A 2D coupled hydro-thermal model for the combined finite-discrete element method

Based on the combined finite-discrete element method (FDEM), a two-dimensional coupled hydro-thermal model is proposed. This model can simulate fluid flow and heat transfer in rock masses with arbitrary complex fracture networks. The model consists of three parts: a heat conduction model of the rock matrix, a heat-transfer model of the fluid in the fracture (including the heat conduction and convection of fluid), and a heat exchange model between the fluid and rock at the fracture surface. Three examples with analytical solutions are given to verify the correctness of the coupled model. Finally, the coupled model is applied to hydro-thermal coupling simulations of a rock mass with a fracture network. The temperature field evolution, the effect of thermal conductivity of the rock matrix thermal conductivity and the fracture aperture on the outlet temperature are studied. The coupled model presented in this paper will enable the application of FDEM to study rock rupture driven by the effect of hydro-thermo-mechanical coupling in geomaterials such as in geothermal systems, petroleum engineering, environmental engineering and nuclear waste geological storage.

     

深海技术装备公共研发平台的建设与思考

建设功能齐全、能够服务于海洋探测技术的公共研发平台是推动我国海洋科学研究、海洋技术装备研发和成果转化的重要支撑。基于此,当前国家深海基地管理中心已开展集装备研发制造、性能测试、规范化海试、技术咨询与培训等功能一体化的深海技术装备公共研发平台的建设工作。本研究以深海技术装备公共研发平台为例,介绍平台在硬件设施建设的基本情况,阐述了平台运行管理制度的建设情况,论述了平台建设过程中的经验和不足之处,以期为其他公共研发平台的建设工作提供有益借鉴和经验。     

基于探空数据的南海表面波导统计特征研究

Based on the global position system(GPS) radiosonde data near the sea surface, the surface duct characteristics over the South China Sea(SCS) were statistically analyzed. The annual surface duct occurrence over the SCS was about 64%. Of the observed surface ducts, duct heights mainly distributed between 18 and 42 m, with M slopes in the range of –0.3 to –0.2 M units/m. Those ducts accounted for about 80% of the ducting cases. For the total profiles, the duct occurrences in a day changed slowly and were more than 60% in all times. The surface ducts formed more easily in the daytime than in the nighttime and most of the duct height were at bellow about 32 m.Additionally, The seasonal variation of the SCS ducts appeared to be evident, except that the mean duct thickness was almost constant, about 33 m for all seasons. The highest occurrence was about 71% in the autumn, followed by in the summer, spring and winter. In spring, their top-height existed more often at a height of more than 48 m.Their mean duct strength became stronger trend from spring to winter, with the M-slope in the range between–0.26 and –0.18 M units/m. Those results agreed well with other studies, provided considering the data resolution.The statistical analysis was reliable and gave the duct estimation for the SCS. Such duct climatology not only has important implications for communication systems and the reliability of the radar observation, but also can provide useful information to improve the accuracy of the meteorological radar measurements.     

Soil CO2 efflux along an elevation gradient in Qinghai spruce forests in the upper reaches of the Heihe River,northwest China

This study was conducted in six plots along an elevation gradient in the Qinghai spruce (Picea crassifolia Kom.) forest ecosystem of the Qilian Mountains, northwest China. Soil CO₂ efflux over bare soil (R _s) and moss covered soil (R _s+m) were investigated from June to September in 2010 and 2011 by means of an automated soil CO₂ flux system (LI-8100). The results showed that R _s ranged from 1.51 to 3.96 (mean 2.64 ± 0.72) μmol m^?2 s^?1 for 2010, and from 1.41 to 4.09 (mean 2.55 ± 0.70) μmol m^?2 s^?1 for 2011. The daily change trend of R _s resembled that of air temperature (T _a), and there was a hysteresis between R _s and soil temperature (T _s). The seasonal variations of R _s at lowlands (i.e., Plot 1, Plot 2 and Plot 3) were driven by soil moisture and temperature (T _a and T _s), while that at highlands (i.e., Plot 4, Plot 5 and Plot 6) were obviously affected by temperature. There were higher values at Plot 2 and Plot 6, which were caused by the interaction between soil moisture and temperature. In addition, soil CO₂ efflux over moss covered soil (R _s+m) was 8.83 % less than that over bare soil (R _s), indicating that moss was another factor affecting R _s. It was concluded that R _s had temporal and spatial variations and was mainly controlled by temperature and soil moisture; the main determinants differed at different elevations; moss could reduce R _s.     

加拿大海盆东南部锚定观测双扩散阶梯的时间演化研究

加拿大海盆上层,分布着高温高盐的大西洋水和相对低温低盐的盐跃层下部水,两水团之间形成一系列的双扩散阶梯。通过分析2005年8月-2011年8月期间的锚定潜标数据,对双扩散阶梯和这两种水团之间的相互作用进行研究。基于固定盐度范围的方法,在盐度廓线中识别阶梯结构,在盐度34.45~34.83范围内,获取18个阶梯结构,并研究阶梯的参数。发现双扩散阶梯的位温主要受与其接近的水团的影响,同时也受其相邻的阶梯生成或消亡的影响,大西洋水对其上方的双扩散阶梯和盐跃层下部水起到加热作用;而盐跃层下部水的深度变化主导着大西洋水和双扩散阶梯的深度变化。两个相邻的阶梯具有一致的位温和深度变化趋势。通过经验公式,估计大西洋水通过双扩散阶梯向上传输的热通量为0.05~0.6 W/m2,且由下至上呈现逐渐增大的趋势。最后,估算由双扩散造成的垂向涡扩散系数为3×10-6~3.3×10-5 m2/s,且由下至上呈现逐渐减小的趋势。     

