Knots with infinitely many incompressible Seifert surfaces

We show that a knot in $S^3$ with an infinite number of distinct incompressible Seifert surfaces contains a closed incompressible surface in its complement.Comment: 16 pages, 6 figure

CFD investigation of airflow around conic tensile membrane structures

This paper is part of continuing research on the airflow around membrane structures. The research explores how the form and orientation of the structure itself affect the ventilation rates and the comfort level within the enclosures and in their immediate vicinity. This paper describes a study of the airflow patterns around and under conic tensile membrane structures covering open and semi-enclosed spaces using CFD (computational fluid dynamics) modelling, carried out in order to ascertain the potential of conic membranes of different forms for modifying the microclimate and improving human comfort. The reason for using CFD modelling is to give the opportunity to explore different geometries, to investigate the use of structure topology to assist in passive cooling and achieving higher comfort rates of spaces covered by membrane structures in hot climates

Environmental behaviour of tensile membrane structures

This paper considers the environmental properties of spaces enclosed by tensile membrane structures (TMS). Limitations in the understanding of the environmental and thermal performance of TMS have to some extent hindered their acceptance by building clients and the building industry. A review of the early attempts to model the thermal environment of spaces enclosed by TMS is given and their environmental and thermal properties are discussed. The lack of appropriate tools for the investigation of their internal environment is identified and a need for further research in this area is suggested as a route to fully realising the potential benefits offered by TMS

Use of fabric membrane topology as an intermediate environment modifier

This paper describes the pattern of airflow around membrane structures, and how they along with the form of the structure itself affect the ventilation rates within their enclosures or their immediate vicinity. Examples that have successfully used membrane skins in the built environment will be reviewed. The possible use of tensile membrane structures topology and orientation to enhance ventilation rates and natural cooling within the semi-enclosed spaces will be discussed. The use of the indigenous fabric skin to tackle key climatic concerns in a simple, elegant manner is discussed along with the review of the wind tunnel experimental visualisation and measurements carried out by the author. These structures go beyond simply providing shading to illustrate innovative, environmentally friendly fabric Architecture, but if properly understood the fabric’s form and topology can play an effective role in the ventilation and natural cooling of spaces in their immediate vicinity

Environmental aspects of tensile membrane enclosed spaces

Buildings enclosed by fabric membranes are very sensitive to changes in environmental conditions as a result of their low mass and low thermal insulation values. Development in material technology and the understanding of the structural behaviour of tensile membrane structures along with the vast progress in computer formfinding software, has made it possible for structural design of tensile membrane structures to be approached with almost total confidence. On the contrary, understanding of the environmental behaviour in the spaces enclosed by fabric membrane and their thermal performance is still in its infancy, which to some extent has hindered their wide acceptance by the building industry. The environmental behaviour of tensile membrane structures is outlined and the possible use of the fabric’s topology and geometry particularly to enhance ventilation rates and airflow velocities within the enclosed space is discussed. A need for further research in this area is identified in order to fully realise the potential benefits offered by these structures

Environmental performance of spaces enclosed or semi-enclosed by fabric membrane structures

. Since the 1960s a large evolution took place in the fabric structures industry, as they became more complex with time, and designers have been able to keep up with the structural implications of this changing situation. Sophisticated analytical models and computer software have facilitated the structural design of tensile membrane structures (TMS) and this has produced a diverse and complex range of design and form solutions. However, environmental issues continue to be dealt with in a cursory manner, which is still today unable to fully satisfy the client’s requirements. With the vast interest in these structures, designers and manufacturers alike realised that if membrane enclosed spaces is to compete with other more conventional enclosures, a clear understanding of their environmental behaviour should be available to them. Moreover that if membrane enclosed spaces were to aspire to the same level of environmental performance as more conventional buildings, it would be necessary to develop tailored analytical techniques, which could be used to assess the likely performance of various design alternatives. This paper explores the thermal performance of membrane structures, and how these structures can be used as climate modifiers in spaces enclosed or semi enclosed by fabric membrane skins, providing thermal comfort for the occupiers. Analytical techniques that are used to investigate the environmental behaviour of fabric membranes and assessing their liability will be reviewed. The paper also looks at some of the work done by other researchers in the investigation of the thermal behaviour of fabric membranes by different techniques

Airflow around conic tensile membrane structures

Sophisticated analytical models and computer software have facilitated the structural design of tensile membrane structures and this has produced a diverse and complex range of design and form solutions. The climate inside a typical fabric membrane enclosure is dependent on factors such as the shape (having a significant clear height) and the thermal properties of the thin “skin”, which differ considerably from traditional or more conventional “heavy” construction. However, there has been little consideration of the effect that these forms “shapes” have on their immediate environment, from the point of view of human comfort, even for the most basic of shapes. Tensile membrane structures can have an attractive dramatic effect and easily span a large area. In addition to the lighting and shading functions normally associated with tensile membrane skins, the topology of the construction type offers exciting opportunities to lend additional functionality and higher levels of comfort to the enclosure (ElNokaly et al, 2002). This paper describes the results of wind tunnel visualization and monitoring of the airflow patterns around and under conic tensile membrane structures covering open and semi-enclosed spaces. The experiments were conducted using a number of physical models representing a simple conical membrane structure. The study was designed primarily in order to ascertain the potential of conic membranes for modifying the microclimate and improving human comfort in their immediate vicinity. (Continued