Validation of 1D model for methane/air/Pt combustion in stagnation flow

A 2D model is built on the package of FLUENT to study the effects of radial aspect ratio （R/W）, length-to-width ratio （L/W）, strain rate （SR）, and buoyancy （Ri=Gr/Re^2） on the validation of the simplified 1D model. In the present 2D model, the methane/air homogeneous reaction mechanism of Peters and the methane/air/platinum heterogeneous reaction mechanism of Deutschmann are applied. By comparison between the 1D and 2D numerical results, it is found that the validation of 1D model is highly related with the catalytic stagnation reactor configuration. For length-to-width ratio L/W = 1 configuration, 1D laminar model is applicable when the radial aspect ratio R/W 〉 0.4. For R/W = 0.6, the reactor exhibited 1D characteristics when L/W 〈 1. Compared with the temperature and species profiles, the velocity distribution along the axis is more sensitive to the change of radial aspect ratio and length-to-width ratio. With increasing of the strain rate, the flame front goes closer to the catalytic wall surface and the difference between the 1D and 2D results decreases. For a valid 1D simulation, it is recommended that the strain rate should be convection can be neglected when Ri〈 5. greater than 20 s^-1. The effects of natural

Estimation of evapotranspiration from artificial forest in mountainous areas of western Loess Plateau based on HYDRUS-1D model

Evapotranspiration is the most important expenditure item in the water balance of terrestrial ecosystems,and accurate evapotranspiration modeling is of great significance for hydrological,ecological,agricultural,and water resource management.Artificial forests are an important means of vegetation restoration in the western Loess Plateau,and accurate estimates of their evapotranspiration are essential to the management and development of water use strategies for artificial forests.This study estimated the soil moisture and evapotranspiration based on the HYDRUS-1D model for the artificial Platycladus orientalis(L.)Franco forest in western mountains of Loess Plateau,China from 20 April to 31 October,2023.Moreover,the influence factors were identified by combining the correlation coefficient method and the principal component analysis(PCA)method.The results showed that HYDRUS-1D model had strong applicability in portraying hydrological processes in this area and revealed soil water surplus from 20 April to 31 October,2023.The soil water accumulation was 49.64 mm;the potential evapotranspiration(ETp)was 809.67 mm,which was divided into potential evaporation(Ep;95.07 mm)and potential transpiration(Tp;714.60 mm);and the actual evapotranspiration(ETa)was 580.27 mm,which was divided into actual evaporation(Ea;68.27 mm)and actual transpiration(Ta;512.00 mm).From April to October 2023,the ETp,Ep,Tp,ETa,Ea,and Ta first increased and then decreased on both monthly and daily scales,exhibiting a single-peak type trend.The average ratio of Ta/ETa was 0.88,signifying that evapotranspiration mainly stemmed from transpiration in this area.The ratio of ETa/ETp was 0.72,indicating that this artificial forest suffered from obvious drought stress.The ETp was significantly positively correlated with ETa,and the R2 values on the monthly and daily scales were 0.9696 and 0.9635(P<0.05),respectively.Furthermore,ETa was significantly positively correlated with temperature,solar radiation,and wind speed,and negatively correlated with relative humidity and precipitation(P<0.05);and temperature exhibited the highest correlation with ETa.Thus,ETp and temperature were the decisive contributors to ETa in this area.The findings provide an effective method for simulating regional evapotranspiration and theoretical reference for water management of artificial forests,and deepen understanding of effects of each influence factors on ETa in arid areas.

基于HYDRUS-1D模型的水库近坝区土壤水分动态模拟

为探究五强溪水库近坝区土壤水分动态变化规律,以研究区内土壤墒情站为研究对象,利用实测逐日降雨与逐日蒸发数据驱动HYDRUS-1D模型反演土壤水力特性参数,分别在深度为10、20、40 cm观察点处进行土壤水分动态模拟,探讨研究区土壤水分动态变化规律及模型的应用效果。结果表明:不同观察点土壤水分模拟值与实测值的决定系数平均值为0.74,纳什效率系数平均值为0.71,均方根误差在0.011~0.035 cm^(3)/cm^(3)之间;0~10 cm深度的土壤水分对降雨和蒸发的响应最灵敏,波动最大;在水库主汛期(4—6月份)土壤水分变化平稳,且保持在较高的水平;研究期内7—12月份土壤水分在较大降雨情况下出现短暂饱和,土壤干湿变化明显,模拟值与实测值吻合度较高;整体上,HYDRUS-1D模型在研究区土壤水分动态模拟中具有较高的精度,可为研究区土壤水分估计及其动态变化规律研究提供有效方法。

