Conference Publications

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Browsing Conference Publications by browse.metadata.impactarea "Aeronautic Systems"

Now showing 1 - 8 of 8
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    Decoupling store and parent aerodynamics for fast prediction of subsonic store trajectories
    (2024-09) Mthembu, N; Ndlovu, Hlamulo P; Ndebele, Bright B; Jamison, Kevin A; Zwane, Lindokuhle
    A method optimised for efficient prediction of subsonic store separation trajectories is described and demonstrated using a wind-tunnel test case. The FastTraj method uses a decoupled flow field approach where it is assumed that in most attached flow subsonic store separation scenarios the presence of the store has little impact on the perturbed flow field generated by the parent aircraft. The inviscid perturbed flow field of the parent aircraft is computed using computational fluid dynamics codes and is captured using a grid. The store aerodynamic model is generated elsewhere and Missile Datcom is used to segment the store model to approximate the effect of the perturbed flow field changing along the length of the store. The 6-DOF trajectory solver interpolates the aerodynamic grid from the parent aircraft to determine the local flow vector at each reference point on the segmented store, in addition to the local flow vector due to the motion of each segment. Good comparisons with the wind-tunnel data are achieved showing that the method’s speed is not at the expense of accuracy and that it is necessary to segment the store to achieve good results.
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    Fatigue properties of additively manufactured tool steel
    (2024-09) Johnston, Charmaine M; Tshabalala, Lerato C; Davids, M
    Tool steel is routinely used by the Experimental Aerodynamics group at the Council for Scientific and Industrial Research (CSIR), South Africa, to manufacture critical components for wind tunnel testing. This steel is known for its high strength properties in both tension and compression, and has a good combination of machinability, ductility, and fracture toughness. The emergence of the Additive Manufacturing (AM) technology provides an alternative to traditional manufacturing procedures in the production of wind tunnel model parts and instrumentation; however, use of the AM technology requires knowledge, inter alia, of the fatigue characteristics of the AM materials. Test specimens were manufactured from tool steel powder using the Selective Laser Melting (SLM) technology and subjected to fatigue and tensile tests. The thermal treatments were used for stress relieving and aging the additively manufactured part; the processes used in this project were found to have an adverse effect on the properties of the material.
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    The first step towards decarbonized air mobility in South Africa: A hydrogen powered unmanned aerial vehicle
    (2022-11) Jamison, Kevin A; Naidoo, Purusha; Ramotsabi, Katleho
    The South African government is investing in the use of hydrogen fuel as a pathway towards decarbonising transport sectors. Hydrogen is likely to be a viable option for decarbonising air transport and it is being investigated intensively around the world. The merits of hydrogen as an air transport fuel relative to other alternatives are discussed. To localise expertise in hydrogen powered aviation in South Africa it was decided that a small hydrogen fuel cell powered unmanned aerial vehicle (UAV) would be developed as a first step. Once hydrogen powered flight is demonstrated at the UAV scale then the expertise gained can be scaled up to the general aviation sector and ultimately, commercial aviation. A concept of the UAV and its hydrogen fuel cell propulsion unit is presented and discussed.
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    Flat Plate Flutter in a Supersonic Flow Field
    (2024-07) Ndebele, Bright B
    The interaction of a two-dimensional cantilevered elastic flat plate with a supersonic flow field was investigated numerically using StarCCM+. The plate was 0.4 m in length and inclined at 15∘ to the freestream at three Mach numbers (1.2, 1.35, and 1.45). The flat plate was assumed to be aluminium. Using StarCCM+, the inviscid Navier-Stokes equations were solved, and the fluid-structure interaction resolved. This way, the flow field around the plate and the plate deflection were calculated. The results indicated that at Mach 1.2, the plate exhibited a steadystate deflection, while at the other investigated Mach numbers, limit cycles were observed. The deformation of the plate caused a flow compression at the top, resulting in a weak shock at Mach 1.2 and strong shocks at 1.35 and 1.45. These findings provide insight into the dynamic response of the plate and the corresponding flow characteristics at different Mach numbers.
