等离子体片边界层电磁不稳定性引起的波－粒输运

采用二级理论研究了在等离子体片边界层电磁不稳定性引起的波-粒输运．结果表明，束流离子被热化和各向同性化，离子最大加热率峰值与电磁不稳定性最大增长率峰值出现在大致相同的方向上．被热化和各向同性化的束流离子可能是等离子体片中心区热离子的来源．这些结果对于理解等离子体片边界层的输运过程具有重要的意义．     

关于震源体物理意义的实验研究

运用固体传压介质岩石三轴试验装置模拟震源失稳振动过程，采取多点布设电阻应变片的方法，对试件突发失稳振动行为及其在试件－压机系统中的传播过程进行观测，测试结果为：应力振动的初动半周期平均约为０．１１ｍｓ，与岩石类型，周压及应力降等因素无关，振幅逐渐衰减；在试件－压机系统中，振动波从试件错动面处向外传播，其速度约为３．３０ｍ／ｍｓ；在失稳初动半周期内，振动波向试件以上传播的距离为３６３ｍｍ，传播的范围     

大气重力波产生的大尺度赤道电离层扰动

本文研究了大气重力波产生的大尺度赤道电离层扰动的性质．当重力波的传播方向与磁场方向倾斜相交时，重力波在Ｆ区产生行进电离层扰动．当重力波垂直于磁场传播时，能触发等离子体Ｒａｙｌｅｉｇｈ－Ｔａｙｌｏｒ不稳定性，形成大尺度赤道扩展Ｆ不均匀体．重力波引起的扩展Ｆ主要出现于晚上，行进电离层扰动则可能出现于任何时间．本文建立了行进电离层扰动和大尺度赤道扩展Ｆ的统一理论模型，深入全面地揭示了电离层扰动的性质．     

地球磁层顶的漂移动力学Alfvn波不稳定性及其反常输运效应

本文用回旋动力学研究了磁层顶等离子体低频漂移动力学不稳定性.在β≥1附近发现两支不稳定的漂移动力学Alfvèn模(DKA).它们可在▽T(∥-▽n)(?)0时激发,速度剪切提供主要的自由能源.两支DKA均具有非零的(δE_y,δE_∥)和(δB_x,δB_∥).在湍动的非线性饱和状态下,δB_x的起伏可导致很强的反常输运,当|δB_x|=1nT时,D_⊥可达到10~9m~2/s的数量级.因此,DKA可能在太阳风-磁层耦合过程中起重要作用.     

Instability of plane parallel shear flow (toward a mechanistic picture of how it works)

This paper reviews work done over the last twelve years on wave overreflection in shear flows, and on the development of a mechanical picture of how overreflection and instability work. It is argued that the wave geometry of a flow configuration is the primary determinant of its stability. It is also argued that the primary mechanism for wave amplification is the Orr mechanism.     

Three-Dimensional Instability of Flow Around Two Circular Cylinders in Tandem Arrangement

The spatial evolution of vortices and transition to three-dimensionality in the wake of two circular cylinders in tandem arrangement have been numerically studied. An improved virtual body method developed from the virtual boundary method is used here. A Reynolds number range between 220 and 270 has been considered, and the spacing between two cylinders is selected as L/D = 3 and L/D = 3.5. When L/D = 3, the secondary vortices of Mode-A are seen to appear at Re = 240 and persist over the range of the Reynolds number of 240 - 270. When L/D = 3.5, the similar critical Reynolds number has been found at Re = 250. No obvious discontinuity has been found in the Strouhal-Reynolds number relationship, and this is different from three-dimensional flow around a single cylinder at the critical Reynolds number. The spanwise wavelength is about four times the diameter of the cylinder, and it is the characteristic wavelength for ModeA instability. This paper can give some foremost insight into the three-dimensional instability of flow by complicated geometrical configuration.     

