Research Publications/Outputs

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A mathematical model of a commercial fuel cell for evaluating efficiency under varying ambient conditions
(2025-09) Ndebele, Bright B; Naidoo, Purusha; Ragimana, Phumudzo; Makhubo, Mamokete
Long-endurance aviation propulsion is currently dominated by carbon-based fuels. However, due to climate change, which is largely attributed to carbon dioxide (CO2) emissions from human activities, aviation contributes approximately 4 %, a more climate friendly fuel is sought. Hydrogen (H2), particularly in proton exchange membrane (PEM) fuel cells, offers a promising carbon-neutral alternative. To assess its viability, a mathematical model of a commercial fuel cell was developed to evaluate efficiency under varying ambient conditions representative of Africa climates and at high-altitude scenarios. The Nernst equation – modified to include terms for activation, polarisation, and Ohmic losses – was used to model an experimentally determined polarisation curve (current against cell voltage curve). When fit to experimental data the modified Nernst equation parameters were found to be: A = 0.0356 V, I0 = 0.0212 Amperes, Rint = 0.0059 Ohms, and Imax = 150 Amperes where A, I0, Rint and Imax are the Tafel slope, limit current, internal resistance, and maximum limit current, respectively. The influence of pressure and temperature were determined by varying the partial pressure of oxygen and temperature in the Nernst equation resulting in an efficiency map (𝜂(𝑃𝑂2,𝑇)). The maps showed that efficiency is high for high ambient pressure and low ambient temperature. However, the influence of ambient pressure and temperature were found to be insignificant compared to the influence of power drawn.
An aerodynamic CFD analysis of inlet swirl in a micro-gas turbine combustor
(2023-07) Meyers, Bronwyn C; Grobler, Jan-Hendrik; Snedden, GC
A combustor was designed for a 200N micro-gas turbine [1, 2] using the NREC preliminary combustor design method [1, 2, 3]. During the design process, there are various aspects where there are no definitive methodologies for specifying the design detail, such as the design of the hole-sets, and multiple options can be derived that can satisfy the required mass flow split and pressure drop for a particular hole-set.
Characterisation of CSIR’s Open-Jet 2-meter wind tunnel for IEC 61400 MEASNET-compliant calibration of cup anemometers
(2025-09) Ragimana, Phumudzo; Dikgale, Moyahabo S; Mabeko, Philimon K
Accurate measurement of wind speed is essential for effective assessment of wind resources and evaluation of turbine performance within the wind energy industry. This paper details the characterization of the Council for Scientific and Industrial Research (CSIR) open-jet 2-meter wind tunnel, which is designed to facilitate MEASNET-compliant calibration of cup anemometers in line with IEC 61400. The test section underwent a rigorous evaluation to determine flow uniformity, turbulence intensity, and both axial and vertical flow alignment, utilizing a grid of calibrated pitot tubes. Measurements were taken across various horizontal and vertical planes to evaluate the spatial velocity distribution and confirm compliance with international calibration standards. The open-jet design presents distinct aerodynamic challenges, especially in maintaining low turbulence and uniform velocity profiles in the wind tunnel test section. Through a process of iterative flow conditioning and systematic testing, the tunnel achieved velocity deviations within ±0.03 m/s, thereby complying with the rigorous criteria for high-precision anemometer calibration. Repeatability tests conducted with a reference anemometer, along with assessments of environmental stability, further substantiated the wind tunnel's performance under different ambient conditions. The findings affirm the tunnel's capability as a national calibration facility, providing traceable and internationally recognised wind speed measurement capabilities. This characterisation establishes a basis for future improvements, including broader calibration ranges, automated testing rigs, and integrated uncertainty modelling to meet the increasing demands of the wind energy sector. This characterisation lays the groundwork for future upgrades, like wider calibration ranges, automated calibration systems, and better uncertainty modelling, to keep up with the growing needs of accurate measurements within the wind energy industry.
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.
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.
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.
Feasibility of rotor fault detection from a fluid dynamics perspective
(2020-05) Robbins, SL; Heyns, PS; Heyns, Johan A
The majority of condition monitoring techniques employed today consider the acquisitioning and analysis of structural responses as a means of profiling machine condition and performing fault detection. Modern research and newer technologies are driving towards non-contact and non-invasive methods for better machine characterisation. Yet current literature lacks investigations into the monitoring and detection of anomalous conditions using fluid dynamic behaviour. If one considers unshrouded rotors which are exposed to a full field of fluid interaction such as helicopter rotors and wind turbines amongst others, such an approach could potentially be beneficial. In this work, time-dependent fluid dynamic data is numerically simulated around a helicopter tail rotor blade using URANS CFD with the Open FOAM software package. Pressures are probed at locations in the field of the rotor and compared to results attained in an experimental investigation where good correlation is seen between the results. A blade is modelled with a seeded fault in the form of a single blade out of plane by 4°. Comparisons are drawn between the blade in its ‘healthy’ and ‘faulty’ configurations. It is observed that the fault can be detected by deviations in the amplitudes of the pressure signals for a single revolution at the probed locations in the field. These deviations manifest as increases in the frequency spectrum at frequencies equivalent to the rotational rate (1 per revolution frequencies). The results described are assessed for their fidelity when the pressure is probed at different locations in the domain of the rotor. Deviations in the pressure profiles over the surface of the blades are also seen for the asymmetric rotor configuration, but may prove too sensitive for practical application.
