3D Wall Research Articles

3D axial and circumferential wall shear stress from 4D flow MRI data using a finite element method and a laplacian approach.

To decompose the 3D wall shear stress (WSS) vector field into its axial (WSSA ) and circumferential (WSSC ) components using a Laplacian finite element approach. We validated our method with in silico experiments involving different geometries and a modified Poiseuille flow. We computed 3D maps of the WSS, WSSA , and WSSC using 4D flow MRI data obtained from 10 volunteers and 10 patients with bicuspid aortic valve (BAV). We compared our method with the centerline method. The mean value, standard deviation, root mean-squared error, and Wilcoxon signed rank test are reported. We obtained an error <0.05% processing analytical geometries. We found good agreement between our method and the modified Poiseuille flow for the WSS, WSSA , and WSSC . We found statistically significance differences between our method and a 3D centerline method. In BAV patients, we found a 220% significant increase in the WSSC in the ascending aorta with respect to volunteers. We developed a novel methodology to decompose the WSS vector in WSSA and WSSC in 3D domains, using 4D flow MRI data. Our method provides a more robust quantification of WSSA and WSSC in comparison with other reported methods. Magn Reson Med 79:2816-2823, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

Atherosclerotic plaque features and distribution in bilateral carotid arteries of asymptomatic elderly population: A 3D multicontrast MR vessel wall imaging study

PurposeThis study sought to investigate the characteristics of morphology, compositions and distribution of carotid atherosclerotic plaques in asymptomatic elderly population using three dimensional (3D) multicontrast magnetic resonance vessel wall imaging. Materials and methods146 asymptomatic elderly subjects (≥60years) were recruited and underwent 3D multicontrast MR vessel wall imaging for bilateral carotid arteries on a 3.0T MR scanner. The presence of carotid atherosclerotic plaque was determined and the stenosis was measured. The characteristics of plaque morphology and compositions were evaluated and compared among distal internal carotid artery (D-ICA), proximal-ICA (P-ICA), carotid bulb (CB), distal common carotid artery (D-CCA) and proximal-CCA (P-CCA). ResultsOf all recruited 140 subjects (72.1±5.7years, 63 males), 87 (62.1%) had carotid plaques, 17 (12.1%) had high-risk plaques and 51 (36.4%) had multiple plaques. Of all 280 carotid arteries, only 16 (5.7%) had luminal stenosis (21.1%±11.4%). Among carotid arteries without luminal stenosis, the prevalence of plaque and high-risk plaques was 43.2% and 8.3%, respectively. Carotid plaques were mostly found in CB segment (33.9%), followed by P-ICA (13.6%), P-CCA (11.1%), D-CCA (4.6%) and D-ICA (3.6%). Age was independently associated with presence of multiple carotid plaques (odds ratio, 1.835; 95% confidence interval, 1.196–2.815; P=0.005). ConclusionCarotid artery atherosclerotic plaques are prevalent and a substantial number of high-risk plaques can be found in the asymptomatic elderly subjects. Longitudinal studies are warranted to investigate the risk of having ischemic stroke for asymptomatic elderly individuals with carotid artery high risk plaques.

P19.01: Application of different frame rates in two‐dimensional speckle‐tracking in fetal echocardiography and their influence on strain analysis

Frame rates (FR) used for strain analysis assessed by speckle tracking in fetal echocardiography show a huge variation. Due to high fetal heart rates, appropriate high FR are requested for application in the fetus. The aim of this study was to investigate the influence of the FR on strain analysis in two-dimensional (2D) speckle tracking. A prospective cross-sectional study was performed. Based on an apical or basal four-chamber view of the fetal heart, cine loops were acquired on a Toshiba Aplio 500 system. Each loop was digitally stored twice: firstly as a DICOM (digital imaging and communications in medicine) file with a FR of 60 frames per second (fps), secondly with the original FR (acoustic FR = AFR). For each loop, fetal global longitudinal peak systolic strain (LPSS) values of both, left (LV) and right ventricle (RV), were assessed by 2D Wall Motion tracking. A total of n=48 healthy fetuses were included. Mean gestational age was 26.5 ± 5.5 weeks. The AFR was 129 ± 23 fps. Relating to global LPSS values of both ventricles, there was a significant difference between DICOM FR and AFR (LV: -17.3% ± 3.6% (DICOM FR) vs. -15.0% ± 3.1% (AFR); RV: -15.9% ± 3.2% (DICOM FR) vs. -14.0% ± 3.1% (AFR); p<0.001). Fetal LPSS values of both, LV and RV, assessed with high AFR, were significantly lower than the corresponding LPSS value analysed with DICOM 60 fps. Ongoing studies need to clarify the correlation of LPSS values acquired with different FR.