Similarities and differences in inherent mechanism and characteristic frequency between the one-dimensional poroelastic model and the layered White model

The similarities and differences in inherent mechanism and characteristic frequency between the onedimensional(1D)poroelastic model and the layered White model were investigated.This investigation was conducted under the assumption that the rock was homogenous and isotropic at the mesoscopic scale.For the inherent mechanism,both models resulted from quasi-static flow in a slow P-wave diffusion mode,and the differences between them originated from saturated fluids and boundary conditions.On the other hand,for the characteristic frequencies of the models,the characteristic frequency of the 1D poroelastic model was first modified because the elastic constant and formula for calculating it were misused and then compared to that of the layered White model.Both of them moved towards higher frequencies with increasing permeability and decreasing viscosity and diffusion length.The differences between them were due to the diffusion length.The diffusion length for the 1D poroelastic model was determined by the sample length,whereas that for the layered White model was determined by the length of the representative elementary volume(REV).Subsequently,a numerical example was presented to demonstrate the similarities and differences between the models.Finally,published experimental data were interpreted using the 1D poroelastic model combined with the Cole-Cole model.The prediction of the combined model was in good agreement with the experimental data,thereby validating the effectiveness of the 1D poroelastic model.Furthermore,the modified characteristic frequency in our study was much closer to the experimental data than the previous prediction,validating the effectiveness of our modification of the characteristic frequency of the 1D poroelastic model.The investigation provided insight into the internal relationship between wave-induced fluid flow(WIFF)models at macroscopic and mesoscopic scales and can aid in a better understanding of the elastic modulus dispersion and attenuation caused by the WIFF at different scales.

基于集合卡尔曼滤波同化方法和HYDRUS-1D模型的土壤水分模拟

研究建立了一个基于集合卡尔曼滤波方法和HYDRUS-1D模型相结合的数据同化方案,利用2021年4月26日—10月5日内蒙古巴彦淖尔五原站0~80 cm的土壤水分观测数据进行模拟验证,以提高土壤水分的模拟精度。结果表明:(1)集合数大小和观测误差的选取对同化系统性能有较大影响。集合数在100以上,土壤含水量的同化精度不再有明显提高。观测误差越小土壤水分模拟精度越高,因此观测误差为0.025时的同化精度最高。(2)数据同化后,各层土壤水分模拟精度较同化前均有明显提高,各层土壤水分同化值与观测值间的相对误差、均方根误差、平均绝对误差分别减少至0.025~0.063、0.01~0.017 cm^(3)·cm^(-3)、0.008~0.016 cm^(3)·cm^(-3)。证明数据同化方法能够有效改善土壤水分模拟效果。(3)0~20 cm土壤水分同化效果最好,20~40 cm次之,40~80 cm土壤水分同化效果较差。模拟精度分析值优于同化预报值,同化预报值优于HYDRUS-1D预报值。

Performance Optimization of Torque Converters Based on Modified 1D Flow Model

A methodology for performance optimization of torque converters is put forward based on the one-dimensional (1D) flow model. It is found that the inaccuracy of 1D flow model for predicting hydraulic performance at the low speed ratio is mainly caused by the separation phenomenon at the stator cascade which is induced by large flow impinging at the pressure side of the stator blades. A semi-empirical separation model is presented and incorporated to the original 1D flow model. It is illustrated that the improved model is able to predict the circumferential velocity components accurately, which can be applied to performance optimization. Then, the Pareto front is obtained by using the genetic algorithm (GA) in order to inspect the coupled relationship among stalling impeller torque capacity, stalling torque ratio and efficiency. The efficiency is maximized on the premise that a target stalling impeller torque capacity and torque ratio are achieved. Finally, the optimized result is verified by the computational fluid dynamics(CFD) simulation, which indicates that the maximal efficiency is increased by 0.96%.