高密度油基钻井液体系优选及其在页岩气水平井的应用

为解决威远-长宁地区泥页岩地层井壁失稳、井眼清洁等问题,通过试验优选出适用于高密度油基钻井液体系使用的乳化剂、有机土和降滤失剂等处理剂;通过正交试验设计确定出一种适用于威远-长宁地区页岩气长短水平井使用的高密度油基钻井液体系。其最终配方比例为：5%主乳化剂+2.0%辅乳化剂+2.0%润湿剂+5%降滤失剂+2%有机土+3%CaO、油水比80∶20（25%CaCl2水溶液）。对其性能进行评价,结果表明该体系可加重密度至2.2 g/cm3,加重后性能稳定,可抗水污染达9%,抗岩屑污染至18%,具有较好的抗污染性能,页岩回收率95.11%,抑制性能好,乳化性能稳定。现场应用表明：高密度油基钻井液满足威204H378井页岩气水平井钻井施工需求,全井性能良好,无井漏,井径规则,测井未见异常,顺利完钻。     

块系岩体滑移失稳中低摩擦效应的理论与试验研究

深部岩体具有块状层次结构,深部动载造成岩块发生相互间的振动脱离产生低摩擦效应,从而极易诱发原先处于平衡状态的岩体的动力变形破坏。在前人研究基础上,将块系岩体振动简化为等效质量-黏弹性模型,引入岩石摩擦滑移速率弱化模式,最终得到块系岩体滑移失稳计算模型。通过计算分析块系岩体自身特性及外荷载特性对岩块间低摩擦效应的影响。理论计算表明：水平静力及外扰动保持不变,增大岩块间弹性系数或者减小黏性系数,更容易引发岩体低摩擦滑移。随着冲击扰动、水平拉力幅值的增加,岩块的水平残余位移量值增加,当它们幅值超过一临界值时,岩块发生自持续滑移失稳运动。冲击扰动诱发岩块间不可逆位移、动力滑移失稳的临界能量与剪切力水平密切相关,在较大的剪切内力条件下,极其微弱的动力扰动即可诱发较大的岩块间不可逆位移甚至岩块的动力滑移失稳,随着剪切内力的减小,诱发岩块滑移失稳的能量阈值不断增大,当剪切内力低于岩块动摩擦强度时,单次冲击扰动只能诱发岩块间的不可逆位移。初步开展扰动诱发含初应力紫砂岩块体滑移试验,试验结果与理论计算基本符合,证明该模型的可行性。     

华南暴雨中尺度对流系统的形成及湿位涡分析

利用MM5模式对发生在1998年5月23～24日华南暴雨和中尺度对流系统(Mesoscale Convective System,简称MCS)模拟的模式输出资料,根据湿位涡守恒原理和倾斜涡度发展理论分析了暴雨和MCS形成和发展的原因.结果表明,暴雨和MCS发生在倾斜湿等熵面具有弱对流稳定性的下陷区,沿湿等熵面下滑的冷空气与倾斜上升并具有较强对流有效位能的暖湿空气在下陷区会合的过程中经历了对流稳定性减小的过程,导致暴雨和MCS发生发展区域有气旋性的涡旋发展.对流发展区域的上空满足条件对称不稳定发生的条件,MCS中上升气流呈倾斜状态.由于湿等熵面倾斜,在暴雨和MCS的发展过程中,水平风垂直切变和湿斜压度的增大也有利于涡旋的发展,使暴雨和MCS得以维持.最后,给出了华南地区湿等熵面上暴雨和MCS发生发展的一个物理概念模型.     

Frost weathering and rockwall erosion in the southeastern Swiss Alps: Long-term (1994–2006) observations

Rates and processes of frost weathering in the Alps were investigated by visual observations of intensively shattered rocks, continuous monitoring of frost wedging and rock temperatures in bedrock and measurements of rockfall activity. Rapid frost weathering of hard-intact rocks occurs along lakes and streams where seasonal freezing promotes ice segregation in the rock. Otherwise, rocks require pre-existing weakness or a long exposure period for intensively shattered. Automated monitoring shows that crack opening occurs at three scales, including small opening accompanying short-term frost cycles, slightly larger movements during seasonal freezing and occasional large opening originating from refreezing of snow-melt water during seasonal thawing. The opening events require at least partial water saturation in the crack. The repetition of crack opening (frost wedging) results in permanent opening and finally debris dislocation. Debris collections below fractured rockwalls show that pebble falls occur at an average rate of about 0.1 mm a^− 1 with significant spatial and inter-annual variations. Occasional large boulder falls significantly raise the rockwall erosion rates, controlled by such factors as the joint distribution in the bedrock, repetition of annual freeze–thaw cycles and extraordinary summer thaw.