3D echocardiographic evaluation of right ventricular function and strain: a prognostic study in paediatric pulmonary hypertension.

To evaluate right ventricular functional indices using 3D echocardiography (3DE) between normal children and paediatric pulmonary hypertension (PH) patients, and to evaluate these indices as outcome predictors in children with PH. Ninety-six paediatric PH patients from 2014 to 2016 were compared with 40 normal controls. All patients underwent 3DE and off-line analysis generated 3D end-diastolic volume, 3D end-systolic volume, 3D stroke volume, 3D right ventricular (RV) ejection fraction (EF), RV longitudinal strain (LS) free wall and septum, tricuspid annular plane systolic excursion (TAPSE), and fractional area change (FAC). PH patients had higher RV volumes, lower RV EF, lower free wall and septal RVLS, lower TAPSE, and lower FAC compared with normal controls (all P < 0.001). 3D RV EF, free wall RVLS, and FAC are predictors of adverse clinical outcomes [hazard ratio (confidence interval) 0.1 (0.03-0.27], P < 0.001; 0.17 (0.07-0.45), P < 0.001; 0.08 (0.03-0.22); P < 0.001, respectively). Paediatric PH patients have impaired RV function compared with normal children. 3D RV EF, volumes, FAC, and free wall RV strain serve as outcome predictors for paediatric PH patients.

Increased apical rotation in patients with severe aortic stenosis assessed by three-dimensional speckle tracking imaging.

Two-dimensional (2D) speckle tracking imaging (STI) is a non-invasive method used to assess subtle changes in left ventricular (LV) function such as strain and rotational dynamics. However, 2D methodology is complicated by issues such as the out-of-plane problem inherent in short-axis imaging. In addition, circumferential rotation contributes to three-dimensional (3D) wall deformations and affects tracking accuracy. By using 3D-STI technique, we evaluated LV global longitudinal strain (GLS) and apical rotation in severe aortic stenosis (AS) patients with preserved LV ejection fraction (EF). LV GLS and apical rotation were evaluated using 3D-STI in 20 severe AS patients (79±8years old; aortic valve area 0.7±0.2cm2) with preserved LVEF (68±7%). Data were compared with those of 11 hypertensive LV hypertrophy (LVH) patients (75±10years old, EF=66±4%) and 12 controls (healthy individuals: 30±14years old, EF=63±6%). Compared with LVH patients, severe AS patients had significantly decreased values of GLS (-13.0±2.4 vs. -10.4±2.0%, p=0.008). In contrast, LV rotation was significantly higher in AS than LVH patients (13.9 ±3.0° vs. 10.8 ±2.5°, p=0.007). There was no significant difference in stroke volume index among three groups. In these three groups, severe AS patients had significantly decreased values of GLS [analysis of variance (ANOVA), p<0.001] and increased LV rotation (ANOVA, p<0.001). In severe AS patients, impaired GLS existed although LVEF was preserved. However, LV rotation was increased in patients with severe AS probably to maintain the LV stroke volume.

Rectangular Blocks vs Polygonal Walls in Archaeoseismology

Collapsed or deformed walls in ancient structures constitute important evidence in archaeoseismology, where damage is interpreted in terms of earthquake ground motion. A large variety of wall types have been developed during the millennia in different cultural backgrounds. Often walls with polygonal-shaped building blocks are regarded as more earthquake-resistant than a wall consisting of rectangular elements and, as is sometimes speculated, that the irregular wall types were intentionally developed for that purpose. We use simply structured discrete element models of four walls with different block geometries, perfect rectangular, an Inka-type structure and two polygonal designs, to test their dynamic behavior. In addition to an analytic calculation of ground motion, we use measured strong motion signals as boundary conditions for the 3D wall models with varying height to width ratios. At peak ground accelerations between 1.0 and 9.0 m/s 2 and major frequencies of 0.5 to 3 Hz, numeric experiments with the horizontally applied analytic ground motions result in clear differences in the resistance of the four wall types with the rectangular block wall being most vulnerable. For more complex measured 3D motions the Inka-type wall proves more stable than the rectangular block wall; however, height to width ratio still has equally strong influence on the stability. Internal deformation of non-collapsed walls shows some correlation with the parameters of the driving motion. For simple impulsive ground motions, a peak ground displacement threshold exists between toppling and remaining upright for all four models but peak acceleration cannot be reliably back calculated.