基于Hydrus-1D模型的淮北平原冬小麦地潜水蒸发规律

选取淮北平原五道沟水文水资源实验站作为研究区,评价Hydrus-1D模型在淮北平原冬小麦地潜水蒸发过程模拟的适用性,并探讨不同降水条件下冬小麦各生育期潜水蒸发规律。结果表明,基于Hydrus-1D模型模拟的潜水蒸发过程与基于水量平衡和Bouchet互补关系理论的潜水蒸发变化过程基本一致,相关系数为0.82、绝对误差为0.04 mm/d、相对误差为12.4%;冬小麦生育期潜水蒸发量受降水条件影响,当降水量偏多时,潜水蒸发总量较大;从冬小麦各生育期的潜水蒸发量来看,灌浆期-成熟期>抽穗期-灌浆期>拔节期-抽穗期>返青期-拔节期。研究结果可为制定淮北平原合理灌溉制度提供理论依据。

基于HYDRUS-1D的秸秆覆盖条件下黑土区玉米田土壤水盐运移规律

为揭示不同秸秆覆盖量对黑土区玉米田农田土壤水盐运移的影响机制,基于田间试验结果,利用HYDRUS-1D模型对秸秆覆盖下农田土壤水盐运移过程进行模拟,分析不同秸秆覆盖量对土壤水盐动态的影响规律。结果表明:秸秆覆盖可以增强土壤保水性、抑制土壤盐分积累,随秸秆覆盖量增加,秸秆覆盖对土壤水盐运移的作用效果更加明显,在玉米全生育期内秸秆半量覆盖及全量覆盖较裸地40 cm耕层内各土层平均含水率分别提高3.38%~5.78%和5.26%~9.62%、平均电导率分别降低4.61%~8.93%和8.87%~12.41%。基于HYDRUS-1D模型模拟结果可知,土壤含水率模拟值与实测值的决定系数介于0.903~0.940,标准误差介于0.010~0.014 cm^(3)·cm^(-3),平均相对误差介于3.46%~4.64%;土壤电导率模拟值与实测值的决定系数介于0.817~0.853,标准误差介于0.091~0.111 mS·cm^(-1),平均相对误差介于4.06%~5.46%。误差分析表明HYDRUS-1D模型模拟精度较高,能够用于模拟研究区秸秆覆盖条件下农田土壤水盐运移过程。

An Implicit Coupled 1D/2D Model for Unsteady Subcritical Flow in Channel Networks and Embayment

In this study, 1D and 2D shallow-water models were coupled to simulate unsteady flow in channel networks and embayment. The 1D model solved the 1D shallow-water equations (St. Venant) using the Preissmann box method and targeted long narrow reaches of the river networks, while the 2D model targeted broad channels and embayment and solved the 2D shallow-water equations using a semi-implicit scheme applied to an unstructured grid of triangular cells. The 1D and 2D models were solved simultaneously by building a matrix for the free surface elevation at every 1D junction and 2D cell center. Velocities were then computed explicitly based on the results at the previous time step and the updated water level. The originality of the scheme arose from a novel coupling method. The results showed that the coupled 1D/2D model produced identical results as the full 2D model in classical to benchmark problems with considerable savings in computational effort. Application of the model to the Pearl River Estuary in southern China showed that complex patterns of tidal wave propagation could be efficiently modeled.

