Cardioplegia heat exchanger design modelling using computational fluid dynamics

A new cardioplegia heat exchanger has been developed by Sorin Biomedica. A three-dimensional computer-aided design (CAD) model was optimized using computational fluid dynamics (CFD) modelling. CFD optimization techniques have commonly been applied to velocity flow field analysis, but CFD analysis was also used in this study to predict the heat exchange performance of the design before prototype fabrication. The iterative results of the optimization and the actual heat exchange performance of the final configuration are presented in this paper. Based on the behaviour of this model, both the water and blood fluid flow paths of the heat exchanger were optimized. The simulation predicted superior heat exchange performance using an optimal amount of energy exchange surface area, reducing the total contact surface area, the device priming volume and the material costs. Experimental results confirm the empirical results predicted by the CFD analysis.     

以CT图像为基础构建人狭窄颈动脉的血流动力学模型

目的探索以CT图像为基础构建动脉血流动力学模型的技术方法,对颈动脉狭窄局部进行计算血流动力学（computationalfluid dynamics,CFD）数值模拟。方法以CT图像为基础进行颈动脉三维几何建模,依据MRI测量的模型出入口血流速度确定数值模拟的边界条件。结果数值模拟结果包括狭窄颈动脉内的速度场和壁面剪应力（wall shear stress,WSS）分布,可见狭窄段血管WSS增高,且在狭窄邻近区域出现新的血液逆流区（对应低或振荡的WSS）。结论以CT图像为基础的CFD技术是在体评价人狭窄颈动脉内血流动力学状况与颈动脉斑块之间关系的有效方法。     

基于流体动力学模拟腹腔温热化疗仪系统的设计

背景：腹腔温热化疗仪应用区域大剂量化疗和温热的协同作用,诱导腹腔内肿瘤癌细胞发生凋亡和坏死,其临床疗效已得到各国学者肯定。然而,当前国内腹腔温热化疗仪温度控制精度低,治疗效果不理想,无法满足治疗需求。目的：基于F2812及流体动力学仿真模拟,讨论了一种腹腔温热化疗仪的系统设计,以期优化参数,达到最佳温度控制精度,利用流体动力学仿真为最佳手术实施布管策略提供数值模拟数据。方法：基于F2812芯片的DSP控制器可快速响应控制加热及循环系统,提高系统温度控制精度。通过PID参数整定得到最佳控制参数：通过流体动力学仿真实验,模拟术中腹腔温度场及速度矢量场,优化腹腔布管策略。流体动力学仿真采用FLUENT软件,讨论了3种常见术中腹腔布管方式,并给出术中腹腔温度场分布。结果与结论：设计了可提高系统温度精度的温度采集控制模块。系统温度控制精度±0.3℃。通过FLUENT仿真结果发现闭腔三进两出方式即可满足治疗要求,并给出三维腹腔温度场分布情况。     

基于流体动力学模拟腹腔温热化疗仪系统的设计

背景:腹腔温热化疗仪应用区域大剂量化疗和温热的协同作用,诱导腹腔内肿瘤癌细胞发生凋亡和坏死,其临床疗效已得到各国学者肯定。然而,当前国内腹腔温热化疗仪温度控制精度低,治疗效果不理想,无法满足治疗需求。目的:基于F2812及流体动力学仿真模拟,讨论了一种腹腔温热化疗仪的系统设计,以期优化参数,达到最佳温度控制精度,利用流体动力学仿真为最佳手术实施布管策略提供数值模拟数据。方法:基于F2812芯片的DSP控制器可快速响应控制加热及循环系统,提高系统温度控制精度。通过PID参数整定得到最佳控制参数;通过流体动力学仿真实验,模拟术中腹腔温度场及速度矢量场,优化腹腔布管策略。流体动力学仿真采用FLUENT软件,讨论了3种常见术中腹腔布管方式,并给出术中腹腔温度场分布。结果与结论:设计了可提高系统温度精度的温度采集控制模块,系统温度控制精度±0.3℃。通过FLUENT仿真结果发现闭腔三进两出方式即可满足治疗要求,并给出三维腹腔温度场分布情况。     

