Aerodynamic optimisation of sports stadiums towards wind comfort

The aim of this work was to investigate the aerodynamic performance of sports stadiums located in the built environment and conduct a design optimisation study to improve the wind comfort conditions for both players and spectators. A 1:300 scale semi-open stadium model was assessed with combined Atmospheric Boundary Layer (ABL) wind tunnel experimentation and Computational Fluid Dynamics (CFD) techniques against pressure and velocity distribution patterns in both interior and exterior areas of the stadium bowl. The validation of the numeric analysis was performed with the experimental results of pressure coefficients. The aerodynamic performance analysis compared two impinging wind angles (0o and 90o) and two building envelope porosities, defined by the existence of an elevated and non-elevated roof configuration. The results indicated that the wind direction caused small differentiations on the developed wind distribution patterns, with the wind angle of 90o generating smaller negative pressures in both interior and exterior stadium surfaces. Further analysis of the air velocity distribution results indicated that the provision of a horizontal ventilation opening between the roof and the upper spectator tiers substantially improves the airflow distribution for the benefit of spectators, but induces up to 25 % higher velocities at the centre of the pitch level. Parametric studies were performed to evaluate the impact of the roof geometry changes on the developed wind comfort conditions for the players and the spectators. By employing coupled CFD-Response Surface Methodology (RSM) techniques, it was found that the wind speeds and the flow homogeneity at the stadium bowl are more susceptible to firstly the roof height and secondly the roof radius. Finally, the generated response surfaces formed the basis for the conduction of a multi-objective optimisation study, which revealed that a drastic reduction of the roof height and the roof radius by 96.9 % and 50 % respectively may reduce the wind speeds and the flow heterogeneity up to 37 % and 49.6 % in the occupied areas

CFD simulation and optimisation of a low energy ventilation and cooling system

Mechanical Heating Ventilation and Air-Conditioning (HVAC) systems account for 60% of the total energy consumption of buildings. As a sector, buildings contributes about 40% of the total global energy demand. By using passive technology coupled with natural ventilation from wind towers, significant amounts of energy can be saved, reducing the emissions of greenhouse gases. In this study, the development of Computational Fluid Dynamics (CFD) analysis in aiding the development of wind towers was explored. Initial concepts of simple wind tower mechanics to detailed design of wind towers which integrate modifications specifically to improve the efficiency of wind towers were detailed. From this, using CFD analysis, heat transfer devices were integrated into a wind tower to provide cooling for incoming air, thus negating the reliance on mechanical HVAC systems. A commercial CFD code Fluent was used in this study to simulate the airflow inside the wind tower model with the heat transfer devices. Scaled wind tunnel testing was used to validate the computational model. The airflow supply velocity was measured and compared with the numerical results and good correlation was observed. Additionally, the spacing between the heat transfer devices was varied to optimise the performance. The technology presented here is subject to a patent application (PCT/GB2014/052263)

Urban integration of aeroelastic belt for low-energy wind harvesting

In this modern age low-energy devices are pervasive especially when considering their applications in the built-environment. The multitude of low-energy applications extend from wireless sensors, radio-frequency transceivers, charging devices, cameras and other small-scale electronic devices. The energy consumptions of these devices range in the milliwatt and microwatt scale which is a result of continuous development of these technologies. Thus, renewable wind energy harnessed from the aeroelastic effect can play a pivotal role in providing sufficient power for extended operation with little or no battery replacement. An aeroelastic belt is a simple device composed of a tensioned membrane coupled to electromagnetic coils and power conditioning components. This simplicity of the aeroelastic belt translates to its low cost and overall modularity. The aim of this study is to investigate the potential of integrating the aeroelastic belt into the built environment using Computational Fluid Dynamics (CFD) simulations. The work will investigate the effect of various external conditions (wind speed, wind direction and physical parameters, positioning and sizing) on the performance of the aeroelastic belt. The results from this study can be used for the design and integration of low-energy wind generation technologies into buildings

A passive cooling wind catcher with heat pipe technology: CFD, wind tunnel and field-test analysis

