Wind-driven cross-ventilation in a single-zone cubic building with two large openings is investigated using a computational fluid dynamics approach. We analyzed the driving force and the ventilation flow rate due to wind as a function of the relative location and geometry of the two ventilation openings. The aim is to understand how well the conventional simple macroscopic method predicts the ventilation flow rate and when the simple method fails. Parametric studies were completed using building envelope porosity as the primary variable of interest.

This paper investigates the single-sided natural ventilation through a VELUX centre pivot roof window under natural weather conditions. The aim of the investigation is to develop an empirical formulation for air flow rate through a roof window based on CFD and tracer gas decay measurement methods. CFD can separate buoyancy and wind effects in the calculation of the air flow rate through a window opening, but it is difficult to isolate wind effect from buoyancy forces during measurements.

The 40 story high-rise headquarter of the Deutsche Post AG in Bonn features an integratedcomfort and low energy concept. Contrary to common high-rise design, the building does not require a central mechanical ventilation system. Instead it is decentrally ventilated by a double faade, which decreases wind loads and allows for natural ventilation through window openings.The typical floor plan is designed to provide a cross ventilation from the double faade through officerooms to a central atrium serving as exhaust duct.

In case of cross ventilation through the large opening, it is well known that the inflow directionat the opening is not normal to the opening. Authors proposed the simplified prediction method of theinflow direction at the inlet opening and the airflow rate simultaneously. It is also well known that the use of general discharged coefficient (CD) values is not suitable for the calculation of cross ventilation rate. First reason is that the simple connection of the pressure loss coefficient of an opening ( ?? as the reciprocal of square CD) in series under-estimates the airflow rate.

Using computational fluid dynamics (CFD) techniques to model buoyancy-driven airflows hasalways proved challenging. This work investigates CFD modelling of buoyancy-driven natural ventilation flows in a single-storey space connected to an atrium. The atrium is taller than the ventilated space and when warmed by internal heat gains producing a column of warm air in the atrium and connect space drives a ventilation flow. Results of CFD simulations are compared with predictions of an analytical model and small-scale experiments [1].

Airflow through openings in a cross ventilated building scale model was investigated in a windtunnel and by numerical predictions. Predictions for a wind direction perpendicular to the building showed an airflow pattern consisting of streamlines entering the room, that originated from approximately the same upstream area in the undisturbed boundary layer and a direction of the flow into the room dependent on opening location with velocity vectors pointing away from the stagnation point.

Experiments were carried out to study transition phenomena in buoyancy-induced natural ventilation in a relatively large-scale enclosure equipped with a localized heat source and two openings (upper and lower) on one of the sidewalls. The process studied is transition from the mixing to the displacement ventilation mode realized by opening the lower vent to different heights while keeping the upper vent fully open. Measurements included inside vertical temperature profiles and air velocity through the upper vent.

The air exchange in a room with different windows and window geometries is investigated. The aim is to get reliable data for the air change rate and the air exchange efficiency for natural ventilation. Before using a CFD program for the calculations experimental studies have been carried out. In order to meet different demands we distinguish between short time and continuous ventilation. The results are availabe as figures, graphs or approximate equations.

The influence of thermal effects on the dispersion of a gas in a naturally-ventilated room is investigated using CFD in conjunction with measurements. The gas dispersion inside the room, with and without thermal effects, is characterised by a statistical analysis of the CFD-predicted gas concentrations at a large number of points across the room with a view to quantifying the thermal effects. It is concluded that even small temperature differences can lead to significantly different cross flow behaviour and rates of gas concentration decay at the relatively low air change rate considered.

The main goal of this work is the modeling of the flow field and temperature distribution in thekitchen of a house where natural ventilation techniques were implemented. The Fluent 6.1 commercial CFD software was used. The k- e turbulence model and the Boussinesq approximation for buoyancy were employed. The heat released from a water heater in continuous operation dictates the temperature distribution in the kitchen. Several simulations were performed by varying the boundary conditions and seeking agreement with the available experimental data.