Simulation of the Hydrodynamic Functioning of the Cavally River Using a Coupled 1D-2D Model in the Ity Area (Zouan-Hounien in Côte d’Ivoire)

In recent years, the Cavally River has been subject to multiple activities, including the construction of diversion channels and a bridge that makes it vulnerable to flooding. In order to assess the impact of these hydraulic structures on the river hydrodynamic functioning, a 1D-2D model was realized. The implementation of the 1D-2D model consisted of first running the 1D model, then the 2D model, and finally in coupling them. The 1D-2D model was designed with the 1988 flood hydrograph, a Manning’s coefficient of 0.052 m1/3/s for the minor bed and 0.06 m1/3/s for the major bed. The results of the hydraulic model show that the velocities are almost identical to those of the Cavally in natural operation. The values of the velocities are included between 0.4 m/s and 1.3 m/s at the level of the minor bed of the river and between 0.06 m/s and 0.71 m/s at the level of the floodplains. The average water level for flood propagation is 262.37 ± 0.44 m before construction of the structures and 262.23 ± 0.85 m after construction of the structures. The 0.41 m reduction in water level due to the diversion canal and bridge is negligible compared to the total fluctuations of the Cavally River, which vary from 6 to 7 m over the year.

基于1D-CNN的近红外光谱定量分析棉/涤纶/羊毛混纺纤维含量方法研究

纤维成分的定性及定量分析在纺织品检测中一直是研究热点,但常规检测手段存在周期长、工序复杂且对环境不友好等问题,因此提出一种对纺织品纤维含量快速、无损且准确的检测方法就显得尤为重要。研究提出一种纺织品纤维含量的定量校正模型,可以准确预测纺织品中棉/涤纶/羊毛的纤维含量,解决传统校正模型无法兼顾准确与多种纤维预测的难点。针对645个羊毛/涤纶、棉/涤纶以及羊毛/涤纶/棉混纺样品为研究对象,采用红外光谱分析仪采集样品的近红外反射光谱,在光谱数据预处理的基础之上,提出一种一维卷积神经网络(1D-CNN)模型,实现对多种纤维含量的同时预测,为了凸显模型的优势,在相同的训练集和测试集样本之上对比3种不同机器学习算法的预测结果。结果表明:选用线性函数归一化、多项式平滑滤波(SG平滑,滑动窗口为9,拟合阶数为7)的预处理方法,结合所提出的1D-CNN模型效果最优,其模型决定系数R-Squared可达到0.998,各含量预测的平均绝对误差(MAE)为0.62,预测均方根误差(RMSE)为1.31。同时采用未参与建模的138个纺织品样品验证模型泛化能力,模型在测试集上的表现为,决定系数R-Squared为0.996,各含量预测的平均绝对误差(MAE)为0.80,预测均方根误差(RMSE)为2.01。采用所提出的模型,可以准确预测羊毛、棉和涤纶混纺织品中纤维含量,为快速无损检测纺织品提供了一种可行的方法,同时为其他混纺纤维含量的定量分析提供了新的思路。

Temperature Distributions in Single Cell of Polymer Electrolyte Fuel Cell Simulated by an 1D Multi-plate Heat-Transfer Model and a 3D Numerical Simulation Model

The purpose of this study is to verify an 1D multi-plate heat-transfer model estimating the temperature distribution on the interface between polymer electrolyte membrane and catalyst layer at cathode in single cell of polymer electrolyte fuel cell, which is named as reaction surface in this study, with a 3D numerical simulation model solving many governing equations on the coupling phenomena in the cell. The results from both models/simulations agreed well. The effects of initial operation temperature, flow rate, and relative humidity of supply gas on temperature distribution on the reaction surface were also investigated. It was found in both 1D and 3D simulations that, the temperature rise （i.e., Treact-Tini） of the reaction surface from initial operation temperature at 70℃ was higher than that at 80℃ irrespective of flow rate of supply gas. The effect of relative humidity of supply gas on Treact- Tini near the inlet of the cell was small. Compared to the previous studies conducted under the similar operation conditions, the Treact - Tini calculated by 1D multi-plate heat-transfer model in this study as well as numerical simulation using 3D model was reasonable.

