Research On Asymmetric Aerodynamic Model And Flow Field Distribution Of Vocal Cord Polyps

The quality of voice directly affects people’s language expression and communication.Serious voice diseases even affect people’s daily life.The number of people suffering from voice problems is increasing year by year due to the deteriorating air quality and poor personal living habits.Vocal cord polyp,vocal cord nodule,vocal cord cyst is the voice disease that causes by vocal cord structural changed,among them vocal cord polyp incidence of a disease is highest,which is a common vocal cord disease.Vocal polyp is a soft,translucent neoplasm of thickened tissue that occurs at the edge of the vocal cordIn this paper,a model of vocal cord aerodynamics is proposed based on the vocal mechanism and the theory of aerodynamics.Firstly,the model was divided into a finite number of discrete regions.and the Navier-Stokes equation of each discrete region was solved.Then,We obtained the flow field of the vocal cord model,and studied the phonation threshold pressure,also analyzed the effect of glottal diameter on the flow field of syrnetrical vocal cords.Because the geometrical abnormality of vocal cords caused by vocal Polyps causes great disturbance to the motion of glottal flow,the asymmetric model of vocal cords polyps is emphatically studied on the basis of the aerodynamic model of vocal cords,we mainly studied the effects of polyp size,subglottal pressure and glottal diameter on vocal cord motion and glottal flow.The specific research contents of this paper are as follows:(1)We proposed and designed a aerodynamics model of vocal cord,and studied the phonation threshold pressure by establishing the relationship between the glottal entrance loss coefficient and glottal diameter.This method can predict the trend of the change of the threshold pressure with glottal diameter,and the prediction error can be as small as 0.36%.(2)Based on the model of vocal cord aerodynamics,to study the changes of flow field in normal vocal cords with the glottal diameter and subglottal pressure.By solving the airflow motion equation in the vocal cord,the flow field change in the vocal cord is obtained.The results show that the change of pressure in the glottis is inversely proportional to the glottal diameter and directly proportional to the pulmonary pressure.When the glottal diameter does not change,the volume flow rate in the vocal cord increases with the increase of pulmonary pressure.(3)The asymmetric aerodynamic model of vocal cord polyp was studied,and the instantaneous flow component was decomposed into the form of mean value plus pulsation value to solve the flow field.It was found that the existence of polyps caused vortices,which would cause energy loss.With the increase of the size of vocal cord polyp,the obstructive effect of polyp on flow is continuously enhanced,and the energy loss is more serious in the process of flow transmission.The pressure gradient on the vocal cord and the volume flow rate in the vocal cord increase with the subglottal pressure and the glottal diameter.It is not conducive to voeal cord vibration when the volume flow rate in the vocal cord is small.Therefore,the size of the polyp will affect the vibration of the vocal cord,and increasing the subglottal pressure and glottal diameter will help to overcome the obstructive effect of the polyp.This study explored the aerodynamic characteristics of vocal cord polyps through the method of vocal cord modeling,which can provide quantitative evaluation reference for the clinical application of the aerodynamic method in voice medicine.