Unraveling the complex interplay between abnormal hemorheology and shape asymmetry in flow through stenotic arteries.

BACKGROUND AND OBJECTIVE: Stenosis or narrowing of arteries due to the buildup of plaque is a common occurrence in atherosclerosis and coronary artery disease (CAD), limiting blood flow to the heart and posing substantial cardiovascular risk. While the role of geometric irregularities in arterial stenosis is well-documented, the complex interplay between the abnormal hemorheology and asymmetric shape in flow characteristics remains unexplored. METHODS: This study investigates the influence of varying hematocrit (Hct) levels, often caused by conditions such as diabetes and anemia, on flow patterns in an idealized eccentric stenotic artery using computational fluid dynamics simulations. We consider three physiological levels of Hct, 25%, 45%, and 65%, representing anemia, healthy, and diabetic conditions, respectively. The numerical simulations are performed for different combinations of shape eccentricity and blood rheological parameters, and hemodynamic indicators such as wall shear stress (WSS), oscillatory shear index (OSI), are relative residence time (RRT) are calculated to assess the arterial health. RESULTS: Our results reveal the significant influence of Hct level on stenosis progression. CAD patients with anemia are exposed to lower WSS and higher OSI, which may increase the propensity for plaque progression and rupture. However, for CAD patients with high Hct level - as is often the case in diabetes - the WSS at the minimal lumen area increases rapidly, which may also lead to plaque rupture and cause adverse events such as heart attacks. These disturbances promote endothelial dysfunction, inflammation, and thrombus formation, thereby intensifying cardiovascular risk. CONCLUSIONS: Our findings underscore the significance of incorporating hemorheological parameters, such as Hct, into computational models for accurate assessment of flow dynamics. We envision that insights gained from this study will inform the development of tailored treatment strategies and interventions in CAD patients with common comorbidities such as diabetes and anemia, thus mitigating the adverse effects of abnormal hemorheology and reducing the ever-growing burden of cardiovascular diseases.

Construction of virtual airway model to assist surgical correction of velopharyngeal insufficiency with posterior pharyngeal flap.

OBJECTIVE: Posterior pharyngeal flap (PPF) is one of the most common surgical technique to correct velopharyngeal insufficiency(VPI), during which controlling the sizes of the lateral pharyngeal ports(LPP) is the key to outcomes. One innovative procedure was developed to well control the size of LPP. MATERIALS AND METHODS: 40 patients with repaired cleft palate were collected from June 2022 to August 2023. All patients were diagnosed with VPI, and treated with modified PPF surgery. For each patient, upper airway model was reconstructed, and the virtual airway model of PPF was designed. The nasal valve area was measured as it was considered to be the narrowest part of the upper airway. The upper airway resistances under different sizes of LPP was predicted through computational fluid dynamics analysis. The minimum size of each lateral pharyngeal port without obviously increase of upper airway resistance was calculated through effect of lateral pharyngeal ports' size on upper airway resistance. Postoperative follow-up was 6-18 months, including speech outcome and respiration outcome. Resting soft palate length (RVL), effective working length of soft palate (EWL) and angle of soft palate elevation (AVL) were measured and compared according to the lateral cephalometric radiograph. RESULTS: There was a linear relationship between the threshold value and nasal valve (R=0.62). Among the forty patients, the average size of nasal valve was 47.81mm2, the average size of the threshold value of LPP was 31.63mm2. The rate of velopharyngeal closure competence after surgery was 95%. Compared with the preoperative measurements, there were significantly increase of RVL, EWL and AVL (P<0.05). There were significantly difference in the nasal obstruction symptom evaluation score in long-term follow-up compared to short-term follow-up (P<0.05), and no one needed flap revision. There was no significant difference in nasal respiration and nasal resistance before and after surgery (P>0.05). CONCLUSION: With the help of computer fluid dynamics analysis, it is possible to predict the threshold size of lateral pharyngeal port without obviously increasing upper airway resistance and reduce the risk of suffering from airway obstruction for patients undergoing PPF surgery.

Anatomical compatibility of a novel total artificial heart-An in-silico study.

