Investigation of helical strut attached vena cava filter hemodynamic performanc

Hemodynamic performance of the Celect Platinum vena cava filter and the revised forms of it with helical flow inducer strut were studied with computational fluid dynamic software Ansys Fluent 18. The central velocity and shear stress increased but overall flow disturbance has been observed minimal level. Central velocity increases to 9.72% with Celect filter, by the single helical flow inducer strut the rate reaches to 14.69%, and with doubled form it reaches to 19.73%. The filter surface shear rate increases to 8.29% with the single helical flow inducer strut and increases 13.31% with doubled attachment. Increased velocity and shear stress on the filter may eliminate short term thrombus build-up problems by breaking the big size particulates with the high shearing forces. The new struts may also contribute to the ability of the filter to capture smaller clots, as well as to dissolve them from being bigger. Shear stress in the vein wall increases approximately 6.63% with the filter placement. It raises to 8.06% and 9.45% with single and double helical flow inducer strut attachment. Increased vein wall shear may reduce the recirculation and clotting in the vein wall and it may prevent the accumulation of clots. The increased shear stress on the filter may cause the migration problem, design improvements can minimize this risk. Helical flow inducer strut attachment can cause efficacy increase, and the flow are normalized.

Patient-specific modelling for the assessment of the hemodynamics risk of failure in endovascular aneurysm repair

Endovascular aneurysm repair (EVAR), despite its advantages over abdominal aortic aneurysm (AAA) open surgery, still presents risks of failure linked to Endograft (EG) migration. We here explore the link between intravascular blood flow features and Displacement Forces (DFs) acting on the EG. DFs are inversely associated with the amount of helical flow within the EG.

Effect of Geometrical Parameters on Extraction Efficiency of the Annular Centrifugal Contactor

The geometrical parameters of annular centrifugal contactors (ACCs) have an important influence on the extraction efficiency. The present work used a home-made 25 mm ACC constructed by 3D printing to investigate the effect of five geometrical parameters on the extraction efficiency. These parameters are annular width (d), clearance height (Hc), rotor inlet diameter (Din), bottom vane number (N), and the bottom vane’s bending direction (S). Central composite design was employed to design the experiment, and the response surface methodology was used to analyze the data. The results show that Hc and Din were positive for efficiency, while d and N were negative. When the bottom vane’s bending direction was the same as the liquid helical flow direction, the efficiency improved compared to the straight vane. It is found that 3 mm d, 5 mm Hc, 6 mm Din, and four clockwise covered vanes are the parameters where the efficiency reached the highest point of 94.5%. We analyzed the interactions between the parameters based on the coefficients of the quadratic equation, and the interactions were not considered in previous studies. This work surprisingly reveals that the effects of the parameters on the extraction efficiency were not independent, and there were interactions between the parameters. The interaction between the rotor inlet diameter and annular width was significant and could not be ignored. These results could serve as a reference for optimizing extraction processes and the design of ACCs.

Helical Flow of Drilling Mud With Cuttings in a Vertical Well

The paper presents the results of an investigation into drilling mud flow with cuttings in a vertical well. The drilling mud rheology was described with the Herschel-Bulkley model. The axial Reynolds number was around 1000, the flow regime changing together with drill pipe RPM. The investigation covered the flow’s structures, integral parameters and cuttings transport in relation to drill pipe RPM and rate of penetration (ROP). In the laminar flow, most of the particles were localized in the quasi-solid region to move together with the last; the integral parameters had little dependence on drill pipe RPM increase. Increasing drill pipe RPM resulted in formation of the Görtler vortices near the channel’s external and internal walls, whose interaction led to the formation of smaller eddies converting the flow into a turbulent one. Due to the turbulence dispersion, the region taken by the particles widened. Particles suppress the vortex intensity near the channel’s external wall. Under the conditions described, increasing drill pipe RPM and ROP resulted in higher pressure drops and lower transport efficiency.

Hemodynamic effects of the human aorta arch with different inflow rate waveforms from the ascending aorta inlet: A numerical study

BACKGROUND: Heart failure (HF) is a common disease globally. Ventricular assist devices (VADs) are widely used to treat HF. In contrast to the natural heart, different VADs generate different blood flow waves in the aorta. OBJECTIVE: To explore whether the different inflow rate waveforms from the ascending aorta generate far-reaching hemodynamic influences on the human aortic arch. METHODS: An aortic geometric model was reconstructed based on computed tomography data of a patient with HF. A total of five numerical simulations were conducted, including a case with the inflow rate waveforms from the ascending aorta with normal physiological conditions, two HF, and two with typical VAD support. The hemodynamic parameters, wall shear stress (WSS), oscillatory shear index (OSI), relative residence time (RRT), and the strength of the helical flow, were calculated. RESULTS: In contrast to the natural heart, numerical simulation showed HF decreasing WSS and inducing higher OSI and RRT. Moreover, HF weakened helical flow strength. Pulsatile flow VADs will elevated the WSS, inducing some helical flow, while continuous flow VAD could not produce any helical flow. CONCLUSIONS: HF leads to an adverse hemodynamic environment by decreasing WSS and reducing the helical flow strength. Pulsatile flow VADs are more advantageous than the continuous flow VADs on hemodynamic effects. Thus, pulsatile flow VADs may be a better option for patients with HF.