bluuebunny/crossref_metadata_2025_split huggingface dataset:
External Threats and Public Opinion: The East Asian Security Environment and Japanese Views on the Nuclear Option
Authors: Matsumura Naoko , Tago Atsushi , Grieco Joseph M. 
Published: February 2023

AbstractThe Japanese public has been assumed to possess a deeply ingrained aversion toward the acquisition of nuclear weapons. We employ a survey experiment to ascertain whether this aversion is unconditional or may erode in the face of hypothetical deterioration in Japan's security situation, and in particular a hypothetical withdrawal of the US security-nuclear umbrella, increased North Korean nuclear weapons testing activities, and movement by South Korea toward the attainment of a nuclear arsenal. We find that the Japanese nuclear aversion may come under stress in the face of such developments. Additionally, we find that the elasticity of Japanese attitudes with respect to the nuclear option in the face of external security deterioration may be associated with an important individual-level demographic characteristic, namely, gender.
Whole-assembly flutter analysis of a low-pressure turbine blade
Authors: I. Sayma A. , Vahdati M. , Imregun M. , Green J. S. 
Published: February 2023

AbstractThis paper reports the findings of a flutter investigation on a low-pressure turbine blade using a 3D, non-linear, integrated aeroelasticity method. The approach has two important features: (i) the calculations are performed in a time-accurate and integrated fashion, whereby the structural and fluid domains are linked via an exchange of boundary conditions at each time step, and (ii) the analysis is performed on the entire bladed-disk assembly, thus removing the need to assume a critical vibration mode shape. Although such calculations are both CPU and in-core memory intensive, they do not require prior knowledge of the flutter mode and hence allow a better understanding of the aeroelasticity phenomena involved.The flow is modelled inviscidly but the steady-state viscous effects are accounted for using a distributed loss model. The structural model was obtained from a standard finite element (FE) representation and a large number of assembly modes were included in the calculations. The study focused on three part-speed conditions at which a number of unstable modes were known to exist from the available experimental data. The whole assembly was modelled using about 664,000 mesh points and predictions were made of aeroelastic modal time histories. From these time histories it was possible to identify the forward and backward travelling waves and to deduce the unstable modes of vibration. The theoretical predictions were found to be in very good agreement with the experimental findings.
AASK — aircraft accident statistics and knowledge: a database of human experience in evacuation, derived from aviation accident reports
Authors: Owen M. , Galea E. R. , Lawrence P. J. , Filippidis L. 
Published: February 2023

AbstractComputer based mathematical models describing the aircraft evacuation process have a vital role to play in aviation safety. However, such models have a heavy dependency on real evacuation data in order to (a) identify the key processes and factors associated with evacuation, (b) quantify variables and parameters associated with the identified factors/processes and finally (c) validate the models. The Fire Safety Engineering Group of the University of Greenwich is undertaking a large data extraction exercise from three major data sources in order to address these issues. This paper describes the extraction and application of data from one of these sources — aviation accident reports. To aid in the storage and analysis of the raw data, a computer database known as AASK (aircraft accident statistics and knowledge) is under development. AASK is being developed to store human observational and anecdotal data contained in accident reports and interview transcripts. AASK comprises four component sub-databases. These consist of the ACCIDENT (crash details), FLIGHT ATTENDANT (observations and actions of the flight attendants), FATALS (details concerning passenger fatalities) and PAX (observations and accounts from individual passengers) databases. AASK currently contains information from 25 survivable aviation accidents covering the period 4 April 1977 to 6 August 1995, involving some 2415 passengers, 2210 survivors, 205 fatalities and accounts from 669 people. In addition to aiding the development of aircraft evacuation models, AASK is also being used to challenge some of the myths which proliferate in the aviation safety industry such as, passenger exit selection during evacuation, nature and frequency of seat jumping, speed of passenger response and group dynamics. AASK can also be used to aid in the development of a more comprehensive approach to conducting post accident interviews, and will eventually be used to store the data directly.
Constrained, multipoint shape optimisation for complex 3D configurations
Authors: Elliott J. , Peraire J. 
Published: February 2023

AbstractA method for performing three-dimensional, multipoint, lift-constrained drag minimisation for complex aircraft configurations is presented. Parameters representing the aircraft geometry are the design variables used in the solution of an optimisation problem. The compressible Euler equations for the flow are discretised on automatically generated unstructured meshes, and the sensitivities of the objective function and the constraints with respect to the design parameters are efficiently calculated using the discrete adjoint method. In addition, the solution algorithm has been parallelised making the approach feasible for practical applications. Several constrained minimisation strategies are discussed and some numerical tests are carried out for a lift-constrained, two-dimensional problem. The strategy found to work best is demonstrated for the three-dimensional optimisation of a wing-body configuration operating in transonic and supersonic conditions. It is concluded that Euler-based optimisation can be useful as a first step in the design process but that most applications involving transonic flows do require viscous flow modelling to avoid unrealistic pressure distributions.
Inverted-profile coaxial jet flows relevant to Astovl applications
Authors: Knowles K. , Kirkham L. 
Published: February 2023