BACKGROUND: ShuttlePump is a novel total artificial heart (TAH) recently introduced to potentially overcome the limitations associated with the current state-of-the-art mechanical circulatory support devices intended for adults. In this study, we adapted the outflow cannulation of the previously established ShuttlePump TAH and evaluated the anatomical compatibility using the virtual implantation technique. METHODS: We retrospectively assessed the anatomical compatibility of the ShuttlePump using virtual implantation techniques within 3D-reconstructed anatomies of adult heart failure patients. Additionally, we examined the impact of outflow cannula modification on the hemocompatibility of the ShuttlePump through computational fluid dynamic simulations. RESULTS: A successful virtual implantation in 9/11 patients was achieved. However, in 2 patients, pump interaction with the thoracic cage was observed and considered unsuccessful virtual implantation. A strong correlation (r <-0.78) observed between the measured anatomical parameters and the ShuttlePump volume exceeding pericardium highlights the importance of these measurements apart from body surface area. The numerical simulation revealed that the angled outflow cannulation resulted in a maximum pressure drop of 1.8 mmHg higher than that of the straight outflow cannulation. With comparable hemolysis index, the shear stress thresholds of angled outflow differ marginally (<5%) from the established pump model. Similar washout behavior between the pump models indicate that the curvature did not introduce stagnation zone. CONCLUSION: This study demonstrates the anatomic compatibility of the ShuttlePump in patients with biventricular failure, which was achieved by optimizing the outflow cannulation without compromising hemocompatibility. Nevertheless, clinical validation is critical to ensure the clinical applicability of these findings.

Deforming Patient-Specific Models of Vascular Anatomies to Represent Stent Implantation via Extended Position Based Dynamics.

PURPOSE: Angioplasty with stent placement is a widely used treatment strategy for patients with stenotic blood vessels. However, it is often challenging to predict the outcomes of this procedure for individual patients. Image-based computational fluid dynamics (CFD) is a powerful technique for making these predictions. To perform CFD analysis of a stented vessel, a virtual model of the vessel must first be created. This model is typically made by manipulating two-dimensional contours of the vessel in its pre-stent state to reflect its post-stent shape. However, improper contour-editing can cause invalid geometric artifacts in the resulting mesh that then distort the subsequent CFD predictions. To address this limitation, we have developed a novel shape-editing method that deforms surface meshes of stenosed vessels to create stented models. METHODS: Our method uses physics-based simulations via Extended Position Based Dynamics to guide these deformations. We embed an inflating stent inside a vessel and apply collision-generated forces to deform the vessel and expand its cross-section. RESULTS: We demonstrate that this technique is feasible and applicable for a wide range of vascular anatomies, while yielding clinically compatible results. We also illustrate the ability to parametrically vary the stented shape and create models allowing CFD analyses. CONCLUSION: Our stenting method will help clinicians predict the hemodynamic results of stenting interventions and adapt treatments to achieve target outcomes for patients. It will also enable generation of synthetic data for data-intensive applications, such as machine learning, to support cardiovascular research endeavors.

Performance of the multi-U-style structure based flow field for polymer electrolyte membrane fuel cell.

The design of the reactant gas flow field structure in bipolar plates significantly influences the performance of proton exchange membrane fuel cells (PEMFCs). In this study, we introduced four innovative U-shaped flow field designs, namely: In-Out Multi-U, Out-In Multi-U, Distro In-Out Multi-U, and Distro Out-In Multi-U. To investigate the impact of these various flow fields on PEMFC performance, we conducted computational fluid dynamics (CFD) numerical simulations, validated through model experiments. Our results indicate that the Distro Out-In Multi-U flow field offers notable advantages compared to the conventional parallel flow field (CPFF) and conventional serpentine flow field (CSFF). These benefits include reduced inlet and outlet pressures, lower liquid water content, more uniform liquid water distribution, and a more even current density distribution. Furthermore, the Distro Out-In Multi-U design demonstrates improved efficiency, consuming less H2 (91.9%) than the CSFF while achieving a higher net power density output (10.1%). As a result, for the same power output, the Distro Out-In Multi-U utilizes only 83.5% of the H2 consumed by the CSFF. In summary, the U-shaped structured flow field exhibits superior output performance, enhanced energy efficiency, and improved resistance to flooding. These findings suggest that the U-shaped flow field design holds significant potential as a reactive flow field for PEMFCs.

Mitigating aerosol-induced respiratory infections in home quarantine: The role of door dynamics and ventilation in residential design.

