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Article
Publication date: 1 December 1955

Maurice Holt

IN the first of these articles it was pointed out that normal supersonic flow can be described theoretically, to a first approximation, by the linearized equation of…

Abstract

IN the first of these articles it was pointed out that normal supersonic flow can be described theoretically, to a first approximation, by the linearized equation of motion. This has the form of the wave equation and governs first order disturbances to fields of uniform flow; for example, flow past thin wings or slender bodies at small angles of incidence, and flow through ducts of varying cross‐section. In the same way small disturbances in a purely subsonic stream can be described by a linearized equation of motion, which can be reduced to Laplace's equation by contracting the co‐ordinate normal to the direction of flow. Transonic flow, in which regions of both supersonic and subsonic flow occur, is not so easily represented.

Details

Aircraft Engineering and Aerospace Technology, vol. 27 no. 12
Type: Research Article
ISSN: 0002-2667

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Article
Publication date: 1 June 1995

Jan‐Kaung Fu

The performance of a spinningsecant‐ogive‐cylinder‐boattail projectile in thetransonic regime in terms of aerodynamic drag has been analyzed numericallyin this study. To…

Abstract

The performance of a spinning secant‐ogive‐cylinder‐boattail projectile in the transonic regime in terms of aerodynamic drag has been analyzed numerically in this study. To obtain an accurate prediction of the spinning effect on individual drag components and total drag of a projectile for the shell design, the implicit, diagonalied, symmetric Total Variation Diminishing (TVD) scheme, accompanied by a suitable grid, is employed to solve the thin‐layer axisymmetric Navier‐Stokes equations associated with the Baldwin‐Lomax turbulence model. The computed results show that, in comparison with the non‐spinning case, to increase the spin rate can result in increases in viscous drag and nose pressure drag, but can cause decreases in boattail drag and base drag. The variations of these drag components result in only a small (less than 5%) increase in total drag; thus the performance of the transonic projectiles is found to be insensitive to the spin rate.

Details

Engineering Computations, vol. 12 no. 6
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 28 May 2021

M.R. Saber and M.H. Djavareshkian

In the present research, the effect of the flexible shells method in unsteady viscous flow around airfoil has been studied. In the presented algorithm, due to the…

Abstract

Purpose

In the present research, the effect of the flexible shells method in unsteady viscous flow around airfoil has been studied. In the presented algorithm, due to the interaction of the aerodynamic forces and the structural stiffness (fluid-structural interaction), a geometrical deformation as the bump is created in the area where the shock occurs. This bump causes instead of compressive waves, a series of expansion waves that produce less drag and also improve the aerodynamic performance to be formed. The purpose of this paper is to reduce wave drag throughout the flight range. By using this method, we can be more effective than recent methods throughout the flight because if there is a shock, a bump will form in that area, and if the shock does not occur, the shape of the airfoil will not change.

Design/methodology/approach

In this simulation pressure-based procedure to solve the Navier-Stokes equation with collocated finite volume formulation has been developed. For this purpose, a high-resolution scheme for fluid and structure simulation in transonic flows with an arbitrary Lagrangian-Eulerian method is considered. To simulate Navier-Stokes equations large eddy simulation model for compressible flow is used.

Findings

A new concept has been defined to reduce the transonic flow drag. To reduce drag force and increase the performance of airfoil in transonic flow, the shell can be considered flexible in the area of shock on the airfoil surface. This method refers to the use of smart materials in the aircraft wing shell.

Originality/value

The value of the paper is to develop a new approach to improve the aerodynamic performance and reduce drag force and the efficiency of the method throughout the flight. It is noticeable that the new algorithm can detect the shock region automatically; this point was disregarded in the previous studies. It is hoped that this research will open a door to significantly enhance transonic airfoil performance.

Details

Aircraft Engineering and Aerospace Technology, vol. 93 no. 4
Type: Research Article
ISSN: 1748-8842

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Article
Publication date: 1 February 1958

A.D.Y.

Transonic flow has been defined as flow in which regions of subsonic and supersonic flow occur each of significant extent, so that across the common boundaries of these…

Abstract

Transonic flow has been defined as flow in which regions of subsonic and supersonic flow occur each of significant extent, so that across the common boundaries of these regions fluid particles are accelerated or decelerated through the speed of sound. By the term ‘significant’ is here implied significant for the particular problem or flow characteristic under consideration. Hence for problems in which viscous effects are of major interest the flow past a body at any main stream supersonic speed is strictly speaking transonic in so far as a region of subsonic flow must exist in the bounday layer adjacent to the surface. The book under review is confined, however, to the theory of transonic flow of an inviscid fluid, and the main application of this theory is to problems that arise in considering the flow past wings and bodies at main stream Mach numbers in the range from about 0.8 to 1.2.

