Solar car racing has created a competitive platform for research into alternative energies, particularly the utilization of solar energy. This paper reports on a numerical optimization of the vehicle body shape, utilizing Computational Fluid Dynamics (CFD). Optimization and validation of the body shape, fairing position, body-and-fairing fillet blend, fairing leading edge curvature, driver position and canopy design were considered. For the purposes of this study, the fairing and driver position optimization will be discussed as a case study to illustrate the design and optimization methodology with the improved product of area and the coefficient of drag (ACd) values recorded. The algorithms developed and procedures followed to adapt the design of the vehicle are presented. The algorithms applied relied on comparing designs based on evaluating shape function curves representing the normalized (body length) sectional area of the body under consideration. With the aid of numerical analysis software and applying the design optimization algorithm by evaluating ACd, it was possible to optimize the shape of the main wing and the placement of the fairings and the driver compartment/canopy. The results of the CFD simulation showed there was a direct correlation between the drag coefficient and the shape function. By utilizing this methodology, significant improvements to the coefficient of drag could be realized. A reduction of 31% in the coefficient of drag was achieved by moving the centered driver position to the side. This design change then also contributed to an energy saving of 442.6 Watt at a speed of 100km/h.

In this paper, the influence of various bench arrangements on the microclimate inside a two-span greenhouse is numerically investigated using three-dimensional Computational Fluid Dynamics (CFD) models. Longitudinal and peninsular arrangements are investigated for both leeward and windward opened roof ventilators. The velocity and temperature distributions at plant level (1m) were of particular interest. The research in this paper is an extension of two-dimensional work conducted previously [1]. Results indicate that bench layouts inside the greenhouse have a significant effect on the microclimate at plant level. It was found that vent opening direction (leeward or windward) influences the velocity and temperature distributions at plant level noticeably. Results also indicated that in general, the leeward facing greenhouses containing either type of bench arrangement exhibit a lower velocity distribution at plant level compared to windward facing greenhouses. The latter type of greenhouses has regions with relatively high velocities at plant level which could cause some concern. The scalar plots indicate that more stagnant areas of low velocity appear for the leeward facing greenhouses. The windward facing greenhouses also display more heterogeneity at plant level as far as temperature is concerned.

Due to wide emphasis on climate change today, alternative fuel research is necessary. Consequently, the South African Solar Challenge has created a competitive platform for research into alternative energies, particularly solar. The University of Johannesburg (UJ) competed in the competition using their uniquely designed and built solar vehicle, Ilanga I. However, due to the constraints of the energy available, the aerodynamics of the vehicle has to be exceptionally good. Subsequently, a large proportion of the total power of the vehicle is used to overcome the aerodynamic resistance posed by the vehicle. Furthermore, much of the remaining power of the vehicle is used to overcome rolling resistance. Consequently, solar vehicles have to be as lightweight as possible in order to effectively reduce the rolling resistance. However, reducing weight of the vehicle results in the vehicle’s stability being greatly affected by side-wind effects. In order to improve on the vehicle, it is very important to test for and obtain its aerodynamic characteristics. This research article aims at obtaining the average drag coefficient felt during the majority of the race as well as the lift coefficients for side-wind cases, in order to investigate vehicle safety. Thus, through the use of Computational Fluid Dynamics (CFD), it was possible to obtain an assessment of the vehicle’s performance. Simulations were performed using the Reynold’s Averaged Navier Stokes (RANS) method with use of the k-ω SST turbulence model. This method of simulation showed reasonable predictions of the results as compared to literature.

This paper presents a parametric study of the indoor climate of a four span greenhouse subjected to natural ventilation. The effect of different heat fluxes through the greenhouse covering on the airflow patterns as well as temperature and velocity distributions were determined. Appropriate effective heat flux boundary conditions were introduced in the CFD model to investigate temperature and velocity distributions at plant level. Initially, three different simulations were done to represent zero wind speed conditions. Secondly, a velocity of 1m/s was specified at the domain inlet boundary. Results indicated that for all cases, the velocity distribution was heterogeneous and quite high for wind still days around midday. Temperature distributions were more homogeneous, decreased with the presence of a wind. Results indicated that a parametric value of 20% of the maximum daily solar radiation approximates previously simulated wall temperatures. It was also concluded that design changes such as additional openings including side and/or more roof ventilators be utilized to enhance ventilation on wind still days, as well as the warmer parts of the day.

In this paper, turbulent buoyancy induced convection in a partitioned square cavity with conducting baffles is numerically investigated to determine overall heat transfer performance. The finite volume method using polyhedral cells is used to solve the governing mass, momentum and energy equations and to predict the flow patterns and heat transfer in the cavity. The cavity consisted of two adiabatic vertical walls, an isothermal horizontal wall located at the bottom at Th and the top wall isothermal at Tc. The configuration was investigated for Ra = 9.1 × 107 to Ra = 1.9 × 109 (turbulent). The conducting baffles are assigned various values of effective thermal resistances, calculated using thermal conductivity. The effects of these conducting baffles and their effective thermal resistance are shown in terms of temperature and velocity contour plots and average Nusselt number. Results indicated that the presence of baffles influenced the heat transfer from the hot wall considerably, and it was concluded that a partitioned enclosure containing conducting partitions can be used to represent an enclosed greenhouse containing raised benches with single/multiple racks.