Processing of Large Underground Excavation System—Skeleton Based Section Segmentation for Point Cloud Regularization

Floodways, where a road embankment is permitted to be overtopped by flood water, are usually designed as broad-crested weirs. Determination of the water level above the floodway is crucial and related to road safety. Hydraulic performance of floodways can be assessed numerically using 1-D modelling or 3-D simulation using computational fluid dynamics (CFD) packages. Turbulence modelling is one of the key elements in CFD simulations. A wide variety of turbulence models are utilized in CFD packages; in order to identify the most relevant turbulence model for the case in question, 96 3-D CFD simulations were conducted using Flow-3D package, for 24 broad-crested weir configurations selected based on experimental data from a previous study. Four turbulence models (one-equation, k-ε, RNG k-ε, and k-ω) ere examined for each configuration. The volume of fluid (VOF) algorithm was adopted for free water surface determination. In addition, 24 1-D simulations using HEC-RAS-1-D were conducted for comparison with CFD results and experimental data. Validation of the simulated water free surface profiles versus the experimental measurements was carried out by the evaluation of the mean absolute error, the mean relative error percentage, and the root mean square error. It was concluded that the minimum error in simulating the full upstream to downstream free surface profile is achieved by using one-equation turbulence model with mixing length equal to 7% of the smallest domain dimension. Nevertheless, for the broad-crested weir upstream section, no significant difference in accuracy was found between all turbulence models and the one-dimensional analysis results, due to the low turbulence intensity at this part. For engineering design purposes, in which the water level is the main concern at the location of the flood way, the one-dimensional analysis has sufficient accuracy to determine the water level.

The transition toward electric vehicles (EVs) in the automotive industry underscores the critical need for efficient thermal management systems (TMS) to ensure the safety, performance, and longevity of key components such as lithiumion batteries, electric motors, and power electronics. These components generate significant heat during operation, with lithium-ion batteries being particularly sensitive to temperature fluctuations. Excessive temperatures accelerate battery degradation and pose risks of thermal runaway, while suboptimal thermal conditions reduce energy efficiency and driving range. This study explores the application of numerical simulation techniques to design and optimize a comprehensive TMS for electric cars, addressing the complex interplay of heat generation, dissipation, and energy consumption. Numerical simulations, employing computational fluid dynamics (CFD) software ANSYS/Fluent, enable modeling of thermal and fluid flow phenomena within the TMS. The momentum and energy equations are solved with various combinations of boundary conditions. The study investigates thermal behavior under diverse operating conditions. Additionally, a comprehensive parametric study is explored to enhance thermal performance of a thermal management system. Simulation results are compared to the experimental results measured in the battery lab, the air flow rates are specified while the battery temperatures are validated against the measured data. The agreement between the numerical results and the lab data demonstrates the success of the numerical model. The results highlight the trade-offs between cooling effectiveness and system energy consumption. The findings underscore the value of numerical simulation as a cost-effective and versatile tool for TMS development. By enabling virtual prototyping and rapid iteration, simulations reduce reliance on physical testing while providing insights into complex multi-component interactions. This approach facilitates the design of lightweight, compact, and scalable TMS architectures tailored to evolving EV requirements.

A multi-objective optimization design framework integrated with CFD for the design of AUVs

Terrestrial laser scanning (TLS) is an important part of urban reconstruction and terrain surveying. In TLS applications, 4-point congruent set (4PCS) technology is widely used for the global registration of point clouds. However, TLS point clouds usually enjoy enormous data and uneven density. Obtaining the congruent set of tuples in a large point cloud scene can be challenging. To address this concern, we propose a registration method based on the voxel grid of the point cloud in this paper. First, we establish a voxel grid structure and index structure for the point cloud and eliminate uneven point cloud density. Then, based on the point cloud distribution in the voxel grid, keypoints are calculated to represent the entire point cloud. Fast query of voxel grids is used to restrict the selection of calculation points and filter out 4-point tuples on the same surface to reduce ambiguity in building registration. Finally, the voxel grid is used in our proposed approach to perform random queries of the array. Using different indoor and outdoor data to compare our proposed approach with other 4-point congruent set methods, according to the experimental results, in terms of registration efficiency, the proposed method is more than 50% higher than K4PCS and 78% higher than Super4PCS.

