The distribution characteristics of the flows in the near-Earth region： TC-1 observational results

TC-1 observational results clearly indicate that the velocity of the flows in the near-Earth region is dependent on the satellite location. The flow speed decreases while satellite moves close to the Earth. The plasma flow in the region close to the Earth tends to drift into the midnight region from the dawn and dusk region while the flow in the region away from the Earth shows an opposite drift. The observational results also show that the tailward flows are mainly located in the plasma sheet boundary while the earthward flow becomes dominant in the plasma sheet. It is found that both the strong tailward and earthward flows are distributed in the region around X= -11 Re, which coincides with the trigger region of the substorm onset. Hence, it may suggest that the flows are related with the trigger of the substorm onset. In addition, the BBFs coming from the mid-tail maily distributed in the region where X〈-9R E a n d ｜Z｜ 〈 3 R E that differs from the convection.     

Braking of high-speed flows in the magnetotail: THEMIS joint observations

The motion and deceleration processes of plasma sheet high-speed flows have great significance to magnetospheric particle acceleration,magnetic field perturbation,magnetic flux transport,triggering of substorm,and the current system formation in the magnetotail.From February to April 2009,two satellites of the Time History of Events and Macroscale Interactions during Substorms mission,THA and THE,were often separated largely in Z direction,but had small X and Y separations.Such special configuration allows simultaneous observations of highspeed flows at the center and boundary of the plasma sheet.Based on selected case study and statistical analysis,it is found that for about 89%of the events we selected,the probe further away from the neutral sheet observed the high-speed flow earlier than the one close to the center,and the flow is mainly field aligned.And for about 95%events the probe further away from the neutral sheet observed higher X component of the plasma flow.With the hypothesis that parallel flow keeps the same speed during its earthward propagation while central plasma sheet stream uniformly or suddenly brakes on its way to the earth,we deduced the position where the deceleration begins to be between 13 Re and 17 Re downtail,where thenear-earth reconnection is supposed to occur.In addition,our statistical results show that dipolarization fronts observed in the central plasma sheet are more prominent than those observed in the plasma sheet boundary layer ahead of the high-speed flow.     

Continuous tailward flow in the near-Earth magnetotail observed by TC-1 satellite

On July 11, 2004, a substorm process in the period of continuous tailward flow was observed by the joint exploration of the TC-1, IMAGE and ACE satellites. The substorm observed by the TC-1 in the near-Earth has three stages: the growth phase (from 11:43 to 12:19), the pre-expansion process (from 12:19 to 12:28) and the dipolarization process. The auroral brightening was at 12:26 recorded by the FUV instrument on IMAGE, and the dipolarization occurred two minutes later. During the 45 min period of the tailward flow, the magnetotail experienced the growth phase and the pre-expansion process. When the dipolarization process began, the TC-1 entered the plasma sheet and observed a high speed earthward flow. The field-aligned tailward flow is characterized by the low temperature and high density, which is consistent with the properties of the flow from the ionosphere detected in the near-Earth magnetotail by other satellites. The tailward flow is closely related with the southward interplanetary magnetic field (IMF), and may have an important effect on the substorm.     

Statistical survey on the magnetic field in magnetotail current sheets: Cluster observations

The distribution properties of the magnetic field in magnetotail current sheets have been explored statistically with the magnetic measurement data of the Cluster mission from June to November of the years 2001–2005. It is found that, on average, the strength of the magnetic field and its B_z component in the current sheet are weaker in the region close to midnight but stronger near the dawnside and duskside flanks, which implies that, in general, a thinner current sheet occurs near midnight and thicker ones near both flanks. The occurrence of tail current sheet flapping is higher on both flanks than in the midnight region, although it is most frequent in the dawn flank. Current sheets with a negative B_z component or a strong B_y component have a higher probability of occurring at magnetic local times of 21:00–01:00, indicating that magnetic activity, e.g. magnetic reconnection and current disruption occur more frequently there. Statistically, the probability distributions of the B_y component and the tilt angle of magnetic field lines in the current sheet are approximately normal distributions, and the occurrence probability of the flattened current sheet is about one third that of the normal current sheet. The magnetic field and B_z component in the current sheet mainly vary from 1 nT to 10 nT. The B_y component in the tail central current sheet is on average twice the IMF B_y at 1 AU.     

Double Star TC-1 observation of the earthward flowing plasmoids in the near magnetotail

We analyze Double Star TC-1 magnetic field data from July to September in 2004 and find that plas-moids exist in the very near-Earth magnetotail. It is the first time that TC-1 observes the plasmoids inthe magnetotail at X > ?13 RE. According to the difference of the magnetic field structure in plasmoids,we choose two typical cases for our study: the magnetic flux rope on August 6 with the open magneticfield and the magnetic loop on September 14 with the closed magnetic field. Both of the cases are as-sociated with the high speed earthward flow and the magnetic loop is related to a strong substorm. Theions can escape from the magnetic flux rope along its open field line, but the case of the closed mag-netic loop can trap the ions. The earthward flowing plasmoids observed by TC-1 indicate that the mul-tiple X-line magnetic reconnection occurs beyond the distance of X=?10 RE from the earth.     

