Fluid Structure Interaction Study for the Performance Evaluation of a Newly Developed Voice Prosthesis Device

Abstract

Total Laryngectomy that involves the complete removal of the voice box is the ultimate curative option for advanced laryngeal (voice box) cancers. The treatment however renders the patient voiceless i.e. Inability to produce any sound. A Voice Prosthesis device is used by these patients to recreate sound. This device is deployed in a puncture made through the common party wall separating the trachea (windpipe) and the oesophagus (food pipe) and the sound is generated by diverting the air from the trachea to the oesophagus through the device. The main component of the device is a one-way valve that opens under high air pressure and the recreated sound is a product of the uninterrupted flow of pulmonary air through the one-way valve and the vibrations developed in the pharyngo- oesophageal segment which acts as the “neoglottis” or the new vocal cord. A Fluid structure interaction (FSI) study was done on a new and improved version of voice prosthesis device for understanding the performance of the device. The computational model for this purpose has multiple domains, one of which is the solid domain and the other the fluid domain. The fluid domain represents the airflow path consisting of the oesophagus and trachea, and the solid domain contains the voice prosthesis device. This was done in Ansys Workbench software by using the system coupling (Fluent and Ansys structural solver) feature available in the same. Boundary conditions were applied only on the fluid domain and the deformation and the valve opening of the solid domain (device) was studied. Transient analysis was done for the study, with inlet velocity boundary condition. The velocity was provided as a function of time. The outlet had a static pressure boundary condition. A two-way system coupling was used to facilitate continuous information flow from the fluid dynamic solver to the structural solver and vice versa. Proper convergence criteria were enforced to ensure the reliability of the results. Dynamic mesh settings were used to account for the large deformation of the solid domain (valve). This setting ensured the minimum mesh quality for the continuously deforming geometries (both solid and fluid domain) by remeshing and smoothing the mesh whenever required. This study was conducted to find out the opening characteristics of the hinged valve of the voice prosthesis device.