The advancement of deep learning technology has been concentrating on deploying end-to-end solutions using high dimensional data, such as images. Recently, a number of methods have been proposed for reconstructing 3D objects using deep learning. One such technique is the method that involves recovering 3D objects as voxel grids using one or multiple images. However, there has been very little work directed towards the generation of 3D objects represented by a set of points, i.e. point cloud, from voxel grids which are ambiguous and coarse. The development of a deep learning model that generates point clouds with details from coarse voxel grids has numerous benefits to quality of life. For example, design professionals can use this model to generate detailed 3D point clouds using a sketched and coarse voxel to enable their creativities. This paper presents an algorithm to generate point clouds from voxel grids. The algorithm explicitly loads 3D objects into voxels without projection operations and associated information loss. To obtain a comprehensive understanding of the voxel grid, the grid is analyzed through various angles, as inspired by how humans observe 3D objects. The features from various angles are passed into a GRU layer to extract patterns across views, which will then be passed to a channel-wise convolutional layer and graph convolution to generated the predicted point cloud. The experimental result of the algorithm indicates that the algorithm is capable of generating high-quality point clouds by understanding the semantic features of the voxel grid.

Results are presented from a numerical simulation of three-dimensional flow hydraulics around a mid-channel bar carried out using the FLUENT/UNS computational fluid dynamics (CFD) software package. FLUENT/UNS solves the three-dimensional Reynolds-averaged form of the Navier–Stokes equations. Turbulence closure is achieved using a RNG k–ϵ model. Simulated flow velocities are compared with measured two-dimensional velocities (downstream and cross-stream) obtained using an electromagnetic current meter (ECM). The results of the simulation are qualitatively consistent with the flow structures observed in the field. Quantitative comparison of the simulated and measured velocity magnitudes indicates a strong positive correlation between the two (r=0·88) and a mean difference of 0·09 m s−1. Deviations between simulated and measured velocities may be identified that are both random and systematic. The former may reflect a number of factors including subgrid-scale natural spatial variability in flow velocities associated with local bed structures and measurement uncertainty resulting from problems of ECM orientation. Model mesh configuration, roughness parameterization and inlet boundary condition uncertainty may each contribute to systematic differences between simulated and measured flow velocities. These results illustrate the potential for using CFD software to simulate flow hydraulics in natural channels with complex configurations. They also highlight the need for detailed spatially distributed datasets of three-dimensional flow variables to establish the accuracy and applicability of CFD software. Copyright © 1999 John Wiley & Sons, Ltd.

본 연구는 스프링클러 헤드 근처에서 형성되는 액막의 자유표면 유동에 대해 CFD 모델을 적용하여 해석하고 스프링클러의 초기분무 특성 예측을 위한 기존 이론식의 결과와 비교를 통해 이론 모델의 타당성을 검토하였다. CFD 해석은 상용 해석프로그램인 CFX 14.0을 이용하였으며 노즐과 디플렉터로 이루어진 단순형상에 대해 표준난류모델과 VOF법을 적용하여 해석을 수행하였다. 평판부의 디플렉터 끝단에서 속도분포는 CFD 해석과 경험식이 매우 잘 일치된 결과를 보였으나 기하학적 형상이 복잡한 부분에서는 속도분포의 차이를 보였다. 이론모델에서 예측된 평균액적크기는 실제 스프링클러 헤드에서 측정된 평균액적크기에 대한 이전 연구결과와 큰 차이를 보였다. 그러나 이론 모델은 스프링클러 헤드의 초기 액적형성과정의 메커니즘을 이해하고 실험적 접근이 용이하지 않은 상황에서 분무 액적의 특성을 예측하는데 유동한 도구로 활용될 수 있다. The present study examined the free surface flow of a liquid sheet near a sprinkler head using a Computational Fluid Dynamics (CFD) model and considered the feasibility of the empirical model for predicting the initial spray characteristics of the sprinkler head through a comparison of the CFD results. The CFD calculation for a simplified sprinkler geometry considering the nozzle and deflector were performed using the commercially available CFD package, CFX 14.0 with the standard <TEX>$k-{\varepsilon}$</TEX> turbulence model and theVolume of Fluid (VOF) method. The predicted velocity of the empirical model at the edge of deflector were in good agreement with that of the CFD model for the flat plate region but there was a certain discrepancy between the two models for the complex geometry region. The mean droplet diameter predicted by the empirical model differed significantly from the measured value of the real sprinkler head. On the other hand, the empirical model can be used to understand the mechanism of droplet formation near the sprinkler head and predict the initial spray characteristics for cases without experimental data.

