Transonic Flow

A special issue of Aerospace (ISSN 2226-4310). This special issue belongs to the section "Aeronautics".

Deadline for manuscript submissions: closed (30 November 2023) | Viewed by 8226

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Department of Aerospace Engineering, Cranfield University, Cranfield MK43 0AL, UK
Interests: aerodynamics; computational fluid dynamics; fluid mechanics; gas dynamics; fluid turbulence; experimental fluid mechanics; flow
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Dear Colleagues,

Transonic flow research has been of critical importance since the development of high-speed propellor aeroplanes and turbojet engines in the mid-1940s. The transonic flow regime has been, and remains, a challenge both for computational prediction and experimental simulation. The close coupling of the shock waves arising from the compressibility of the air and the viscous flow on the aircraft surfaces leads to highly unsteady and complicated flows that often involve detrimental flow separations. These can lead to unsteady loading that can cause structural vibrations of aircraft components. An understanding of unsteady transonic flow is therefore fundamental to the safe design of high-speed aircraft.

Today’s aircraft industry is challenged to develop revolutionary new aircraft concepts to address the aviation impact on climate change and noise. This is driving reassessments in design philosophy to achieve step changes in aerodynamic and propulsive efficiency, involving much closer coupling of the aircraft fuselage, wings, and engines. Emerging data on the transonic performance of these revolutionary designs have revealed how different the flows are to those that we understand around conventional tube and swept-wing designs.

Transonic flow research therefore remains critical to the development of high-speed aircraft today, as it ever was, and it is fitting that this Special Issue of Aerospace is devoted to this important topic.

Prof. Dr. Simon Prince
Guest Editor

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Related Special Issue

Published Papers (3 papers)

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Research

15 pages, 9708 KiB  
Article
Passive Transonic Shock Control on Bump Flow for Wing Buffet Suppression
by Davide Di Pasquale and Simon Prince
Aerospace 2023, 10(6), 569; https://doi.org/10.3390/aerospace10060569 - 20 Jun 2023
Cited by 1 | Viewed by 2390
Abstract
Since modern transport aircraft cruise at transonic speeds, shock buffet alleviation is one indispensable challenge that civil transport research needs to be addressed. Indeed, in the transonic flow regime shock-induced separation and transonic buffet compromise the flight envelope of an aircraft, and therefore [...] Read more.
Since modern transport aircraft cruise at transonic speeds, shock buffet alleviation is one indispensable challenge that civil transport research needs to be addressed. Indeed, in the transonic flow regime shock-induced separation and transonic buffet compromise the flight envelope of an aircraft, and therefore its operational safety and structural integrity. One possible solution is to control and delay the boundary layer separation. The aim of this work was to study whether sub-boundary layer scale period roughness, which locally increases the boundary layer displacement thickness, can act as a virtual shock bump, with aim of bifurcating the foot of the shock wave to reduce the shock’s adverse effect on the boundary layer in the same way as solid shock bumps are known to act. This passive approach can then enhance the buffet margin, consequently extending the safe flight envelope. An experimental investigation was performed, applying this passive technique on a wind tunnel wall bump model which simulated the flow over the upper surface of an aerofoil. The results, in terms of surface pressure distribution and corresponding shadowgraph flow visualisation, showed that such periodic roughness can, indeed, bifurcate the shock wave and delay shock-induced separations, depending on the orientation of the roughness and its periodicity. A virtual shock bump effect can be produced using the displacement effect of periodic sub-boundary layer scale roughness. Full article
(This article belongs to the Special Issue Transonic Flow)
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17 pages, 5500 KiB  
Article
Fast Inverse Design of Transonic Airfoils by Combining Deep Learning and Efficient Global Optimization
by Feng Deng and Jianmiao Yi
Aerospace 2023, 10(2), 125; https://doi.org/10.3390/aerospace10020125 - 29 Jan 2023
Cited by 3 | Viewed by 2302
Abstract
In this paper, a deep learning model trained to generate well-posed pressure distributions at transonic speeds is coupled by the efficient global optimization (EGO) algorithm to speed up the inverse design process for transonic airfoils. First, the Wasserstein generative adversarial network (WGAN) is [...] Read more.
In this paper, a deep learning model trained to generate well-posed pressure distributions at transonic speeds is coupled by the efficient global optimization (EGO) algorithm to speed up the inverse design process for transonic airfoils. First, the Wasserstein generative adversarial network (WGAN) is trained to generate well-posed pressure distributions at transonic speeds. Then, the EGO algorithm is used to pick up a pressure distribution in WGAN by solving the associated optimization problem defined for matching the prescribed pressure features, such as the suction peak and the shock-wave position. Finally, a deep convolutional neural network (DCNN) for nonlinear mapping is adopted to obtain the corresponding airfoil shape. Several cases with prescribed pressure features were performed to verify the feasibility and efficiency of the proposed method. Test cases indicate that the airfoil shape with the desired pressure distribution can be found in around one minute using a desktop computer with an Intel i5-9300H CPU. Full article
(This article belongs to the Special Issue Transonic Flow)
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16 pages, 6771 KiB  
Article
Cooperation of Trailing-Edge Flap and Shock Control Bump for Robust Buffet Control and Drag Reduction
by Shenghua Zhang, Feng Deng and Ning Qin
Aerospace 2022, 9(11), 657; https://doi.org/10.3390/aerospace9110657 - 27 Oct 2022
Cited by 2 | Viewed by 2292
Abstract
At transonic flight conditions, the buffet caused by the interaction between the shock waves and the boundary layers can degrade an aircraft’s aerodynamic performance and even threaten its safety. In this paper, the shock control bumps, originally designed to reduce the wave drag [...] Read more.
At transonic flight conditions, the buffet caused by the interaction between the shock waves and the boundary layers can degrade an aircraft’s aerodynamic performance and even threaten its safety. In this paper, the shock control bumps, originally designed to reduce the wave drag at cruise speeds, are applied to enhance the robustness of the closed-loop buffet control system using the trailing-edge flap. For the OAT15A supercritical airfoil, a closed-loop buffet control system is first designed with a feedback signal of lift coefficient. Then, the shock control bumps designed for drag reduction are integrated into the active buffet control system. The results show that the closed-loop flap control can be greatly enhanced by coupling with the shock control bumps. At the steady state under control, the shock control bumps can slightly increase the airfoil lift–drag ratio. More importantly, the ranges of control parameters that can effectively suppress the buffet are significantly enlarged with the help of the bumps; thus, the robustness of the control system is greatly enhanced. Full article
(This article belongs to the Special Issue Transonic Flow)
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