AbstractAn experimental investigation has been performed into the free jet and wall jet characteristics of high pressure ratio coaxial jets operating with inverted velocity profiles and impinging onto a ground plane. Pitot-static probes have been used to record free jet properties at various distances from the jet exit plane, and wall jet properties of the impinging jets at various radial positions. Jet properties such as velocity decay and spreading rates were calculated and compared to published literature. Wall jet development was investigated and recorded. Inner and outer nozzle pressure ratio (NPR) were altered to give a range of jet exit conditions. The results obtained showed variations in the wall jet properties as jet exit conditions were altered, but wall jet self-similarity was found and varying either nozzle height above the ground plane or NPR did not alter this. Free jet data showed large variations in behaviour with changes in NPR. The inverted profile jets behaved similarly to annular jets, showing similar characteristics. Inner jet pressurisation was observed for inverted profile jets and also significant acceleration of the flow from the inner, lower NPR, jet when this was subcritical.
Inviscid and viscous simulations of spoiler performance
Authors: Xu C. , Yeung W. W. H. , Guo R. W. 
Published: February 2023

AbstractInviscid and viscous computational models have been used to predict two-dimensional steady separated flow around an aerofoil with a spoiler. First, an attempt is made to construct an inviscid panel method in which piece-wise linear vortex panels are placed on the aerofoil and spoiler. The separated region is modelled with potential flow analysis by using free vortex sheets placed on the separation streamline from the spoiler tip and aerofoil trailing-edge. The shapes of the vortex sheets require an iteration to be established. The calculation is based on an assumption of the length of the free vortex sheets. Second, a viscous procedure based on a finite control volume scheme is used to solve the Navier-Stokes equations for turbulent flow by making used of the k-ε model. An algebraic pressure correction is incorporated in the calculation. The predictions from the two models are in reasonable agreement with experimental measurements.
A review of current analysis capabilities applicable to the high frequency vibration prediction of aerospace structures
Authors: Langley R.S. , Bardell N.S. 
Published: February 2023

AbstractMany situations arise in which aerospace structures are subjected to high frequency excitation, in the sense that the wavelength of the induced dynamic response is much shorter than the overall dimensions of the structure. The application of the conventional finite element method to this type of problem faces two difficulties: (i) the short wavelength of the structural deformation requires the use of many elements, which renders the method computationally expensive or even impracticable, and (ii) the response of the structure at high frequencies can be very sensitive to structural detail, and thus response predictions for an ‘ideal’ structure may differ significantly from the performance of the actual system. For a number of years research effort has been directed towards the development of alternative analysis methods for high frequency vibrations, and recent developments in this area are reviewed in the present paper. The methods considered are: (i) hierarchical versions of the finite element method, (ii) the dynamic stiffness method, (iii)periodic structure theory, (iv)statistical energy analysis and (v) wave intensity analysis.
The influences on optimal structural designs of the modelling processes and design concepts
Authors: Anastasiadis P. T. , Morris A. J. , Hornlein H. R. E. M. , Krammer J. 
Published: February 2023

AbstractThe paper examines the influence on optimal structural designs of changing the design criteria and concepts for an unmanned air-vehicle wing, for both single and twin-spar rib configurations. The results indicate that the influence of such factors as panel buckling, aeroelastic efficiency, the number of design variables and the number of ribs can be significant. It is also shown that the best design is given by the twin-spar layout.
A generic control anticipation parameter for aircraft handling qualities evaluation
Authors: Gautrey J. E. , Cook M. V. 
Published: February 2023

AbstractThe established control anticipation parameter longitudinal handling qualities criterion is based on the assumption that the short term dynamic response of the aeroplane is classical, or second-order-like. Modern fly-by-wire aircraft often have longitudinal short term dynamics which are not second-order-like and to which it is difficult to apply the criterion. This paper presents a proposed generic control anticipation parameter which is a modified version of the control anticipation parameter and which may be applicable to both unaugmented and augmented aircraft of all types. The appropriateness of the modified criterion was illustrated by designing a number of command and stability augmentation control laws, constrained to meet the criterion, for application to a medium weight fly-by-wire civil transport aircraft. The handling characteristics conferred by the control laws were assessed in a series of flight simulator trials, the results of which are briefly presented.
Experiments on cruise propulsion with a hydrogen scramjet
Authors: Stalker R. J. , Paull A. 
Published: February 2023

