O Shed tem aberturas no nível inferior da fachada e aberturas elevadas no nível superior do telhado. Quando a abertura localizada no nível superior capta o vento o Shed é chamado de Shed Cata-vento e quando ele é usado para extrair o ar interior do edifício usando a região com pressão negativa é chamado de Shed a sotavento. Os Sheds permitem a ventilação natural e a entrada da luz natural tem maior intensidade e uniformidade que um telhado plano com aberturas laterais. Esta pesquisa foca-se em edifícios com Sheds a sotavento e verifica-se o potencial da sua geometria para aumentar a ventilação vertical cruzada gerada pelo efeito do vento. Emprega-se simulações de Dinâmica dos Fluidos Computacional (CFD) para analisar o fluxo de vento ao redor do edifício e quantificar a ventilação natural por meio das taxas de fluxo de volume e a velocidade do fluxo de ar. Simulações CFD são realizdas utilizando as equações de Navier-Stokes baseadas em médias do número de Reynolds (RANS). Analisa-se a sensibilidade da malha e a validação numérica é realizada com medições em túnel de vento, previamente publicados, usando Velocimetria de Imagem de Partículas (PIV). A validação do modelo de turbulência mostra que o SST K- fornece os resultados mais precisos e, a influência do parâmetro a para o cálculo da energia cinética turbulenta com um valor de 0,5 resulta na melhor concordância com as medições experimentais. Uma sistemática análise da sensibilidade de diversos parâmetros de Shed a sotavento é levada a cabo usando 3D RANS em combinação com o modelo de turbulência SST k-. Os resultados mostram que o ângulo de inclinação do telhado (RIA) tem uma significativa influência na velocidade. Quando um ângulo de inclinação de 45° é empregado, a taxa de fluxo de volume é 22% mais elevada do que um telhado plano.A geometria do Shed é fundamental para maximizar a zona de pressão negativa na parte posterior do edifício. Para um ângulo de inclinação de telhado com 27°, a geometria convexa tem taxas de fluxo de volume 13% superiores aos de uma geometria côncava. Os beirais aumentam o fluxo de ventilação em até 24%. Os beirais a barlavento aumentam a taxa de volume de fluxo significativamente (até 15%) e proporcionam um fluxo de ar interior mais horizontalmente dirigido. Os beirais a sotavento têm uma influência reduzida e a aplicação de ambos (barlavento e sotavento) resulta em um aumento adicional (4%) da taxa de fluxo de volume. Sheds de um e de dois vãos são também investigados; as geometrias côncavas resultam em um ligeiro aumento da taxa de fluxo de volume em comparação com Sheds de um vão. A redução da taxa de abertura (Ainlet / Aoutlet; totais) de 1 para 0,5 resulta num aumento da taxa de volume de 23-39%, dependendo da geometria do telhado. A geometria interna na abertura de saída é importante no desempenho da ventilação.

Sawtooth roofbuildings can contribute to a sustainable and healthy indoor environment as they can allow additional daylight and natural ventilation compared to a standard flat roof. Sawtooth roof buildings have lower level openings in the (windward) façade and also upper-level openings near the roof top in the opposite (leeward) façade. When the upper-level opening captures the wind the sawtooth roof is called wind catcher and when it is used to extract indoor air from the building using the underpressure region in the wake of a building it is called a leeward sawtooth roof. This PhD study focuses on low-rise leewar sawtooth roof buildings. The main goal of the research is to verify the potential of the leeward sawtooth roof geometry to increase the wind-driven upward cross-ventilation. This research employs Computational Fluid Dynamics (CFD) simulations to analyze the wind flow around the building and quantify the natural ventilation by means of the volume flow rates and the airflow patterns (indoor velocity). CFD simulations are performed using the 3D steady Reynolds-Averaged Navier-Stokes (RANS) equations. The simulations are based on a grid-sensitivity analysis and on validation with previously published wind-tunnel measurements using Particle Image Velocimetry (PIV). The results show that the shear-stress transport (SST) k- and the Renormalization-group (RNG) k- turbulence models provide the best agreement with the experimental data. Once the numerical model is validated, a sensitive analysis of different building parameters on a single-zone isolated building model is carried out using the 3D steady RANS approach in combination with the SST-k- turbulence model to provide closure to the governing equations. The following building parameters are systematically tested: (i) roof inclination angle and vertical outlet opening position; (ii) roof geometry; (iii) windward and leeward cavesinclination angle and the combination