The Aeronautical Journal

Journal Information
ISSN / EISSN : 0001-9240 / 2059-6464
Published by: Cambridge University Press (CUP) (10.1017)
Total articles ≅ 4,581
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S. Paul, A. Vinoth Raj, C. Senthil Kumar
The Aeronautical Journal pp 1-28; https://doi.org/10.1017/aer.2022.65

Abstract:
This paper consists of CFD and experimental study for shell projectile at angle of attack 00 and at various Mach numbers (0.7, 0.9, 1.0, 1.5 and 2.0), without spin effect. Passive method of base modification is used to reduce base drag. The goal of this study is to reduce base drag by utilising a base bleed approach called the Inward Turning Base Bleed Method (IWTB). The concept of IWTB is to draw relatively high-pressure air behind the driving band and allow it to pass through the bleed holes and direct it into the low-pressure base. This will in turn raise the base pressure and lower the base drag. The study comprises of (i) basic model with a boattail angle of $8^{\circ}$ , (ii) eight different cavity models having different lip thickness and depth thickness ratios and (iii) nine different IWTB configurations for the optimised cavity model. At first, cavity model is optimised by varying the lip thickness and depth thickness ratio. Later IWTB parameters such as the bleed hole entry angles $10^{\circ}$ , $12^{\circ}$ & $15^{\circ}$ , exit bleed hole angles $30^{\circ}$ , $45^{\circ}$ & $60^{\circ}$ , bleed hole diameters 3mm, 4mm, 5mm & 6mm and number of bleed holes i.e., 4 & 8 were studied and optimised. Based on this study, the model with 8 holes, 3mm base bleed hole diameter, $15^{\circ}$ entry and $60^{\circ}$ exit angle gives comparatively lower base drag. CFD result shows, in supersonic region the base drag reduction for optimised shell projectile is $3.08\%$ ; at Mach number 0.9 the base reduction is $75.63\%$ ; and in subsonic region it reduces to $23.53\%$ . CFD results were compared with experimental result, is found to be good and the differences lies within $3.85\%$ .
J.A. Branch, B. Zang, M. Azarpeyvand, D. Jones, E. Jinks, M. Fernandino Westin
The Aeronautical Journal pp 1-27; https://doi.org/10.1017/aer.2022.66

Abstract:
This paper investigates the hydrodynamic near-field of a NACA 16-616 aerofoil over a range of angles-of-attack, encompassing the pre-stall, stall and post-stall flow regimes. In both the static pressure and the pressure fluctuation results, it is shown that each flow regime is easily distinguished, and it is further shown that each regime has different spectral behaviour and boundary layer characteristics. It is found that the NACA 16-616 aerofoil stalls by an abrupt leading-edge mechanism, characterised by a sudden change in the static pressure and unsteady surface pressure spectra between $16^\circ $ and $17^\circ $ angles-of-attack, but of more interest is that there is a secondary yet significant trailing-edge flow separation mechanism occurring upstream of the trailing-edge and moving further upstream as the angle-of-attack increases in the pre-stall regime. A comparison is made between the spectra and coherence of the unsteady surface pressure of the NACA 16-616 aerofoil and those of the classic NACA 0012 aerofoil and shows that such a secondary mechanism has a significant impact for large pre-stall angles-of-attack on the unsteady surface pressure. This will have a significant impact on the radiated far-field sound, distinguishing the NACA 16-616 aerofoil from aerofoils that do not have this secondary mechanism. The existence and extent of this secondary trailing-edge separation mechanism is further shown by the hot-wire anemometry boundary layer velocity results that indicate separation within the pre-stall regime.
, X. Wu, Q. Yang
The Aeronautical Journal pp 1-21; https://doi.org/10.1017/aer.2022.41