嫦娥一号绕月探测卫星精密定轨实现

利用最新的月球重力场模型GL0660b对嫦娥三号探测器定轨的影响进行分析,并与LP150Q和SGM150模型进行了比较。首先计算了三个重力场模型的功率谱,分析了系数阶方差和误差阶方差的性质,GL0660b大大提升了月球重力场模型的阶数和解算精度;然后讨论了各模型在月球外部空间不同高度处截断到不同阶次的重力异常分布。利用这三个重力场模型对嫦娥三号环月期间的轨道进行解算,计算结果表明,利用GL0660b模型截断至150阶次,100 km×100 km轨道重叠弧段精度约为22 m,和LP150Q,SGM150全阶次模型精度相当;对于100 km×15 km轨道,GL0660b模型截断至360阶次,重叠弧段精度约为21 m,优于LP150Q和SGM150计算结果。     

峡东地区的“三峡奇石”——沉积结核

峡东地区大量发现的具有极大观赏价值的三峡奇石,实际上是夹持在沉积岩中的同生大型钙(硅)质沉积结核.通过对这些奇石野外特征、内部组成、形成环境等方面的研究,表明它们应该是形成于强还原环境中陆棚浅海一滞流(海湾)盆地,稳定水动力条件下的产物.本文借鉴“人工合成锰矿物实验及其产物”报道的经验和“晶体成核理论”以及国外有关学者的近期研究见解,全面深入地分析、讨论了该类罕见的同生钙质结核的形成机理.     

东北太平洋Explorer Ridge热液羽状流位温浊度异常和物质能量通量估算

深海热液流体与周围海水之间存在明显的物理和化学差异,通过检测海水的位温浊度异常是探测深海热液活动的重要手段之一。本文采用"海底火山带项目（Submarine Ring of Fire 2002）"拖曳式温盐深测量仪数据资料,研究了东北太平洋Explorer Ridge热液场的水文特征及物质能量通量的释放。结果表明Explorer Ridge热液场热液羽状流中性浮力层所在深度范围约为1 600~1 900 m,距离海底的高度约为200 m,最大位温、盐度和浊度异常分别为0.04℃、0.004和0.18 NTU;中性浮力层热液羽状流帽呈椭圆结构,其长轴与洋中脊线重合,羽状流帽总面积约为27 km2;热液羽状流在中性层范围内存在明显的分层现象,通过经验公式计算得到Explorer Ridge热液场观测范围内热液喷口的总的浮力通量为6.19×10-2 m4/s3,平均值为2.063×10-2 m4/s3;总的体积通量为9.884×10-2 m3/s,平均值为3.295×10-2 m3/s;总的热通量为194.9 MW,平均值为64.967 MW。     

夏季江南地区暖区暴雨的统计分析

本文首先给出江南地区暖区暴雨的定义,并按天气形势将其分为暖切变型、冷锋锋前型、副热带高压(以下简称副高)型和强西南急流型四类。然后利用2010—2016年5—9月常规和自动站逐时降水等非常规观测资料统计暖区暴雨的时空分布特征和降水性质等,并对暖区暴雨的形成原因进行初步分析。最后利用NCEP FNL全球分析资料,基于中尺度分析技术给出四类暖区暴雨的系统配置:(1)四类暖区暴雨均为分散性局地降水,降水多发生于山区、平原和湖泊交界处等不均匀下垫面附近。其中,暖切变型降水范围广、强度最大、极端性最明显且主要位于江南中西部;冷锋锋前型降水集中、强度较大且具有一定极端性,主要位于江南中部;副高型降水强度较弱,主要位于江南中东部;强西南急流主要位于江南西部。(2)暖切变型和强西南急流型以夜间降水为主,副高型降水集中在午后,冷锋锋前型降水日变化不明显。(3)暖区暴雨由稳定性和对流性降水共同组成且降水量越大,降水对流性越明显。(4)在低层高湿、不稳定能量积聚等有利背景下,暖切变型、冷锋型和副高型暖区降水多由边界层(地面)中尺度辐合线配合高低空急流耦合产生,强西南急流型一般形成于低空急流上的中尺度风速脉动及地面辐合线附近,且低空急流越强,暴雨强度越大。(5)暖切变型和冷锋型暖区暴雨的落区分别位于低层850hPa暖切变以南和地面锋前的显著湿区内,副高型和强西南急流型的暴雨落区分别位于副高内和强低空急流出口区左前侧的水汽充沛且大气层结不稳定区内。四类暖区暴雨常表现为长生命史的移动型中尺度雨团途经山区或河流湖泊等不均匀下垫面时,强度增大、移速减慢,形成暖区局地强降水。     

A Method for Calculating Bottom Backscattering Strength Using Omnidirectional Projector and Omnidirectional Hydrophone

A method of obtaining bottom backscattering strength by employing an omnidirectional projector and omnidirectional hydrophone is proposed. The backscattering strength is extracted from monostatic backscattering data. The method was adopted in an experiment conducted in the South Yellow Sea of China. The seafloor surface was relatively smooth and covered by a small quantity of shell fragments, as observed through a digital camera system. Sampling data showed that the main component of the sediment at this experimental site was fine sand. In this paper, we detail the calculation method. Preliminary results of backscattering strength as a function of grazing angle(20?–70?) in the frequency range of 6–24 kHz are presented. The measured backscattering strength increased with the grazing angle and changed more rapidly at large grazing angles(60?–70?). A comparison of the data at different frequencies reveals that the measured backscattering strength substantially rises with the increase of acoustic frequency. A fitting curve of Lambert's law against the measured data shows that the backscattering strength deviates from Lambert's law at large grazing angles.