Unsteady natural convection Couette flow of heat generating/absorbing fluid between vertical parallel plates filled with porous material

The extended Brinkman Darcy model for momentum equations and an energy equation is used to calculate the unsteady natural convection Couette flow of a viscous incompressible heat generating/absorbing fluid in a vertical channel （formed by two infinite vertical and parallel plates） filled with the fluid-saturated porous medium. The flow is triggered by the asymmetric heating and the accelerated motion of one of the bounding plates. The governing equations are simplified by the reasonable dimensionless parameters and solved analytically by the Laplace transform techniques to obtain the closed form solutions of the velocity and temperature profiles. Then, the skin friction and the rate of heat transfer are consequently derived. It is noticed that, at different sections within the vertical channel, the fluid flow and the temperature profiles increase with time, which are both higher near the moving plate. In particular, increasing the gap between the plates increases the velocity and the temperature of the fluid, however, reduces the skin friction and the rate of heat transfer.

CAD/CAE OF THE WORKING CHARACTERISTICS OF A NEW TYPE OF FLUID COUPLING SHOCK ABSORBER

For purpose of simulation of the working characteristics of a new type offluid coupling shock absorber for vibration protection of sensitive equipment, a physical model ispresented by analyzing the internal fluid dynamic phenomenon with respect to the coupling shockabsorber and implemented in MATLAB software package. Using the model it is possible to evaluate theimportance of different factors for design of the shock absorber. In the meantime, the key-modelmachine is designed for coupling dynamic test. Comparisons with experimental results confirm thevalidity of the model. So the CAD/CAE software has been developed in MATLAB for design andexperimental test of the new coupling shock absorber.

DESIGN METHOD OF MAGNETORHEOLOGICAL FLUID SHOCK ABSORBER FOR CAR SUSPENSION

The Bingham constitutive model, which is previously used in depiction of magnetorheological （MR） fluids rheological behaviors for design devices, exhibits discontinuous characteristics in representation of pre-yield behaviors and post-yield behaviors. A Biviscous constitutive model is presented to depict rheological behaviors of MR fluids and design automotive shock absorber. Quasi-static flow equations of MR fluids in annular channels are set theoretically up based on Navier-Stokes equations and several rational simplifications are made. And both flow boundary conditions and flow compatibilities conditions are established. Meantime, analytical velocity profiles of MR fluids though annular channels are obtained via solution of the quasi-static flow equations using Biviscous constitutive model. The prediction methodology of damping force offered by MR fluid shock absorber is formulated and damping performances are predicated in order to determine design parameters. MR fluid shock absorber for Mazda 323 car suspension is designed and fabricated in Chongqing University, China. Measurements from sinusoidal displacement cycle by Shanchuan Shock Absorber Ltd. of China North Industry Corporation reveal that the analytical methodology and design theory are reasonable.

Dynamical Stability of Cantilevered Pipe Conveying Fluid with Inerter-Based Dynamic Vibration Absorber

Cantilevered pipe conveying fluid may become unstable and flutter instability would occur when the velocity of the fluid flow in the pipe exceeds a critical value.In the present study,the theoretical model of a cantilevered fluid-conveying pipe attached by an inerter-based dynamic vibration absorber(IDVA)is proposed and the stability of this dynamical system is explored.Based on linear governing equations of the pipe and the IDVA,the effects of damping coefficient,weight,inerter,location and spring stiffness of the IDVAon the critical flow velocities of the pipe system is examined.It is shown that the stability of the pipe may be significantly affected by the IDVA.In many cases,the stability of the cantilevered pipe can be enhanced by designing the parameter values of the IDVA.By solving nonlinear governing equations of the dynamical system,the nonlinear oscillations of the pipe with IDVA for sufficiently high flow velocity beyond the critical value are determined,showing that the oscillation amplitudes of the pipe can also be suppressed to some extent with a suitable design of the IDVA.

