A study of the actual airflow over a physical conical tensile membrane model (original) (raw)

Wind tunnel tests of an inflated membrane structure. Two study cases: with and without end-walls

Ingeniería Investigación y Tecnología

The use of textile membranes in architecture and civil engineering has increased rapidly in the last decades. Membrane structures are lightweight, economic structures with unique shapes. At the same time, their structural analysis is particular compared to the analysis of conventional structures. The form-finding procedure, the large displacements of the structures, and the special properties of the composite material all require unique tools. The wind analysis of membrane structures is one of the most challenging parts of the design because the design codes do not provide the pressure coefficients of the doubly curved shapes of membrane structures. The main scope of the present research was to determine the mean pressure coefficient fields over an inflated membrane structure by wind tunnel experiments. The structure, composed of six inflated circular arches, was analyzed with and without end-walls for three wind directions. The equilibrium shape of the inflated structure was determ...

CFD Analysis of Tensile Conical Membrane Structures as Microclimate Modifiers in Hot Arid Regions

Extensive research has been undertaken to understand form finding and the structural behaviour of tensile membrane structures (TMS). In comparison, little is known about the environmental behaviour of this class of structure and a lack of predictive tools for informing their design serves as a barrier to their wider acceptance by the building industry. This paper presents part of a research study carried out to investigate the effect of various forms, configurations and orientations of conical TMS on the airflow behaviour under, around and above these structures for application in hot arid climates. The airflow behaviour and airspeed in an enclosed or semi-enclosed space significantly influence thermal comfort in hot-arid climates. Part of this research involved a parametric study of the airflow behaviour of conical TMS scaled models with different geometrical configurations and orientations in an environmental wind tunnel. The results of this experimental investigation were compared with results from investigations carried out in computational fluid dynamics (CFD) software “FLUENT 5.5” on 1:20 and 1:1 models. The comparison showed that the CFD modelling was able to replicate much of the behaviour observed in the wind tunnel and the approach was extended to explore arrays of conical TMS. This paper presents the CFD modelling undertaken to explore airflows over varying conical tensile fabric structures. The modelling is carried over single conical structures either inverted or straight. These investigations explore how the form, geometry and orientation of a conical TMS affect the airflow rates. The paper concludes with a discussion of how the form and geometrical configuration affect the airflow behaviour and hence the thermal comfort level of the occupants of the semi-enclosed space.

Use of fabric membrane topology as an intermediate environment modifier

2003

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.

Experimental study on interaction between membrane structures and wind environment

Earthquake Engineering and Engineering Vibration, 2010

The interaction between membrane structures and their environment can be either static or dynamic. Static interaction refers to interaction with static air, while dynamic interaction refers to wind and its effects. They can be evaluated by two parameters, added mass and radiation /aerodynamic damping, which are experimentally investigated in this study. The study includes the effects of both the static and dynamic interaction on structural dynamic characteristics, and the relationship between the interaction parameters and the covered area of a membrane structure for the static interaction and the relationship between the interaction parameters and wind direction and speed for the dynamic interaction. Experimental data show that the dynamic interaction is strongly correlated with the structural modes, i.e., the interaction of the symmetric modes is much larger than the anti-symmetric modes; and the infl uence of the dynamic interaction is signifi cant in wind-induced response analysis and cannot be ignored. In addition, it is concluded that the structural natural frequency is remarkably decreased by this interaction, and the frequency band is signifi cantly broadened.

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

2003

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.

External Pressures Distribution on Tensioned Membrane Roofs

Proceedings of the enviBUILD 2019, 2020

The tensioned membrane roofs have wide areas of applications. One of them is agricultural structure. It can be used for intensive and extensive animal production structures or plant production. One of the most important parameters in these objects with animal production is thermal comfort. It is necessary to ensure the efficient ventilation, in the best case the natural. Optimal shape of building and roof has strong impact on ventilation parameter. The first stage of the article is a preliminary investigation of the optimal shape of the duopitch roof from the point of view of wind loading. Duopitch roofs were investigated experimentally in a wind tunnel at the scaled rigid models. Experiments are carried out in the Boundary Layer Wind Tunnel in Bratislava. Wind conditions as the intensity of turbulence, wind speed and direction of wind are crucial for overall wind loads and effectiveness of natural ventilation. The aim of our article is a wind analysis of various shapes of duopitch boundary tensioned membranes with various pitch angles and wind directions. The purpose of this work is to quantify the external pressure coefficient. The results of wind tunnel measurements are analyzed in pressure coefficient maps. They can be used for more efficient design of agricultural structures.

