Abstract
The current research aimed to obtain mean pressure distribution over an air-inflated membrane structure using Computational Wind Engineering tools. The steady-state analysis applied the Reynolds-Averaged Navier-Stokes equations with the
1 Introduction
Membrane structures offer lightweight, environmentally friendly, and cost-effective construction solutions to cover large public spaces like concert halls or stadiums [1]. Moreover, lightweight houses can be built like the ones described by [2], representing cheap shelters for emergency situations. Membrane structures can be permanent or temporary buildings; some even possess the deployable characteristic that allows the change of their configuration whenever needed e.g., deployable umbrellas [3].
Tensile membrane structures are composed of flexible textile membrane and a tensioning system that might include arches, masts, rings, and cables [4].
Pneumatic membrane structures are supported and stabilized by the enclosed, compressed air; therefore, they are extremely light structures. Pneumatic structures can be divided into subgroups: air-supported and air-inflated [4–6]. In the case of air-supported structures, the covered air volume is closed and compressed; therefore, special entrances are built to enter or exit the construction. Air-inflated structures are tensioned by the enclosed, pressurized air in their walls; the structure and the covered space can be open, and no special entrances are needed.
The design procedure of membrane structures must consider the strong relationship between geometry and membrane forces. Special numerical methods are applied to determine the equilibrium shape according to the material properties, tensioning system, and external load actions. With their geometry and prestress, the membrane structures must carry downward and upward wind actions or any snow/rain load without wrinkling, ponding, or fluttering problem [1].
The structural design for wind requires knowledge about the pressure distribution on the structure, which can be given by the dimensionless pressure coefficient
Numerical approaches, also known as Computational Wind Engineering (CWE), apply the governing equations that describe the fluid eddy motions to solve the aerodynamic wind effects around the building [11–13]. This technique may include steady-state or time-dependent analysis where material properties and deformations can also be analyzed (fluid-structure interaction). It should be mentioned that CWE cannot be considered a completely reliable technique, so its validation with experimental results is strongly recommended. Numerical investigations to analyze the aerodynamic behavior of different tensile membrane structures are described in [13–15]. The current research validated the CWE analysis of an open air-inflated membrane.
2 Methodology
2.1 Former wind tunnel tests
The structure selected for the CWE analysis was previously tested in a wind tunnel [16]. The prototype structure consists of six inflated tubes with a diameter of 3 m (Fig. 1); its total length (L) and height (H) are 13 m; meanwhile, the width (W) is 26 m. The experiments were completed in the open-circuit wind tunnel with a test section of 1 × 1 × 1.5 m of the Autonomous University of Yucatan, Mexico. The 3D printed model had a scale ratio of 1:72.5. The pressure on the external and internal surface of the model was measured at 102 points for three wind directions 0°, 45°, and 90°.
2.2 Numerical analysis
The 3D steady-state analysis followed the recommendations of [16–18]. The numerical simulations were based on the so-called Reynolds-Averaged Navier-Stokes (RANS) equations, which are suitable for analyzing mean pressure distribution, discarding any transient flow effect. The applied turbulence model was
The studied wind directions were 0°, 30°, 45°, 60°, and 90°. The CWE analysis was performed using ANSYS-Fluent 2019 R3 [20].
2.3 Domain size dimensions and mesh resolution
The creation of the flow domain with double inlet/outlet faces followed the suggestions presented in [21–23]. The double inlet/outlet allows a more straightforward application in the case of non-orthogonal wind directions. The distance from the structure to the inlet and to the top faces was 5H; to the outlet surfaces was 15H, based on [17, 18].
The semi-structured mesh integrated tetrahedral elements close to the structure and hexahedral elements in the rest of the domain (Fig. 2). Around the membrane surface, inflation layers were also considered. The minimum element size was 0.5 m, whereas the maximum was 5.0 m; the total number of nodes and elements were 5.0·106 and 5.5·106, respectively.
2.4 Boundary conditions and convergence criterion
- a)Inlet face: the inlet velocity profile followed the power law equation (Eq. 1) to characterize a flat type terrain [23–25]:
- b)Outlet face: 0 Pa gauge pressure;
- c)Walls: no-slip, free-slip, or symmetry condition. Additionally, the near-wall treatment was in accordance with scalable wall functions approximation. The lower y+ limit for those cells near the walls was 30.
For all wind directions, the membrane surface and the ground surface had the no-slip wall condition, whereas the top domain surface had the symmetry condition. The other abovementioned boundary conditions depended on the current wind direction. For example, for the 0° wind flow, the inlet boundary was the surface perpendicular to the Y-axis on the windward side of the structure. In contrast, the wall on the positive side of the Y-axis (and perpendicular to it) was the outlet boundary face. Additionally, for this wind direction, both boundary walls perpendicular to the X-axis followed the free-slip boundary condition.