Fluid structure interaction for circulation valve of hydraulic shock absorber

Based on the working principle and the damping characteristic of hydraulic shock absorber,a fluid structure interaction method was presented,which was used to analyze the microcosmic and high-frequency processing mechanism of fluid structure interaction between circulation valve and liquid of hydraulic shock absorber.The fluid mesh distortion was controlled by the CEL language,and the fluid structure interaction mathematical model was established.The finite element model was established by ANSYS CFX software and was analyzed by dynamic mesh technique.The local sensitive computational area was meshed by prismatic grid,which could reduce the negative volume problem during the simulation.The circulation valve and liquid of hydraulic shock absorber were simulated and analyzed under the condition of sinusoidal inlet velocity loads.Flow characteristic and dynamics characteristic were obtained.The pressure distribution and the displacement of circulation value were obtained,and the acceleration curve of circulation valve was simulated and analyzed.The conformity of the final simulation results with the experimental datum indicates that this method is accurate and reliable to analyze the dynamics characteristic between circulation valve and liquid of hydraulic shock absorber,which can provide a theoretical foundation for optimizing hydraulic shock absorber in the future.

可吸收止血绒S-100在骨折内固定手术患者中的应用效果

目的:分析可吸收止血绒S-100在骨折内固定手术患者中的应用效果。方法:回顾性选取2022年3月—2023年6月河南省胸科医院收治的106例骨折内固定手术患者作为研究对象。根据可吸收止血绒S-100的使用情况将其分为对照组和观察组,各53例。对照组术中采用气囊止血带止血,观察组术中采用可吸收止血绒S-100。比较两组围手术期指标,引流量及引流管拔管时间,术前及术后第3天凝血功能。结果:观察组手术时间及住院时间均短于对照组,术中出血量少于对照组,差异有统计学意义(P<0.05)。观察组术后24 h、48 h引流量少于对照组,引流管拔管时间短于对照组,差异有统计学意义(P<0.05)。术后第3天,两组凝血酶原时间(PT)、活化部分凝血活酶时间(APTT)均降低,纤维蛋白原(FIB)及D-二聚体(D-D)均明显升高,观察组PT及APTT均高于对照组,FIB及D-D均低于对照组,差异有统计学意义(P<0.05)。结论:可吸收止血绒S-100应用在骨折内固定手术中止血效果显著,能减少局部渗出,缩短引流周期,对患者凝血功能影响较小。

Application of sustainable basil seed as an eco-friendly multifunctional additive for water-based drilling fluids

Basil seed,containing anionic heteropolysaccharides in its outer pericarp,swells as gelatinous hydrocolloid when soaked in water.In this study,basil seed powder(BSP)was used as a multifunctional additive for water-based drilling fluids.The chemical composition,water absorbency,rheological properties of aqueous suspension of BSP were tested.The effect of BSP on the rheological and filtration of bentonitebased drilling fluid before and after thermal aging was investigated.The inhibition characteristics were evaluated by linear swelling,shale cuttings dispersion and shale immersion test.Lubricity improvement by BSP was measured with extreme pressure lubricity test.The results revealed that incorporation of BSP into bentonite suspension improved rheological and filtration properties effectively after thermal aging of 120℃.BSP exhibited superior inhibitive capacity to xanthan and synergistic effect with KCl.BSP could reduce friction by forming hydration layer.The nanoscale three-dimensional network structures enable BSP to maintain high water retention and absorb strongly on bentonite and metal surface,contributing to enhanced rheology,filtration,inhibition and lubrication properties.The versatile characteristic of BSP,as well as biodegradation makes it a promising additive using in high performance water-based drilling fluid and a potential alternative to conventional synthetic polymers.

A REMARK ON THE ATTRACTORS OF NON-NEWTONIAN FLUIDS

This paper corrects some mistakes in the proof of absorbing sets theorem of at-tractors of non-Newtonian fluids, and establishes again the existence of bounded absorbing sets.