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    The numerical aerodynamic investigation of swirling inlet flow in a vaporizer tube micro-gas turbine combustor
    (2022-09) Meyers, Bronwyn C; Grobler, Jan-Hendrik; Snedden, GC
    A combustor was designed for a 200N micro-gas turbine for the model aircraft industry using the NREC design method. Multiple designs resulted which varied in terms of annular area split configuration, hole area splits and relative hole positions. In a previous study two likely preferable designs were selected using a devised scoring method. For this study, the effect of inlet (diffuser outlet) swirl on the internal aerodynamics of the two combustor designs previously chosen was investigated using a RANS CFD analysis. For each of the two designs a set of varying flow angles was applied at the inlet to the simulation domain. The effect on the establishment of the primary zone features is of specific interest; however, the effects and consequences of the swirl throughout the combustor were investigated. Some of the results such as mass flow splits and pressure drop are already quantitative in nature, however, the evaluation of the quality of the recirculation zone, mixing and outlet plane flow are of a more qualitative nature. A scoring system was previously devised in order to apply a quantitative value to the qualitative aspects of the flow, such as Recirculation zone (Rz), Outlet and Mixing, which are initially analysed subjectively. For each feature, the designs were subjectively evaluated relative to each other and given a rating/score. This scoring methodology for ranking different combustor designs proved to be an effective method for evaluating the effect of inlet swirl on the flow features and behaviour of the chosen combustor designs and thus provide an indication of the likely performance changes to be expected. The methodology was able to indicate which of the two top designs was the better option when considering inlet swirl, however the potential for improvement was revealed when considering scoring in a global context. This study suggests that for this engine, the inlet swirl could allow for the removal of NGV before the turbine since the flow is fairly well conditioned and “pre-turned” due to the swirling flow progressing to the outlet of the combustor. The removal of the traditional NGV allows for a reduction in NGV pressure losses which compensates for the increased combustor pressure loss experienced due to increased inlet swirl.
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    Selecting munition design features and operational concepts using a trade study supported by simulated operational scenarios
    (2021-09) Jamison, Kevin A; Roux, Jeanne M; Zwane, Lindokuhle
    A development of an existing munition aimed at an entirely new target set was planned. A trade study was performed to identify the key design features and employment concepts that generate the optimum outcomes in a demanding operational scenario. The trade study was configured as a Multi-Attribute Tradespace Exploration (MATE) using a trade study matrix that considers the key design and operational variables to be investigated. The baseline munition concept was parameterised such that design changes are described by those key variables. For each set of tradespace variables the baseline munition design was optimised to maximise its operational range while complying with constraints and meeting the design requirements. The characteristics of each optimised munition was determined for input into a simulation model of an operational scenario modelling the operational environment and the threat systems to determine the best performing munition solution. This paper outlines the implementation of the MATE approach and the lessons learned that can be incorporated in the broader systems engineering discipline.
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    A systems engineering framework for integrating stores with aircraft
    (2023-10) Jamison, Kevin A
    Military and some civilian aircraft need to carry stores to perform their mission. There is a huge diversity of carriage aircraft and types of stores ranging from missiles, drop tanks, space launchers, and rescue equipment. Adding stores to aircraft has a significant impact on the airworthiness of the carriage aircraft. Stores affect aircraft in multiple ways, making the integration of stores a complex multidisciplinary engineering problem that is often costly to resolve. The current regulatory and technical framework for store integration is reviewed. A systems engineering approach to store integration is presented where both aircraft and stores are designed from the outset to facilitate store integration. While some examples of this being done can be found, much still needs to be done to facilitate cost-effective store integration. Two case studies are presented and discussed showing the utility of this approach.
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    Validation of CSIR wind tunnel calibration data under different barometric conditions using comparisons with a reference laboratory
    (2024-09) Dikgale, Moyahabo S
    This paper presents the validation of the calibration data of the Council of Scientific and Industrial Research (CSIR) Calibration Wind Tunnel by evaluating its accuracy under different barometric conditions. Using a reference laboratory with established calibration standards as a benchmark, we compared the CSIR wind tunnel's measurements against those from the reference facility across a range of wind speeds. Our methodology involved a series of controlled calibration designed to assess the consistency and reliability of the wind tunnel's calibration data in different atmospheric conditions. The results demonstrated that the CSIR wind tunnel maintains a high degree of accuracy and reliability, with deviations falling within acceptable limits relative to the reference laboratory's data. This validation highlights the robustness of the CSIR wind tunnel calibration process and its capability to deliver precise wind speed measurements’ calibration across different environmental conditions.