Similarly, for the 90° wind direction, the inlet and outlet boundaries were the domain walls perpendicular to X-axis. Finally, for oblique wind directions, the X and Y components of the wind velocity vectors were set at the walls on the negative side of the X and Y axes; then, the outlet boundaries were the walls on the positive side. Figure 3 depicts the boundary conditions for orthogonal and oblique wind directions.
The solution method involved the SIMPLEC scheme for the pressure-velocity coupling and second-order spatial discretization. The convergence criterion was a limit of
3 Results and discussion
Accuracy factors for different wind directions
Wind direction | Surface | MAE | MSE |
0° | External | 0.21 | 0.07 |
Internal | 0.18 | 0.07 | |
45° | External | 0.14 | 0.03 |
Internal | 0.23 | 0.08 | |
90° | External | 0.12 | 0.03 |
Internal | 0.19 | 0.04 | |
Deformed structure (90°) | External | 0.23 | 0.10 |
Internal | 0.09 | 0.01 |
Two sets of measurement points were selected for further comparison. Point set A represents six points on the top and on the bottom of the arches, in the symmetry plane that contains the central axis of the structure. Point set B corresponds to the points on the external and internal surfaces of the two central arches. Figure 4 depicts the pressure coefficients in these set of points on the external surface, and Fig. 5 on the internal one.
Figures 4a and 5a show the
Figures 4b and 5b represent the
Figures 4c and 5c depict
Figure 6 and Table 2 give a more general view of the pressure distribution. Figure 6 includes the pressure coefficient fields based on CWE results for all analyzed wind directions. Table 2 summarizes the maximum and minimum
Maximum and minimum
Wind direction | Surface | WT | CWE | ||
Max. | Min. | Max. | Min. | ||
0° | External | −0.297 | −1.228 | −0.261 | −1.139 |
Internal | −0.069 | −0.794 | −0.306 | −1.235 | |
30° | External | − | − | 0.260 | −1.752 |
Internal | − | − | 0.471 | −1.654 | |
45° | External | 0.770 | −1.388 | 0.643 | −1.515 |
Internal | 0.692 | −1.196 | 0.705 | −1.861 | |
60° | External | − | − | 0.782 | −1.352 |
Internal | − | − | 0.785 | −2.473 | |
90° | External | 0.731 | −0.802 | 0.785 | −1.039 |
Internal | −0.039 | −0.636 | 0.073 | −0.344 |
On the external membrane surface, the most significant suction
In the case of the 45° wind direction, the largest suction determined by CWE (
4 Deformed shape wind analysis
The large displacements of membrane structures and their effect on the pressure distribution cannot be considered during the conventional WT tests. Previous research proved that the impact of the displacements could be significant on the pressure distribution and on the according membrane forces as well [26].
In the current research, following the method presented in [26], the deformed shape of the structure according to 90° wind direction was determined by the Dynamic Relaxation Method (DRM). During the DRM analysis of the membrane structure the considered dynamic pressure was
The pressure distribution over the deformed shape was determined by WT test and CWE analysis following the methodology introduced at the analysis of the undeformed structure. MAE and MSE factors show that the CWE analysis provides a good approximation to the experimental results (Table 1).
Table 3 compares the maximum and minimum
Maximum and minimum pressure coefficients on the deformed structure
Surface | WT | CWE | ||
Max. | Min. | Max. | Min | |
External | 0.591 | −0.935 | 0.646 | −1.693 |
Internal | 0.000 | −0.585 | −0.038 | −0.506 |
5 Conclusion
This paper presented the pressure coefficient maps for an open air-inflated membrane structure based on 3D steady-state numerical simulation. The RANS equations with the
Acknowledgements
This work was supported by NKFI under Grant K138615, and VEKOP-2.3.3-15-2017-00017 project “Establishment of an Atmospheric Flow Laboratory”.
References
- [1]↑
A. L. Marbaniang, S. Dutta, and S. Ghosh, “Tensile membrane structures: an overview,” in Advances in Structural Engineering. Lecture Notes in Civil Engineering, K. Subramaniam and M. Khan, Eds, Singapore: Springer, vol. 74, 2020, pp. 29–40.
- [2]↑
A. Gueroui, M. Halada, and E. Fatehifar, “A lightweight shelter for the survivors after 2016 earthquake in Accumoli,” Pollack Period., vol. 16, no. 3, pp. 133–138, 2021.