针对叠加节流阀片厚度的响应面优化设计

以液压减振器的阻尼元件—叠加节流阀片为研究对象,对叠加节流阀片的厚度进行优化设计。为降低叠加节流阀片的等效应力,以其强度与刚度为约束条件,对各个叠加节流阀片厚度与直径进行优化,并进行流固耦合数值仿真,验证叠加节流阀片的三级控制要求、变形量以及等效应力。研究表明,优化后的叠加节流阀片的结构参数合理,能够更好的满足减振器的三级控制要求。

气吸双滚筒式棉花精量排种器的设计与试验

【目的】为提高气吸滚筒式排种器充种性能,降低负压风机能耗,设计了一种气吸双滚筒式排种器。【方法】理论分析排种过程中棉花种子的受力状态,利用Solidworks对排种器进行三维建模,运用流体仿真软件对3.8 mm孔径的滚筒进行内流场模拟,掌握内流场速度及压力变化的规律,对比有无内置滚筒结构对型孔处气体流速的影响。利用Design-expert 13.0软件设计了两因素五水平二次旋转正交组合试验方案,以负压和前进速度为试验因素,建立了漏播率、合格率和重播率等评价指标的响应曲面,进而对工作性能进行评价。【结果】通过优化回归方程得到最佳参数组合,并经台架试验验证。在负压为2.39 kPa、前进速度为4.55 km/h的条件下,排种器播种棉花种子的合格率为91.8%,漏播率为3.3%,重播率为4.9%。【结论】自行设计的排种器可满足棉花种子精量播种的农艺要求,显著降低风机能耗,为机械化播种提供技术性参考。

一种航天用磁性液体吸振器的减振性能研究

为抑制航天器大型柔性结构的低频振动,研究了一种基于磁性液体悬浮原理的新型吸振器。建立了该吸振器的动力学模型,推导了磁性液体悬浮力和黏性阻尼力方程。针对方程中磁性液体的界面求解问题,根据磁性液体的伯努利方程和界面方程,分析了磁性液体界面与磁场强度的关系,建立了磁性液体界面、悬浮力和黏性阻尼力的仿真方法。通过仿真和试验研究了壳体高度对磁性液体悬浮力和黏性阻尼力的影响规律,分析了仿真与试验的差异。基于铜板的自由振动试验,验证了该吸振器抑制低频自由振动的有效性。结果表明,该吸振器具有较好的线性特征,对1.1 Hz,5 mm的自由振动时间最高可缩减85%。

螺旋微肋管腔体吸热器强化换热特性研究

吸热器作为碟式太阳能聚光集热系统的核心部件,其光热转换效率的提高具有重大意义。采用实验与fluent模拟相结合的方法,探究220 mm×160 mm圆柱腔体吸热器和螺旋微肋盘管组装模型的换热特性,研究表明,1 mm直径25 mm螺距的微肋丝结构涡流和二次流形成效果较为明显,综合换热效果较好。换热实验中,微肋丝能够加强流体的扰动,有效削减流体的径向温差;70 L/h入口流量的换热温升效果较为明显。光热转换实验中,吸热器热损与入口流量呈负相关,20 L/h之后达到最低;吸热器的光热转换效率与腔体工质温差的变化呈负相关,最高可以达到68%。

30种静脉用药序贯输注组间冲管液安全剂量研究

目的测定临床常用30种静脉用药序贯输注过程中组间冲管液的安全剂量,为临床护理操作提供参考。方法选取临床上常用且能采用紫外分光光度仪测定药物吸光度的30种静脉用药作为实验对象,按照药品使用说明书将其配制成临床常用成品输液,模拟体外临床输注。输液结束时,更换与溶剂一致的0.9%氯化钠或者5%葡萄糖注射液作为冲管液,依次留取样本1 mL,共留取70个样本。利用紫外分光光度仪测定不同阶段冲管液量标本的吸光度,根据标准曲线计算浓度,当冲管液量样本浓度为0时,判定输液管内残留药液已被冲洗干净。结果30种静脉用药的冲管液体积24~65 mL,其中24~<30 mL 12种,30~<40 mL 10种,40~<50 mL 6种,50 mL 1种,65 mL 1种。22种(73.33%)药品组间冲管安全剂量在40 mL以内。结论多种静脉用药序贯输液时,当有配伍禁忌或无法确定有无配伍禁忌时,均需要使用安全剂量行组间冲管,以利于临床静脉用药安全。