3D cardiac wall thickening assessment for acute myocardial infarction

Acute myocardial infarction (AMI) is the most severe form of coronary artery disease leading to localized myocardial injury and therefore irregularities in the cardiac wall contractility. Studies have found very limited differences in global indices (such as ejection fraction, myocardial mass and volume) between healthy subjects and AMI patients, and therefore suggested regional assessment. Regional index, specifically cardiac wall thickness (WT) and thickening is closely related to cardiac function and could reveal regional abnormality due to AMI. In this study, we developed a 3D wall thickening assessment method to identify regional wall contractility dysfunction due to localized myocardial injury from infarction. Wall thickness and thickening were assessed from 3D personalized cardiac models reconstructed from cine MRI images by fitting inscribed sphere between endocardial and epicardial wall. The thickening analysis was performed in 5 patients and 3 healthy subjects and the results were compared against the gold standard 2D late-gadolinium-enhanced (LGE) images for infarct localization. The notable finding of this study is the highly accurate estimation and visual representation of the infarct size and location in 3D. This study provides clinicians with an intuitive way to visually and qualitatively assess regional cardiac wall dysfunction due to infarction in AMI patients.

Fibrosis and Atrial Fibrillation: Computerized and Optical Mapping; A View into the Human Atria at Submillimeter Resolution.

Recent studies strongly suggest that the majority of atrial fibrillation (AF) patients with diagnosed or subclinical cardiac diseases have established or even pre-existing fibrotic structural remodeling, which may lead to conduction abnormalities and reentrant activity that sustain AF. As conventional treatments fail to treat AF in far too many cases, an urgent need exists to identify specific structural arrhythmogenic fibrosis patterns, which may maintain AF, in order to identify effective ablation targets for AF treatment. However, the existing challenge is to define what exact structural remodeling within the complex 3D human atrial wall is arrhythmogenic, as well as linking arrhythmogenic fibrosis to an underlying mechanism of AF maintenance in the clinical setting. This review is focused on the role of 3D fibrosis architecture in the mechanisms of AF maintenance revealed by submillimeter, high-resolution ex-vivo imaging modalities directly of human atria, as well as from in-silico 3D computational techniques that can be able to overcome in-vivo clinical limitations. The systematic integration of functional and structural imaging ex-vivo may inform the necessary integration of electrode and structural mapping in-vivo. A holistic view of AF driver mechanisms may begin to identify the defining characteristics or "fingerprints" of reentrant AF drivers, such as 3D fibrotic architecture, in order to design optimal patient-specific ablation strategies.

3D domain wall memory-cell structure, array architecture and operation algorithm with anti-disturbance

Domain wall memory (DMW) or Racetrack memory (RM) has attracted great attention for its enormous capacity. However, the array architecture are not clear. Prior arts have very low capacity utilization (only 50%) as well as high shift voltage. This paper proposed a 1 transistor X cells (1TXC) array architecture based on X-bar cell structure for 3D DWM, which realizes 100% capacity utilization, 50% shift power reduction and attains simplified peripheral decoding circuit as well as cost efficiency. Further, a corresponding anti-disturbance read operation algorithm is put forward, which can inhibit misread problem caused by sneaking current.

Direct Observation of Current-Induced Motion of a 3D Vortex Domain Wall in Cylindrical Nanowires

The current-induced dynamics of 3D magnetic vortex domain walls in cylindrical Co/Ni nanowires are revealed experimentally using Lorentz microscopy and theoretically using micromagnetic simulations. We demonstrate that a spin-polarized electric current can control the reversible motion of 3D vortex domain walls, which travel with a velocity of a few hundred meters per second. This finding is a key step in establishing fast, high-density memory devices based on vertical arrays of cylindrical magnetic nanowires.