Respiratory infectious diseases, notably recurring waves of COVID-19 during autumn and winter, have significantly impacted global health and strained public health systems. Home isolation has emerged as a crucial and economical strategy to mitigate these impacts. This study investigates aerosol transmission and infection risks in home isolation environments using the Lattice Boltzmann Method with Large Eddy Simulation (LBM-LES). We focused on the impact of door operations and various natural ventilation rates on aerosol transmission and exposure risk in adjacent rooms. Our findings reveal that, without ventilation, aerosol leakage through door gaps poses a minimal infection risk to adjacent rooms, with an average probability of less than 2 × 10-5. However, with adequate ventilation, the infection risk for individuals in adjacent rooms for over 3 h can reach 60 %-70 %. Brief door movements have limited impact on infection risk (p ≤ 0.05, d ≤ 0.20), with aerosol leakage mainly occurring through door gaps rather than door movements. To reduce cross-infection during home isolation, we recommend avoiding prolonged stays near downwind walls facing the door. This research provides insights into aerosol dynamics in home isolation scenarios, offering theoretical guidance for designing safe isolation spaces and practical advice for healthy family members to minimize infection risk.

Minimum Local Anesthetic Dose of Ropivacaine in Cesarean Section for Real-Time Ultrasound-Guided Spinal Anesthesia Using 24-Gauge versus 26-Gauge Needles Based on Fluid Simulation Technology: A Randomized Controlled Trial.

Purpose: Previous research has demonstrated that real-time ultrasound-guided (UG) spinal anesthesia requires a higher minimum local anesthetic dose (MLAD) compared to traditional methods. However, the precise MLAD of ropivacaine for UG cesarean sections remains undetermined. In this study, we ascertained the MLAD of ropivacaine for cesarean section. We also investigated the mechanism underlying the diffusion of ropivacaine within the spinal canal using fluid simulation technology. Patients and Methods: We randomly placed 60 healthy parturients undergoing elective cesarean section with real-time UG spinal anesthesia into Groups I (26-gauge spinal needle) and II (24-gauge spinal needle). For the first parturient in both groups, 15 mg of ropivacaine was administered intrathecally. Based on the effective or ineffective response of the previous parturient, the dose for the subsequent parturient was increased or decreased by 1 mg. Spinal anesthesia characteristics and side effects were recorded. A computer-generated spinal canal model was developed. Leveraging fluid dynamics simulation technology, we documented the diffusion of ropivacaine in the spinal canal using 26-and 24-gauge spinal needles. Results: The MLADs in Groups I and II were 12.728 mg (12.339-13.130 mg) and 9.795 mg (9.491-10.110 mg), respectively. No significant difference was observed in the onset times and durations of sensory or motor blocks, incidence of complications, or neonatal Apgar scores between both groups. Fluid simulation modeling indicated that the 26-gauge spinal needle achieved a higher distribution level more quickly; however, its peak drug concentration was lower compared to the 24-gauge spinal needle. Conclusion: For cesarean section anesthetization, the required MLAD of ropivacaine when using a real-time UG 26-gauge spinal needle is significantly greater than that with a 24-gauge needle. The spinal needle diameter influences ropivacaine's MLAD by markedly affecting its diffusion rate within the spinal canal.

A scalable convolutional neural network approach to fluid flow prediction in complex environments.

We evaluate the capability of convolutional neural networks (CNNs) to predict a velocity field as it relates to fluid flow around various arrangements of obstacles within a two-dimensional, rectangular channel. We base our network architecture on a gated residual U-Net template and train it on velocity fields generated from computational fluid dynamics (CFD) simulations. We then assess the extent to which our model can accurately and efficiently predict steady flows in terms of velocity fields associated with inlet speeds and obstacle configurations not included in our training set. Real-world applications often require fluid-flow predictions in larger and more complex domains that contain more obstacles than used in model training. To address this problem, we propose a method that decomposes a domain into subdomains for which our model can individually and accurately predict the fluid flow, after which we apply smoothness and continuity constraints to reconstruct velocity fields across the whole of the original domain. This piecewise, semicontinuous approach is computationally more efficient than the alternative, which involves generation of CFD datasets required to retrain the model on larger and more spatially complex domains. We introduce a local orientational vector field entropy (LOVE) metric, which quantifies a decorrelation scale for velocity fields in geometric domains with one or more obstacles, and use it to devise a strategy for decomposing complex domains into weakly interacting subsets suitable for application of our modeling approach. We end with an assessment of error propagation across modeled domains of increasing size.

