The paper deals with a CFD based study of the transverse permeability of a textile woven structure. The reported numerical investigation is preconditioned by both previous experimental and CFD study on jet systems. It is also based on detailed experimental investigation of the porous structure of single layer woven fabrics, made of staple fiber yarns. The flow in through-thickness direction of the woven structures is presented as jet systems, issuing from set of orifices. Two different types of jet system (3×3 jets and 5×5 jets) with two types of jet cross sections (square and circular), corresponding to two different woven structures, are simulated. An analysis is made in terms of the structure of the woven fabrics (area and shape of the interstices between the threads), the parameters of the flow passing through the textile (velocity profiles and velocity fields through isosurfaces), the role of the type of the jet systems, representing the flow and the influence of the shape of the interstices between the threads on the flow pattern. It was found that the applied approach could be effectively used for studying of the transverse permeability of the woven fabrics.

No abstract

The thermal environment in an indoor space is determined by the thermal state of the human body, and the local thermal discomfort. The draught rate (DR) is one of the indices for thermal discomfort. The achievement of air distribution without draught is one of the goals of the ventilation methods. It is especially important in the design of climate chambers, where the volume is small, and the research studies may require prolonged occupants’ exposure. Our study shows results from the CFD simulations of a mechanically ventilated climate chamber, performed in the design stage of the chamber’s construction. Velocity profiles distribution, temperature distribution and DR are used to assess the thermal comfort of the person in the chamber. The results obtained allowed designing of the proper indoor environment with desired characteristics for air distribution and human exposure.

No abstract

Despite the effort done by member states during the last decade, failure in the implementation of the Ambient Air Quality Directive is being continuously registered in many European cities for different air pollutants. One of the biggest concerns in Bulgaria is the exceeded PM10 concentration in the ambient air, measured in all six air quality zones during the winter period. This has induced numerous activities (at the national and European level) focused on the following issues: identification of the level of exceedance of the air quality norms for PM10; the general emission sources; the most prominent omissions and discrepancies in the legislative framework; the level of implementation of the prescribed measures and many others. However, the PM10 exceedance is still of a significant concern in at least 28 municipalities in Bulgaria. Thus, the present work introduces a brief report on the current state of the problem in the country. For that purpose, benchmarking analyses was applied for obtaining the range of discrepancies and the tendencies of the PM10 concentrations, monitored in the ambient air at the affected municipalities. The investigation was carried out using merely officially reported and freely accessible data and covered a relatively short period of time of six years. The latest national and European environmental reports present data confirming the primary role of residential heating and transport during the winter period as well as at the occurrence of particular atmospheric conditions.