Effect of engineering constraints on charged particle wall heat loads in DEMO

The presently predicted total heating power of the demonstration fusion reactor DEMO is ∼3 times the ITER value, while the major radius is only 1.5 times larger (R. Wenninger, et al., The DEMO Wall Load Challenge, Nucl. Fusion 57 (2017) 046002 (11pp)) [1]. The current DEMO technological wall heat load removal capability is limited to ∼1MW/m2, due to structural material limitations and the tritium breeding requirements, while the ITER first wall (FW) is designed for values up to 4.7MW/m2. This paper focuses on the evaluation of the effect of the engineering constraints on the required limitation of charged particle heat load.First, a 2D field-mapping tool is used together with a simple model to take into account the peaking factors present on an engineering 3D wall design. A sensitivity analysis is performed on a set of realistic FW 3D features considering a preliminary estimate of misalignments. The impact on the heat flux to the wall due to different machine geometries, plasma shapes variation, stationary plasma and plasma transients, is presented. An automatic procedure to define the 2D poloidal contour of the FW for minimized particle loads is presented. A subset of the resulting engineering wall design is analyzed using the 3D field line tracing code PFCflux.

3D Motion Modeling and Reconstruction of Left Ventricle Wall in Cardiac MRI.

The analysis of left ventricle (LV) wall motion is a critical step for understanding cardiac functioning mechanisms and clinical diagnosis of ventricular diseases. We present a novel approach for 3D motion modeling and analysis of LV wall in cardiac magnetic resonance imaging (MRI). First, a fully convolutional network (FCN) is deployed to initialize myocardium contours in 2D MR slices. Then, we propose an image registration algorithm to align MR slices in space and minimize the undesirable motion artifacts from inconsistent respiration. Finally, a 3D deformable model is applied to recover the shape and motion of myocardium wall. Utilizing the proposed approach, we can visually analyze 3D LV wall motion, evaluate cardiac global function, and diagnose ventricular diseases.

Application of Echocardiographic Three-Dimensional Printed Left Atrial Appendage Model to Guide Transcatheter Left Atrial Appendage Occlusion

This study aimed to determine the feasibility of three dimensional (3D) printed left atrial appendage (LAA) models based on 3D transesophageal echocardiography (3D TEE) data and its application value in the interventional LAA closure. Eighteen patients who had interventional LAA occlusion underwent pre-procedure TEE and cardiac CT. TEE 3D full volume raw data of the LAA were acquired and post-processed to create a 3D model file. Two modes of the LAA model (cardiac chamber model, cardiac wall model) were printed out by 3D printer. The LAA morphologic classification was assessed by 3D printed chamber model and the LAA dimension measurement was performed on 3D printed wall model. Additionally, preoperative rehearsal was performed on the 3D printed cardiac wall models in the cases with complex LAA structure. In all the patients, 3D TEE full volume data of the LAA were successfully reprocessed and printed out as 3D LAA chamber models and 3D LAA wall models. The consistency of LAA morphologic classification judgment based on 3D printed models and cardiac CT was 0.918 (P<0.01).The LAA ostium dimension measured on 3D printed model was greater than 2D TEE (P<0.01) and smaller than X-ray (P=0.02), and the LAA depth was greater than 2D TEE (P<0.01) whereas was not significantly different with X-ray (P=0.54).Based on 3D model morphology, there were 3 complex LAA which were recommended a particular occlusion plan after pre-procedure rehearsal on 3D model. The occlusion success rate was 100%. Echocardiographic 3D printing technique is feasible and have promising value in supporting planning the transcatheter LAA occlusion.

Longitudinal Evaluation of Aortic Hemodynamics in Marfan Syndrome: New Insights from a 4D Flow Cardiovascular Magnetic Resonance Multi-Year Follow-Up Study

BackgroundThe aim of this 4D flow cardiovascular magnetic resonance (CMR) follow-up study was to investigate longitudinal changes in aortic hemodynamics in adolescent patients with Marfan syndrome (MFS).Methods4D flow CMR for the assessment of in-vivo 3D blood flow with full coverage of the thoracic aorta was performed twice (baseline scan t1/follow-up scan t2) in 19 adolescent MFS patients (age at t1: 12.7 ± 3.6 years, t2: 16.2 ± 4.3 years) with a mean follow-up duration of 3.5 ± 1.2 years. Ten healthy volunteers (24 ± 3.8 years) served as a control group. Data analysis included aortic blood flow visualization by color-coded 3D pathlines, and grading of flow patterns (helices/vortices) on a 3-point scale (none, moderate, severe; blinded reading, 2 observers). Regional aortic peak systolic velocities and systolic 3D wall shear stress (WSS) along the entire aortic wall were quantified. Z-Scores of the aortic root and proximal descending aorta (DAo) were assessed.ResultsRegional systolic WSS was stable over the follow-up duration, except for a significant decrease in the proximal inner DAo segment (p = 0.02) between t1 and t2. MFS patients revealed significant lower mean systolic WSS in the proximal inner DAo compared with volunteers (0.78 ± 0.15 N/m2) at baseline t1 (0.60 ± 0.18 N/m2; p = 0.01) and follow-up t2 (0.55 ± 0.16 N/m2; p = 0.001). There were significant relationships (p < 0.01) between the segmental WSS in the proximal inner DAo, DAo Z-scores (r = −0.64) and helix/vortex pattern grading (r = −0.55) at both t1 and t2. The interobserver agreement for secondary flow patterns assessment was excellent (Cohen’s k = 0.71).ConclusionsMFS patients have lower segmental WSS in the inner proximal DAo segment which correlates with increased localized aberrant vortex/helix flow patterns and an enlarged diameter at one of the most critical sites for aortic dissection. General aortic hemodynamics are stable but these subtle localized DAo changes are already present at young age and tend to be more pronounced in the course of time.