HYDRUS-1D模型对河套灌区不同灌施情景下氮素迁移的模拟

选取河套灌区五原建丰的典型土壤,应用HYDRUS-1D模型对不同灌溉强度、不同表施浓度以及将表施改为灌施3类情景下土壤氮元素的迁移进行了动态模拟,研究了灌溉和施肥对河套灌区典型区域土壤氮元素迁移的影响.结果表明,灌水强度小于0.10 cm.h-1时,铵态氮与硝态氮累积流出通量变化极为缓慢;强度大于0.14 cm.h-1时,累积流出通量急剧攀升,表明氮元素大量向土层深层流失.铵态氮表施浓度的变化对氮素的迁移几乎没有影响.保持相同的施肥量,灌施情景对铵态氮迁移几乎无影响,但表施换为灌施后硝态氮下渗浓度增加47%,更易于向深层渗漏.

基于野外观测实验的中国东部湿润区降雨入渗模拟分析——以宁波画龙溪流域为例

本文以中国东部湿润区典型小流域浙江宁波画龙溪为例,将野外原位定点观测与模型模拟分析相结合,建立了HYDRUS-1D土壤水模拟模型,选取2016年9月29日、2016年10月7日典型降雨事件分别对模型进行率定和验证,并对2016―2020年不同降雨强度下不同土地利用类型的场次土壤水分入渗开展了观测与模拟,以揭示中国东部湿润区不同土地利用类型下的降雨-入渗规律。结果表明:(1)从土壤水分变化过程模拟来看,HYDRUS-1D模型模拟土壤水分动态变化特征具有较高的精度,90%模拟结果的纳什效率系数达到0.80以上。(2)在同等降雨强度下,4种土地利用类型土壤下渗量从大到小依次为农田、杨梅林、坡耕地、竹林。下渗率受降雨量及降雨强度影响较大,不同土地利用下土壤下渗量随着降雨强度增强而显著增加。(3)土壤下渗量同时也受到降雨历时与前期降雨情况深刻影响。当降雨强度从小雨逐级增加到大暴雨,各土地利用类型下渗量略微增加,但增加量均小于5%。对于历时短、强度高的极端降雨事件,降雨强度超过了下渗强度,形成超渗产流,将出现降雨量大但下渗量反而小的现象。本研究成果可为中国东部湿润区农业生产、三水转化规律等提供理论参考。

基于地震反演技术的地应力建模方法在江汉新沟嘴组页岩油中的应用

江汉盆地新沟嘴组页岩油地质评价资源量为3.6×108 t,具有良好的勘探潜力,其中地质评价Ⅰ类有利区陈沱口凹陷有多口井在新沟嘴组新下段Ⅱ油组泥质白云岩中获得油流。由于页岩油井通常采用“水平井+分段压裂”工艺实现经济开采,因而地应力研究对该区水平井储层压裂改造具有重要的意义。三维地应力建模研究的核心问题在于提升井间地应力预测效果,传统的有限元方法由于方法本身的限制,井间预测效果较差,有必要利用地震资料反演技术来提升井间地应力预测的效果。针对该区页岩层矿物组分多、局部发育硫酸盐岩、地应力条件复杂的问题,首先对新沟嘴组页岩层开展基于实验室测量值约束的精细测井评价,其结果与岩心全岩X衍射测量结果吻合;在此基础上,选择自相容近似地震岩石物理建模流程,对目标层的弹性参数进行了正演模拟,正演结果与实测曲线基本吻合。然后,基于地层压力、实验室测量的岩石力学性能参数和测井解释结果,依据不同岩性的动静态关系,采用有效应力比值和构造应变法计算井的地应力参数。最后运用基于地震叠前反演技术的三维地应力建模方法,使用与一维地质力学建模相同的相关性和参数约束,建立了新沟嘴组页岩油的三维地应力模型。与一维地质力学研究成果相比,该三维地应力模型提取的伪曲线与工区大部分井一维地应力结果基本吻合,验证了该方法在新沟嘴页岩油地应力评价中的适用性和准确性。

应用HYDRUS-1D模型模拟农田土壤水渗漏及硝态氮淋失特征

在定位试验基础上,应用HYDRUS-1D模型对黄淮海平原典型土壤(黄潮土)中土壤水渗漏及硝态氮淋失动态进行了模拟分析。结果表明:在传统水氮管理模式下,黄潮土2m土体深处的土壤水渗漏和硝态氮淋失非常严重,2个轮作期内,土壤水渗漏总量占地表总入水量的23.7%,硝态氮淋失总量占总输入N量的15.9%,冬小麦生长季的硝态氮淋失量大于夏玉米生长季;改良灌溉和改良施肥模式下产生的硝态氮淋失量比传统灌溉和传统施肥模式减少74.7%,节约灌溉水211.5mm、节省施N423.5kg·hm-2。