Role of disturbed wall shear stress in the development of cerebral aneurysms.

Although the hemodynamics of cerebral aneurysms have been extensively studied using patient-specific computational fluid dynamics techniques, no specific hemodynamic factors characteristic of cerebral aneurysm development have yet been identified. We believe that one problem with previous hemodynamic studies of cerebral aneurysms has been the manner in which control groups were created for comparison with experimental groups. The purpose of this study was to determine hemodynamic factors that correlated with the development of cerebral aneurysms. The control group was established in a manner that differed from those of previous works. This allowed us to demonstrate the effectiveness of our method. We artificially removed aneurysms in the middle cerebral artery bifurcations of nine patients and reconstructed the vessel geometries before the aneurysms had occurred. Pulsatile blood flow simulations were performed using the vessel geometries ipsilateral and contralateral to the sites of aneurysm removal, and hemodynamic metrics were calculated. Use of the ipsilateral and contralateral sides as the experimental and control sites, respectively, allowed us to evaluate statistically the hemodynamic metrics between the two corresponding sites/groups. The results showed that only the normalized transverse wall shear stress (NtransWSS) was significantly higher at the MCA bifurcation ipsilateral to the site of aneurysm removal than at the contralateral bifurcation (p = 0.01). There were no significant differences in the other hemodynamic metrics between the bilateral bifurcations. Our findings imply that multi-directional disturbed wall shear stress, which is detected by the NtransWSS metric, may be one hemodynamic risk factor for the development of cerebral aneurysms.

The effect of torus tubarius size on upper airway aerodynamics in children: a computational fluid dynamics study.

PURPOSE: Some children with sleep-disordered breathing (SDB) continue to experience symptoms after adenotonsillectomy. One possible cause is the excessive size of the torus tubarius. METHODS: In this study, the relationship between torus tubarius size and surgical outcome in 24 children with SDB who underwent adenotonsillectomy was retrospectively analyzed based on cone beam computed tomography (CBCT) imaging measurements and medical records. A computational fluid dynamics (CFD) approach was used to quantitatively compare the effects of different torus tubarius sizes on upper airway (UA) aerodynamics in children. RESULTS: The percentage of UA area occupied by the torus tubarius (TTA%) was significantly different between the excellent and poor groups (10.4 ± 3.58% vs. 17.71 ± 4.7%, p < 0.001). The results of CFD simulation showed that the mean airflow velocity, wall shear stress (WSS) and pressure drop (ΔP) in the nasopharynx significantly increased when the TTA% was > 15%. CONCLUSION: Our study confirmed the effect of round pillow size on the aerodynamics of the UA in children. When the TTA% exceeds 15%, it causes change in aerodynamics, which may affect the outcome of children with SDB.

Basic surgical skill training before a vascular course improves the quality of vascular anastomoses: a randomized controlled trial: Basic skill training benefits vascular surgery course.

OBJECTIVES: During the past decade simulation has become standard in most surgical training programs, but objective evaluation of the performance has been a challenge. The optimal components of open surgery's simulation have also been questioned. The goal of this study was to evaluate the benefit of adding a hands-on exercise prior to a formal vascular training course. The participants' performance was objectively evaluated using Computional Fluid Dynamics (CFD) assessment of vascular anastomoses. METHODS: In this study 51 residents participated in an on-line surgical hands-on training course, performing six end-to-side anastomoses. The residents were randomly divided into two groups. Group 1. also underwent basic surgical skill training (BSST) before starting the vascular course. The groups were compared based on CFD assessment of vascular anastomoses, combined with on-line personalized feedback. RESULTS: Among measured parameters of functional assessment, the mean of six anastomoses showed significantly better results in Group 1. when compared with control Group 2 (Oscillatory Shear Index: 0,022 vs. 0,025 p=0,002; Maximum pressure: 7939 vs. 7971 p=0,00037; Velocity: 0,12 vs. 0,12 p=0,0000; Helicity: 297 vs. 393 p=0,0065; Vorticity: 5258 vs. 6628 p=0,0019; Wall Shear Stress: 1,83 vs. 1,97 p= 0,000047). These results showed no significant correlation between participants' experience level, specialization, and workplace. CONCLUSIONS: BSST before a formal vascular simulation course positively affects the anastomosis quality, independent of experience level, specialization, and workplace. BSST is suggested before a vascular course to improve performance and progress. Further studies are needed to analyse the impact of this combined simulation training on performing anastomoses.

