Visual hull based 3D reconstruction of shocks in under-expanded supersonic bevelled jets
Three-dimensional shock structures produced by Mach 1.45 supersonic bevelled jets were digitally reconstructed based on schlieren photography and a voxel-based visual hull technique. By taking advantage of the strong edge features commonly found in schlieren images of shock waves, the proposed techn...
| Main Authors: | , , , |
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| Other Authors: | |
| Format: | Journal Article |
| Language: | English |
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2019
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| Subjects: | |
| Online Access: | https://hdl.handle.net/10356/107562 http://hdl.handle.net/10220/50314 |
| _version_ | 1824456900256727040 |
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| author | Lim, Desmond Haoxiang New, Tze How Mariani, Raffaello Cui, Y. D. |
| author2 | School of Mechanical and Aerospace Engineering |
| author_facet | School of Mechanical and Aerospace Engineering Lim, Desmond Haoxiang New, Tze How Mariani, Raffaello Cui, Y. D. |
| author_sort | Lim, Desmond Haoxiang |
| collection | NTU |
| description | Three-dimensional shock structures produced by Mach 1.45 supersonic bevelled jets were digitally reconstructed based on schlieren photography and a voxel-based visual hull technique. By taking advantage of the strong edge features commonly found in schlieren images of shock waves, the proposed technique demonstrates the possibility of performing shock wave reconstruction in supersonic jet applications without prior knowledge of the global density or velocity field. Semi-synthetic camera parameters were introduced as a method to circumvent camera calibration issues faced in the reconstruction procedure. This is key to achieving accurate and high-resolution reconstructed shock waves for both axisymmetric and asymmetric test cases with an average of 2.5% error when validated against raw schlieren images. When applied to bevelled jets with non-uniform nozzle exit geometries, an additional assumption was made to address the problem of schlieren line-of-sight blockage by the non-conventional nozzle, and reconstruction errors were found to be larger near regions of poorer shock wave contrast. Current results indicate that the technique is robust and fast during image calibration and processing, with accuracy of reconstructed shock waves in both conventional and non-conventional nozzles strongly dependent on shock wave contrast. Compared to existing techniques that can be used to reconstruct 3D shock structures, the proposed technique has the advantage of being totally non-intrusive as compared to point or particle-based measurements, requires significantly less computation than tomographic methods, offers high resolution reconstruction even with limited camera resolution and projected schlieren views, and is easy and cost effective to implement. |
| first_indexed | 2025-02-19T04:01:27Z |
| format | Journal Article |
| id | ntu-10356/107562 |
| institution | Nanyang Technological University |
| language | English |
| last_indexed | 2025-02-19T04:01:27Z |
| publishDate | 2019 |
| record_format | dspace |
| spelling | ntu-10356/1075622024-10-04T03:51:08Z Visual hull based 3D reconstruction of shocks in under-expanded supersonic bevelled jets Lim, Desmond Haoxiang New, Tze How Mariani, Raffaello Cui, Y. D. School of Mechanical and Aerospace Engineering Engineering Three-dimensional shock structures produced by Mach 1.45 supersonic bevelled jets were digitally reconstructed based on schlieren photography and a voxel-based visual hull technique. By taking advantage of the strong edge features commonly found in schlieren images of shock waves, the proposed technique demonstrates the possibility of performing shock wave reconstruction in supersonic jet applications without prior knowledge of the global density or velocity field. Semi-synthetic camera parameters were introduced as a method to circumvent camera calibration issues faced in the reconstruction procedure. This is key to achieving accurate and high-resolution reconstructed shock waves for both axisymmetric and asymmetric test cases with an average of 2.5% error when validated against raw schlieren images. When applied to bevelled jets with non-uniform nozzle exit geometries, an additional assumption was made to address the problem of schlieren line-of-sight blockage by the non-conventional nozzle, and reconstruction errors were found to be larger near regions of poorer shock wave contrast. Current results indicate that the technique is robust and fast during image calibration and processing, with accuracy of reconstructed shock waves in both conventional and non-conventional nozzles strongly dependent on shock wave contrast. Compared to existing techniques that can be used to reconstruct 3D shock structures, the proposed technique has the advantage of being totally non-intrusive as compared to point or particle-based measurements, requires significantly less computation than tomographic methods, offers high resolution reconstruction even with limited camera resolution and projected schlieren views, and is easy and cost effective to implement. 2019-11-01T05:40:43Z 2019-12-06T22:34:08Z 2019-11-01T05:40:43Z 2019-12-06T22:34:08Z 2018 Journal Article Lim, D. H., New, T. H., Mariani, R., & Cui, Y. D. (2018). Visual hull based 3D reconstruction of shocks in under-expanded supersonic bevelled jets. Experimental Thermal and Fluid Science, 99, 458-473. doi:10.1016/j.expthermflusci.2018.08.022 0894-1777 https://hdl.handle.net/10356/107562 http://hdl.handle.net/10220/50314 10.1016/j.expthermflusci.2018.08.022 en Experimental Thermal and Fluid Science Experimental Thermal and Fluid Science doi:10.21979/N9/LPIJIJ doi:10.21979/N9/SWETTX © 2018 Elsevier Inc. All rights reserved. This paper was published in Experimental Thermal and Fluid Science and is made available with permission of Elsevier Inc. 48 p. application/pdf |
| spellingShingle | Engineering Lim, Desmond Haoxiang New, Tze How Mariani, Raffaello Cui, Y. D. Visual hull based 3D reconstruction of shocks in under-expanded supersonic bevelled jets |
| title | Visual hull based 3D reconstruction of shocks in under-expanded supersonic bevelled jets |
| title_full | Visual hull based 3D reconstruction of shocks in under-expanded supersonic bevelled jets |
| title_fullStr | Visual hull based 3D reconstruction of shocks in under-expanded supersonic bevelled jets |
| title_full_unstemmed | Visual hull based 3D reconstruction of shocks in under-expanded supersonic bevelled jets |
| title_short | Visual hull based 3D reconstruction of shocks in under-expanded supersonic bevelled jets |
| title_sort | visual hull based 3d reconstruction of shocks in under expanded supersonic bevelled jets |
| topic | Engineering |
| url | https://hdl.handle.net/10356/107562 http://hdl.handle.net/10220/50314 |
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