Details

Aircraft Engineering and Aerospace Technology, vol. 30 no. 2
Type: Research Article
ISSN: 0002-2667

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Article
Publication date: 13 June 2019

Hanan Lu, Qiushi Li, Tianyu Pan and Ramesh Agarwal

For an axial-flow compressor rotor, the upstream inflow conditions will vary as the aircraft faces harsh flight conditions (such as taking off, landing or maneuvering) or…

Abstract

Purpose

For an axial-flow compressor rotor, the upstream inflow conditions will vary as the aircraft faces harsh flight conditions (such as taking off, landing or maneuvering) or the whole compressor operates at off-design conditions. With the increase of upstream boundary layer thickness, the rotor blade tip will be loaded and the increased blade load will deteriorate the shock/boundary layer interaction and tip leakage flows, resulting in high aerodynamic losses in the tip region. The purpose of this paper is to achieve a better flow control for tip secondary flows and provide a probable design strategy for high-load compressors to tolerate complex upstream inflow conditions.

Design/methodology/approach

This paper presents an analysis and application of shroud wall optimization to a typical transonic axial-flow compressor rotor by considering the inlet boundary layer (IBL). The design variables are selected to shape the shroud wall profile at the tip region with the purpose of controlling the tip leakage loss and the shock/boundary layer interaction loss. The objectives are to improve the compressor efficiency at the inlet-boundary-layer condition while keeping its aerodynamic performance at the uniform condition.

Findings

After the optimization of shroud wall contour, aerodynamic benefits are achieved mainly on two aspects. On the one hand, the shroud wall optimization has reduced the intensity of the tip leakage flow and the interaction between the leakage and main flows, thereby decreasing the leakage loss. On the other hand, the optimized shroud design changes the shock structure and redistributes the shock intensity in the spanwise direction, especially weakening the shock near the tip. In this situation, the shock/boundary layer interaction and the associated flow separations and wakes are also eliminated. On the whole, at the inlet-boundary-layer condition, the compressor with optimized shroud design has achieved a 0.8 per cent improvement of peak efficiency over that with baseline shroud design without sacrificing the total pressure ratio. Moreover, the re-designed compressor also maintains the aerodynamic performance at the uniform condition. The results indicate that the shroud wall profile has significant influences on the rotor tip losses and could be properly designed to enhance the compressor aerodynamic performance against the negative impacts of the IBL.

Originality/value

The originality of this paper lies in developing a shroud wall contour optimization design strategy to control the tip leakage loss and the shock/boundary layer interaction loss in a transonic compressor rotor. The obtained results could be beneficial for transonic compressors to tolerate the complex upstream inflow conditions.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 29 no. 11
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 1 June 2004

L. Djayapertapa and C.B. Allen

Transonic flutter and active flap control, in two dimensions, are simulated by coupling independent structural dynamic and inviscid aerodynamic models, in the time domain…

Abstract

Transonic flutter and active flap control, in two dimensions, are simulated by coupling independent structural dynamic and inviscid aerodynamic models, in the time domain. A flight control system, to actively control the trailing edge flap motion, has also been incorporated and, since this requires perfect synchronisation of fluid, structure and control signal, the “strong” coupling approach is adopted. The computational method developed is used to perform transonic aeroelastic and aeroservoelastic calculations in the time domain, and used to compute stability (flutter) boundaries of 2D wing sections. Open and closed loop simulations show that active control can successfully suppress flutter and results in a significant increase in the allowable speed index in the transonic regime. It is also shown that active control is still effective when there is free‐play in the control surface hinge. Flowfield analysis is used to investigate the nature of flutter and active control, and the fundamental importance of shock wave motion in the vicinity of the flap is demonstrated.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 14 no. 4
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 26 October 2012

M. Tutar and Ü. Sönmez

The purpose of this paper is to numerically study inflow turbulence effects on the transitional flow in a high pressure linear transonic turbine at the design incidence.

Abstract

Purpose

The purpose of this paper is to numerically study inflow turbulence effects on the transitional flow in a high pressure linear transonic turbine at the design incidence.