Using computational fluid dynamics to evaluate a novel venous cannula (Smart canula) for use in cardiopulmonary bypass operating procedures

Peripheral access cardiopulmonary bypass (CPB) is initiated with percutaneous cannulae (CTRL) and venous drainage is often impeded due to smaller vessel and cannula size. A new cannula (Smartcanula, SC) was developed which can change shape in situ and, therefore, may improve venous drainage. Its performance was evaluated using a 2-D computational fluid dynamics (CFD) model. The Navier-Stokes equations could be simplified due to the fact that we use a steady state and a 2-dimensional system while the equation of continuity (p constant) was also simplified. We compared the results of the SC to the CTRL using CFDRC (Version 6.6, CFDRC research corporation, Huntsville, USA) at two preloads (300 and 700 Pa). The SC's mass flow rate outperformed the CTRL by 12.1% and 12.2% at a pressures of 300 and 700 Pa, respectively. At 700 Pa, a pressure gradient of 50% was measured for the CTRL and 11% for the SC. The mean velocity at the 700 Pa for the CTRL was 1.0 m.s(-1) at exit while the SC showed an exit velocity of 1.3 m.s(-1). Shear rates inside the cannulae were similar between the two cannulae. In conclusion, the prototype shows greater mass flow rates compared to the classic cannula; thus, it is more efficient. This is also advocated by a better pressure gradient and higher average velocities. By reducing cannula-tip surface area or increasing hole surface area, greater flow rates are achieved.     

The planning and design of a new PET radiochemistry facility.

The objectives of the Mayo positron emission tomography (PET) radiochemistry facility are the production of PET drugs for clinical service of our in-house patients, commercial distribution of PET drug products, and development of new PET drugs. The factors foremost in the planning and design phases were the current regulatory climate for PET drug production, radiation safety issues, and effective production flow. A medium-energy cyclotron was preferred for its small footprint to allow a compact vault, its high-proton energy to offer a higher product radioactivity; and its research capabilities. A vault installation was chosen instead of a self-shielded machine for improved access and ease of maintenance. Adjacent to the cyclotron is an area that houses the support equipment and a large dedicated workshop to support machine maintenance and targetry development. The total floor area of the PET radiochemistry facility is 344.2 m(2) (3,705.5 ft(2)), of which the radiochemistry laboratory occupies 130.7 m(2) (1,407 ft(2)). To reduce environmental contamination of PET drug products, the laboratory contains a controlled-air environment class 10,000 (M5.5) clean room with access via an interlocking entry change area. A fully shielded isolator (class 100 [M3.5]) is located in the clean room. The PET drugs are delivered via shielded tubing between the synthesizer and isolator. Inside the isolator, there is an automated device for dispensing the PET drug into either a bulk-activity vial or a unit-dose syringe. The dispensed PET radiopharmaceutical then passes through a hatch to a dedicated area where it is packaged for in-house use or commercial distribution. Unit doses for in-house patients are transported via pneumatic tube to the PET imaging area 76.2 m (250 ft) away. There is extensive radiation area monitoring throughout the facility that continuously measures radiation levels. We believe that our new PET radiochemistry facility not only meets overall objectives, but also provides an ergonomic, efficient working environment for the production and development of PET drugs.     

Evaluation of flow velocities after carotid artery stenting through split spectrum Doppler optical coherence tomography and computational fluid dynamics modeling

Hemodynamics plays a critical role in the development of atherosclerosis, specifically in regions of curved vasculature such as bifurcations exhibiting irregular blood flow profiles. Carotid atherosclerotic disease can be intervened by stent implantation, but this may result in greater alterations to local blood flow and consequently further complications. This study demonstrates the use of a variant of Doppler optical coherence tomography (DOCT) known as split spectrum DOCT (ssDOCT) to evaluate hemodynamic patterns both before and after stent implantation in the bifurcation junction in the internal carotid artery (ICA). Computational fluid dynamics (CFD) models were constructed to simulate blood velocity profiles and compared to the findings achieved through ssDOCT images. Both methods demonstrated noticeable alterations in hemodynamic patterns following stent implantation, with features such as slow velocity regions at the neck of the bifurcation and recirculation zones at the stent struts. Strong correlation between CFD models and ssDOCT images demonstrate the potential of ssDOCT imaging in the optimization of stent implantation in the clinical setting.OCIS codes: (170.4500) Optical coherence tomography, (170.3880) Medical and biological imaging, (120.5050) Phase measurement     