- [3]↑
M. Halada, “Bending cantilevered retractable umbrella,” Pollack Period., vol. 10, no. 2, pp. 45–56, 2015.
- [4]↑
W. Lewis, Tension Structures Form and Behavior, 2nd ed. Westminster, London: ICE Publishing, 2018.
- [5]
J. I. de Llorens, Ed. Fabric Structures in Architecture, Woodhead Publishing, 2015.
- [6]
P. Beccarelli, Biaxial Testing for Fabrics and Foils: Optimizing Devices and Procedures, Springer Cham, 2015.
- [7]↑
F. Rizzo, “Wind tunnel test on hyperbolic paraboloid roofs with elliptical plane shapes,” Eng. Struct., vol. 45, pp. 536–558, 2012.
- [8]
F. Rizzo, “Wind tunnel pressure series statistics for the case of a large span canopy roof,” Iran J. Sci. Technol. Trans. Civ. Eng., vol. 45, pp. 2201–2230, 2021.
- [9]
F. Rizzo and F. Ricciardelli, “Design pressure coefficients for circular and elliptical plan structures with hyperbolic paraboloid roof,” Eng. Structures, vol. 139, pp. 153–169, 2017.
- [10]
J. Colliers, J. Degroote, M. Mollaert, and L. De Laet, “Mean pressure coefficient distributions over hyperbolic paraboloid roof and canopy structures with different shape parameters in a uniform flow with very small turbulence,” Eng. Struct., vol. 205, 2020, Paper no. 110043.
- [11]↑
B. Blocken, “50 years of computational wind engineering: Past, present and future,” J. Wind Eng. Ind. Aerodyn., vol. 129, pp. 69–102, 2014.
- [12]
E. Simiu and D. Yeo, Wind Effects on Structures: Modern Structural Design for Wind, John Wiley & Sons Ltd, 2019.
- [13]↑
J. G. Valdés-Vázquez, A. D. García-Soto, and M. Chiumenti, “Response of a double hypar fabric structure under varying wind speed using fluid-structure interaction,” Latin Am. J. Sol. Struct., vol. 18, no. 4, 2021, Paper no. e366.
- [14]
A. Michalski, B. Gawenat, P. Gelenne, and E. Haug, “Computational wind engineering of large umbrella structures,” J. Wind Eng. Ind. Aerodyn., vol. 144, pp. 96–107, 2015.
- [15]
N. A. Mokin, A. A. Kustov, and S. I. Trushin, “Numerical simulation of an air-supported structure in the air flow,” in VIII International Conference on Textile Composites and Inflatable Structures, Munich, Germany, October 9–11, 2017, pp. 383‒393.
- [16]↑
S. J. Pool-Blanco, M. Gamboa-Marrufo, K. Hincz, and C. J. Dominguez-Sandoval, “Wind tunnel test of an inflated membrane structure. Two study cases: with and without end-walls,” Ingeniería Investigación y Tecnología, vol. 23, no. 2, pp. 1–12, 2021.
- [17]↑
B. Blocken, “Computational fluid dynamics for urban physics: Importance, scales, possibilities, limitations and ten tips and tricks towards accurate and reliable simulations,” Build. Environ., vol. 91, pp. 219–245, 2015.
- [18]↑
J. Tu, G. H. Yeoh, and C. Liu, Computational Fluid Dynamics, 3rd ed., Butterworth-Heinemann, 2018.
- [19]↑
B. E. Launder and D. B. Spalding, “The numerical computation of turbulent flows,” Comput. Methods Appl. Mech. Eng., vol. 3, no. 2, pp. 269–289, 1974.
- [21]↑
E. Amaya-Gallardo, A. Pozos-Estrada, and R. Gómez, “RANS simulation of wind loading on vaulted canopy roofs,” KSCE J. Civ. Eng., vol. 25, pp. 4814–4833, 2021.
- [22]
H. Montazeri and B. Blocken, “CFD simulation of wind-induced pressure coefficients on buildings with and without balconies: Validation and sensitivity analysis,” Build. Environ., vol. 60, pp. 137–149, 2013.
- [23]↑
ASCE/SEI 7-10:2013, Minimum Design Loads for Buildings and Other Structures, American Society of Civil Engineers, 2013.
- [24]↑
Manual of Civil Structures: Wind Design (in Spanish). Ch. 1.4, Comisión Federal de Electricidad, Mexico City, Mexico, 2020.
- [25]
EN 1991-1-4:2005, Eurocode 1: Actions on Structures, Part 1-4: General Actions-Wind Actions, Brussels, Belgium: European Committee for Standardization, 2010.
- [26]↑
K. Hincz and M. Gamboa-Marrufo, “Deformed shape wind analysis of tensile membrane structures,” J. Struct. Eng., vol. 142, no. 3, pp. 1–5, 2016.