Modeling of energy production and heat transfer by carbon combustion and electrical arc is performed using Fluent computational fluid dynamic (CFD) software in this manuscript. The heat energy generated by carbon burning and electric arc radiation during combustion of the scrap in the EAO has been examined in detail. For this reason, modeling studies have utilized the combustion reactions of carbon particles and electromagnetically emitted radiation. Firstly, particle surface and gas reactions are investigated in terms of injected carbon burning. The result of the chemical reaction at the burner outlet is about 3000 K of the core temperature during combustion. It has been determined that the temperature which acts on the slag is 2200 K. The radiation temperature was found to be highest in the area under the electrodes and fell to 1850 K in the area where the melt was poured. Under steady operating conditions, it was seen that electric energy was absorbed by about 5.5% of the electrodes. As a result of this study, CFD software can be used to model combustion and radiation and energy generation and heat transfer for an electric arc furnace at the design study.

An increased interest in immersive applications has drawn attention to\nemerging 3D imaging representation formats, notably light fields and point\nclouds (PCs). Nowadays, PCs are one of the most popular 3D media formats, due\nto recent developments in PC acquisition, namely with new depth sensors and\nsignal processing algorithms. To obtain high fidelity 3D representations of\nvisual scenes a huge amount of PC data is typically acquired, which demands\nefficient compression solutions. As in 2D media formats, the final perceived PC\nquality plays an important role in the overall user experience and, thus,\nobjective metrics capable to measure the PC quality in a reliable way are\nessential. In this context, this paper proposes and evaluates a set of\nobjective quality metrics for the geometry component of PC data, which plays a\nvery important role in the final perceived quality. Based on the popular PSNR\nPC geometry quality metric, the novel improved PSNR-based metrics are proposed\nby exploiting the intrinsic PC characteristics and the rendering process that\nmust occur before visualization. The experimental results show the superiority\nof the best-proposed metrics over the state-of-the-art, obtaining an\nimprovement of up to 32% in the Pearson correlation coefficient.\n

To simulate toxic gas dispersion over urban area with consideration of the influence of wind, buildings and other obstacles within the dispersion site, an integrated strategy incorporating computational fluid dynamics (CFD) and GIS technologies is investigated. CFD is able to couple wind field with pollutant dispersion process and provide realistic simulation for geometrically complex scenarios, however, inadequate of geometry construction for urban scale applications. This paper focuses on how to take advantage of the available GIS data, the visualization and spatial discretization capabilities of GIS in CFD modeling. Topography and building data stored in GIS database are used to extract the detailed coordinates and heights of the buildings around the area of interest. Furthermore, a methodology of domain discretization, with restrict to underneath geometrical boundary, is proposed to construct computational grids for CFD simulations. For illustration purposes, a mixed residential and commercial area of Lujiazui in Shanghai is investigated. The CFD software, CFX5.5, is employed to predict plume concentrations, and the output can be rendered dynamically in GIS environment.

This article describes an optimization design of a sugar evaporative crystallizer using numerical simulation experiments. Computational fluid dynamics (CFD) is used to simulate the circulation flow of sugar juice in the crystallizer, and the numerical experiments are designed according to orthogonal experiment matrix. First, based on the specific working characteristics of sugar evaporative crystallizer, major factors influencing the cane sugar evaporative crystallization process were identified. Then CFD software was utilized to establish various three‐dimensional CFD models of the sugar evaporative crystallization with different factors and levels. Statistics software (IBM SPSS) is used to analyze the CFD simulation results. In order to measure circulation velocity under different conditions, physical experiments were conducted in the experiment platform in our laboratory. The circulation velocity measured under the optimal condition was increased by 128%, and the crystallization efficiency could be guaranteed.Practical ApplicationsComputation fluid dynamics (CFD) enables studying the details within the crystallizer, making the invisible become visible. The orthogonal test replaces all tests with partial tests. The orthogonal test coupled CFD technique can hugely decrease the cost of optimization design. The application of this method will benefit the optimization design of food engineering.

