77th Annual Meeting of the APS Division of Fluid Dynamics (November 24, 2024 — November 26, 2024)

P2694507: Laboratory scale visualization of building leakage via background oriented schlieren

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Authors

• Dorothy Lindula, New Mexico Institute of Mining & Technology
• Maria Nicola. D'Orazio, New Mexico Institute of Mining and Technology
• Frank A. Mier, New Mexico Institute of Mining & Technology

DOI: https://doi.org/10.1103/APS.DFD.2024.GFM.P2694507

When considering buildings in the United States, 4% of the consumed energy is wasted due to air leakage from walls and roofs. To evaluate existing buildings in the built environment to increase energy efficiency and reduce energy waste, a field-portable system must be applicable for most situations and include minimal equipment and setup. Background oriented schlieren (BOS) fits all those criteria. A typical BOS system includes a camera, a light source, and a high-contrast, typically randomized, patterned background, which is needed so that the camera observes refractive distortions. The pattern can vary based on the situation, coming from laser speckle, a provided backdrop, or the area itself if it provides an irregular pattern [2].This laboratory-scale demonstration shows how BOS can easily be applied and used to detect leaks. A randomly patterned backdrop was used, as shown in Figure 1, to collect the raw data. Helium was pumped into the model from the bottom to represent building leaks. The pixel shift for each collected frame was found using image processing, which could then be used to generate a BOS image, as shown in Figure 2. The model house was added back into the processed image via masking a front-illuminated image captured before the start of each test set.Five sets were collected, as shown in Figures 4 through 7, which show the processed BOS image at a certain frame. The model was tested before any holes were drilled in, and Figure 6 shows there were already leaks. Figure 7 shows the inclusion of a straw to represent a chimney, demonstrating the potential impact on the leaks. Future work includes using different background patterns, such as laser speckles on a wall or a projected background.[1] P. Boudreaux, S. Venkatakrishnan, E. Iffa, and D. Hun, 'Application of reference-free natural background-oriented schlieren photography for visualizing leakage sites in building walls,' Building and Environment, vol. 223, p. 109529, Sep. 2022, doi: 10.1016/j.buildenv.2022.109529.[2] G. S. Settles and M. J. Hargather, 'A review of recent developments in schlieren and shadowgraph techniques,' Measurement Science and Technology, vol. 28, no. 4, p. 042001, Feb. 2017, doi: 10.1088/1361-6501/aa5748.