Offsetting Dense Particle Sedimentation in Microfluidic Systems.

Sedimentation is an undesirable phenomenon that complicates the design of microsystems that exploit dense microparticles as delivery tools, especially in biotechnological applications. It often informs the integration of continuous mixing modules, consequently impacting the system footprint, cost, and complexity. The impact of sedimentation is significantly worse in systems designed with the intent of particle metering or binary encapsulation in droplets. Circumventing this problem involves the unsatisfactory adoption of gel microparticles as an alternative. This paper presents two solutions-a hydrodynamic solution that changes the particle sedimentation trajectory relative to a flow-rate dependent resultant force, and induced hindered settling (i-HS), which exploits Richardson-Zaki (RZ) corrections of Stokes' law. The hydrodynamic solution was validated using a multi-well fluidic multiplexing and particle metering manifold. Computational image analysis of multiplex metering efficiency using this method showed an average reduction in well-to-well variation in particle concentration from 45% (Q = 1 mL/min, n = 32 total wells) to 17% (Q = 10 mL/min, n = 48 total wells). By exploiting a physical property (cloud point) of surfactants in the bead suspension in vials, the i-HS achieved a 58% reduction in the sedimentation rate. This effect results from the surfactant phase change, which increases the turbidity (transient increase in particle concentration), thereby exploiting the RZ theories. Both methods can be used independently or synergistically to eliminate bead settling in microsystems or to minimize particle sedimentation.

A Synergistic Overview between Microfluidics and Numerical Research for Vascular Flow and Pathological Investigations.

Vascular diseases are widespread, and sometimes such life-threatening medical disorders cause abnormal blood flow, blood particle damage, changes to flow dynamics, restricted blood flow, and other adverse effects. The study of vascular flow is crucial in clinical practice because it can shed light on the causes of stenosis, aneurysm, blood cancer, and many other such diseases, and guide the development of novel treatments and interventions. Microfluidics and computational fluid dynamics (CFDs) are two of the most promising new tools for investigating these phenomena. When compared to conventional experimental methods, microfluidics offers many benefits, including lower costs, smaller sample quantities, and increased control over fluid flow and parameters. In this paper, we address the strengths and weaknesses of computational and experimental approaches utilizing microfluidic devices to investigate the rheological properties of blood, the forces of action causing diseases related to cardiology, provide an overview of the models and methodologies of experiments, and the fabrication of devices utilized in these types of research, and portray the results achieved and their applications. We also discuss how these results can inform clinical practice and where future research should go. Overall, it provides insights into why a combination of both CFDs, and experimental methods can give even more detailed information on disease mechanisms recreated on a microfluidic platform, replicating the original biological system and aiding in developing the device or chip itself.

Analyzing Homogeneity of Highly Viscous Polymer Suspensions in Change Can Mixers.

The mixing of highly viscous non-Newtonian suspensions is a critical process in various industrial applications. This computational fluid dynamics (CFD) study presents an in-depth analysis of non-isothermal mixing performance in change can mixers. The aim of the study was to identify parameters that significantly influence both distributive and dispersive mixing in these mixers, which are essential for optimizing industrial mixing processes. The study employed a numerical design of experiments (DOE) approach to identify the parameters that most significantly influence both distributive and dispersive mixing, as measured by the Kramer mixing index (MKramer) and the Ica Manas-Zloczower mixing index λMZ¯. The investigated parameters included mixing time, number of arms, arm size ratio, revolutions per minute (RPM), z-axis rotation, z-axis movement, and initial and mixing temperatures. The methodology involved employing the bootstrap forest algorithm for predicting the mixing indices, achieving an R2 of 0.949 for MKramer and an R2 of 0.836 for λMZ¯. The results indicate that the z-axis rotation has the greatest impact on both distributive and dispersive mixing. An increased number of arms negatively impacted λMZ, but had a small positive effect on MKramer. Surprisingly, in this study, neither the initial temperature of the material nor the mixing temperature significantly impacted the mixing performance. These findings highlight the relative importance of operational parameters over traditional temperature factors and provide a new perspective on mixing science.

