A review of water tank modeling of the convective atmospheric boundary layer

Several studies have been selected to review water tank modeling of the atmospheric boundary layer (ABL) and demonstrate that water tank simulations have been a key factor in developing scientific knowledge and promoting further research of the ABL. The areas discussed include similarity analysis of modeling, basic dispersion processes, characteristics of the convective boundary layer (CBL), parameterizations of the entrainment zone (EZ), the characteristics of turbulence in the CBL, and the influence of plain-valley terrain and other inhomogeneities on atmospheric boundary layer structure. Technical values of some parameters are noted and potential improvements in water tank modeling based on continuing advances in new technology are also discussed. The limitations of water tank models for characteristics of the CBL and possible solutions to their limitations are briefly discussed.     

Wind load on a container crane located in atmospheric boundary layers

Wind environment nearby a container crane located in a port was simulated in a wind tunnel test section. A scale-downed model of the container crane was embedded in an atmospheric boundary layer (ABL). Wind load acting on the container crane model was measured using a seven-component balance with varying wind direction (yaw angle) in two different ABLs. Reynolds number effect on the aerodynamic coefficients was investigated with varying Reynolds number. Effects of ABL, adjacent structures and boom positions on the wind load variation were evaluated experimentally. In addition, the effect of the minute structures attached at the crane model such as stairways, wheels, handrails, etc., were also investigated in this study.     

New inflow boundary conditions for modelling the neutral equilibrium atmospheric boundary layer in computational wind engineering

Modelling neutral equilibrium atmospheric boundary layers (ABL) in CFD is an important aspect in computational wind engineering (CWE) applications. In this paper, new inflow boundary conditions are introduced from the viewpoint that these boundary conditions should satisfy the turbulence model employed. The new set of inflow turbulence boundary conditions is an approximate solution to the standard k-ε model transport equations. The capability of these boundary conditions to produce an equilibrium ABL is demonstrated by performing numerical simulations in an empty domain. The new inflow turbulence boundary conditions in this paper support future practical applications in CWE and future research in modelling equilibrium ABLs.     

Longitudinal, lateral and torsional oscillations of a square section tower model in an atmospheric boundary layer

The longitudinal, lateral and torsional response of a square building under an atmospheric boundary layer is determined using a linear model with three degrees of freedom for different angles of incidence of wind. The experimental results are compared with existing analytical models, and an expression for predicting the lateral response for different angles of incidence and for a wide range of reduced velocities is presented.     

Large-eddy simulation of atmospheric boundary layer flow through wind turbines and wind farms

Accurate prediction of atmospheric boundary layer (ABL) flow and its interactions with wind turbines and wind farms is critical for optimizing the design (turbine siting) of wind energy projects. Large-eddy simulation (LES) can potentially provide the kind of high-resolution spatial and temporal information needed to maximize wind energy production and minimize fatigue loads in wind farms. However, the accuracy of LESs of ABL flow with wind turbines hinges on our ability to parameterize subgrid-scale (SGS) turbulent fluxes as well as turbine-induced forces. This paper focuses on recent research efforts to develop and validate an LES framework for wind energy applications. SGS fluxes are parameterized using tuning-free Lagrangian scale-dependent dynamic models. These models optimize the local value of the model coefficients based on the dynamics of the resolved scales. The turbine-induced forces (e.g., thrust, lift and drag) are parameterized using two types of models: actuator-disk models that distribute the force loading over the rotor disk, and actuator-line models that distribute the forces along lines that follow the position of the blades. Simulation results are compared to wind-tunnel measurements collected with hot-wire anemometry in the wake of a miniature three-blade wind turbine placed in a boundary layer flow. In general, the characteristics of the turbine wakes simulated with the proposed LES framework are in good agreement with the measurements in the far-wake region. Near the turbine, up to about five rotor diameters downwind, the best performance is obtained with turbine models that induce wake-flow rotation and account for the non-uniformity of the turbine-induced forces. Finally, the LES framework is used to simulate atmospheric boundary-layer flow through an operational wind farm.     