AbstractMeasurements of drag have been made, in a shock tunnel, on a simple integrated vehicle-engine combination for hypersonic cruise with hydrogen scramjet propulsion. The test flow Mach number was 6·4, and the velocity was 2·45 kms-1. Zero drag, which is the necessary condition for cruise, was achieved as the equivalence ratio approached one. It was found that an analysis using established aerodynamic concepts was adequate for predicting drag in the case of no combustion. When combustion occurred results of direct connect experiments provided a qualitative guide to the measured levels of drag, and indicated that thrust nozzle combustion was taking place. An heuristic analysis is used to point to the important effect this may have on propulsive lift.
An airborne windshear detection system
Authors: McLean D. , Zouaoui Z. 
Published: February 2023

AbstractFor a long time there has been growing awareness in the international aviation community of the considerable danger which an encounter with the atmospheric phenomenon of windshear can bring to an aircraft in flight. Considerable statistical evidence is now available which points to the fact that aircraft windshear encounters in initial climb, final approach, or landing are extremely hazardous, often leading to fatal accidents. The paper presents details of a preliminary design for an airborne windshear detection system suitable for use in general aviation aircraft. First, an elementary explanation of windshear, and its most dangerous form, the microburst, is given, together with a short account of the hazards that such atmospheric phenomena can present to aircraft in flight, particularly at takeoff and landing. Then a novel windshear detection algorithm is described and associated simulation results are presented. The algorithm is based upon observer theory and uses only a restricted number of measurements. The system is shown to provide very good estimates of the horizontal and vertical components of some windshear encounters. These estimates of the windshear components are then used to provide the pilot with a warning of the presence of windshear together with an indication of its severity. Digital simulation has been used to show the effectiveness of the proposed design.
Performance of straight-walled annular diffusers with swirling flow
Authors: Klomp E. D. 
Published: February 2023

AbstractPerformance data are presented for eight annular diffuser families, a family being defined by the inner and outer cone angles and the inlet hub-tip ratio. These results include profiles of velocity and total pressure across the inlet and outlet lanes as well as overall pressure recovery coefficients. Diffuser outer cone angles range from 10° to 60° and inner cone angles from 59° to -19°. Swirl angles were varied from 0° up to 44°. Each diffuser family was tested over a range of lengths and swirl angles resulting in over ninety different tests. A procedure for extending the non-swirling definition of effectiveness to swirling flows is presented and used to evaluate a limiting swirl angle for separation for free-vortex-type inlet swirl. Comparisons are made to several measured values of flow separation. Some experimental diffusers exhibited a violently unsteady hub stall which apparently consisted of rotating reverse flow regions.
Studies of vortex flaps for different sweepback angle delta wings
Authors: Rinoie K. 
Published: February 2023

AbstractLow speed windtunnel measurements were made on a 50° delta wing with leading edge vortex flaps. Improvements in the lift/drag ratio were obtained by deflecting the leading edge vortex flap. Comparisons were made between the previously measured 60° and 70° delta wing results and the present 50° wing results. Improvements in the lift/drag ratio of the 50° delta wing were attained over a wider lift coefficient range than for the 70° delta wing. The highest lift/drag ratio for the 50° delta wing is achieved when the flow attaches to the flap surface without any large area of separation. Estimations of the aerodynamic forces were also made using a quasi-vortex lattice method coupled with the leading edge suction analogy for the 50°, 60° and 70° delta wings. The results obtained from this analysis agree qualitatively with the experimental results.
Operational experience and test results in the adaptive test section of the DLR transonic tunnel
Authors: Holst H. , Bock K-W. , Lorenz-Meyer W. , Oberdieck F. , Hermes M. 
Published: February 2023

AbstractThe transonic facility of DLR Göttingen (TWG) has been modernised with respect to an improved flow quality and flow simulation, as well as to the logistics of exchangeable test sections, operational reliability and productivity. It is presently equipped with a Laval nozzle for supersonic flow measurements, a perforated test section (6% open, 60° slanted holes) for transonic measurements, and a two-dimensional adaptive test section for subsonic measurements. The latter can perform two-dimensional adaptive tests on wing profiles, using the Cauchy integral formula for wall adaptation, as well as two-dimensional wall adaptation for three-dimensional models, utilising the Wedemeyer/Lamarche procedure, also known as the VKI method. For both cases, it is shown that the wall adaptation was successful. The 3D force results compare quite well to test results from the perforated test section, as well as to nominally interference-free results. The pressure distribution from the wing profile tests compare quite well to theoretical calculations. In the course of windtunnel modernisation, the transonic facility of DLR Göttingen has been equipped with the new software system DeAs for data acquisition and control of experimental facilities. In this environment the wall adaptation programs had to be implemented. Before adjusting the computed wall shape, it has to be controlled in the loop for sufficient accuracy and tolerable bending stresses. A simplified finite element method — also taking into account the pressure loads at the wall — is used for this purpose. The simplified approach has been checked against more detailed computations using ANSYS and NASTRAN.
Windtunnel testing of parachutes for the Huygens probe
Authors: Underwood J. C. , Sinclair R. J. 
Published: February 2023