of both (windward and leeward); and, (iv) a comparison between a single-span and a double-span leeward sawtooth roof with the same and with lower inlet-outlet opening ratio. In Chapter 1 the relevance, the driving forces of the natural ventilation phenomena, the problem statement and the methodology of the current research are introduced. Chapter 2 presents the validation study and shows that the SST k- turbulence model provides the most accurate results, followed by the RNG k- model, the standard k- model and the Reynolds stress model show larger deviations from the measured velocities. The influence of the parameter a for the calculation of the turbulent kinetic energy profiles at the inlet of the computational domain is tested; the results show that a value of 0.5 results in the best agreement with the wind-tunnel measurements. In addition, the impact of the roof inclination angle (RIA) is tested and it is observed that it strongly influences the indoor air velocity and the volume flow rate. The latter increases with a roof inclination angle larger than 18°. When a 45° roof inclination angle is employed, the volume flow rate is 22% higher then a flat roof and it additionally increases from 22% to 25% when the outlet opening is located near the roof. The vertical outlet opening position is less important as it can just increase the volume flow rate by around 4% and increases or decreases the indoor air velocity by to 41% and 21%, respectively. In Chapter 3 five different roof geometrics are studied; one straight and four curved roofs. The curved roofs can be subdivided in one concave, one bybrid (convex-concave) and two convex roof geometries. It is observed thet the roof geometry is an important design parameter to maximize the size and magnitude of the underpressure zone in the wake of the building and the pressure difference over the building.A roof that directs the external wind flow behind the building upwards will result in a larger underpressure zone and larger underpressures and consequently in higher volume flow rates. For a normal wind incidence angle (0°), from all the roof geometrics with a 27° roof inclination angle, the convex roof and the straight roof result in volume flow rates that are up to 13% higher than those of concave roof geometrics. In Chapter 4 the impact of the caves is explored. It is shown that, in addition to their well-known beneficial effects concerning solar radiation and wind-driven rain, eaves can increase wind-driven cross-ventilation flow by up to 24%. Windward eaves with an inclination angle of 27° result in the highest increase of the volume flow rate (15%) and in a more horizontally directed flow through the occupied zone. On the other hand, leeward eaves appear to have less influence on the ventilation flow than upwind eaves; the maximum increase in volume flow rate is only 5% when eaves with a 90° inclination angel are employed. Application of both a windward eaves and a leeward eaves results in a additional increase (4%) of the flow rate in a single-span building. In Chapter 5 an analysis of single-span and double-span sawtooth roofs is presented. It is shown that the straight and concave double-span leeward sawtooth roof geometries result in a slight increase of the volume flow rate compared to single-span roof geometries with a similar geometry type. However, the convex double-span roof geometry E2x2-OR1 reaches a 12% lower volume flow rate then found for its reference case, the single-span roof geometry E2, which is the result of the narrow internal geometry at the outlet opening. It is also shown that reducing the opening ratio (Ainlet/Aoutlet;toal) from 1 to 0.5 for the double-span roof geometries results in an increase of the volume flow rate with 23-29%, depending on the roof geometry.For convex double-span cases the building geometry near the outlet-opening plays an important role in the ventilation performance. The internal geometry contraction near the outlet openings generates a resistance to the airflow and reduces the volume flow rate. Chapter 6 provides a discussion based on the limitations of the presented research and points out recommendations for future research. Chapter 7 summarizes the main conclusions of the current research. Whereby it is highlighted that the optimum leeward sawtooth roof building design for increasing cross-ventilation is achieved by the interaction of these four main parameters: (a) roof inclination, (b) roof geometry, (c) eave location and angle, and (d) inlet-outlet opening ratio. In addition, it is pointed out that a single-span with 12 m depth reaches a higher volume flow rate than a single-span with 6 m depth with the same roof geometry type, despite the fact that a lower underpressure is present at the outlet opening.