Abstract:
Based on erosion coupon tests, a sand erosion model for 17-4PH steel was developed. The developed erosion model was validated against the results of compressor erosion tests from a generic rig and from other researchers. A high-fidelity computational fluid dynamics (CFD) model of the test rig was built, a user-defined function was developed to implement the erosion model into the ANSYS CFD software, and the turbulent, two-phase flow-field in multiple reference frames was solved. The simulation results are consistent with the test results from the compressor rig and with experimental findings from other researchers. Specifically, the sand erosion blunts the leading edge, sharpens the trailing edge and increases pressure-surface roughness. The comparisons between the experimental observations and numerical results as well as a quantitative comparison with three other sand erosion models indicate that the developed sand erosion model is adequate for erosion prediction of engine components made of 17-4PH steel.
F. Rasimarzabadi, C. Clark, M. Neuteboom, D. Orchard, H. Martensson
The Aeronautical Journal pp 1-17; https://doi.org/10.1017/aer.2022.67

Abstract:
A new aerodynamic open-circuit test rig for studying boundary layer ingestion (BLI) propulsion has been developed by National Research Council of Canada. The purpose is to demonstrate the advantages of BLI in reducing the power required for a given thrust and to validate the performance of BLI fan concepts. The rig consists of a boundary layer generator to simulate boundary layer development over an aircraft fuselage. The boundary layer generator can be used to create a natural boundary layer due to skin friction but also comprises an array of perforated plates through which pressurised air can be blown to manipulate the boundary layer thickness. The size of the boundary layer thickness can be controlled upstream of the fan blades. Parametric studies of boundary layer thickness were then feasible. The test calibration was conducted to validate the concept.
A. Belmouhoub, S. Medjmadj, Y. Bouzid, S. H. Derrouaoui, M. Guiatni
The Aeronautical Journal pp 1-24; https://doi.org/10.1017/aer.2022.72

Abstract:
Robust control of non-linear systems is a challenging task, notably in the presence of external disturbances and uncertain parameters. The main focus of this paper is to solve the trajectory tracking problem of an unconventional quadrotor with rotating arms (also known as a foldable drone), while overcoming some of the challenges associated with this type of vehicle. Therefore, in a first step, the model of this vehicle is presented, taking into account the change of the inertia, the centre of gravity, and the control matrix. The theoretical foundations of backstepping control, based on the finite time Lyapunov stability theory and enhanced by a Super-Twisting algorithm, are then discussed. Numerical simulations are performed to demonstrate the efficiency of the suggested control approach. Finally, a qualitative and quantitative comparative study of the proposed controller with the conventional backstepping controller is performed. Overall, the obtained results show that the proposed control strategy outperforms in terms of accuracy and resilience.
S.A. Peddakotla, J. Yuan, E. Minisci, M. Vasile, M. Fossati
The Aeronautical Journal pp 1-30; https://doi.org/10.1017/aer.2022.69

Abstract:
The evaluation of the on-ground casualty risk assessments due to a controlled or uncontrolled re-entry is highly sensitive to the accurate prediction of fragmentation events during an atmospheric re-entry. The main objective of this study is an investigation into the use of peridynamics (PD) to improve the analysis of fragmentation during atmospheric re-entry with respect to currently adopted semi-empirical approaches. The high temperatures characterising such scenarios may substantially impact fragmentation, which requires appropriate modelling of the damage process within the PD method. The damage models in PD require experimentally determined fracture mechanical properties that are unavailable as a function of temperature. This work proposes a numerical methodology to estimate the PD damage parameters changes with temperature to enable the study of fragmentation during atmospheric re-entry. Initially, tensile-testing simulation experiments are performed in peridynamics to calibrate material parameters for steel and aluminium alloys as a function of temperature. Then, a parametric study is carried out to evaluate the temperature-dependent damage model parameters for the same materials. The applicability of the proposed methodology is showcased using a re-entry test case scenario.
The Aeronautical Journal pp 1-28; https://doi.org/10.1017/aer.2022.52

