Computational fluid dynamics (CFD)

Building airtightness tests have become very common in several countries, either to comply with minimum requirements of regulations or programs, or to justify input values in calculation methods. This raises increasing concerns for the reliability of those tests. Despite the extensive debates about how the building pressurization test standard ISO 9972 should address sources of uncertainties, no change has been implemented. According to the current standard, the zero-flow pressure shall not exceed 5 Pa for the test to be valid.

In the present paper the impact of natural cross-ventilation on thermal comfort levels in sustainable residential buildings is evaluated. A sustainable dwelling is designed in Crete and various scenarios of different combinations of open windows and doors in the ground floor, the first floor and between the floors are tested to determine the final scenarios with the best possible airflow movement.

Typical heat sources in indoor environments include humans, electrical devices, and computers. The number of such sources in operating room environments is even higher due to the presence of surgical staff members and medical equipment. The exchange of thermal energy between indoor surfaces and air is usually modelled by considering contributions from both radiation and convection. Complete heat transfer simulations in indoor environments are normally difficult since radiation models have a tendency to generate numerical instability and, hence, problems with convergent solutions.

In the preceding companion paper (Part I), a method with one sensor that could identify the indoor contaminant source location and strength in short time was presented. On the basis of further theoretical study, a method with two sensors is presented in this paper to identify contaminant source with higher accuracy. This paper demonstrates how to use the method with two sensors to find the location of contaminant source in a threedimensional room. In addition, the accuracy of two types of methods was compared.

In case contaminants are released in occupied rooms, it is necessary to determine the contaminant source location and strength rapidly so that prompt response measures can be taken to protect indoor occupants. This paper presents a new method with one sensor to identify the contaminant source location and strength. It completes the time-consuming computational fluid dynamics (CFD) simulations before the release event, and finds the source in real time during the event. In addition, an index called “correctness probability” for evaluating the accuracy of this method is proposed.

In case contaminants are found in an aircraft cabin, it is useful to identify the contaminant source location and strength. This can be done through inverse Computational Fluid Dynamics (CFD) modeling. Since inverse CFD equations are ill-posed, this study proposes to solve a quasi-reversibility (QR) equation and a pseudo-reversibility (PR) equation. The QR equation improves the numerical stability by replacing the second-order diffusion term with a  fourth-order stabilization term in the governing equation of contaminant transport.

Air age is an important parameter to assess indoor air quality in ventilated rooms. In order to consider the contribution of ductwork and recirculation, the concept of total air age was proposed for ventilation systems with ductwork and recirculation in previous study. In this paper, about 16 typical cases are simulated with computational fluid dynamics after introducing the method to calculate total air age for ventilation systems with only one AHU and one room in which several inlets and outlets exist.

This study evaluated various ventilation strategies for efficiently removing house dust in the indoor environment. Experiments and simulations were performed to study the flow and diffusion fields that are affected by different locations and shapes of outlets. In this study, two kinds of ventilation strategies were considered i.e. ceiling exhaust and slit exhaust. In each case, experimental measurements showed that the characteristics of airflow within the whole room are generally similar except for airflow close to the outlet. CFD flow field and diffusion field simulations were also made.

This paper is concerned with a building situated in the west of Scotland which faces severe weatherconditions with high wind speeds and driving rain occurring frequently. This results in extensivedamage to the building fabric, and affects the internal climate which leads to a serious issue in buildingconstruction. In this study, a three-dimensional numerical model of airflow around the building isinvestigated. This investigation is part of ongoing research on wind-driven rain which has establishedthe importance of moisture stresses, wind flow and rain impacts on a commercial building.

Methods of computational fluid dynamics (CFD) have been applied to predict the details of air,contaminant and thermal transport within isolated building zones, yet zone transport processes do notoccur in isolation they result from and interact with transport from the larger building system in whichthey are embedded. Consequently, there is a growing interest in combining CFD models of individualzones within multizone models of enclosing building systems to more faithfully model both the largerbuilding interactions and the intrazonal details.