The influence of turbulence model and two and three-dimensional domain selection on the simulated performance characteristics of vertical axis tidal turbines

The influence of Computational Fluid Dynamics (CFD) modeling techniques on the accuracy of fixed pitch vertical axis turbine power output predictions was investigated. Using Two-Dimensional (2D) and Three-Dimensional (3D) models, as well as the Baseline-Reynolds Stress Model (BSL-RSM) and the k-ω Shear Stress Transport (k-ω SST) model in its fully turbulent and laminar-to-turbulent formulation, differences in power output modeling accuracy were evaluated against experimental results from literature. The highest correlation was found using a 3D domain model that fully resolved the boundary layer combined with the k-ω SST laminar-to-turbulent model. The turbulent 3D fully resolved boundary layer k-ω SST model also accurately predicted power output for most rotational rates, at a significantly reduced computational cost when compared to its laminar-to-turbulent formulation. The 3D fully resolved BSL-RSM model and 3D wall function boundary layer k-ω SST model were found to poorly simulate power output. Poor output predictions were also obtained using 2D domain k-ω SST models, as they were unable to account for blade tip and strut effects. The authors suggest that 3D domain fully turbulent k-ω SST models with fully resolved boundary layer meshes are used for predicting turbine power output given their accuracy and computational efficiency.

Construction and histological analysis of a 3D human arterial wall model containing vasa vasorum using a layer-by-layer technique.

There is considerable global demand for three-dimensional (3D) functional tissues which mimic our native organs and tissues for use as in vitro drug screening systems and in regenerative medicine. In particular, there has been an increasing number of patients who suffer from arterial diseases such as arteriosclerosis. As such, in vitro 3D arterial wall models that can evaluate the effects of novel medicines and a novel artificial graft for the treatment are required. In our previous study, we reported the rapid construction of 3D tissues by employing a layer-by-layer (LbL) technique and revealed their potential applications in the pharmaceutical fields and tissue engineering. In this study, we successfully constructed a 3D arterial wall model containing vasa vasorum by employing a LbL technique for the first time. The cells were coated with extracellular matrix nanofilms and seeded into a culture insert using a cell accumulation method. This model had a three-layered hierarchical structure: a fibroblast layer, a smooth muscle layer, and an endothelial layer, which resembled the native arterial wall. Our method could introduce vasa vasorum into a fibroblast layer in vitro and the 3D arterial wall model showed barrier function which was evaluated by immunostaining and transendothelial electrical resistance measurement. Furthermore, electron microscopy observations revealed that the vasa vasorum was composed of single-layered endothelial cells, and the endothelial tubes were surrounded by the basal lamina, which are known to promote maturation and stabilization in native blood capillaries. These models should be useful for tissue engineering, regenerative medicine, and pharmaceutical applications. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 814-823, 2017.

Correspondence optimization in 2D standardized carotid wall thickness map by description length minimization: A tool for increasing reproducibility of 3D ultrasound-based measurements.

