Very High Temperature Reactors are complex reactors and various system codes have been developed to design different aspects such as neutronics, thermal hydraulics etc. Flownex is one of the system codes and it has been used to model the flow and heat transfer for a pebble fuel element and pebble-bed reactor. Although Flownex has been used to model the High Temperature Test Reactor, the prismatic block was modelled in a simplified manner. The aim of this study was to develop a more integrated model for a single block. A one sixth block was modelled in Flownex and the results were validated by comparing the results with results obtained using the Computational Fluid Dynamics (CFD) code STAR-CCM+. The conduction heat transfer through the prismatic blocks containing the fuel elements in a Very High Temperature Reactor is of crucial importance for the proper operation of the reactor under normal operating conditions and upset conditions. In this study, a model developed in a system code, Flownex is discussed. The model comprised of a collection of 1-D solid conduction heat transfer, convection heat transfer and pipe elements that were arranged in such a manner to represent the heat transfer and fluid flow in the prismatic block using a network approach. The validity of the model was investigated by comparing the heat transfer and temperature distribution in the block for various scenarios with the corresponding values obtained using a detailed CFD model of one twelfth of a prismatic block. Cubical and triangular block verification cases were conducted in Flownex and the results were validated by STAR-CCM+. The results were very comparable; however one issue has to be addressed. The one sixth integrated prismatic block was then modelled for a steady state and the results were also comparable. The outlet helium temperatures predicted by the STAR-CCM+ model was 542.94 C, at the same time the Flownex model predicted 542.98 C. Although the Flownex model did not provide the same detail as the STAR-CCM+ model the agreement between the results obtained with the two codes was satisfactory. Based on these findings it was concluded that Flownex could be used to build a representative integrated network model for a prismatic block reactor. / MIng (Nuclear Engineering), North-West University, Potchefstroom Campus, 2015

Very High Temperature Reactors are complex reactors and various system codes have been developed to design different aspects such as neutronics, thermal hydraulics etc. Flownex is one of the system codes and it has been used to model the flow and heat transfer for a pebble fuel element and pebble-bed reactor. Although Flownex has been used to model the High Temperature Test Reactor, the prismatic block was modelled in a simplified manner. The aim of this study was to develop a more integrated model for a single block. A one sixth block was modelled in Flownex and the results were validated by comparing the results with results obtained using the Computational Fluid Dynamics (CFD) code STAR-CCM+. The conduction heat transfer through the prismatic blocks containing the fuel elements in a Very High Temperature Reactor is of crucial importance for the proper operation of the reactor under normal operating conditions and upset conditions. In this study, a model developed in a system code, Flownex is discussed. The model comprised of a collection of 1-D solid conduction heat transfer, convection heat transfer and pipe elements that were arranged in such a manner to represent the heat transfer and fluid flow in the prismatic block using a network approach. The validity of the model was investigated by comparing the heat transfer and temperature distribution in the block for various scenarios with the corresponding values obtained using a detailed CFD model of one twelfth of a prismatic block. Cubical and triangular block verification cases were conducted in Flownex and the results were validated by STAR-CCM+. The results were very comparable; however one issue has to be addressed. The one sixth integrated prismatic block was then modelled for a steady state and the results were also comparable. The outlet helium temperatures predicted by the STAR-CCM+ model was 542.94 C, at the same time the Flownex model predicted 542.98 C. Although the Flownex model did not provide the same detail as the STAR-CCM+ model the agreement between the results obtained with the two codes was satisfactory. Based on these findings it was concluded that Flownex could be used to build a representative integrated network model for a prismatic block reactor. / MIng (Nuclear Engineering), North-West University, Potchefstroom Campus, 2015

Harbours play a vital role in the economies of most countries since a significant amount of international trade is conducted through them. Ships rely on harbours for the safe loading and unloading of cargo and the harbour infrastructure relies on breakwaters for protection. As a result, the design and analysis of breakwaters receives keen interest from the engineering community. Coastal engineers need an easy-to-use tool that can model the way in which waves interact with large numbers of interlocking armour units. Although the study of fluid–structure interaction generates a lot of research activity, none of the reviewed literature describes a suitable method of analysis. The goal of the research was to develop a simulation algorithm that meets all the criteria by allowing CFD software and physics middleware to work in unison. The proposed simulation algorithm used Linux “shell scripts” to coordinate the actions of commercial CFD software (Star-CCM+) and freely available physics middleware (PhysX). The CFD software modelled the two-phase fluid and provided force and moment data to the physics middleware so that the movement of the armour units could be determined. The simulation algorithm was verified numerically and experimentally. The numerical verification exercise was of limited value due to unresolved issues with the CFD software chosen for the analysis, but it was shown that PhysX responds appropriately given the correct force data as input. Experiments were conducted in a hydraulics laboratory to study the interaction of a solitary wave and cubes stacked on a platform. Fiducial markers were used to track the movement of the cubes. The phenomenon of interest was the transfer of momentum from the wave to the rigid bodies, and the results confirmed that the effect was captured adequately. The study concludes with suggestions for further study. / MIng (Mechanical Engineering), North-West University, Potchefstroom Campus, 2014

