Calibration and validation of a three-dimensional subsurface irrigation hydrology model

An enhanced subsurface irrigation hydrology model, developed by Buyuktas & Wallender (Journal of Irrigation and Drainage Engineering, ASCE 128(3): 71–81), is calibrated and validated using 2 years of data collected in a field in Broadview Water District in California, USA. The first year data is used to calibrate the model, while the second year data is used for model validation. Calibration of the model is achieved by trial-and-error adjustments of model parameters to match simulated results with measured cumulative drain flow, water table depth and salinity of the drain flow. Adjustments of the model input parameters include van Genuchten soil hydraulic function parameters (n and K_s), maximum allowed pressure head at the soil surface and irrigation duration. For validation of the model, a particular case is chosen to match the measured drain flow, water table depth and drain flow salinity, based on the graphical and objective functions used. It is found, through model validation, that the predicted drain flow is slightly lower than the observed data, while the predicted water table depth is slightly higher.     

旋风分离式集沙仪的标定

详细阐述了旋风分离式集沙仪的标定原理与标定系统的实现方法,并借助于移动式风蚀风洞对旋风分离式集沙仪进行了标定试验.结果表明,标定系数不随风洞中心风速、采样时间、试样种类的改变而变化,且集沙仪具有较高的稳定性,其值确定为5.08‰.     

西气东输站场压力及差压变送器免拆解校验方法

西气东输站场以往校验压力变送器、差压变送器时,需要拆解引压管接头、二阀组组件和五阀组组件上的排污管,然后连接校表仪器校验。通过对未带二阀组组件的压力变送器加装改进的二阀组组件、对已带二阀组组件的压力变送器和差压变送器的排污管加装校表专用接头的方法,实现了压力变送器、差压变送器校验时的免拆解。避免了由于多次拆解引起的引压管接头处易漏气、丝扣处易滑丝、引压管变形安装后产生应力等生产运行风险,减小了校表人员的工作量和设备在校表期间的不备用时间,相对提高了设备的可用率,可为解决类似管道问题提供参考借鉴。（图6,参6）     

CottonPlus模型土壤参数校正研究——以河北省曲周县为例

利用1998年中国农业大学曲周试验站的试验资料,校正了站出和站东两个试点的CottonPlus模型的土壤参数,并对校正结果进行了较全面的验证,从整体来看,模拟值和实测值的相符程度较高,模拟结果基本上能反映土壤剖面水分动态的实际情况,从而可以说明所获得的土壤参数是可靠的。     

GLEAMS模型在我国东南地区模拟硝氮淋失的检验

利用我国东南亚热带地区农业小流域不同土地利用方式的硝氮渗漏淋失实测数据检验了GLEAMS(Groundwater Loading Effects of Agricultural Management Systems)模型在该地区的适用性。通过现场试验和实地调查并结合模型手册,获取模型所需的水文和营养盐参数,参考模型参数的敏感性分析结果对模型进行调试。结果表明模型对水稻田除外的其它土地利用方式的硝氮渗漏淋失模拟效果较好。水稻田渗漏模拟效果差的主要原因在于模型的水分平衡方程不能反应水稻田长期淹水的实际情况。模型模拟结果的精度可以接受,从而验证了GLEAMS模型在该流域的适用性。     

Field measurements of the water content in the top soil using a new capacitance sensor with a flat sensitive volume

Water content directly near the soil surface plays an essential role for degradation of natural organic material and agrochemicals by soil microbes. Furthermore, the water losses by evaporation depend sensitively on the top‐soil water content. Rain, irrigation, evaporation, and the water flow between the soil horizons together with the natural inhomogeneity of soils cause a high spatial gradient and a pronounced time dependence of the water content in the top soil. To understand processes in top soil such as redox gradients, the knowledge on ecological conditions in the top soil, which is subject to rapid changes, is essential. In order to meet the requirements for such field measurements, a capacitance sensor with a depth resolution of 1 cm and an active area of 7.5 cm × 14 cm was constructed and operated by a special electronic circuit. Field measurements using these sensors at 1 cm depth showed the high dynamics when measurements were carried out every 10 min. As simultaneous measurements of the soil temperature at 1 cm depth exhibit large temperature variations during the day, its influence on the measurements must be compensated for. As the data, measured during drying periods, allow the assessment of the temperature coefficient, the water content at a reference temperature can be calculated. The course of the water content reflects precipitation events and quantifies the drying of the soil, providing these parameters for process evaluation. Furthermore, the diurnal variation exhibits the drying during the day and the possible rewetting from deeper horizons during the night.     

