Effects of coagulation on the two-phase peristaltic pumping of magnetized Prandtl biofluid through an endoscopic annular geometry containing a porous medium

In this article, motivated by more accurate simulation of electromagnetic blood flow in annular vessel geometries in intravascular thrombosis, a mathematical model is developed for elucidating the effects of coagulation (i.e. a blood clot) on peristaltically induced motion of an electrically-conducting (magnetized) Prandtl fluid physiological suspension through a non-uniform annulus containing a homogenous porous medium. Magnetohydrodynamics is included owing to the presence of iron in the hemoglobin molecule and also the presence of ions in real blood. Hall current which generates a secondary (cross) flow at stronger magnetic field is also considered in the present study. A small annular tube (endoscopic) with sinusoidal peristaltic waves traveling along the inner and outer walls at constant velocity with a clot present is analyzed. The governing conservation equations which comprise the continuity and momentum equations for the fluid phase and particle phase are simplified under lubrication approximations (long wavelength and creeping flow conditions). The moving boundary value problem is normalized and solved analytically (with appropriate wall conditions) for the fluid phase and particle phase using the homotopy perturbation method (HPM) with MATHEMATICA software. Validation is conducted with MAPLE numerical quadrature. A parametric study of the influence of clot height (δ), particle volume fraction (C), Prandtl fluid material parameters (α, β), Hartmann number (M), Hall parameter (m), permeability parameter (k), peristaltic wave amplitude (φ) and wave number (δ̅ ) on pressure difference and wall shear (friction forces) is included. Pressure rise is elevated with clot height, medium permeability and Prandtl rheological material parameters whereas it is reduced with increasing particle volume fraction and magnetic Hartmann number. Friction forces on the outer and inner tubes of the endoscope annulus are enhanced with clot height and particle volume fraction whereas they are decreased with Prandtl rheological material parameters, Hall parameter and permeability parameter. The simulations provide a good benchmark for more general computational fluid dynamics studies of magnetic endoscopic multi-phase peristaltic pumping

Numerical simulation and nasal air-conditioning

Heating and humidification of the respiratory air are the main functions of the nasal airways in addition to cleansing and olfaction. Optimal nasal air conditioning is mandatory for an ideal pulmonary gas exchange in order to avoid desiccation and adhesion of the alveolar capillary bed. The complex three-dimensional anatomical structure of the nose makes it impossible to perform detailed in vivo studies on intranasal heating and humidification within the entire nasal airways applying various technical set-ups. The main problem of in vivo temperature and humidity measurements is a poor spatial and time resolution. Therefore, in vivo measurements are feasible only to a restricted extent, solely providing single temperature values as the complete nose is not entirely accessible. Therefore, data on the overall performance of the nose are only based on one single measurement within each nasal segment. In vivo measurements within the entire nose are not feasible

A generalised porous medium approach to study thermo-fluid dynamics in human eyes

The present work describes the application of the generalised porous medium model to study heat and fluid flow in healthy and glaucomatous eyes of different subject specimens, considering the presence of ocular cavities and porous tissues. The 2D computational model, implemented into the open-source software OpenFOAM, has been verified against benchmark data for mixed convection in domains partially filled with a porous medium. The verified model has been employed to simulate the thermo-fluid dynamic phenomena occurring in the anterior section of four patient-specific human eyes, considering the presence of anterior chamber (AC), trabecular meshwork (TM), Schlemm’s canal (SC), and collector channels (CC). The computational domains of the eye are extracted from tomographic images. The dependence of TM porosity and permeability on intraocular pressure (IOP) has been analysed in detail, and the differences between healthy and glaucomatous eye conditions have been highlighted, proving that the different physiological conditions of patients have a significant influence on the thermo-fluid dynamic phenomena. The influence of different eye positions (supine and standing) on thermo-fluid dynamic variables has been also investigated: results are presented in terms of velocity, pressure, temperature, friction coefficient and local Nusselt number. The results clearly indicate that porosity and permeability of TM are two important parameters that affect eye pressure distribution

Towards a Clinically Applicable Computational Larynx Model

The enormous computational power and time required for simulating the complex phonation process preclude the effective clinical use of computational larynx models. The aim of this study was to evaluate the potential of a numerical larynx model, considering the computational time and resources required. Using Large Eddy Simulations (LES) in a 3D numerical larynx model with prescribed motion of vocal folds, the complicated fluid-structure interaction problem in phonation was reduced to a pure flow simulation with moving boundaries. The simulated laryngeal flow field is in good agreement with the experimental results obtained from authors’ synthetic larynx model. By systematically decreasing the spatial and temporal resolutions of the numerical model and optimizing the computational resources of the simulations, the elapsed simulation time was reduced by 90% to less than 70 h for 10 oscillation cycles of the vocal folds. The proposed computational larynx model with reduced mesh resolution is still able to capture the essential laryngeal flow characteristics and produce results with sufficiently good accuracy in a significant shorter time-to-solution. The reduction in computational time achieved is a promising step towards the clinical application of these computational larynx models in the near future