Abstract:
This paper presents a new concept of the control strategy in prevention program for the airlines to prevent the injuries of passengers and crew members for transport aircraft. A twin-jet transport aircraft encountered severe clear-air turbulence at transonic flight in descending phase is the study case of the present paper. The nonlinear and unsteady flight controllability models based on flight data mining and the fuzzy-logic modeling of artificial intelligence technique, are utilised to support this new concept. The proposed flight controllability models with the function of nonlinear dynamic inversion are employed to provide flight control strategy through flight simulations of dynamic inversion process; it is an innovation in mathematical modelling of aerospace engineering. Since the sudden plunging motion with the abrupt change in attitude and gravitational acceleration (i.e. the normal load factor) to affect the flight safety the most, hazard mitigation is a great concern for the aviation community. The present study is initiated to examine possible mitigation concepts of accident prevention to provide a training course for loss of control in-flight program to the airlines.
D. Kumar, G. Singh, P.M. Mohite, E.M. Lau, Y.-C. Wang
The Aeronautical Journal pp 1-20; https://doi.org/10.1017/aer.2022.71

Abstract:
This work investigates the role of flexibility and resonant excitation on the deformation mechanism and aerodynamic performance of flapping wings. A hummingbird-inspired wing (HIW) is considered and designed to have a bone-like stiffener made of carbon fibre/epoxy (CF/E) composite attached to a membrane made of carbon nanotubes/polypropylene (CNTs/PP) nanocomposite representing the flexible part of the natural wing. The designed HIW model is analysed through fluid-structure interaction simulations performed at frequencies near and at resonant frequency. It is found that HIW generates desired bending and twisting deformations that are coupled. These deformation mechanisms are studied in detail with the help of time-varying deflections and bending-twisting angles. Further, the simultaneous effect of these parameters on the aerodynamic performance of the wing is also investigated. It is observed that the coupled nature of bending and twisting deformations is critical in enhancing the aerodynamic performance of flapping wings. In addition to that, the resonance generates higher amplitude of desired structural deformations that further enhances thrust as well as lift generation capability of the wing. The underlying mechanism for this is also explained by studying the flow around the deflected surface of the wing. Compared to off-resonant frequencies, vorticity and pressures are substantially higher for the wing at resonance. A physical model of HIW is realised using CNTs/PP and CF/E composites to perform experimental wing motion analysis and to validate the computational results. In conclusion, the present study provides a basis to design efficient biomimetic flapping wings for micro aerial vehicles (MAVs) by exploring flexibility and resonant excitation.
T. Takeshita, R. Fukunaga, S. Nakao, , K. Miki
The Aeronautical Journal pp 1-18; https://doi.org/10.1017/aer.2022.68

Abstract:
A new measurement technique to reconstruct the density field of the shock-wave/boundary-layer interaction (SWBLI) in a confined duct is proposed. With this technique, it is possible to quantitatively capture in detail the structures of the density field both in the regions of the shock-systems in the central core and boundary-layer flows near the duct wall concurrently. The novel feature of the proposed technique is to make use of the schlieren images with the rainbow filters of the vertical and horizontal cutoff settings and then to reconstruct the two-dimensional density field integrated over the line-of-sight direction using the corresponding filter calibration curves. The proposed technique is applied for the first time to a shock train in a constant-area straight duct under the upstream condition of the shock train: the freestream Mach number is 1.42, the incoming boundary layer thickness normalised by the duct half height is 0.175, and the corresponding unit Reynolds number $Re/m$ is $2.99 \times 10^7$ m-1. The calculated isopycnic field depicts the streamwise and transverse density variations inside the shock train, the mixing region after the shock train, and the boundary-layer of the interaction region. This technique is shown to be capable of identifying the locations of shocks in a shock train more precisely than a conventional approach measuring the static pressure distribution along the duct wall. In addition, various quantitative visual representations such as a shadowgraphy and a bright-field schlieren can be extracted from the density field acquired by the present approach, and the spatial evolution of the shape and strength of each shock constituting the shock train as well as the boundary layer flow properties can be quantitatively clarified.
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