UV-Unwrapping Method for Respiratory Airflows

Introduced in: Surface mapping for visualization of wall stresses during inhalation in a human nasal cavity. Respiratory Physiology and Neurobiology (2014) 190(1): p.54-61.

Also applied in the following:

• Dong, J., Shang, Y., Inthavong, K., Chan, H.-K., & Tu, J. (2018). Numerical Comparison of Nasal Aerosol Administration Systems for Efficient Nose-to-Brain Drug Delivery. Pharmaceutical Research, 35(1), 5.
• Dong, J., Shang, Y., Tian, L., Inthavong, K., & Tu, J. (2018). Detailed deposition analysis of inertial and diffusive particles in a rat nasal passage. Inhalation Toxicology, 1-11.
• Shang, Y., Dong, J., Inthavong, K., & Tu, J. (2017). Computational fluid dynamics analysis of wall shear stresses between human and rat nasal cavities. European Journal of Mechanics-B/Fluids, 61, 160-169.
• Shang, Y., Inthavong, K., & Tu, J. (2015). Detailed micro-particle deposition patterns in the human nasal cavity influenced by the breathing zone. Computers & Fluids, 114, 141-150.
• Shang, Y. D., Dong, J. L., Inthavong, K., & Tu, J. Y. (2015). Comparative numerical modeling of inhaled micron-sized particle deposition in human and rat nasal cavities. Inhalation Toxicology, 27(13), 694-705.
• Tian, L., Shang, Y., Chen, R., Bai, R., Chen, C., Inthavong, K., & Tu, J. (2017). A combined experimental and numerical study on upper airway dosimetry of inhaled nanoparticles from an electrical discharge machine shop. Particle and Fibre Toxicology, 14(1), 24.

During respiration, a multitude of physiological functions occur simultaneously including air conditioning, filtering out foreign particles, olfaction, and clearance mechanisms. Airflow analysis can assist in better understanding the physiology, however the human nasal cavity is an extremely complicated geometry that is difficult to visualise in 3D space, let alone in 2D space. In this paper, a computationally reconstructed nasal cavity is unwrapped and transformed into a 2D space, into a UV-domain (where u and v are the coordinates) to allow a complete view of the entire wrapped surface. This visualisation technique allows surface flow parameters to be analysed with greater precision.

A UV-unwrapping tool is developed and a strategy is presented to allow deeper analysis to be performed. This includes i) the ability to present instant comparisons of geometry and flow variables between any number of different nasal cavity models through normalisation of the 2D unwrapped surface; ii) visualisation of an entire surface in one view; and iii) a planar surface that allows direct 1D and 2D analytical solutions of diffusion of inhaled vapors and particles through the nasal walls. This work lays a foundation for future investigations that incorporates toxicology and health responses to local inhalation of gases and particles.

Downloads

• Download Matlab GUI application for Matlab 2012
• Download Matlab GUI application for Matlab v2017b
• Instructions can be downloaded here

Instructions for Matlab v2017b

1. The GUI was created in Matlab 2017b. Please make sure you installed the corresponding Matlab Runtime.
2. The folder contains 4 files. One is the executable GUI file named 'Nasal_Cavity_Mapping.exe' and the others are for tutorial.
3. Export a data file from Fluent including geometric information along with a variable (such as wall shear stress). The version of Fluent I am using is 18.0. I have exported a file named 'DUN001_mapping_example_tec.dat' as an example.
4. Open the executable file. Due to the Matlab Runtime environment, it may take as long as one minute to open, depending on your computer capability.
5. Copy the file name of the data file into the GUI, select data type as 3D, then click 'Import'. Wait until a 3D model appears in the bottom-left window for 3D visualisation.
6. If the model looks correct, click 'Export .Obj' button and you will find a new file named 'Geometry.obj' being created.
7. Open and edit the .obj file in a UV-Mapping software 'Unfold3D'. I am using version 9 but the latest version is 10. Unwrap the geometry as you wish, and then save as another .obj file. Please see the example unwrapped file 'Geometry_mapped.obj'. By the way, you can use other unwrapping tools such as Maya, 3ds Max, Blender, Geomagic etc. But I can't guarantee the GUI works fine with them because I have never tried.
8. Copy the unwrapped file name into the GUI and select data type as '2D', click 'Import'. You will see the unwrapped geometry appearing in the bottom-right window for 2D visualisation. In addition, division curves that are pre-defined in the unwrapping software will be added to geometries in both windows.
9. Export particle deposition coordinates from Fluent. You can find an example deposition file named 'nc_deposition.dpm'. Copy the particle deposition file name into the GUI and select data type as 'Particle', click 'Import'. Particles will be immediately appearing in the bottom-left window for 3D visualisation.
10. If the visualised particle distribution looks correct, click 'Project Particles' button, then particles will be automatically projected into the unwrapped domain in the bottom-right window.
11. You can tick on/off light shading, particle view and additional variable view (such as WSS) at the right sides of both windows for 3D and 2D visualisation. If you wish to export an image, simply click 'Enlarge' button and you will get a standard Matlab Figure Dialogue.