Harbours play a vital role in the economies of most countries since a significant amount of international trade is conducted through them. Ships rely on harbours for the safe loading and unloading of cargo and the harbour infrastructure relies on breakwaters for protection. As a result, the design and analysis of breakwaters receives keen interest from the engineering community. Coastal engineers need an easy-to-use tool that can model the way in which waves interact with large numbers of interlocking armour units. Although the study of fluid–structure interaction generates a lot of research activity, none of the reviewed literature describes a suitable method of analysis. The goal of the research was to develop a simulation algorithm that meets all the criteria by allowing CFD software and physics middleware to work in unison. The proposed simulation algorithm used Linux “shell scripts” to coordinate the actions of commercial CFD software (Star-CCM+) and freely available physics middleware (PhysX). The CFD software modelled the two-phase fluid and provided force and moment data to the physics middleware so that the movement of the armour units could be determined. The simulation algorithm was verified numerically and experimentally. The numerical verification exercise was of limited value due to unresolved issues with the CFD software chosen for the analysis, but it was shown that PhysX responds appropriately given the correct force data as input. Experiments were conducted in a hydraulics laboratory to study the interaction of a solitary wave and cubes stacked on a platform. Fiducial markers were used to track the movement of the cubes. The phenomenon of interest was the transfer of momentum from the wave to the rigid bodies, and the results confirmed that the effect was captured adequately. The study concludes with suggestions for further study. / MIng (Mechanical Engineering), North-West University, Potchefstroom Campus, 2014

Diploma thesis deals with numerical simulations of an air flow in a water cooled charge air cooler (WCAC), specifically with pressure drops in inlet/outlet chamber. The simulations have been performed in a proprietary software Star-CCM+. Physical phenomena have been solved by the Reynolds-averaged Navier-Stokes (RANS) equations and consequently a matrix of pressure drops for miscellaneous variations of chamber's geometry and the initial flow conditions has been created. Based on the CFD results, dependence between calculated pressure drops and changing parameters has been analyzed and finally a 1D solver has been developed and implemented into a software OpenModelica.

The master´s thesis is focused on construction of one-man car body of sports car. Work contains aerodynamic analysis of car body too and optimization of the CAD model.

<p>The nuclear safety industry makes extensive use of thermalhydraulics system analysis and computational fluid dynamics codes for validation and predictive purposes. These codes take different approaches to provide the user with reasonable estimates of system and component behaviors. With each displaying its own strengths, it is only logical to pursue coupled systems of these codes to create increasingly accurate, versatile, and more computationally efficient safety analysis tools. This work presents results of the attempted coupling of CD-ADAPCO's STAR-CCM+, a computational fluid dynamics (CFD) code, to Atomic Energy of Canada's CATHENA thermalhydraulics (TH) code. This coupled system is used in the simulation of the conditions within an inlet header of the RD-14M experimental facility under single phase conditions in the initial phase of selected test. This inlet header is removed from a modified CATHENA test B9401 deck and instead modelled in STAR-CCM+. Custom applications were written to allow information exchange at the newly created boundaries to provide an attempt at a coupled system. Results are provided through multiple stages of development of the coupled system, from the unmodified B9401 test case of CATHENA into a coupled system with header behavior predicted by STAR-CCM+. Though successful information transfer between codes was established at each desired time step and interval, the current technique was found to be insufficient for establishing acceptable steady-state conditions for the commencement of more complex (transient and two-phase) conditions.</p> / Master of Applied Science (MASc)

The research and development effort for the next generation of nuclear power stations is being coordinated by the Generation IV International Forum (GIF). The supercritical water reactor (SCWR) is one of the six reactor technologies currently being pursued by the GIF. The unique nature of supercritical water necessitates further examination of its heat transfer regimes. The GIF SCWR blind computational benchmark exercise is focused on furthering the understanding of the heat transfer to supercritical water as well as its prediction. A methodology for computational fluid dynamics (CFD) simulations using STAR-CCM+ 9.02.005 has been developed for submission to the GIF SCWR computational benchmark exercise. The experiments of the GIF SCWR computational benchmark exercise were those conducted by the Japan Atomic Energy Agency (JAEA). They are of supercritical water flowing upward in a 7 rod bundle. Of the three experimental cases there are (i) an isothermal case, (ii) a low enthalpy, low heat flux case and (iii) a high enthalpy, high heat flux case. A separate effects study has been undertaken and the SST turbulence model has been chosen to model each of the three experiments. A near wall treatment that ensures a y+<0.09 has been used for both of the heated cases and a near wall treatment that ensures a y+<0.53 has been used for the isothermal case. This computational approach was determined to be the optimal choice which balances solution accuracy with computation time. Final simulation results are presented in advance of the release of the experimental results in June 2014. / Thesis / Master of Applied Science (MASc)