基于FLAC3D的隧道分台阶开挖数值模拟与分析

基于有限差分法的FLAC3D数值模拟,对隧道的分台阶开挖进行了计算与分析,研究了隧道开挖过程中的位移变化和稳定状态,提出了相应的预防措施和建议,分析结果为隧道施工控制提供了理论支持。     

Consistent boundary conditions for flows within the atmospheric boundary layer

In computational wind engineering the neutrally stable atmospheric boundary layer (ABL) is often simulated using the standard k-ε model. The application of boundary conditions that are inconsistent with the profiles used at the inflow boundary causes streamwise gradients in the solution and prevents the simulation of a horizontally homogeneous boundary layer. In the present work these problems are overcome by applying a simple extension of the shear stress boundary condition at the top of the domain and by using one-dimensional models to generate inflow profiles in equilibrium with the ground boundary condition. This procedure allows the impact of the inconsistent boundary conditions to be quantitatively assessed. It is shown that inconsistent boundary conditions at the top of the domain result in erroneous streamwise gradients throughout the domain. These errors are reduced by enlarging the domain in the vertical direction but are not removed. The errors are also found in simulations with idealised and real topography included in the domain. A brief discussion of the impact of the errors on simulations of wind energy projects is given.     

粉煤灰混凝土二维和三维碳化研究

本文首先建立了2D和3D碳化测试方法,在此基础上系统研究了粉煤灰混凝土在加速碳化试验中2D和3D碳化深度的依时变化规律,探讨了粉煤灰掺量(0%、10%、20%、40%、60%)、粉煤灰种类(Ⅰ级、Ⅱ级)、水胶质量比(0.3,0.35,0.4)、胶凝材料用量(458,380kg/m3)、养护龄期(28,90d)5个重要因素对粉煤灰混凝土2D和3D碳化深度的影响规律。另外,还将2D和3D碳化试验结果与同条件下1D碳化进行了定量比较,发现2D和3D碳化明显存在交互作用,为量化该交互作用提出了2D和3D碳化交互系数概念,并给出了2D和3D碳化交互系数随时间变化的数学表达式。以期为准确预测实际混凝土结构在真实状态下碳化寿命提供科学依据。     

在水平成层土体中波动数值模拟的人工边界

利用ABAQUS软件平台,建立分层土体的动力有限元模型,边界条件分别采用透射边界,无限元边界,固定边界和远置边界,分析比较表明:基于透射边界理论和ABAQUS软件DISP子程序施加的透射边界,获得的数据结果更接近于远置边界条件。     

高拱坝坝肩岩体变形稳定性的三维数值模拟

以金沙江上游拟建某水电站高拱坝坝肩为研究对象,应用有限差分程序FLAC-3D对坝肩岩体在天然和荷载后的应力、变形和破坏的发展特征模拟分析,重点分析了坝肩岩体在正常工程荷载下的变形稳定性及坝肩超载特性,得到了坝肩岩体的变形破坏特征及超载安全系数。     

某堆积体开挖后的稳定性FLAC~(3D)模拟分析

在堆积体稳定性地质宏观判断基础上,利用FLAC3D软件对堆积体开挖前后的稳定性进行了模拟分析,通过建立数值计算模型和选取合理的计算参数,模拟堆积体开挖前后的应力分布状况和变形规律,综合分析模拟结果,并结合宏观地质判断,对堆积体开挖后的稳定性作出正确评价。     

二维与三维边坡稳定性对比分析

基于二维与三维模型,对同一边坡进行了稳定性考察,计算结果表明：坡硕面荷载的分布范围越小,边坡的安全系数越大,其与二维计算结果相差越大,因此,一般情况下,三维模型的计算结果大于二维模型的计算结果,采用二维模型考察边坡稳定性可能低估了边坡的安全系数。     

规划二三维网络综合管理平台的设计与实现

在规划局现有的规划数据资源基础上,充分运用地理信息技术、网络技术、CAD技术、三维GIS技术等建设“规划资源一体数据库”,并以此库为基础,进行需求调研、熟悉规划审批流程和业务需求,确定平台功能,设计系统平台二三维技术路线,搭建系统平台框架,实现“规划二三维网络综合管理平台”,从而更加高效的辅助业务人员办公,促进规划局业务平台的智能化。     

裂隙岩体在单轴加载过程中变形、破裂规律的PFC2D数值模拟研究

运用离散元软件PFC2D模拟裂隙岩体,建立一个包含不同倾角、不同组数,宽度5cm、厚度1mm裂隙的10cm×10cm模型,分析单轴加载情况下岩体的变形、破裂规律。结果显示,在单轴加载情况下,随着倾角的增加,岩体的单轴抗压强度出现先减后增的趋势,且裂纹不断增多;随着裂隙的增多,单轴抗压强度逐渐减小。岩体的破裂区集中在裂隙的尖端点部位,以翼裂纹、次生共面裂纹和次生倾斜斜纹为主。通过分析破裂后岩体的颗粒速度分布,从微观层面发现岩体破坏的主要形式及破裂原因。     

Train-induced vibration prediction in tunnels using 2D and 3D FEM models in time domain

The purpose of this study is to develop a 3D numerical FEM model of a railway tunnel to predict railway induced vibrations, which is calibrated and validated with in situ measurements. After that, two different 2D FEM models are constructed following the same assumptions as in the 3D model but different methodologies to introduce the loads. The results from the different models are used to determine the existing differences among each type of model, and the scope of each one. Vertical accelerations are obtained from each model and compared among them, concluding that the 3D FEM models provide more accurate results with a longer calculation time and require huge computational requirements.     

