European journal of vascular and endovascular surgery : the official journal of the European Society for Vascular Surgery.

Spray drying: An overview on wall deposition, process and modeling

Scale-up of pharmaceutical spray drying using scale-up rules: A review.

Aortic dissection is a major aortic catastrophe with a high morbidity and mortality risk caused by the formation of a tear in the aortic wall. The development of a second blood filled region defined as the “false lumen” causes highly disturbed flow patterns and creates local hemodynamic conditions likely to promote the formation of thrombus in the false lumen. Previous research has shown that patient prognosis is influenced by the level of thrombosis in the false lumen, with false lumen patency and partial thrombosis being associated with late complications and complete thrombosis of the false lumen having beneficial effects on patient outcomes. In this paper, a new hemodynamics-based model is proposed to predict the formation of thrombus in Type B dissection. Shear rates, fluid residence time, and platelet distribution are employed to evaluate the likelihood for thrombosis and to simulate the growth of thrombus and its effects on blood flow over time. The model is applied to different idealized aortic dissections to investigate the effect of geometric features on thrombus formation. Our results are in qualitative agreement with in-vivo observations, and show the potential applicability of such a modeling approach to predict the progression of aortic dissection in anatomically realistic geometries.

/pdf/mathematical-modeling-of-thrombus-formation-in-idealized-3pd14xg3g4.pdf

Mathematical modeling of thrombus formation in idealized models of aortic dissection: initial findings and potential applications

Spray drying and electrospraying are well-established drying processes that already have proven their value in the pharmaceutical field. However, there is currently still a lack of knowledge on the fundamentals of the particle formation process, thereby hampering fast and cost-effective particle engineering. To get a better understanding of how functional particles are formed with respect to process and formulation parameters, it is indispensable to offer a comprehensive overview of critical aspects of the droplet drying and particle formation process. This review therefore closely relates single droplet drying to pharmaceutical applications. Although excellent reviews exist of the different aspects, there is, to the best of our knowledge, no single review that describes all steps that one should consider when trying to engineer a certain type of particle morphology. The findings presented in this article have strengthened the predictive value of single droplet drying for pharmaceutical drying applications like spray drying and electrospraying. Continuous follow-up of the particle formation process in single droplet drying experiments hence allows optimization of manufacturing processes and particle engineering approaches and acceleration of process development.

https://www.mdpi.com/1999-4923/12/7/625/pdf

Unraveling Particle Formation: From Single Droplet Drying to Spray Drying and Electrospraying

A 3D model of thrombus formation in a stent-graft after implantation in the abdominal aorta.

This article presents both theoretical and experimental determination of the hydrodynamics of drying air in an industrial countercurrent spray dryer. Air velocity measurements were performed in selected areas of the tower to determine the flow pattern in the dryer and to collect data to validate the computational fluid dynamics (CFD) modeling and verify the results. For no-swirl operation mode, 3D CFD calculations showed high instability of the air flow in the dryer. A bent, pillow-shaped flow above the drying air inlet, which promotes deposition of particles in this area of the wall, was detected. CFD calculations also proved that when drying air was introduced to the tower tangentially; from 20° to 30° in relation to the initial air flow configuration in the spray-drying tower, the air flow was stabilized and air velocity near the wall increased, which might reduce wall deposition of particles. Comparison of experimental and theoretical results showed that the CFD model of countercurrent spray-drying pr...

Modeling of Air Flow in an Industrial Countercurrent Spray-Drying Tower

Currently, studies connected with Computational Fluid Dynamic (CFD) techniques focus on assessing hemodynamic of blood flow in vessels in different conditions e.g. after stent-graft’s placement. The paper propose a novel method of standardization of results obtained from calculations of stent-grafts' “pushing forces” (cumulative WSS—Wall Shear Stress), and describes its usefulness in diagnostic process. AngioCT data from 27 patients were used to reconstruct 3D geometries of stent-grafts which next were used to create respective reference cylinders. We made an assumption that both the side surface and the height of a stent-graft and a reference cylinder were equal. The proposed algorithm in conjunction with a stent-graft “pushing forces” on an implant wall, allowed us to determine which spatial configuration of a stent-graft predispose to the higher risk of its migration. For stent-grafts close to cylindrical shape (shape factor φ close to 1) WSS value was about 267Pa, while for stent-grafts different from cylindrical shape (φ close to 2) WSS value was about 635Pa. It was also noticed that deformation in the stent-graft’s bifurcation part impaired blood flow hemodynamic. Concluding the proposed algorithm of standardization proved its usefulness in estimating the WSS values that may be useful in diagnostic process. Angular bends or tortuosity in bifurcations of an aortic implant should be considered in further studies of estimation of the risk of implantation failure.

/pdf/a-novel-attempt-to-standardize-results-of-cfd-simulations-3wr601p2lb.pdf

A Novel Attempt to Standardize Results of CFD Simulations Basing on Spatial Configuration of Aortic Stent-Grafts.

CFD technique was used to determine the effect of a stent-graft spatial configuration and hematocrit value on blood flow hemodynamic and the risk of a stent-graft occlusion. Spatial configurations of an endovascular prosthesis placed in Abdominal Aortic Aneurysm (AAA) for numerical simulations were developed on the basis of AngioCT data for 10 patients. The results of calculations showed that narrows or angular bends in the prosthesis as well as increased hematocrit affects blood flow reducing velocity and WSS which might result in thrombus development.

http://cejsh.icm.edu.pl/cejsh/element/bwmeta1.element.oai-journals-pan-pl-84678/c/oai-journals-pan-pl-84678_full-text_05-ZS-paper.pdf

Effects of stent-graft geometry and blood hematocrit on hemodynamic in abdominal aortic aneurysm

The paper presents a unique methodology of CFD modeling of heat and mass transfer during a counter-current spray-drying process based on the concept of a negative heat source reflecting the energy necessary for evaporation of water. The volumetric internal heat source term in Navier-Stokes equations describing heat transfer was used to determine energy transfer from explicit to latent heat. Total power consumption during the drying process was estimated on the basis of extensive industrial measurements of air temperature distribution along the axis and radius during regular tower operation. The probability function to control the distribution of density of power consumption as a function of the distance from the atomizers was determined by the trial and error method to fit experimental temperature measurements in the industrial tower. This approach allowed us to carry out 3D CFD accurate calculations of the counter-current spray-drying process analyzing continuous phase only. General methodology applied i...

Marek Podyma

Papers

A 3D model of thrombus formation in a stent-graft after implantation in the abdominal aorta.

Modeling of Air Flow in an Industrial Countercurrent Spray-Drying Tower

A Novel Attempt to Standardize Results of CFD Simulations Basing on Spatial Configuration of Aortic Stent-Grafts.

Effects of stent-graft geometry and blood hematocrit on hemodynamic in abdominal aortic aneurysm

Model of Heat and Mass Transfer in an Industrial Counter-Current Spray-Drying Tower