The thesis work described in this report is about simulation of the cooling of an electrical machine rotor. Limitations and simplifications were made on the CAD model of the rotor with the purpose of reducing the simulation time, for it to then be used for CFD-simulations using STAR-CCM+. This was done to see the temperature, as well as its distribution, in the model. By changing various parameters, one at the time whilst the rest were kept at their assigned standard values, the changes could be analysed and thereafter compared. The tests include smaller geometry changes, parameters of the coolant and its flow, parameters for the airgap and the materials in the laminates and the material around the magnets, as well as changes in loss values. The simulations for geometry changes involving the magnets and their surrounding material resulted in minor temperature increases. An inner rotor radius increase gave a relatively large temperature decrease (although this change would be more difficult to make in practice). Most of the mean values of the temperature changes in the regions of the model were within 10% from the standard simulation used. Increased thermal contact resistance between the Bakelite and the laminates, and increased losses had the worst impact on the cooling. Meanwhile the changes in coolant parameters (as well as the its inlet temperature and mass flow) and reduced losses had the best impact on the cooling. Generally, the temperature distributions looked similar for the different simulations. There were more differences in the distributions for the simulations with changed material properties or thermal contact resistance. / Examensarbetet som beskrivs i denna rapport handlar om simulering av kylningen av en elmaskinsrotor. Avgränsningar och vissa förenklingar gjordes på en CAD modell av rotorn för att reducera simuleringstiden. Sedan användes CFD-simuleringsprogrammet STAR-CCM+ för att simulera temperaturfördelningen i modellen. Genom att ändra olika parametrar, en åt gången medan resten hölls vid sina bestämda standardvärden, kunde förändringarna undersökas och sedan jämföras. Det som testades inkluderar bland annat mindre geometriförändringar, parametrar för kyloljan och dess flöde, parametrar för luftgapet och materialen i laminaten och runt permanentmagneterna, samt förlustförändringar. Geometriförändringarna som gjordes för magneterna och det omgivande materialet gav små temperaturökningar. En ökad inre radie på rotorn gav relativt stor temperaturminskning (men denna ändring vore svårare att genomföra på rotorn i praktiken). Majoriteten av medelvärdena av modellregionernas temperaturförändringar var inom 10% från standardsimuleringen som användes. Ökat termiskt kontaktmotstånd mellan Bakeliten och laminaten samt ökade förluster hade sämst påverkan för kylningen, medan förändring i kylvätskans egenskaperna (samt inflödestemperaturen och massflödet) samt minskade förluster hade bäst inverkan. Generellt så såg temperaturfördelningarna lika ut för de olika simuleringarna. Det var främst när materialegenskaperna eller det termiska kontaktmotståndet ändrades som fördelningen såg annorlunda ut.

Glass has sophisticated front properties and are used as facades in high buildings. During cold periods, these glass facades could cause thermal discomfort, due to cold downdraught. Cold downdraught can be countered by placing heaters under glass surfaces. Nowadays technology offers highly insulating windows, which is why there is an interest to investigate the indoor climate with only underfloor heating. The research in this area is limited, and few empirical methods are available. Theoretical analysis has begun but it still brand new. The aim of this investigation was to present the thermal indoor climate influenced by various parameters, such as outdoor temperature, U-value and the glass height. The results were also meant to be used as reference tools in future projects. A reference building was modeled in simulation software called CFD Star-CCM+. The assignment was initiated by Incoord, a leading consulting company in energy, indoor climate and installation planning. The results showed that the air velocity increases with decreasing outdoor temperature and decreases with increasing thermal insulation (lower U-value). At the edges of the glass the air velocity becomes twice as large compared to the velocity of the air in the middle of the atrium. The air velocity (maximum and average) at 0.1 m above the floor is always higher than at 2.0 m. The lowest air velocities start from about 0.25 m/s at 0 ℃ and reaches to 0.60 m/s at -20 ℃. That means these air velocities are too high for what is accepted as a good indoor climate, where the maximum allowable air velocity is 0.15 m/s. The outdoor temperatures and the glass facade’s U-value also have an effect on the surface temperature of the glass facade. This decreases the surface temperature with decreased outdoor temperature, and the surface temperature increases at lower U-value. The height of the glass facades proved to affect both the air velocity in the occupied zone and in the glass surface temperature. The air velocity increases with the glass’ height. The increase is higher at 0.1 m than at 2.0 m above the floor. The result shows also that the average air velocity is lower than 0,15 m/s at window height lower than 5 m. But, at the same height the maximum air velocity is higher than 0.3 m/s. The surface temperature of the glass facades increases with the glass’ height. This is because the indoor heat transfer coefficient increases with height. The outdoor heat transfer coefficient is a function of the wind speed and was assumed to be constant. The underfloor heating, which is represented in the simulations with a floor surface temperature of 27 ℃, is not enough to maintain a good indoor climate in any of simulations. The results of this thesis showed a strong relation between indoor climate, outdoor temperature, U-value and the glass height. This study also showed that the floor heating is not enough to counteract the cold draft during extreme cold periods, in high glass buildings. The presented results can be used as a reference tool for the assessment of air velocities and surface temperatures, in similar high buildings.