Design/methodology/approach

The three‐dimensional (3‐D) compressible turbulent flow in a turbine inlet guide vane is simulated using a finite volume based fluid solver coupled with dynamic large eddy simulation (LES) computations to investigate the effects of varying inflow turbulence length scale and the turbulence intensity on the aero‐thermal flow characteristics and the laminar‐turbulent transition phenomena. The computational analyses are extended to very high exit Reynolds number flow conditions to further study the effect of high exit Reynolds numbers on the transitional behavior of the present flow around the inlet guide vane cascades of the turbine. The calculations are performed with varying degree of inflow turbulence intensity values ranging from 0.8 to 6 percent and the inflow turbulence length scales ranging from one to five percent of pitch for different exit isentropic Mach and Reynolds numbers.

Findings

The numerical predictions in comparison with the experimental data demonstrate that the level of inflow turbulence closure provided by the present LES computations offers a reliable framework to predict complex turbulent flow and transition phenomena in high free‐stream turbulence environments of high pressure linear turbines.

Originality/value

This is the first instance in which both artificially modified random flow generation method in association with the dynamic procedure of LES application is employed to represent the realistic inflow turbulence conditions in the high pressure turbine and to resolve the transitional flow in a dynamic approach.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 22 no. 8
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 6 November 2017

Mojtaba Tahani, Mehran Masdari, Hamidreza Eivazi and Massoud Tatar

This paper aims to investigate numerical solution of transonic flow around NACA0012 airfoil under sinusoidal pitch oscillation. Accordingly, effects of the amplitude and…

Abstract

Purpose

This paper aims to investigate numerical solution of transonic flow around NACA0012 airfoil under sinusoidal pitch oscillation. Accordingly, effects of the amplitude and frequency of oscillations on aerodynamic coefficients are evaluated and the efficiency of the turbulent models, K-ω shear-stress transport (SST), scale adaptive simulation (SAS) and delayed detached eddy simulation (DDES), in simulation of the nonlinear phenomena – i.e. the interaction between shock and boundary layer and the shock oscillations – is studied.

Design/methodology/approach

K-ω SST, SAS and DDES models are used as turbulence approaches. The numerical results are compared with available experimental and numerical information.

Findings

According to the results inside the buffet boundaries, the DDES turbulent model expresses results that are more appropriate; however, SAS and SST models are not efficient enough in evaluating the characteristics of nonlinear flow.

Originality/value

In this research study, hybrid RANS-LES turbulence model is engaged to simulate transonic flow around pitching NACA0012 airfoil, and results are compared to the SAS and Reynolds Average Navier–Stocks simulations as well as available numerical and experimental data. In addition, effects of the amplitude and frequency of oscillations on aerodynamic coefficients are evaluated in buffet regions.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 27 no. 11
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 1 August 2003

Abdurrahman Hacıogˇlu and I˙brahim Özkol

In this study, the power of vibrational genetic algorithm (VGA) for transonic airfoil design and optimisation problems, which are generally characterized by multi‐model…

Abstract

In this study, the power of vibrational genetic algorithm (VGA) for transonic airfoil design and optimisation problems, which are generally characterized by multi‐model topology in the design parameter space, has been introduced. This type of problem is characterized by search and computational time to achieve satisfying solutions. In order to obtain more robust and faster algorithm, vibration concept, our earlier study, is further developed. This developed VGA is coupled with a full potential flow‐field solver for inverse design and airfoil optimisation problem in transonic case. The performance of this implemented strategy is compared with that offered by a classical or more commonly used genetic algorithm.

Details

Aircraft Engineering and Aerospace Technology, vol. 75 no. 4
Type: Research Article
ISSN: 0002-2667

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Article
Publication date: 1 November 1961

Over the years, theories of the forces on bodies moving with purely subsonic or purely supersonic velocities through gases have been evolved as required by current…

Abstract

Over the years, theories of the forces on bodies moving with purely subsonic or purely supersonic velocities through gases have been evolved as required by current aeronautical practice; the development of such theories has not proved unduly difficult. Moreover, the theories have been monitored and checked by corresponding experimental investigations. In view of the complexity of some of the subsonic work, it might have been expected that supersonic theory would prove intractable; in the event, it has proved that, in some respects at least, supersonic theory is simpler than subsonic. By contrast with these fields, studies of transonic phenomena have lagged badly. For one thing, experimental work at transonic speeds is comparatively recent: until the development of slotted or perforated walls for transonic tunnels, it used to be said that one could only test at M=l a model of infinitesimal size—anything finite choked the tunnel. On the theoretical side the investigator is faced with the study of a region involving mixed flows, different parts of the field obeying different laws, with an unspecified sonic line at the boundary. Clearly, even in steady conditions this is a problem of great complexity.

Details

Aircraft Engineering and Aerospace Technology, vol. 33 no. 11
Type: Research Article
ISSN: 0002-2667

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