Inference of alveolar capillary network connectivity from blood flow dynamics.

The intricate lung structure is crucial for gas exchange within the alveolar region. Despite extensive research, questions remain about the connection between capillaries and the vascular tree. We propose a computational approach combining three-dimensional morphological modeling with computational fluid dynamics simulations to explore alveolar capillary network connectivity based on blood flow dynamics.We developed three-dimensional sheet-flow models to accurately represent alveolar capillary morphology and conducted simulations to predict flow velocities and pressure distributions. Our approach leverages functional features to identify plausible system architectures. Given capillary flow velocities and arteriole-to-venule pressure drops, we deduced arteriole connectivity details. Preliminary analyses for non-human species indicate a single alveolus connects to at least two 20 µm arterioles or one 30 µm arteriole. Hence, our approach narrows down potential connectivity scenarios, but a unique solution may not always be expected.Integrating our blood flow model results into our previously published gas exchange application, Alvin, we linked these scenarios to gas exchange efficiency. We found that increased blood flow velocity correlates with higher gas exchange efficiency.Our study provides insights into pulmonary microvasculature structure by evaluating blood flow dynamics, offering a new strategy to explore the morphology-physiology relationship that is applicable to other tissues and organs. Future availability of experimental data will be crucial in validating and refining our computational models and hypotheses.

Hemodynamic Analysis in Aortic Dilatation after Arterial Switch Operation for Patients with Transposition of Great Arteries Using Computational Fluid Dynamics.

After an arterial switch operation for complete transposition of the great arteries, neo-aortic root dilatation occurs, with unclear hemodynamic effects. This study analyzes three groups (severe dilation, mild dilation, and normal) using computational fluid dynamics (CFD) on cardiac CT scans. Aortic arch angles in severe (median 72.3, range: 68.5-77.2) and mild dilation (76.6, 71.1-85.2) groups are significantly smaller than the normal group (97.3, 87.4-99.0). In the normal and mild dilatation groups, Wall Shear Stress (WSS) exhibits a consistent pattern: it is lowest at the aortic root, gradually increases until just before the bend in the aortic arch, peaks, and then subsequently decreases. However, severe dilation shows disrupted WSS patterns, notably lower in the distal ascending aorta, attributed to local recirculation. This unique WSS pattern observed in severely dilated patients, especially in the transverse aorta. CFD plays an essential role in comprehensively studying the pathophysiology underlying aortic dilation in this population.

Analysis of pedestrian second crossing behavior based on physics-informed neural networks.

Pedestrian two-stage crossings are common at large, busy signalized intersections with long crosswalks and high traffic volumes. This design aims to address pedestrian operation and safety by allowing navigation in two stages, negotiating each traffic direction separately. Understanding crosswalk behavior, especially during bidirectional interactions, is essential. This paper presents a two-stage pedestrian crossing model based on Physics-Informed Neural Networks (PINNs), incorporating fluid dynamics equations to determine characteristics such as speed, density, acceleration, and Reynolds number during crossings. The study shows that PINNs outperform traditional deep learning methods in calculating and predicting pedestrian fluid properties, achieving a mean squared error as low as 10-8. The model effectively captures dynamic pedestrian flow characteristics and provides insights into pedestrian behavior impacts. The results are significant for designing pedestrian facilities to ensure comfort and optimizing signal timing to enhance mobility and safety. Additionally, these findings can aid autonomous vehicles in better understanding pedestrian intentions in intelligent transportation systems.

Current advances and future prospects of in-situ desulfurization processes in oxy-fuel combustion reactors.