The computational fluid dynamics (CFD) grid application platform provides a grid environment for CFD applications using high performance computing. It adopts service oriented architecture (SOA), is based on IBM's Service Domain, extends and customizes it for CFD applications in several modules, such as service requesting, job scheduling, job management, failure recovery, etc. By defining general CFD application interfaces such as data format, the platform integrates different CFD applications, including mesh generation, domain decomposition and resolvers, to follow the workflow customized by end-users to finish a complete CFD job. Furthermore, CFD application development specifications and packages are provided to facilitate migrating most sequential and parallel CFD applications to the platform. Currently, a prototype system is available online to the public for testing.

In this paper, interaction of a nonlinear solitary wave with a submerged breakwater as well as a breakwater with zero freeboard are modeled using Computational Fluid Dynamic (CFD). Simulation results of water particle velocities as well as water surface elevations at the vicinity of breakwater are validated by comparison to experimental data. In order to find out the best turbulence modeling appropriate for wave-breakwater interaction problem, simulations are conducted using standard K-Epsilon, SST-K Omega, and inviscid models available within the CFD software. In cases involving wave breaking, simulations are also repeated using second order SST-K-Omega model. The overall pattern of the wave interaction with breakwater is adequately reproduced by the CFD software. The processes of wave reflection, wave breaking, and vortical motion at the vicinity of breakwater are correctly captured. The good results achieved are promising regarding the use of CFD for design of breakwaters and other marine structures subject to waves.

Emergency condition should be evaluated during the siting of Nuclear Power Plants (NPP). One of the criteria is the capability of emergency evacuation for the purpose of protecting the NPP staff and public. Exposure dose received by evacuees is a key factor to evaluate the effectiveness of emergency evacuation, which can be characterized by the atmospheric dispersion factors over the evacuation paths. Gaussian plume model is usually applied in the atmospheric dispersion factor calculation for NPPs. However, for some NPP sites with complex terrain like mountain and lake which has significant influence on the local flow field and the nuclides transportation, the calculations based on Gaussian model will not be accurate enough for the evaluation of the evacuation capability. In such cases, Computational Fluid Dynamics (CFD) method with fine calculation grids and rich physical models can be used in the atmospheric dispersion modeling of small-scale region, to get much more accurate results. This paper is devoted to the research on the impact of these complex terrain on atmospheric dispersion with CFD method. The local atmospheric dispersion around a NPP site located on an island is modeled, where there is a mountain on the way of evacuation. For the limitation of the geographic barrier, two evacuation paths, which are located closely with small difference in direction, are planned along different sides of the mountain. Utilizing STAR-CCM+ CFD software, local atmospheric dispersion factors are fine simulated under six worse wind directions. Based on the simulation results, the impact of the mountain on the flow field and of the radiological plume on the evacuation paths is analyzed. Results show that due to the blocking effect of the mountain, those two evacuation paths have little probability to be simultaneously covered by the radiological plume. By the choosing of suitable routes during the evacuation, the radiological risk of public is acceptable and emergency evacuation can be carried out effectively. These results also demonstrate that CFD modeling method is effective in the evaluation of local atmospheric dispersion over complex terrain, which can be applied in the analysis of emergency evacuation of NPP sites with complex terrain.

The principle of air-splicing appears to be simple at first sight, but is actually complicated to explain in detail. Direct observation of splice formation is difficult, because the process occurs in the splicer extremely quickly. So far our research on air-splicing has been primarily based on analyzing experimental data only. This paper applies computational fluid dynamics (CFD) to the theoretical study of a pneumatic splicer, with a three-dimensional model developed to predict its performance. Several geometric parameters are varied in 3D CAD for the splicing chamber. The fluid flow in the splicing chamber is turbulent, and the standard k - ε model can be used to simulate it. The performance simulation of the pneumatic splicer is then studied and realized by the combination of UGII, a CAD/CAM software, and FLUENT, a CFD software, which can aid further discussion on applying CFD technology to the study of pneumatic splicing.