计算流体动力学技术在人体呼吸系统疾病研究中的应用

人体呼吸系统内气体流动情况与其生理功能和病理变化具有密切关系。利用计算流体动力学技术可有效模拟呼吸系统内的气流组织形式,为诊断和治疗呼吸系统疾病提供帮助。本文就计算流体动力学技术在人体呼吸系统疾病研究中的应用进行综述。     

Scaling of a catalytic cracking fluidized bed downer reactor based on computational fluid dynamics simulations

Circulating fluidized bed downer reactors (downer reactors) exhibit good heat and mass transfer, and the flow behavior approaches the ideal plug flow. This reactor is superior for catalytic cracking reactions in which the intermediate is the desired product. However, the hydrodynamic behavior and reactor performance have mostly been investigated in small-scale or laboratory-scale reactors. The objective of this study was to investigate the up-scaling of the catalytic cracking of heavy oil in three downer reactors with heights of 5, 15, and 30 m, using computational fluid dynamics simulations. A two-fluid model with the kinetic theory of granular flow was used to predict the hydrodynamics and performance of the chemical reactions. The kinetics of catalytic cracking of heavy oil were described by a 4-lump kinetic model. The chemical performance similarity was identified by using radial and axial distributions of heavy oil conversion, gasoline mass fraction, and gasoline selectivity. The chemical performance similarity cannot be achieved by using the hydrodynamic similarity parameter . A modified up-scaling parameter was proposed, . The chemical performance similarity of identical catalytic cracking downer reactors can be achieved with deviation in the range of ±10% and mean relative absolute error of less than 5%.

Circulating fluidized bed downer reactors (downer reactors) exhibit good heat and mass transfer, and the flow behavior approaches the ideal plug flow.     

Relating neuronal dynamics for auditory object processing to neuroimaging activity: a computational modeling and an fMRI study

We investigated the neural basis of auditory object processing in the cerebral cortex by combining neural modeling and functional neuroimaging. We developed a large-scale, neurobiologically realistic network model of auditory pattern recognition that relates the neuronal dynamics of cortical auditory processing of frequency modulated (FM) sweeps to functional neuroimaging data of the type obtained using PET and fMRI. Areas included in the model extend from primary auditory to prefrontal cortex. The electrical activities of the neuronal units of the model were constrained to agree with data from the neurophysiological literature regarding the perception of FM sweeps. We also conducted an fMRI experiment using stimuli and tasks similar to those used in our simulations. The integrated synaptic activity of the neuronal units in each region of the model, convolved with a hemodynamic response function, was used as a correlate of the simulated fMRI activity, and generally agreed with the experimentally observed fMRI data in the brain areas corresponding to the regions of the model. Our results demonstrate that the model is capable of exhibiting the salient features of both electrophysiological neuronal activities and fMRI values that are in agreement with empirically observed data. These findings provide support for our hypotheses concerning how auditory objects are processed by primate neocortex.     

下肢动脉狭窄三维模型建立及流体力学计算

背景:随着计算机技术的发展,血管虚拟现实已成为可能。目的:基于CT断层图像建立下肢动脉局部狭窄的三维立体模型并进行有限元数字网格划分,用于下肢动脉局部狭窄血管的血液动力学分析。方法:采集患者下肢动脉CTA中一段局部狭窄血管的DICOM数据,在MIMICS14.0中建立三维模型,再导入到有限元软件ANSYS11.0中进行有限元模型的建立,并模拟真实血流条件下的流体力学分析。结果与结论:在MIMICS14.0软件中得到了局部狭窄血管的三维模型。在ANSYSworkbench中得到了血管的有限元模型,模型节点总数7335,单元总数为43415。有限元计算得到了一系列的可视化的计算流体数据。表明该方法可以得到下肢动脉局部狭窄段流体力学分析所需的三维立体模型和有限元模型,得到流体力学分析所需相关数据。     

