Dole, James E. Lewis, Joseph R. Badick, Brian A. Johnson(Authors)
- 2016(Publication Date)
- Wiley-Interscience(Publisher)
Chapter 16 High‐Speed FlightIn this chapter we discuss the airflow as the aircraft approaches the speed of sound (high subsonic), transonic flight, and supersonic flight. Hypersonic flight is not discussed.In subsonic flight, the density change in the airflow is so small that it can be neglected in the flow equations without appreciable error. The airflow at these lower speeds can be compared to the flow of water and is called incompressible flow. At high speeds, however, density changes take place in the airstream that are significant. Thus, this type of airflow is called compressible flow. Transonic, supersonic, and hypersonic flight all involve compressible flow.Flight speeds have been arbitrarily named as follows:
- Subsonic Aircraft speeds where the airflow around the aircraft is completely below the speed of sound (about Mach 0.7 or less)
- Transonic Aircraft speeds where the airflow around the aircraft is partially subsonic and partially supersonic (from about Mach 0.7 to Mach 1.3)
- Supersonic Aircraft speeds where the airflow around the aircraft is completely above the speed of sound but below hypersonic airspeed (from about Mach 1.3 to Mach 5.0)
- Hypersonic Aircraft speeds above Mach 5.0
THE SPEED OF SOUND
The speed of sound is an important factor in the study of high‐speed flight. Small pressure disturbances are caused by all parts of an aircraft as it moves through the air. These disturbances move outward from their source through the air at the speed of sound. A two‐dimensional analogy is that of the ripples on a pond that result when a stone is thrown in the water.The speed of sound in air is a function of temperature alone:where(16.1 )a = speed of sound a0 = speed of sound at sea level, standard day (661 kts) θ = temperature ratio, T/T0 Since Eq. 16.1
eBook - PDF- Patrick H. Oosthuizen, William E. Carscallen(Authors)
- 2013(Publication Date)
- CRC Press(Publisher)
373 11 Hypersonic Flow Introduction Hypersonic flow was loosely defined in Chapter 1 as flow in which the Mach number is greater than about 5. No real reasons were given at that point as to why Supersonic Flows at high Mach numbers were different from those at lower Mach numbers. However, it is the very existence of these differences that really defines hypersonic flow. The nature of these hypersonic flow phenomena, and therefore the real definition of “hypersonic flow,” will be presented in the next section. Hypersonic flows have, up to the present, mainly been associated with the reentry of orbiting and other high altitude bodies into the atmosphere. For example, a typical Mach number with altitude variation for a reentering satellite is shown in Figure 11.1. It will be seen from this figure that because of the high velocity that the craft had to possess to keep it in orbit, very high Mach numbers—values that are well into the hypersonic range—exist during reentry. Discussions and studies of passenger aircraft that can fly at hypersonic speeds at high altitudes have also been undertaken. A typical proposed such vehicle is shown in Figure 11.2. This chapter, which presents a brief introduction to hypersonic flow, is the first of three interrelated chapters. One of the characteristics of hypersonic flow is the presence of so-called high-temperature gas effects, and these effects will be discussed more fully in the next chapter. Hypersonic flow is also conventionally associated with high altitudes where the air density is very low, and “low-density flows” will be discussed in Chapter 13. Characteristics of Hypersonic Flow As mentioned above, hypersonic flows are usually loosely described as flows at very high Mach numbers, say greater than about 5. However, the real definition of hypersonic flows is that they are flows at such high Mach numbers that phenomena occur that do not exist at low supersonic Mach numbers.
eBook - PDFElements of Aerodynamics
A Concise Introduction to Physical Concepts
- Oscar Biblarz(Author)
- 2022(Publication Date)
- Wiley(Publisher)
10 Transonic and Hypersonic Aerodynamics 10.1 Introduction In this chapter we examine two separate flight regimes that while based on the same overall fluid dynamic principles are sufficiently different from other aerodynamics regimes to merit separate treatment. Transonic and hypersonic flows are also different from each other and need to be treated in a more advanced manner than our coverage of flow regimes in previous chapters. Their impor- tance is nearly matched by their complexity, so we will only consider topics that can be presented without the aid of numerical tools. Our study of transonic and hypersonic flows will focus on some aspects of their unique character. Formulations with compressible-flow boundary layers and high temperature gas effects are beyond the scope of our presentation. Supersonic flight is presently routinely achieved, but to get there the aircraft needs to pass through the transonic region (Mach 0.7–1.4), one that generates high drag forces and often signif- icant flow unsteadiness thereby challenging thrust production from ordinary low-speed power- plants and requiring advanced controls on the aircraft. Recall that when going through Mach 1, the aerodynamic center location, or “neutral point” on the wing (where the moment coefficient is independent of angle of attack), changes from the quarter chord to the half chord. With transonic flows we need to depart from our default thin airfoils’ assumptions because research has shown that for cruising at this regime “supercritical airfoils” need to be thick to minimize overall drag unlike more conventional wing designs. We will examine the supercritical airfoil at a discrete airfoil loca- tion, namely, the upper aft region where shocks and boundary layer separation most often occur.