AbstractWindtunnels are generally used for testing models of solid, aerodynamic objects, such as aircraft. The test articles are generally manufactured to have a representative external profile but provide sufficient strength to survive the harsh windtunnel environment without damage to the test article or tunnel. It is somewhat unusual, however, to test lightweight, high drag, fabric models (i.e. parachutes) in supersonic flow.This paper describes the testing carried out on the parachutes for the Huygens probe, the techniques developed for the testing and the lessons learned.Tests were carried out to characterise the drag coefficient of the parachute designs throughout the Mach range of 0.05 to 1.5, and the stability coefficients at incidences of up to 15° at low Mach numbers.
Numerical modelling of unsteady flow in a twin side-by-side intake system
Authors: Causon D. M. , Ingram D. M. 
Published: February 2023

AbstractThe unsteady flowfield in a twin side-by-side intake arrangement arising as a result of a surge in one of the engines has been studied numerically by solving the Euler equations. Unsteadiness was introduced by prescribing a pressure disturbance at the exit plane of one of the intakes. The two cases considered correspond to static ground-running of the engines and a flight Mach number of 0.6 with a single rapidly increasing exit plane pressure disturbance representative of a pop surge. The amplitude of the imposed pressure disturbance varied between 100% and 200% of the mean exit static pressure. In the cases considered, the results indicate that static pressure attenuation of the propagating hammer shock occurs upstream of the intake entry plane, resulting in a relatively weak rarefaction wave travelling down the adjacent intake. No evidence of increased dynamic flow distortion likely to lead to a complementary surge in the adjacent engine was observed. These conclusions have been confirmed by available test data thus demonstrating the value of CFD techniques for modelling complex unsteady transient flow phenomena of this type.
Low thrust orbit raising with J2 regression
Authors: Mclnnes C. R. 
Published: February 2023

AbstractClosed form solutions for low thrust orbit raising are well known for mission analysis and vehicle performance prediction. This paper provides extended solutions which include nodal regression through the effect of the J2 oblateness term in the geopotential. Since regression is a strong function of orbit radius, the resulting change in ascending node angle is coupled to the in-plane orbital motion. However, it is demonstrated that the resulting dynamical equations may be separated and solved sequentially. Nodal regression during orbit raising is of importance for solar electric vehicles due to the resulting variation of sun aspect angle and eclipse conditions.
On the prediction of aerofoil unsteady stall criticality
Authors: Graceyt M. W. , Coton F. N. , Galbraith R. A. McD. 
Published: February 2023

AbstractFor practical purposes, it is beneficial to be able to predict the useful operating range of an aerofoil in oscillatory motion before the onset of the strong non-linear effects associated with dynamic stall. In the current work, a range of criteria which have been used to indicate the onset of dynamic stall are presented. It is observed that, since all of these are based on physical manifestations of the dynamic stall process, they may only provide an indication that the process has started rather than identifying the initiation itself. A more suitable criterion for this is the concept of critical angle, first proposed by Wilby. It is shown that the critical angle, which is normally determined through an extensive programme of oscillatory tests on a given aerofoil, is achieved in advance of all the other criteria. The present work presents a correlation which has the potential to determine the critical angle, and hence the useful oscillatory range of an aerofoil, on the basis of simple ramp function tests.
Comparisons between low Reynolds number two-equation models for computation of a shockwave-turbulent-boundary layer interaction
Authors: Yoon B. K. , Chung M. K. , Park S. O. 
Published: February 2023

AbstractA comparative study is made on the performance of several low Reynolds number k-ε models and the k-ω model in predicting the shockwave-turbulent-boundary layer interaction over a supersonic compression ramp of 16°, 20° and 24° at a Mach numbers of 2.85, 2.79 and 2.84, respectively. The model equations are numerically solved by a higher order upwind scheme with the 3rd order MUSCL type TVD. The computational results reveal that all of the low Reynolds number k-ε models, particularly those employing y+ in their damping functions give erroneously large skin friction in the redeveloping region. It is also interesting to note that the k-ε models, when adjusted and based on DNS data, do not perform better, as expected, than the conventional low Reynolds number k-ε models. The k-ω model which does not adopt a low Reynolds number modification brings about reasonably accurate skin friction, but with a later onset of pressure rise. By recasting the ω equation into the general form of the ε equation, it is inferred that the turbulent cross diffusion term between k and ε is critical to guarantee better performance of the k-ω model for the skin friction prediction in the redeveloping region. Finally, an asymptotic analysis of a fully developed incompressible channel flow, with the k-ε and the k-ω models, reveals that the cross diffusion mechanism inherent in the k-ω model contributes to the better performance of the k-ω model.