砂井地基数值计算中的三维排水板单元及其验证

根据砂井地基中的塑料排水板的力学、渗流特点,提出了三维排水板单元的有限元格式、矩阵表达式,并将其结合到三维Biot固结有限元程序当中。将排水板单元有限元法与常规有限元、Hansbo解进行了比较,结果表明排水板单元有限元法能较好地模拟塑料排水板在砂井地基中的应用。     

三维激光扫描技术在文物三维重建中的应用研究

三维激光扫描技术为文物高精度三维重建提供了新的途径,为文物的数字化展示、数字博物馆的建立、文物鉴赏以及文化遗产的保存提供了新的思路。本文通过对三维点云数据处理、三维构网、纹理映射、三维模型构建及三维浏览等关键技术研究,解决了三维激光扫描系统用于高精度文物三维重建中的若干技术难题,并精确重建出文物三维模型。     

Investigation of the vertically-layered structure and surface roughness parameters of the urban boundary layer

Atmospheric flow is the main factor affecting the wind load of urban buildings. The measured data observed continuously from the 325-m-tall Beijing Meteorological Tower (BMT) during 2013–2017 is employed to investigate the vertically-layered structure and surface roughness parameters of the urban boundary layer. Based on the local similarity theory and analysis results of the atmospheric stability and local friction velocity, it can be determined that the height of 80 m is near the bottom of the inertial sub-layer, the range below this height belongs to the roughness sub-layer, 140 m belongs to the inertial sub-layer, and 200 m and 280 m are in the mixing layer. The local friction velocity at 80 m can be considered a relatively reliable value as the friction velocity. Moreover, seasonal effect on local friction velocity is minimal. According to the fitting result of near-neutral strong wind samples by the log-law, it is concluded that to obtain a more accurate wind speed profile, all layers should be included when picking fitting heights. In addition, surface roughness parameters are affected by the wind direction and speed. The variation according to the wind direction corresponds to the topographical distribution surrounding the BMT, and the higher range of wind speed may be more applicable for estimating surface roughness parameters.     

基于AutoLISP的三维模型快速建立与精度分析

建筑物的三维模型是数字城市重建的重要组成部分，而建筑物高精度三维模型的快速建立一直是三维数字仿真亟待解决的问题。本文通过无协作目标电子全站仪采集建筑的三维坐标，基于AutoLISP实现了数据的导入、建筑物墙面的拟合、特征点的投影及门窗等构件的自动生成，从而快速生成建筑物的三维模型，并对生成的建筑模型进行精度分析。基于AutoLISP构建建筑物的三维模型，大大提高了建模速度；并能有效控制三维建筑模型的质量。     

Debris flow simulation 2D (DFS 2D): Numerical modelling of debris flows and calibration of friction parameters

Debris flows are rapid mass movements with a mixture of rock, soil and water. High-intensity rainfall events have triggered multiple debris flows around the globe, making it an important concern from the disaster management perspective. This study presents a numerical model called debris flow simulation 2D (DFS 2D) and applicability of the proposed model is investigated through the values of the model parameters used for the reproduction of an occurred debris flow at Yindongzi gully in China on 13 August 2010. The model can be used to simulate debris flows using three different rheologies and has a user-friendly interface for providing the inputs. Using DFS 2D, flow parameters can be estimated with respect to space and time. The values of the flow resistance parameters of model, dry-Coulomb and turbulent friction, were calibrated through the back analysis and the values obtained are 0.1 and 1000 m/s², respectively. Two new methods of calibration are proposed in this study, considering the cross-sectional area of flow and topographical changes induced by the debris flow. The proposed methods of calibration provide an effective solution to the cumulative errors induced by coarse-resolution digital elevation models (DEMs) in numerical modelling of debris flows. The statistical indices such as Willmott's index of agreement, mean-absolute-error, and normalized-root-mean-square-error of the calibrated model are 0.5, 1.02 and 1.44, respectively. The comparison between simulated and observed values of topographic changes indicates that DFS 2D provides satisfactory results and can be used for dynamic modelling of debris flows.