磁流变液制备及其流动特性有限元仿真

基于某品牌汽车磁流变减振器的性能要求,对磁流变液的组成结构、工作原理进行研究。将表面活性剂与基础载流液充分混合均匀后,加入混合微纳米球形铁粉颗粒、触变剂、干燥剂和润滑剂,采用高速搅拌器进行机械搅拌,配置出一种性能优异的磁流变液。使用旋转黏度计检测磁流变液黏度并根据自然沉降法进行稳定性检测,结果表明零场黏度为600 mPa·s且静置6个月后沉降率为18%,具有较低的零场黏度和较高沉降稳定性能。通过建立磁流变减振器电磁阀主活塞工作简化模型,采用Fluent流动模拟仿真,得出了磁流变液压力与流速情况。其中,磁流变液在主活塞入口处的压力最大,且随着磁流变液在通道的流动逐渐降低,在出口处达到最低值;而流速则是通道中心大于通道两壁。最后探究了磁流变液流动压力与流速产生变化的原因,为研发性能优越的智能磁流变器件提供了有效参考,具有实际工程应用价值。

PML Absorbing Boundary Condition for Seismic Numerical Modeling by Convolutional Differentiator in Fluid-Saturated Porous Media

The perfectly matched layer（PML） was first introduced by Berenger as an absorbing boundary condition for electromagnetic wave propagation.In this article,a method is developed to ex-tend the PML to simulating seismic wave propagation in fluid-saturated porous medium.This non-physical boundary is used at the computational edge of a Forsyte polynomial convolutional differenti-ator（FPCD） algorithm as an absorbing boundary condition to truncate unbounded media.The incor-poration of PML in Biot＇s equations is given.Numerical results show that the PML absorbing bound-ary condition attenuates the outgoing waves effectively and eliminates the reflections adequately.

汽车磁流变减振器设计原理与实验测试

根据磁流变体的滨汉塑性模型描述 ,提出了混合工作模式的汽车磁流变减振器的设计原理 ,按照长安微型汽车的技术和磁流变体的性能设计和制作了微型汽车磁流变减振器 ,并根据长安微型汽车前悬架减振器的技术条件对此进行了实验测试。实验结果表明 ,提出的设计原理是可行的 ,对设计特殊阻尼特性的磁流变减振器有一定的指导意义。

汽车磁流变减振器设计准则探讨

提出了微型汽车磁流变减振器的设计准则 ,建立了磁流变减振器的理论分析模型来预估减振器阻尼力的大小。测试结果表明 ,减振器的阻尼力由粘性阻尼力和磁场阻尼力组成 ,随着磁场强度的增加 ,减振器的阻尼力也增大 ,基本上符合理论预估值 ,说明所建立的理论分析模型是可行的。

基于Poiseuille流动的汽车磁流变减振器分析与测试

用牛顿流体模型和滨汉流体模型 ,对基于Poiseuille流动的汽车磁流变减振器进行了分析 ,设计制作了微型汽车磁流变减振器 ,并对此进行了测试 ,测试结果表明 :所提出的分析方法是可行的 。

高稳定磁流变液的制备和性能分析

采用X—ray衍射、扫描电子显微镜及振动样品磁强计等表征手段，研究通过气体渗氮在羰基铁颗粒表面形成的氮化物薄层，分析了羰基铁颗粒氮化后的形貌、抗氧化性能和磁性能。将氮化后的羰基铁粉加入高分散性添加剂，用高速分散的方法制备了高稳定磁流变液，分析了该磁流变液的磁性能、流变性能和抗沉降性能，并研究了该磁流变液在器件应用中的稳定性。结果表明：采用该工艺制备的磁流变液的摩擦系数降低至0．054，3个月沉降〈10％，零场黏度≤1．0Pa·s，最大剪切应力≥60kPa，在20～125℃范围内，阻尼器阻尼力最大衰减率14．3％。氮化提高了磁流变液悬浮相的表面抗磨、耐蚀性能，改善了磁流变液抗沉降团聚稳定性。

基于混合模式的汽车磁流变减振器阻尼特性分析与测试

根据牛顿流体模型和滨汉塑性流体模型 ,分别对混合工作模式的汽车磁流变减振器进行了理论分析研究。按照长安微型汽车的技术要求 ,设计和制作了汽车磁流变减振器 ,并对此进行了试验测试。试验结果表明 ,应用所提出的理论分析模型是可行的 ,对设计特殊阻尼特性的磁流变减振器有一定的指导意义。