Oxy-fuel circulating fluidized bed combustion is known as one of the most potent fuel combustion technologies that capture ultra-low greenhouse gases and pollutant emissions. While many investigations have been conducted for carbon capturing, the associated in-situ desulfurization process using calcium-based sorbents should also be underlined. This paper critically reviews the effects of changes in the operating environment on in-situ desulfurization processes compared to conventional air combustion. A comprehensive understanding of the process, encompassing hydrodynamic, physical and chemical aspects can be a guideline for designing the oxy-fuel combustion process with effective sulfur removal, potentially eliminating the need of a flue gas desulfurization unit. Results from thermogravimetric analyzers and morphological changes of calcium-based materials were presented to offer an insight into the sulfation mechanisms involved in the oxy-fuel circulating fluidized beds. Recently findings suggested that in-situ direct desulfurization is influenced not only by the desulfurization kinetics but also by the fluidization characteristics of calcium-based materials. Therefore, a complex reaction analysis that incorporated oxy-combustion reactions, computational fluid dynamics modeling, in-situ desulfurization reaction models and particle behavior can provide a thorough understanding of desulfurization processes across the reactor. Meanwhile, machine learning as a robust tool to predict desulfurization efficiency and improve operational flexibility should be applied with consideration of environmental improvement and economic feasibility.

Intra-abdominal temperature variation during hyperthermic intraperitoneal chemotherapy evaluated via computational fluid dynamics modeling.

Background: Hyperthermic intraperitoneal chemotherapy (HIPEC) targets intraperitoneal tumors with heated drug solutions via catheters inserted into the peritoneal space. Although studies have focused on clinical outcomes, the flow dynamics at specific intra-abdominal locations at-risk of harboring malignant cells remain poorly understood but are likely to impact the drug pharmacokinetics. Consequently, optimal protocols remain uncertain, with efficacy critically dependent on drug temperature and flow rate. This study tested the hypothesis that fluid flow dynamics at specific at-risk locations could be evaluated via a computational fluid dynamics (CFD) model of closed HIPEC in a simulated human abdominal cavity, with the goal to enable protocol optimization. Methods: A computer-aided-design (CAD) model of a human intraperitoneal cavity (30 L) was coupled with computational fluid dynamics analysis. The tested HIPEC cycle parameters included catheter position and flow rates. The cavity was subjected to forward (superior to inferior flow) or reverse flow directions at 800 or 1,120 cc/min through four catheters, two as inlets and two as outlets, placed in upper and lower abdominal positions (net fluid volume: 18.5 L). Probes to measure temperature and flow were simulated between small and large bowels, inferior to small bowel mesentery, next to duodenum, superior to liver, superior to fundus, posterior to stomach, and posterior to liver. Results: The simulations highlight heterogeneity in temperatures and flow that may occur during HIPEC at particular at-risk locations as a function of chemotherapy flow rate and direction. Temperature and fluid flow over the course of 90 min respectively varied from 0.93 K and <0.001 m/s inferior to small bowel mesentery (800 cc/min forward flow) to 3.6 K and 0.01 m/s next to the duodenum (either 800 or 1,120 cc/min forward flow). The results further suggest that monitoring outflow temperature may be inadequate for assessing HIPEC performance at at-risk locations. Conclusions: Without intra-abdominal temperature monitoring at at-risk locations, it may be unfeasible to determine whether target temperatures and temperature homogeneity are being achieved during HIPEC. This work demonstrates that computational analysis offers the capability to monitor intra-abdominal locations at-risk of suboptimal heating and fluid flow given specific HIPEC parameters, and represents a first step towards designing efficacious tumor targeting during HIPEC.

Evaluation of cavitation phenomena in three-way globe valve through computational analysis and visualization test.

A three-way valve has a multi-port structure with three openings, which allows control of the fluid direction. However, owing to the complicated trim shape of the internal flow, an irregular fluid flow occurs, which hinders precise fluid flow control. In severe cases, cavitation induces mechanical damage owing to abrupt changes in the fluid direction. In this study conducted a computational fluid dynamics (CFD) analysis was performed to estimate the localized cavitation around the bottom plug of the three-way valve. To quantify localized cavitation, the percentage of cavitation (POC) was derived using the vapor volume fraction (VVF). The POC, defined by the cavitation occurrence zone with VVF > 0.5 divided by the volume of the cavitation danger zone, was 34.90%. Cavitation at this POC level could cause mechanical damage; therefore, a size optimization was performed. The lengths of the optimized waist and tail regions of the bottom plug were obtained wherein the POC level decreased by 19.06%. In addition, experiments were conducted using a flow visualization test setup. The experimental results were quantified into the POC employing the image gradients method, and the results were in good agreement with the CFD analysis.