低温工质双相流加速压降与摩阻压降的比较

本文研究了低温工质双相流加速压降与摩阻压降的问题。用均相流模型进行了分析,另外采用Steiner对液氮的压降试验结果,设法分解出加速压降和摩阻压降两部分,并与理论分析结果进行比较。研究结果给出了热流密度、压力、质量流速、干度诸因素对压降比的影响,以及均相流模型的适用范围。     

水平管内气液两相螺旋流压降规律实验研究

在气液两相流实验装置上进行了流型和压降的实验。以空气和水为实验介质,对水平管内气液两相螺旋流的流型进行了研究。依次得到螺旋波状分层流、螺旋泡状流、螺旋弥散流三种典型的流型图像。并分析了流型、体积含气率、气液折算流速以及叶轮起旋参数等因素对气液两相螺旋流压降的影响。最后实验表明,流型是影响压降规律的主要因素,其他因素对压降的影响亦有影响。螺旋弥散流是压降梯度最小的流型。以上结果对今后相关的研究以及工程实际应用具有重要的指导意义。     

特低渗油藏渗流阻力梯度的非线性特征

根据边界层理论,运用三次函数形式对特低渗岩心试验曲线进行拟合分析,在此基础上,运用微分线性描述方法,建立考虑边界层及启动压力梯度影响的特低渗储层渗流阻力梯度的数学模型,得到渗流阻力梯度与驱替压力梯度及渗透率的关系图版.结果表明,渗流阻力梯度随驱替压力梯度增加而降低,随渗透率减小而增大,且渗透率越小,渗流阻力梯度增幅越大,其非线性变化特征越明显.     

垂直井筒气液段塞流压力梯度的简便算法

以流动机理研究为基础，应用等效段塞单元分析方法，建立了垂直气液段塞流压力梯度的计算模型，依据实验数据确定了模型中液相段塞持液率的预测方法，借用公开发表的相关实验数据对新建模型进行了验证。经对比分析认为，所提出的压力梯度计算方法不仅涉及的中间参量少、计算简便，而且对不同来源的数据适应性好、计算精度高。另外，不同液相段塞持液率相关式的计算结果相差较大，但实验条件下对压力梯度的预测值影响并不大。     

汽车消声器性能计算中的气流与温度因素

发动机排气噪声是汽车噪声中一个主要声源,消声器是控制排气噪声的一个重要方法.该文推导出两种消声单元的传递矩阵,在消声器性能计算过程中考虑气流和温度梯度的影响,并采用三维谱图方法研究气流对消声器消声性能的影响.编写了性能计算程序,计算结果与实验结果吻合较好,计算与实验精确性有待进一步提高.     

地形坡度对基流中地形Rossby波振幅的影响

 利用考虑地形作用的浅水波模式对基流中地形Rossby波振幅特征进行了数值计算.结果表明,地形坡度对地形Rossby波振幅具有增幅作用,在强基本气流中,增幅作用更明显,地形坡度的作用还使地形Rossby波最大振幅中心位置北移.     

梯度优化的多尺度视频光流估计

提出一种基于梯度优化的不同运动幅度视频图像光流估计的新算法。先用Loggabor滤波器对原视频图像进行相位、尺度滤波,再用所得的特征图像来计算时空梯度,最后根据时空梯度计算光流。该算法模型同时运用由粗到精的图像金字塔方法对视频图像分层处理。理论分析和实验结果表明,该算法适用于大幅度的视频运动光流估计,不仅能得到适合人眼视觉分辨率特性的图像,而且使时空梯度更加优化,光流计算更准确。并且在时间复杂度上与传统光流计算方法相当,在计算精度上优于Horn和Schunck、段先华等人提出的算法。     

低渗透油藏聚合物驱启动压力梯度研究

为了描述低渗透油藏聚合物驱的渗流规律及启动压力梯度特征,借鉴水驱启动压力梯度的试验测定方法,将压差-流量法和毛细管平衡法相结合,在不同储层渗透率和体系黏度下开展低渗透储层聚合物驱渗流试验;在此基础上,基于非线性渗流理论量化表征聚合物驱启动压力梯度,建立聚合物驱非线性渗流系数与体系黏度、储层渗透率和流度的量化关系。结果表明,随着储层渗透率的降低或体系黏度的增大,相同渗流速度下聚合物驱的渗流阻力增加、压力梯度增大;聚合物渗流曲线用非线性方法表征吻合较好,且随着储层渗透率降低、体系黏度增大或流度降低,聚合物驱非线性渗流系数均增大;流态图版包含对不流动区、非线性渗流区和拟线性渗流区的定量描述。     

