Cornell University Biological and Environmental Engineering

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Turbulent Flow Modeling in the Upper Airway of Racehorses

This is a joint project with Professor Normand Ducharme of the College of Veterinary Medicine at Cornell. The aim in this study is to model turbulent airflow in the nasal cavity of a horse for the entire cycle of respiration by constraining the tracheal pressure as obtained directly from experiments. Turbulent flow analysis will be done using different geometries for expiration and inspiration reconstructed from CT scans and the results will be validated by comparison with experimental flow data.

Project Summary

The larynx of a horse has two cartilage flaps, the arytenoid cartilages, that open the airways when the horse needs to breathe and close it when the horse needs to swallow. Laryngeal hemiplegia is a condition affecting racehorses in which the left flap is paralyzed. The current treatment is a tie-back surgery (laryngoplasty) to suture the paralyzed laryngeal flap permanently open. This project seeks to determine the implications of different degrees of flapper opening on the airflow and thereby predict the minimal larynx opening needed to allow normal airflow. This in turn would help in setting the appropriate degree of flapper opening during laryngoplasty. To achieve this final goal, turbulent airflow modeling in the nasal cavity of a normal horse starting from CT scanned images was done for the entire cycle of respiration. Subsequently, airflow through the nasal cavity for different flapper opening sizes will be modeled by stitching 75% and 50% abducted larynx, also obtained from CT scans, to the original nasal cavity model and doing the analysis.

Method

CT scans were performed in a male Thoroughbred racehorse and the 2-D CT scanned images were processed in a reconstruction software to create 3D visualization of the anatomy that included the nasal cavity, sinuses, nasopharynx, pharynx, larynx and cranial trachea. The saved stereo lithography file (stl) was imported in MAGICS (Materialise, Ann Arbor, MI) to separate the flow boundaries, smooth the 3D surface and improve surface mesh. Finally a tetrahedral volume mesh was created in TGrid (Fluent, Lebanon, NH). The continuity and Reynolds Averaged Navier Stokes (RANS) equations were solved for the unsteady, isothermal, incompressible, turbulent flow. The standard k-e turbulence model was used.

For more details on the project, please see the presentation below.

Horse Airflow Model