eBook - PDFAdvances in Aeronautical Sciences
Proceedings of the First International Congress in the Aeronautical Sciences, Madrid, 8-13 September 1958
- Th. Von Kármán(Author)
- 2014(Publication Date)
- Pergamon(Publisher)
A REVIEW OF SOME RECENT DEVELOPMENTS IN HYPERSONIC FLOW* By ANTONIO FERRI Polytechnic Institute of Brooklyn I N T R O D U C T I O N f THE field of hypersonic aerodynamics is dominated by two conflicting characteristics: The phenomena to be investigated are much more complex and less amenable to simplified schemes of analysis and to experimental investigation than other fields of fluid dynamics while at the same time much more precise detailed knowledge of the flow field is required in order to obtain the information necessary for practical applications. The complexity of hypersonic flow can be attributed to two main reasons: In very high speed flow fields of practical interest the fluid behaves as nonideal gas with variable properties; chemical-physical transformations can take place in limited regions of the flow; at the same time the flow to be investigated is highly nonlinear, rotational and, in important regions, of the transonic type. Against this formidable increase of difficulties with respect to Supersonic Flow stands the necessity of obtaining more accurate and more detailed information of the flow field. In hypersonic flow problems, it is important to determine the heat transfer to the body together with the determination of forces and pressure distribution. For the determination of the forces only integral characteristics of the flow field are required; these can be obtained by means of simplified representations of the overall phenomenon, without the necessity of representing correctly the details of the flow, while the determination of heat transfer requires a precise knowledge of velocity and pressure gradients, of pressure and entropy distributions in the flow field, of chemical-physical transformations taking place inside and outside the boundary layer, and of laminar, turbulent and transitional boundary layer flows.
eBook - PDF- G. G. Chernyi(Author)
- 2013(Publication Date)
- Academic Press(Publisher)
The acceleration of vehicles to these high speeds has been brought about by an increase in the power of rockets and by the successful development of automatic guidance and con-trol. Through the use of rocket propulsion, long-range ballistic ve-hicles and earth satellites with velocities from 6 to 8 km/sec have been developed. The time is near at hand when lifting vehicles will also attain these velocities. For this reason, parallel with the further development of the theoretical and experimental aerodynamics of flight at moderate supersonic speeds, i.e., speeds not greater than four to five times the speed of sound, an intensive development of the aerodynamics of hypersonic flow was begun. The basis for systematic investigations in the regime of hypersonic aerodynamics can be traced to the work of [54] and also to the works which followed it [55-57]. Let us briefly look into some of the specific features of this new branch of aerodynamics. As was already pointed out, for hypersonic flows past slender bodies the velocity perturbations are small compared with the free stream velocity, but are not small compared with the free stream sound velocity. Under these conditions many of the results of linear-ized theory, which are so useful for studying flows past slender bodies at moderate supersonic speeds, can no longer be applied. As a SEC. 1] HISTORICAL REMARKS 5 result it becomes necessary in any theoretical analysis to retain non-linear terms in the flow equations. This feature materially complicates the methods of calculating flows at hypersonic speeds compared to moderate supersonic speeds. This is not the only difliculty in the theoretical study of hypersonic flow, however. The gas temperature near the surface of the body increases to very high values at hypersonic flight speeds.
eBook - ePubElements of Aerodynamics
A Concise Introduction to Physical Concepts
- Oscar Biblarz(Author)
- 2022(Publication Date)
- Wiley(Publisher)
10 Transonic and Hypersonic Aerodynamics 10.1 Introduction In this chapter we examine two separate flight regimes that while based on the same overall fluid dynamic principles are sufficiently different from other aerodynamics regimes to merit separate treatment. Transonic and hypersonic flows are also different from each other and need to be treated in a more advanced manner than our coverage of flow regimes in previous chapters. Their importance is nearly matched by their complexity, so we will only consider topics that can be presented without the aid of numerical tools. Our study of transonic and hypersonic flows will focus on some aspects of their unique character. Formulations with compressible‐flow boundary layers and high temperature gas effects are beyond the scope of our presentation. Supersonic flight is presently routinely achieved, but to get there the aircraft needs to pass through the transonic region (Mach 0.7–1.4), one that generates high drag forces and often significant flow unsteadiness thereby challenging thrust production from ordinary low‐speed powerplants and requiring advanced controls on the aircraft. Recall that when going through Mach 1, the aerodynamic center location, or “neutral point” on the wing (where the moment coefficient is independent of angle of attack), changes from the quarter chord to the half chord. With transonic flows we need to depart from our default thin airfoils’ assumptions because research has shown that for cruising at this regime “supercritical airfoils” need to be thick to minimize overall drag unlike more conventional wing designs
eBook - ePubFly the Wing
A flight training handbook for transport category airplanes
- Billy Walker(Author)
- 2018(Publication Date)
- Aviation Supplies & Academics, Inc.(Publisher)
This is illustrated in a very simplified manner in Figure 3-4. The high-speed (but still subsonic) airstream flows up over the leading edge of the wing, increasing in velocity as it does so, and passes the speed of sound. The air flowing over the wing increases in speed for a short distance and then passes through a normal shock wave, decreasing from supersonic to subsonic speed in the process. Notice that the shock wave was formed only during the instantaneous decrease in speed from Supersonic Flow to subsonic flow and not during the gradual increase in speed over the leading edge of the wing. Figure 3-4. Normal shock wave. This clearly depicts a rule that always holds true: The transition of air from subsonic to supersonic is always smooth and unaccompanied by shock waves; but the change from supersonic to subsonic flow is always sudden and accompanied by rapid and large changes in pressure, temperature, and density across the shock wave that is formed. Therefore, when a plane flies fast enough, the air flowing over the leading edge and top of the wing may increase to supersonic speed. This air then decreases in speed as it flows over the wing, and a shock wave is formed. This wave is usually near the center of lift when it first forms and is scarcely noticeable to the pilot at this point. But let’s see what happens as the plane goes faster. In Figure 3-5, we can see that as the speed of the air over a typical wing section increases, the area of Supersonic Flow increases, and the shock wave begins to move back toward the trailing edge of the wing. The air passing under the wing also forms into a Supersonic Flow, and another shock wave is formed beneath the wing as this airflow reduces to subsonic speed. Finally, when the wing itself has reached supersonic speed, the shock waves on both the bottom and top of the wing have moved all the way back to the trailing edge
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