The previously described 2D standardized vessel-wall-plus-plaque thickness (VWT) maps constructed from 3D ultrasound vessel wall measurements using an arc-length (AL) scaling approach adjusted the geometric variability of carotid arteries and has allowed for the comparisons of VWT distributions in longitudinal and cross-sectional studies. However, this mapping technique did not optimize point correspondence of the carotid arteries investigated. The potential misalignment may lead to errors in point-wise VWT comparisons. In this paper, we developed and validated an algorithm based on steepest description length (DL) descent to optimize the point correspondence implied by the 2D VWT maps. The previously described AL approach was applied to obtain initial 2D maps for a group of carotid arteries. The 2D maps were reparameterized based on an iterative steepest DL descent approach, which consists of the following two steps. First, landmarks established by resampling the 2D maps were aligned using the Procrustes algorithm. Then, the gradient of the DL with respect to horizontal and vertical reparameterizations of each landmark on the 2D maps was computed, and the 2D maps were subsequently deformed in the direction of the steepest descent of DL. These two steps were repeated until convergence. The quality of the correspondence was evaluated in a phantom study and an in vivo study involving ten carotid arteries enrolled in a 3D ultrasound interscan variability study. The correspondence quality was evaluated in terms of the compactness and generalization ability of the statistical shape model built based on the established point correspondence in both studies. In the in vivo study, the effect of the proposed algorithm on interscan variability of VWT measurements was evaluated by comparing the percentage of landmarks with statistically significant VWT-change before and after point correspondence optimization. The statistical shape model constructed with optimized correspondence was more compact and had a better generalization ability than that constructed using the AL approach in both the phantom and in vivo studies. A statistical test on the group-average VWT-Change at each point of the 2D carotid template showed that the group-average VWT-change was significantly different from 0 in 18% of landmarks when the AL approach was used, and this percentage was reduced to 11% after correspondence optimization. The optimized correspondence resulted in a more compact and generalizable statistical shape model, and the algorithm was shown to reduce interscan variability of point-wise VWT measurements obtained using the previously described arc-length scaling parameterization approach.

A simple estimation model for 3D braced excavation wall deflection

A series of two-dimensional (2D) and three-dimensional (3D) finite element analyses using the Hardening Soil (HS) model were carried out to investigate the influences of soil properties, wall stiffness, excavation length, excavation depth, clay thickness at the base of the excavation and wall embedment depth, on the maximum wall deflection induced by braced-excavation. The results show that the 3D maximum wall deflections are generally much smaller than those for 2D. Comparisons were also made with other commonly used semi-empirical charts. Based on the finite element results in this study, a simple wall deflection equation was developed for estimating the maximum wall deflection that takes the 3D effects into consideration through different ratios of excavation length over excavation width.

Multi-Scale Visualization Analysis of Bus Flow Average Travel Speed in Qingdao

Public transportation is a kind of complex spatiotemporal behaviour. The traffic congestion and environmental pollution caused by the increase in private cars is becoming more and more serious in our city. Spatiotemporal data visualization is an effective tool for studying traffic, transforming non-visual data into recognizable images, which can reveal where/when congestion is formed, developed and disappeared in space and time simultaneously. This paper develops a multi-scale visualization of average travel speed derived from floating bus data, to enable congestion on urban bus networks to be shown and analyzed. The techniques of R language, Echarts, WebGL are used to draw statistical pictures and 3D wall map, which show the congestion in Qingdao from the view of space and time. The results are as follows:(1) There is a more severely delay in Shibei and Shinan areas than Licun and Laoshan areas; (2) The high congestion usually occurs on Hong Kong Middle Road, Shandong Road, Nanjing Road, Liaoyang West Road and Taiping Road;(3) There is a similar law from Monday to Sunday that the congestion is severer in the morning and evening rush hours than other hours; (4) On Monday morning the severity of congestion is higher than on Friday morning, and on Friday evening the severity is higher than on Monday evening. The research results will help to improve the public transportation of Qingdao.

Development of 3D transient wall filming mechanism during combustion by coupling Eulerian-Lagrangian approach and particle-wall interaction model

In the present study, the developments of 3D wall filming mechanism for coal combustion in a small scale furnace under air and oxy-fuel combustion conditions are presented. The principle objective of this study is to develop the film flow behavior and particle deposition characteristics on the furnace refractory wall using a commercial CFD code coupled with some user-defined sub-routines. Eulerian-Lagrangian approach of the gas-particle flow is coupled with the particle-wall interaction mechanisms including particle capturing, entrainment and wall burning sub-models. A case study has been presented to validate the model in a small scale furnace by comparing the available temperature, species data for coal-water slurry combustion and reasonable agreement has been observed. Visualization of the transient film formation and flow characteristics under air and oxy-firing cases are presented. The film thickness deposited on the refractory wall was found to be reasonably in good range with the available data. The deposited film thicknesses for both the conditions are found in the range of 0–1.0mm. The average molten film velocity was 0.0001m/s due to higher viscosity and greater surface tension properties. Slightly higher amount of films are formed in oxy-firing condition due to slower char oxidation rate.