Wind catchers are natural ventilation systems based on the design of traditional architecture, intended to provide ventilation by manipulating pressure differentials around buildings induced by wind movement and temperature difference. Though the movement of air caused by the wind catcher will lead to a cooling sensation for occupants, the high air temperature in hot regions will result in little cooling to occupants. In order to maximise the properties of cooling by wind catchers, heat pipes were incorporated into the design. Computational Fluid Dynamics (CFD) was used to investigate the effect of the cooling devices on the performance of the wind catcher, highlighting the capabilities of the system to deliver the required fresh air rates and cool the ventilated space. Qualitative and quantitative wind tunnel measurements of the airflow through the wind catcher were compared with the CFD data and good correlation was observed. Preliminary field testing of the wind catcher was carried out to evaluate its thermal performance under real operating conditions. A cooling potential of up to 12 °C of supply air temperature was identified in this study

Climatic analysis of a passive cooling technology for the built environment in hot countries

The aim of this work was to determine the ventilation and cooling potential of a passive cooling windcatcher operating under hot climatic conditions by replicating the monthly wind velocity, wind direction, temperature and relative humidity (RH) observed in a hot-desert city. The city of Ras-Al-Khaimah (RAK), UAE was used as the location of the case-study and available climatic data was used as inlet boundary conditions for the numerical analysis. The study employed the CFD code FLUENT 14.5 with the standard k–ε model to conduct the steady-state RANS simulation. The windcatcher model was incorporated to a 3 × 3 × 3 m3 test room model, which was identical to the one used in the field test. Unlike most numerical simulation of windcatchers, the work will simulate wind flows found in sub-urban environment. The numerical model provided detailed analysis of the pressure, airflow and temperature distributions inside the windcatcher and test room model. Temperature and velocity profiles indicated an induced, cooler airflow inside the room; outside air was cooled from 38 °C to 26–28 °C, while the average induced airflow speed was 0.59 m/s (15% lower compared to a windcatcher w/out heat pipes). Field testing measurements were carried out in the Jazira Hamra area of RAK during the month of September. The test demonstrated the positive effect of the integration of heat pipes on the cooling performance but also highlighted several issues. The comparison between the measured and predicted supply temperatures were in good agreement, with an average error of 3.15%

Integration of aero-elastic belt into the built environment for low-energy wind harnessing: current status and a case study

Low-powered devices are ubiquitous in this modern age especially their application in the urban and built environment. The myriad of low-energy applications extend from wireless sensors, data loggers, transmitters and other small-scale electronics. These devices which operate in the microWatt to milliWatt power range and will play a significant role in the future of smart cities providing power for extended operation with little or no battery dependence. Low energy harvesters such as the aero-elastic belt are suitable for integration with wireless sensors and other small-scale electronic devices and therefore there is a need for studying its optimal installation conditions. In this work, a case study presenting the Computational Fluid Dynamics modelling of a building integrated with aero-elastic belts (electromagnetic transduction type) was presented. The simulation used a gable-roof type building model with a 27° pitch obtained from the literature. The atmospheric boundary layer flow was employed for the simulation of the incident wind. The work investigates the effect of various wind speeds and aero-elastic belt locations on the performance of the device giving insight on the potential for integration of the harvester into the built environment. The apex of the roof of the building yielded the highest power output for the aero-elastic belt due to flow speed-up maximisation in this region. This location produced the largest power output under the 45° angle of approach, generating an estimated 62.4 mW of power under accelerated wind in belt position of up to 6.2 m/s. For wind velocity of 10 m/s, wind in this position accelerated up to approximately 14.4 m/s which is a 37.5% speed-up at the particular height. This occurred for an oncoming wind 30° relative to the building facade. For velocity equal to 4.7 m/s under 0° wind direction, airflows in facade edges were the fastest at 5.4 m/s indicating a 15% speed-up along the edges of the building

Towards an integrated computational method to determine internal spaces for optimum environmental conditions