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.
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.
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.
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.
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.
The numerical aerodynamic evaluation of geometrical configurations of a vaporizer tube micro-gas combustor
(2019) Meyers, Bronwyn C; Grobler, Jan-Hendrik
A combustor was designed for a 200N micro-gas turbine for the Model aircraft industry using the NREC design method. During the design process, there are various aspects where there are no definitive methodologies for specifying the design detail, such as the design of the hole-sets, and multiple options can be derived that can satisfy the required mass flow split and pressure drop for a particular hole-set. For this study, the various solutions for hole-set configurations were tested using CFD before experimental development will be pursued. The three design parameters tested were 1) annular area split configuration, 2) Hole area splits and 3) Relative hole positions. CFD simulations for a chosen 9 designs were run and the data were processed, analysed and interpreted. 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. In order to apply a more quantitative method for choosing a preferable design, a scoring system was devised in order to apply a quantitative value to the aspects of the flow which are initially analysed subjectively. The evaluation was broken up into the relevant aspects/features, namely, Recirculation zone (Rz), Outlet and Mixing. For each feature, the designs were subjectively evaluated relative to each other and given a rating/score. The scoring methodology for ranking combustors proved to be an effective method for evaluating the large mass of data that is generated using CFD and allowed for the use of this data to inform choices when narrowing down the mass of combustor designs that are generated in the preliminary design phase.
Thermal aging of additively manufactured maraging steel
(2024-12) Davids, Micaela; Johnston, Charmaine M; Tshabalala, Lerato C
The mechanical properties of Additively Manufactured M300 Maraging Steel were tested after two thermal treatments. It was found that the stress-relief process resulted in tensile strength comparable to the powder specification, but low ductility compared to the specifications, whilst the addition of an aging process resulted in substandard tensile strength and extreme brittleness. The results of a hardness test and the tensile properties achieved suggest that the material was embrittled by both thermal processes. The samples were inspected using an Optical Microscope (OM) after testing.
Two dimensional vortex shedding from a rotating cluster of cylinders
(2023-09) Ndebele, Bright B; Gledhill, IMA
The dynamics of two-dimensional vortex shedding from a rotating cluster of three cylinders was investigated using Computational Fluid Dynamics (CFD) and Dynamic Mode Decomposition (DMD). The cluster was formed from three circles with equal diameters in mutual contact and allowed to rotate about an axis passing through the cluster centroid. While immersed in an incompressible fluid with Reynolds number of 100, the cluster was allowed to rotate at non-dimensionalised rotation rates (Ω) between 0 and 1. The rotation rates were non-dimensionalised using the free-stream velocity and the cluster characteristic diameter, the latter being equal to the diameter of the circle circumscribing the cluster. CFD simulations were performed using StarCCM+. Dynamic Mode Decomposition based on the two-dimensional vorticity field was used to decompose the field into its fundamental mode-shapes. It was then possible to relate the mode-shapes to lift and drag. Transverse and longitudinal mode-shapes corresponded to lift and drag, respectively. Lift–drag polars showed a more complex pattern dependent on Ω in which the flow fields could be classified into three regimes: Ω less than 0.3, greater than 0.5, and between 0.3 and 0.5. In general, the polars formed open curves in contrast to those of static cylinders, which were closed. However, some cases, such as Ω = 0.01, 0.22, and 0.28, formed closed curves. Whether a lift-drag polar was closed or open was deduced to be determined by the ratio of Strouhal numbers calculated using lift and drag time series, with closed curves forming when the ratio is an integer.
Unlocking clean aviation in Africa: Challenges to localising hydrogen aviation propulsion in South Africa
(2025-09) Naidoo, Purusha; Jamison, Kevin A
The global aviation industry has adopted ICAO’s Long-Term Aspirational Goal (LTAG) to achieve net-zero emissions by 2050. Hydrogen fuel cell propulsion is recognised as a key enabler of zero emission aviation. While South Africa has strong potential for green hydrogen production due to its renewable energy resources, the country does have challenges in localising hydrogen aviation propulsion technologies. This paper explores these challenges through the CSIR’s H2UAV project, which is a hydrogen powered long-endurance unmanned aerial vehicle (UAV) designed to localise aviation hydrogen propulsion expertise, demonstrate hydrogen propulsion feasibility, and support a roadmap toward decarbonisation in aviation. Challenges identified include underdeveloped regulatory frameworks, limited early-stage funding, infrastructure inefficiencies, and a shortage of aerospace product development expertise. This study draws on global hydrogen aviation trends and proposes mechanisms for overcoming these obstacles in emerging economies like South Africa to boost the implementation of low carbon aviation propulsion technologies.
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.
Wind tunnel testing - A career at high speed - while standing still! 1990-2022
(2022-11) Morelli, Mauro F
This item is the John Weston Memorial Lecture and comprises a conference presentation providing details on a career involving wind tunnel testing (1990-2022).

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