鄂尔多斯盆地长7致密油启动压力梯度变化规律研究

针对致密油岩心驱替实验时常规压差流量法,流量和压力误差较大的问题,提出采用低压定压装置作为压力源进行驱替、光电式微流量检测计计量流量的新方法。实验结果表明:单相水启动压力梯度和束缚水状态下油启动压力梯度都随气测渗透率的降低而增大,且在相同渗透率条件下,束缚水状态下油启动压力梯度大于单相水启动压力梯度;对于储层渗透率介于(0.1~0.3)×10-3μm2的长庆油田下一步稳产致密油资源,单相水下的拟启动压力梯度平均值为0.31 MPa/m,真实启动压力梯平均值为0.18 MPa/m,启动压力梯度为渗透率大于0.3×10-3μm2的储层相应启动压力梯度的10倍以上;束缚水下的拟启动压力梯度平均值为3.19 MPa/m,真实启动压力梯平均值为0.58 MPa/m,启动压力梯度为渗透率大于0.3×10-3μm2的储层相应启动压力梯度的5倍以上,掌握致密油启动压力变化规律对于制定合理的开发技术政策有至关重要的意义。     

转动参照系中流体的压强和伯努利方程

给出了相对转动参照系静止的理想流体内部的压强及稳定流动时的伯努利方程,并应用导出的压强公式和伯努利方程求解了两个问题．     

流体在内管做行星运动的环空中流动的压力梯度

利用待定系数法对牛顿流体在内管做行星运动的环空中流动的运动方程进行了变换,得到了给定流量条件下牛顿流体在内管做行星运动的环空中流动的压力梯度计算公式.采用有限差分法对水在内管做行星运动的环空中流动的压力梯度进行了数值计算.结果表明,压力梯度随环空偏心度的增大而减小,随流量的增大而增大.     

水平管气液分层流压力梯度和含气率计算方法研究

在内径为80mm的大型多相流实验环道上，深入研究了高气相流速下气液分层流压力梯度和截面含气率特性，截面含气率采用双能伽马射线密度仅测量．通过对相间剪切应力的研究，提出应用气相动量方程计算压力梯度和界面含气率．采用FLAT、ARS、MARS 3种界面形状模型计算了水平管气液两相分层流压力梯度和截面含气率，并将计算结果与实验结果进行了对比分析,ARS和MARS模型的预测结果接近且误差小，因此推荐采用ARS或MARS模型预测高气相流速分层流压力梯度和截面含气率．     

三元流场中速度梯度方程的分析

以准正交面法求解三元流场的理论为基础,依据实际计算模型,提出了水力机械流场计算中的速度梯度方程在曲线坐标系下计算的思路,给出了计算表达式．并通过空间点源的计算实例,对数值解与解析解做了比较,证明本文所提出的计算方法是可靠的．     

致密储层垂直裂缝井压力动态特征

 针对致密储层非达西渗流规律及垂直裂缝井的特殊流动模式,采用考虑井筒存储和裂缝表皮的三线性流模型描述早、中期流动阶段及考虑启动压力梯度的有效井径模型反映晚期拟径向流阶段。通过三线性流模型和有效井径模型的优化组合,建立了致密储层垂直裂缝井不稳定渗流试井分析模型,采用最小二乘法拟合三线性流模型与有效井径模型的压力解。分析了无量纲导流系数、裂缝表皮及启动压力梯度对井壁压力及压力导数动态曲线的影响,结果表明：无量纲导流系数越大,压力降越小,从而能量损耗越小;裂缝表皮主要影响早、中期压力动态;启动压力梯度越大,后期无量纲压力增加越明显,说明渗流过程能量损失增大。     

压裂气井返排压力新模型研究

气井压裂后返排阶段压力的准确预测对于优化返排工作制度具有重要意义,目前的返排压力模型缺乏对两相返排阶段的研究,压力模型不完善。为此,根据质量守恒原理、能量守恒原理、岩石力学理论和地层渗流理论,建立了考虑裂缝闭合前后不同返排规律和压力变化规律的返排压力新模型。新模型包含单相压裂液返排和气液两相返排的不同阶段,将压裂返排过程与地层产能综合分析,最终得到从停泵返排初期直至气井稳定产气整个过程的返排压力变化规律。现场实例表明,新模型的计算结果与现场实测压力吻合较好。放喷油嘴尺寸越大、裂缝闭合时间越短,到达稳定产气阶段的时间越短,稳定产气阶段的井底压力也越低。新模型可为现场合理返排制度的确定提供理论指导。