Hydrus-1D模型在田间水循环规律分析中的应用及改进

为分析农田水分运移规律,以华北平原位山引黄灌区典型田间为研究对象,应用Hydrus-1D模型连续模拟了2006-2009年的田间水分运移过程。对模型中表面阻抗的计算方法进行了改进,从而改善了蒸散发的模拟结果,与涡度相关系统的实测蒸散发数据对比表明了改进的合理性。对蒸散发的分析表明,对于种植季节性作物的农田,叶面积指数(leafarea index,LAI)是影响蒸散发季节变化过程的重要因素,而气象条件主要决定其在较短时间尺度(如一周)内的波动。与时域反射仪(time domain reflectometry,TDR)实测土壤含水率的对比表明,模型对土壤含水率的模拟精度较高。水量平衡分析结果表明,降雨和灌溉的80%由蒸散发消耗,在汛期农田通过排水发生田间渗漏损失。

基于Hydrus-1D模型的大安灌区旱田灌溉入渗补给研究

以吉林省大安灌区为研究对象,在野外调查和资料收集的基础上,借助Hydrus-1D模型,模拟分析了旱田(玉米地)灌溉条件下地下水入渗补给过程。结果表明:模拟期间蒸散发动态变化较大,蒸腾量约为蒸发量的2.18倍,玉米生育期内,土壤水分蒸腾损失约占蒸散发消耗的79.74%,蒸散发在作物生长旺季以蒸腾为主,其它时段则以蒸发为主;旱田灌溉条件下,降水灌溉大量入渗形成土壤水,土壤水与地下水发生双向的、动态的水量频繁交换,模拟中地下水入渗补给量约为33.63 mm,入渗比为5.21%,其与研究区细密的包气带介质岩性有关。研究成果可为进一步开展旱田灌溉合理方案的制定提供科学依据。

应用HYDRUS-1D模型评价土壤水资源量

利用焉耆盆地典型试验区观测资料,以土壤水动力学原理为基础,建立起浅埋区(埋深≤2m)植被覆盖条件下田间土壤水分数学模型,对典型试验区土壤水资源量补给项、排泄项和消耗项进行计算与评价,评价结果表明:地下水资源和土壤水资源转化十分频繁,水量交换是双向的、动态的;在浅埋区土壤水库调蓄能力较弱,造成部分灌溉水的渗漏。

不同降雨量及雨强条件下兰州南山人工侧柏林土壤水分入渗规律

[目的]降雨是干旱半干旱地区土壤水分的主要来源,将野外观测和模型模拟相结合研究降雨入渗规律,可以更系统地掌握土壤水分亏缺状况。[方法]通过定点观测,应用Hydrus-1d模型对兰州南山人工侧柏林土壤水分动态变化进行模拟,评估模型在干旱区的适用性,分析不同降雨条件下土壤水分响应状况和入渗机制。[结果]Hydrus-1d模型在兰州南山人工侧柏林有较好的适用性,且深层模拟效果更优。降雨量<30 mm时,10 cm处土壤含水量对降雨响应最为强烈,30,50 cm处受降雨影响相对较小且有明显的滞后,70 cm以下没有响应;降雨量>8.2 mm时存在湿润峰。模拟期内,最大入渗深度为70 cm,最大入渗量为23.7 mm,入渗深度随时间增加而入渗量和入渗速率却随时间延长而减小。降雨量与入渗量、入渗深度和入渗速率呈显著正相关(p<0.05)。降雨量<20 mm时,降雨强度对入渗量、入渗深度和入渗速率存在显著影响。[结论]使用Hydrus-1d模型可以较好地模拟兰州南山人工侧柏林土壤水分动态变化并计算入渗量、入渗速率和入渗深度,且分析发现降雨量对该地土壤水入渗过程的影响更显著。