Measurements of the performance of a wind-driven ventilation terminal

This paper presents the results of the measured ventilation flow rates through a roofmounted inflow/outflow natural ventilator and of the wind pressure measurements on the terminal under real conditions. The experiments were conducted at full-scale at the former Silsoe Research Institute (SRI) wind engineering test site using a 6 m cubic test building, referred to as the Silsoe Cube, and a Test House. Ventilation rates and free-stream wind speed were measured using ultrasonic anemometers. The nominally 800 mm x 800 mm ventilation terminal on the Silsoe Cube achieved a peak ventilation rate of 0.06 m 3 s −1 per m s −1 wind speed although the data also indicated periods when the ventilation rate dropped to approximately zero for a specific wind direction due to the vent then being in the position of flow re-attachment following separation at the windward leading-edge of the roof. This has led to better knowledge in relation to the siting of such terminals. A similar terminal monitored on the Test House achieved a peak ventilation rate of nearly 0.1 m 3 s −1 per m s −1 wind speed. The ventilation unit proved to be an effective means of providing natural ventilation and is likely to broaden the application of natural ventilation and help to reduce CO 2 emissions from buildings. The results of pressure measurements on the terminal louvres and the internal pressure in the cube, coupled with the measurements of the corresponding ventilating flow rate mechanisms, provide unique data with which to establish procedures for the rational design of such terminals, which is also outlined in the paper. of fossil fuels accounted for emissions of 529 MtCO 2 1 . It is estimated that almost half of UK 4 CO 2 emissions can be attributed to energy consumed in buildings 2 . A growing proportion 5 of these emissions is due to the increased use of air-conditioning. In a business-as-usual 6 scenario, Hitchin and Pout 3 estimate that up to 40% of UK commercial floor space will be 7 air-conditioned by 2020 compared with around 10% in 1994.

Shaded Dome: a hybrid air-supported – tensile membrane structure

IABSE Congress, New York, New York 2019: The Evolving Metropolis, 2019

The Shaded Domepatented is a semi-permanent facility, comprised of an air-supported dome covered by a tensile membrane shade. The two layers are separated by a grid of spacers, through which forces are transferred. In the space between the two layers a constant natural air flow is present, which enables a pleasant internal microclimate. This passive design element provides protection from extreme climatological conditions like solar radiation, wind, high air temperature, humidity and precipitation. The concept provides a design challenge concerning the force balance between the air-supported dome, as the primary stability structure, and the tensile membrane shade which must remain in shape. The Shaded dome provides a solution for example for temporary events, such as World Cups or the Olympics, to replace the large and expensive venues, which often are abandoned once the event is over.Shaded Dome Technologies explored the basic principles of an air-supported dome covered by a shade ...

Wind Tunnel and CFD Investigation of the Performance of "Windcatcher" Ventilation Systems

Experimental investigations and CFD simulations were carried out to evaluate the performance of square and circular section wind-driven systems for natural ventilation applications in buildings. Wind tunnel and smoke visualisation tests were conducted on a full-scale model based on a commercial "windcatcher" design. The experimental set-up consisted of each system being connected to a model test room. The devices are divided internally into four quadrants/segments for the purpose of air supply and extract. Pressure coefficients distribution, internal air speed and volumetric air flow rate were measured for various wind speeds and for different wind directions. In addition, CFD simulations were carried out to obtain the pressure distribution and air flow pattern around the square section system. The results show that the performance of the devices depends mainly on the speed and direction of the prevailing wind. Although the ventilation rate increases with wind speed it was found to decrease with the increase in the wind direction angles from 0° to 45°, measured from the normal to the face of the square system.

The Thermal Behaviour of a Cylindrical Air Layer Enclosed between Double Fabric Roof Membranes

2021

Objects covered by fabric roof membranes are specific in terms of energy consumption, primarily because of the negligible thickness of the material and its good thermal conduction properties. One of the ways of improving the energy efficiency of these objects is the implementation of a double fabric roof membrane structure with an enclosed non ventilated air layer. This paper analyzes the thermal-insulation behaviour of the air layer enclosed between tensile fabric roof membranes which are used for structural purposes. The compilation of the necessary data was carried out by measuring a real object covered by a double fabric roof membrane, semi-cylindrical in shape. The surface temperatures of each membrane were measured, as were the outside and inside air temperature and the air temperature between the membranes during the summer months. In addition, the solar irradiance during the same period was also measured. The analysis of the measured data took into consideration all the pres...