建立下肢动脉血管有限元模型及模拟计算流体力学

下肢动脉疾病已成为危害大众健康的重要疾病之一.对于下肢动脉的血流动力学研究由来已久,有学者[1]使用硅胶玻璃或生物材料制作仿生血管建立血管模型,却不能达到完全的仿真效果,且实验参数也仅限于速度、压力等,无法满足临床要求.近年来,很多学者开始尝试以数字模拟的方法研究下肢动脉血液流体力学,但现有模型大部分均是经过简化处理或利用CAD技术绘制而成[2],基于这些模型得到的计算结果无法真实反映下肢动脉的血流动力学特点[3];且大部分研究[4-5]将流体假设为理想流体,流体性质为定常流,偏离了生理实际.     

The use of altered rapid response calling criteria in a tertiary referral facility

PurposeThe purpose of this study was to examine the current utilisation of altered rapid response calling criteria (ARRCCs) at a tertiary hospital.MethodsA retrospective review of all acute care admissions across 17 months was undertaken using the hospital administration system and electronic medical record to identify patients with ARRCCs. In patients with altered criteria, the type of alteration, frequency of rapid response calls, cardiac arrest, intensive care admission, and death in the hospital were identified. Comparisons were made using standard statistical methods.ResultsThe total hospital admissions numbered 45 912, with ARRCCs used in 768 (1.7%). Patients with an ARRCC during hospital admission were older (68.5 [55.5, 79.0] vs 59.0 [43.0, 72.0] years, p < 0.001) and had a significantly longer length of hospital stay (6.9 [3.0, 16.3] vs 2 [1, 5] days, p < 0.001).Compared with the total group of patient admissions, patients with ARRCCs more frequently triggered a rapid response team (9.0% vs 14.2%, χ²(1, n = 46 680) = 23.87, p < 0.001), more frequently suffered a cardiac arrest (0.2 vs 0.9%, χ²(1, n = 46 678) = 20.34, p < 0.001), more frequently died in the hospital (p < 0.001), and were less frequently discharged home (χ²(1, n = 46 680) = 43.91, p < 0.001).ConclusionPatients with an ARRCC stayed longer in the hospital and were at increased risk of cardiac arrest and death during hospitalisation. Further exploration of the role of ARRCCs in facilitating individualised care to meet the needs and treatment goals of each patient in the acute hospital setting is required.     

应用冠状动脉CTA和计算流体力学无创性评价心肌桥对冠状动脉血流动力学的影响

目的:探讨应用冠脉CT血管成像(CTA)和计算流体力学无创性评价心肌桥对血流储备分数(fractional flow reserve,FFRCT)和壁面切应力(wall shear stress,WSS)变化的影响.方法:选择2020年5月至2020年12月复旦大学附属中山医院行冠脉CTA检查发现的左前降支心肌桥患者5...     

Chemical reaction-transport model of oxidized diethylzinc based on quantum mechanics and computational fluid dynamics approaches

We developed and studied a chemical reaction-transport model for the production of zinc oxide (ZnO) with diethylzinc (DEZn) and oxygen (O₂). It was confirmed that a large number of ZnO particles were generated during the growth process by testing the internal particles of the cavity by X-ray diffraction. The formation of Zn₃O₃ in the gas phase reaction was simulated using density functional theory, and the effect of nucleation and formation of nanoparticles on the growth of the films was revealed. We also speculate that the adsorption of Zn-containing gas on the wall is the main route by which a ZnO film is formed. The mechanism calculated by quantum chemistry was applied in computational fluid dynamics (CFD) simulations using Fluent14.0 software, and the concentration distribution and gas reaction path of the reaction chamber were calculated and analyzed. Finally, a 9 gas phase reaction model and an 8 surface reaction model were established. Together with the transport model, a complete chemical reaction-transport reaction model was constructed for the ZnO–MOCVD cavity. The validity of the model was verified, and the optimum temperature range of DEZn and oxygen-stabilized growth of ZnO films was determined to be 673–873 K. Using the results of the chemical reaction transport model, the geometry and operation parameters of the reactor can be optimized to improve the characteristics of the epitaxial layer.

Chemical reaction-transport model of ZnO thin film deposited by DEZn and O₂ in MOCVD.