Surgery of the turbinates and “empty nose” syndrome

Surgical therapy of the inferior and/or middle turbinate is indicated when conservative treatment options have failed. The desired goal is a reduction of the soft tissue volume of the turbinates regarding the individual anatomic findings, whilst simultaneously conserving as much mucosa as possible. As the turbinates serve as a functional entity within the nose, they ensure climatisation, humidification and cleaning of the inhaled air. Thus free nasal breathing means a decent quality of life, as well

Statistical Shape Modelling and Segmentation of the Respiratory Airway

The human respiratory airway consists of the upper (nasal cavity, pharynx) and the lower (trachea, bronchi) respiratory tracts. Accurate segmentation of these two airway tracts can lead to better diagnosis and interpretation of airway-specific diseases, and lead to improvement in the localization of abnormal metabolic or pathological sites found within and/or surrounding the respiratory regions. Due to the complexity and the variability displayed in the anatomical structure of the upper respiratory airway along with the challenges in distinguishing the nasal cavity from non-respiratory regions such as the paranasal sinuses, it is difficult for existing algorithms to accurately segment the upper airway without manual intervention. This thesis presents an implicit non-parametric framework for constructing a statistical shape model (SSM) of the upper and lower respiratory tract, capable of distinct shape generation and be adapted for segmentation. An SSM of the nasal cavity was successfully constructed using 50 nasal CT scans. The performance of the SSM was evaluated for compactness, specificity and generality. An averaged distance error of 1.47 mm was measured for the generality assessment. The constructed SSM was further adapted with a modified locally constrained random walk algorithm to segment the nasal cavity. The proposed algorithm was evaluated on 30 CT images and outperformed comparative state-of-the-art and conventional algorithms. For the lower airway, a separate algorithm was proposed to automatically segment the trachea and bronchi, and was designed to tolerate the image characteristics inherent in low-contrast CT images. The algorithm was evaluated on 20 clinical low-contrast CT from PET-CT patient studies and demonstrated better performance (87.1±2.8 DSC and distance error of 0.37±0.08 mm) in segmentation results against comparative state-of-the-art algorithms

Análisis de patrones de flujo aéreo en el interior de las fosas nasales con un modelo matemático

La obstrucción nasal es una de las patologías más prevalentes dentro del área otorrinolaringológica. El conocimiento de los medios diagnósticos es fundamental para objetivar y cuantificar la permeabilidad nasal de los pacientes que presentan obstrucción nasal. La anamnesis y la simple inspección y análisis de los hallazgos anatómicos de las fosas nasales no son suficientes para conocer la función respiratoria nasal; además, se debe considerar que la obstrucción nasal posee un componente importante de subjetividad. La anamnesis, la clínica, la exploración física, la rinomanometría anterior activa y la endoscopia nasal son técnicas complementarias, cada una de ellas por si solas no explican adecuadamente la clínica de IRN. Surge la necesidad de realizar un estudio para objetivar la permeabilidad nasal, ante la discrepancias encontradas en muchos pacientes. Se observan enfermos con patología evidente y síntomas concordantes, otros con patología evidente y síntomas no concordantes, enfermos con patología sin síntomas, además pacientes sin patología con sensación subjetiva de obstrucción nasal. Recientemente se ha desarrollado un programa informático capaz de crear un molde tridimensional de las fosas nasales a partir de las imágenes de TC de un paciente. Contamos también con un software basado en un modelo matemático que puede realizar medidas de flujo en dicho molde. En este trabajo se utiliza una aproximación alternativa para el estudio del flujo a través de la cavidad nasal, denominada Mecánica de Fluidos Computacional. La Mecánica de Fluidos Computacional (MFC) ha demostrado ser una herramienta muy útil para el estudio de la dinámica de fluidos. Consiste en resolver numéricamente las ecuaciones que gobiernan el movimiento de un fluido, por tanto permite simular el comportamiento de un flujo. Con esta nueva herramienta para estudiar el flujo aéreo se pretende complementar el conocimiento de la permeabilidad de la fosa nasal. La herramienta se estudia en un grupo control de 13 sujetos carentes de patología nasal y en 18 sujetos que son el grupo intervención con patología obstructiva nasal. Se determina la correlación existente de los datos obtenidos de flujo y resistencia al paso de aire con el programa informático de simulación de flujo (cuya información procede del TAC de senos paranasales realizado con vasoconstricción previa de las fosas nasales) con la historia clínica, la exploración clínica y la rinomanometría (exploración y rinomanometría con y sin vasoconstricción). Se concluye que el software basado en el modelo matemático ha demostrado su utilidad como técnica de medida complementaria de los medios tradicionales de evaluación de la anatomía y la función de las fosas nasales. Se ha encontrado correlación en los resultados de parámetros cuantitativos y cualitativos con los resultados de la exploración nasal realizada a los sujetos con patología nasal.Medicin