Computational Fluid Dynamics tools and Response Surface Methodology optimization techniques were coupled for the evaluation of an optimum window opening design that improves the ventilation efficiency in a naturally-ventilated building. The multi-variable optimization problem was based on Design of Experiments analysis and the Central Composite Design method for the sampling process and estimation of quadratic models for the response variables. The Screening optimization method was used for the generation of the optimal design solution. The generated results indicated a good performance of the estimated response surface revealing the strength correlations between the parameters. Window width was found to have greater impact on the flow rate values with correlation coefficient of 73.62%, in comparison to the standard deviation 55.68%, where the window height prevails with correlation coefficient of 96.94% and 12.35% for the flow rate. The CFD results were validated against wind tunnel experiments and the optimization solution was verified with simulation runs, proving the accuracy of the methodology followed, which is applicable to numerous environmental design problems

CFD optimisation of a stadium roof geometry: a qualitative study to improve the wind microenvironment

The complexity of the built environment requires the adoption of coupled techniques to predict the flow phenomena and provide optimum design solutions. In this study, coupled computational fluid dynamics (CFD) and response surface methodology (RSM) optimisation tools are employed to investigate the parameters that determine the wind comfort in a two-dimensional stadium model, by optimising the roof geometry. The roof height, width and length are evaluated against the flow homogeneity at the spectator terraces and the playing field area, the roof flow rate and the average interior pressure. Based on non-parametric regression analysis, both symmetric and asymmetric configurations are considered for optimisation. The optimum design solutions revealed that it is achievable to provide an improved wind environment in both playing field area and spectator terraces, giving a further insight on the interrelations of the parameters involved. Considering the limitations of conducting a two-dimensional study, the obtained results may beneficially be used as a basis for the optimisation of a complex three-dimensional stadium structure and thus become an important design guide for stadium structures

Design and Optimisation of a Novel Passive Cooling Wind Tower

Buildings are responsible for almost 40% of the world energy usage. Heating Ventilation and Air-Conditioning (HVAC) systems consume more than 60% of the total energy use of buildings. In hot climates, the percentage of energy consumption by air conditioning is significantly larger due to the more extreme conditions of the local climate. Clearly any technology which reduces the HVAC consumption will have a dramatic effect on the energy performance of the building. Natural ventilation offers the opportunity to eliminate the mechanical requirements of HVAC systems by using the natural driving forces of external wind and buoyancy effect. A technology which incorporates both wind and buoyancy driven forces is the wind tower. Wind towers are natural ventilation systems based on the design of traditional architecture. Though the movement of air caused by the wind tower will lead to a cooling sensation for occupants, the high air temperature in hot climates will result in little cooling. In order to maximise the properties of cooling by wind towers, heat transfer devices were incorporated into the design to reduce the supply air temperature. The aim of this work was to design and optimise a wind tower integrated with heat transfer devices using CFD modelling, validated with wind tunnel and field experiments. Care was taken to generate a high-quality CFD grid and specify boundary conditions. An experimental model was created using 3D printing. Qualitative and quantitative wind tunnel measurements were compared with the CFD data and good correlation was observed. Field testing of the wind tower was carried out to evaluate its performance under real operating conditions. A prototype of the device was produced and installed on top of a test facility in Ras Al Khaimah, UAE. The study highlighted the potential of the wind tower in reducing the temperature by up to 12˚C and supplying the required fresh air rates. The technology presented here is subject to a patent application

CFD optimisation of a stadium roof geometry: a qualitative study to improve the wind microenvironment

The complexity of the built environment requires the adoption of coupled techniques to predict the flow phenomena and provide optimum design solutions. In this study, coupled computational fluid dynamics (CFD) and response surface methodology (RSM) optimisation tools are employed to investigate the parameters that determine the wind comfort in a two-dimensional stadium model, by optimising the roof geometry. The roof height, width and length are evaluated against the flow homogeneity at the spectator terraces and the playing field area, the roof flow rate and the average interior pressure. Based on non-parametric regression analysis, both symmetric and asymmetric configurations are considered for optimisation. The optimum design solutions revealed that it is achievable to provide an improved wind environment in both playing field area and spectator terraces, giving a further insight on the interrelations of the parameters involved. Considering the limitations of conducting a two-dimensional study, the obtained results may beneficially be used as a basis for the optimisation of a complex three-dimensional stadium structure and thus become an important design guide for stadium structures