黑水虻处理的猪粪有机肥离散元仿真模型参数标定

为准确快速获取黑水虻处理的猪粪有机肥颗粒的离散元仿真模型参数,该研究采用圆筒提升堆积物理试验与EDEM仿真结合的方法,选取"Hertz-MindlinwithJKR"作为接触模型,以堆积角为响应值,基于响应面法优化标定了黑水虻处理的含水率为43.6%的猪粪有机肥仿真参数。采用Design-Expert8.0.6设计Plackett-Burman试验,筛选出对堆积角有显著影响的参数,即有机肥泊松比、有机肥颗粒密度、有机肥-有机肥滚动摩擦系数。通过最陡爬坡试验确定了显著参数的最优值区间,进一步以有机肥堆积角为响应值,基于Box-Behnken试验获得堆积角与显著性参数的二阶回归模型,以物理试验测得的堆积角为响应目标,针对显著性参数进行寻优,得到最佳组合:有机肥泊松比0.11、有机肥颗粒密度1 703 kg/m~3、有机肥-有机肥滚动摩擦系数0.13。运用最佳参数组合进行仿真分析,得到堆积角均值为38.61°,与物理试验测得的堆积角相对误差为1.88%,且堆积形状具有较高相似性,无明显差异,表明标定的参数准确,研究结果可为黑水虻处理猪粪后的有机肥相关收集与筛分机械的设计提供理论参考。     

SX2002管网式降雨模拟装置的试验研究

介绍了适于在室内进行土壤侵蚀模型试验的SX2002管网式降雨模拟装置和试验方法。率定试验的结果表明,雨强在1.2~4.0 mm/m in时,其雨滴中值粒径在1.2~2.0 mm之间,降雨动能与天然降雨接近,有效降雨均匀度超过80%。在SX2002管网式模拟降雨装置中,把雨强作为主要控制参数来实现降雨模拟的动能相似在实际操作中是方便可行的。     

测定直链淀粉含量的三种校准曲线法的比较

本文研究了脂肪,支链淀粉,介质pH和碘试剂浓度等因子对直链淀粉含量测定的影响。结果表明,由于脂肪的影响,使直链淀粉含量的测定值偏低,其影响在碱性介质中比在酸性介质中更为明显;不同脱脂方法的效果亦不同。支链淀粉的存在使测定值偏高,其干扰作用在酸性介质中较明显,而在碱性介质中被抑制。适当增大碱性试剂浓度可以在一定程度上补偿脂肪、介质的pH对直链淀粉含量测定的影响。比较三种校准曲线法的结果表明,标准样品校准法可以克服脂肪、支链淀粉等多种因子的影响,使测定的结果较为一致,具有较好的稳定性和重现性。     

包衣棉种物性参数测定与离散元仿真参数标定

针对目前在EDEM(离散元法)中直接建立的棉种颗粒模型与实际棉种在外形上存在一定差异,且缺乏准确的包衣棉种仿真参数的问题,采用物理试验方法测定‘新陆中67号’棉种的基本物理力学参数,研究包衣对棉种与有机玻璃板间的接触参数(碰撞恢复系数、静摩擦因数和滚动摩擦因数)的影响,基于逆向工程技术建立棉种离散元颗粒模型,运用响应曲面分析法建立包衣棉种种间接触参数与休止角相对误差的二阶回归模型,结合物理试验和仿真试验对仿真参数进行标定,确定包衣棉种种间碰撞恢复系数、静摩擦因数和滚动摩擦因数的最优参数组合,并利用棉花精密排种器排种试验对仿真参数进行验证。结果表明:‘新陆中67号’棉种的泊松比为0.27,剪切模量为14 MPa,包衣剂对棉种表面摩擦特性有一定影响,包衣棉种与有机玻璃之间的碰撞恢复系数、静摩擦因数和滚动摩擦因数分别为0.25、0.49和0.21,包衣棉种种间碰撞恢复系数、静摩擦因数和滚动摩擦因数分别为0.19、0.23和0.13,此最优参数组合下排种仿真试验与台架试验的合格率和漏播率相对误差均小于5%,包衣棉种离散元颗粒模型和仿真参数可用于离散元仿真模拟试验。