H YPERSONIC flight began in February 1949 when a WAC Corporal rocket was ignited from a U.S.-captured V-2 rocket [1]. In the six decades since this milestone, there have been significant investments in the development of hypersonic vehicle technologies. The NASA X-15 rocket plane in the early 1960s represents early research toward this goal [2,3]. After a lull in activity, the modern era of hypersonic research started in the mid-1980s with the National Aerospace Plane (NASP) program [4], aimed at developing a single-stage-to-orbit reusable launch vehicle (RLV) that used conventional runways. However, it was canceled due mainly to design requirements that exceeded the state of the art [1,5]. A more recent RLV project, the VentureStar program, failed during structural tests, again for lack of the required technology [5]. Despite these unsuccessful programs, the continued need for a low-cost RLV, as well as the desire of the U.S. Air Force (USAF) for unmanned hypersonic vehicles, has reinvigorated hypersonic flight research. An emergence of recent and current research programs [6] demonstrate this renewed interest. Consider, for example, the NASA Hyper-X experimental vehicle program [7], the University of Queensland HyShot program [8], the NASA Fundamental Aeronautics Hypersonics Project [9], the joint U.S. Defense Advanced Research Projects Administration (DARPA)/USAF Force Application andLaunch fromContinentalUnited States (FALCON) program [10], the X-51 Single Engine Demonstrator [11,12], the joint USAF Research Laboratory (AFRL)/Australian Defence Science and Technology Organisation Hypersonic International Flight Research Experimentation project [13], and ongoing basic hypersonic research at the AFRL (e.g., [14–20]). The conditions encountered in hypersonic flows, combined with the need to design hypersonic vehicles, have motivated research in the areas of hypersonic aeroelasticity and aerothermoelasticity. It is evident from Fig. 1 that hypersonic vehicle configurations will consist of long, slender lifting body designs. In general, the body, surface panels, and aerodynamic control surfaces are flexible due to minimum-weight restrictions. Furthermore, as shown in Fig. 2, these

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Aeroelastic and Aerothermoelastic Analysis in Hypersonic Flow: Past, Present, and Future

A review of the state-of-the-art in hypersonic aeroelasticity and aerothermoelasticity is provided. Recently, the main focus in this area has been on the development of computational aeroelastic and aerothermoelastic methods capable of studying complete hypersonic vehicles. Thus, in addition to a survey of studies conducted in this area over the past six decades, two important issues are a focus of this review, namely: 1) modeling unsteady hypersonic aerodynamics; and 2) incorporation of the heat transfer between the fluid and the structure into the aeroelastic solution process. Finally, future directions of hypersonic aeroelasticity and aerothermoelasticity are outlined. Since air-breathing hypersonic vehicles exhibit strong coupling between the airframe, propulsion, and control systems, future directions point to the incorporation of advanced computational aerothermoelastic methods into a comprehensive vehicle analysis.

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Aeroelastic and Aerothermoelastic Analysis of Hypersonic Vehicles: Current Status and Future Trends

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Multidimensional numerical simulation of reactive flow in internal combustion engines

In oil and gas drilling operations, predictions of pressure losses and cuttings concentration in the annulus are very complex due to the combination of interacting drilling parameters. Past studies have proposed many empirical correlations to estimate pressure losses and cuttings concentration. However, these developed correlations are limited to their experimental data range and setup, and hence, they cannot be applicable to all cases. CFD methods have the advantages of handling complex multiphase flow problems, as well as, an unlimited number of physical and operational conditions. The present study employs the inhomogeneous (Eulerian-Eulerian) model to simulate a two-phase solid-fluid flow and predict pressure losses and cuttings concentration in eccentric horizontal annuli as a function of varying drilling parameters: fluid velocity, diameter ratio (ratio of inner pipe diameter to outer pipe diameter), inner pipe rotation speed, and fluid type. Experimental data for pressure losses and cuttings concentration from previous literature compared very well with simulation data, confirming the validity of the current model. The study shows how reliable CFD methods can replicate the actual, yet complex oil and gas drilling operations.

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CFD Method for Predicting Annular Pressure Losses and Cuttings Concentration in Eccentric Horizontal Wells

The mathematical and physical basis of the SHIP computer program which embodies a finite-difference, implicit numerical procedure for the computation of hydrogen injected into a supersonic airstream at an angle ranging from normal to parallel to the airstream main flow direction is described. The physical hypotheses built into the program include: a two-equation turbulence model, and a chemical equilibrium model for the hydrogen-oxygen reaction. Typical results for equilibrium combustion are presented and exhibit qualitatively plausible behavior. The computer time required for a given case is approximately 1 minute on a CDC 7600 machine. A discussion of the assumption of parabolic flow in the injection region is given which suggests that improvement in calculation in this region could be obtained by use of the partially parabolic procedure of Pratap and Spalding. It is concluded that the technique described herein provides the basis for an efficient and reliable means for predicting the effects of hydrogen injection into supersonic airstreams and of its subsequent combustion.

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Combustion of hydrogen injected into a supersonic airstream (the SHIP computer program)

A solution method for three-dimensional turbulent boundary layers on bodies of arbitrary shapes

Development of a mathematical model of flow, heat transfer and combustion in a stratified charge engine

A new computer program has been written to calculate the properties of the recirculating base flow region of a rocket exhaust plume. The nozzle stream and the freestream, either of which may be supersonic, mix turbulently to form an axisymmetric compressible free boundary layer. Solutions of the elliptic differential equations, which incorporate a two-equation model of turbulence closure, are obtained using an iterative finite-difference technique coupled to a point-by-point solution of the chemical kinetics. Predictions are presented for the velocity, pressure, temperature, and species concentration distributions in the base recirculation region of a rocket exhaust plume under supersonic flight conditions.

Analysis of Combustion in Recirculating Flow for Rocket Exhausts in Supersonic Streams

This paper deals with flow in narrow skewed annuli; it provides predictions for the static-pressure and velocity fields in this flow situation, together with demonstrations of convergence and grid-size effects. The main features of the mathematical analysis and the numerical solution of the problem are reported, together with sufficient information to aid interpretation of the predictions obtained.

D.B. Spalding

Papers

Combustion of hydrogen injected into a supersonic airstream (the SHIP computer program)

A solution method for three-dimensional turbulent boundary layers on bodies of arbitrary shapes

Development of a mathematical model of flow, heat transfer and combustion in a stratified charge engine

Analysis of Combustion in Recirculating Flow for Rocket Exhausts in Supersonic Streams

Flow in an annulus of non-uniform gap