An extended social force model on unidirectional flow considering psychological and behavioral impacts of hazard source

An accurate assessment of the evacuation efficiency in case of disasters is of vital importance to the safety design of buildings and street blocks.Hazard sources not only physically but psychologically affect the pedestrians,which may further alter their behavioral patterns.This effect is especially significant in narrow spaces,such as corridors and alleys.This study aims to integrate a non-spreading hazard source into the social force model following the results from a previous experiment and simulation,and to simulate unidirectional pedestrian flows over various crowd densities and clarity–intensity properties of the hazard source.The integration include a virtual repulsion force from the hazard source and a decay on the social force term.The simulations reveal(i)that the hazard source creates virtual bottlenecks that suppress the flow,(ii)that the inter-pedestrian push forms a stabilisation phase on the flow-density curve within medium-to-high densities,and(iii)that the pedestrians are prone to a less orderly and stable pattern of movement in low clarity–intensity scenarios,possibly with lateral collisions passing the hazard source.

A simple method for solving unidirectional methane gas flow in coal seam based on similarity solution

The equation used to model the unidirectional flow of methane gas in coal seams is usually formulated as a nonlinear partial differential equation, which needs to be solved numerically with a computer program.Nevertheless, for people without access to the computer program, the conventional numerical method may be inconvenient. Thus, the objective here is to seek some method simpler than the conventional one for solving the flow problem. A commonly used model of the unidirectional methane gas flow is considered, where the methane adsorption is described by the Langmuir isotherm and the free gas is treated as real gas. By introducing the similarity solution, a simple method for solving the flow model is proposed, which can be done on a hand calculator. It is shown by two examples that the gas pressure profile obtained by the proposed method agrees well with the direct numerical solution of the flow model.

Unsteady unidirectional micropolar fluid flow

This paper considers the unsteady unidirectional flow of a micropolar fluid, produced by the sudden application of an arbitrary time dependent pressure gradient, between two parallel plates. The no-slip and the no-spin boundary conditions are used. Exact solutions for the velocity and microrotation distributions are obtained based on the use of the complex inversion formula of Laplace transform. The solution of the problem is also considered if the upper boundary of the flow is a free surface. The particular cases of a constant and a harmonically oscillating pressure gradient are then examined and some numerical results are illustrated graphically.

A New D-GCL for Unidirectional Motion with Large Displacement

Numerical simulations of unsteady flow problems with moving boundaries commonly require the use of geometric conservation law(GCL).However,in cases of unidirectional large mesh deformation,the cumulative error caused by the discrete procedure in GCL can significantly increase,and a direct consequence is that the calculated cell volume may become negative.To control the cumulative error,a new discrete GCL(D-GCL)is proposed.Unlike the original D-GCL,the proposed method uses the control volume analytically evaluated according to the grid motion at the time level n,instead of using the calculated value from the D-GCL itself.Error analysis indicates that the truncation error of the numerical scheme is guaranteed to be the same order as that obtained from the original D-GCL,while the accumulated error is greatly reduced.For validation,two challenging large deformation cases including a rotating circular cylinder case and a descending GAW-(1)two-element airfoil case are selected to be investigated.Good agreements are found between the calculated results and some other literature data,demonstrating the feasibility of the proposed D-GCL for unidirectional motions with large displacements.

不锈钢细长管内表面卧式单向旋转磨粒流加工研究

以304不锈钢细长管为研究对象,采用卧式单向旋转磨粒流加工技术对细长管内表面进行加工。基于FLUENT仿真软件,探究不同流道形状和不同粘度磨料对磨粒流加工效果的影响,设计正交实验研究工件转速、磨粒目数、磨粒浓度和加工次数对表面粗糙度下降率以及沿细长管长度方向加工均匀性的影响。结果表明,增加加工次数和给细长管施加旋转运动,可以提高细长管沿长度方向的加工均匀性;加工次数对细长管表面粗糙度下降率影响最大,工件转速对细长管沿长度方向的加工均匀性影响最大。经卧式单向旋转磨粒流加工后,细长管内表面的表面粗糙度由Ra 1.57μm降到Ra 0.7μm,表面粗糙度下降率达到53.2%,进出口表面粗糙度下降率差值为1.67%。

Solid particle size characterization by a high-frequency collision response in pneumatic particulate flow

A novel triaxial vibration method is developed for the real-time characterization of the solid particle size distribution(PsD)in pneumatic particulate flow,which is critical for chemical industry.In this work,the particle-wall collision and friction behaviours were analysed by the time-domain statistical and timefrequency joint methods to narrow the high-frequency response range by the initial experiment of free fall for a single particle,interparticle,and multiple particles.Subsequently,verification experiments of PSD characterization in pneumatic flow were performed.First,the quantitative triaxial energy response model that considers the particle size,shape,and mass factors were established.Second,a good agreement of the particle number identification was found between the triaxial vibration energy and mean particle size of 150-550μm.Moreover,the performance with the best accuracy was focused on a range of 42-43 kHz in the x-axis and z-axis and 36.8-38.8 kHz in the y-axis.Finally,the individual particle energy was inversely analysed by the triaxial vibration response within the optimized frequency bands,and the PSD was characterized in real-time by a low error rate,that is,5.2% from the XZ-axis direction of sand(42-43 kHz)and 5.6% from the XYZ-axis of glass(30.9-33.9 kHz,46.2-47.2 kHz,38.3-41.3 kHz for each axis response).Therefore,this research complements the existing approaches for PsD characterization in particulate multiphase flow.

基于流固耦合的航空发动机滑动轴承性能分析

以某型航空发动机齿轮传动系统所使用的滑动轴承为研究对象,基于单向流固耦合方法,采用Mixture多相流模型,对滑动轴承内的油膜进行仿真分析,并将求解后的油膜压力加载至轴瓦结构内表面进行静态分析,研究不同入口压力、不同转子转速以及不同润滑油黏性系数对油膜压力和轴瓦变形量的具体影响。结果表明:入口压力在20000 Pa到80000 Pa的变化范围内对油膜压力和轴瓦变形量的影响不显著;随着转子转速由400 r/min逐步提升至1000 r/min,油膜压力和轴瓦变形量均呈现显著的增长趋势,油膜最大压力平均增长率为164.88%,轴瓦最大变形量平均增长率为171.83%;此外,润滑油黏性系数由0.02 Pa·s增加到0.08 Pa·s时,油膜压力和轴瓦变形量也随之显著增大,最大平均增长率分别达到293.49%和296.55%;相较于转速的影响,润滑油黏性系数对滑动轴承油膜压力及轴瓦变形量的影响更大。

Marangoni Bifurcation Flow in a Microchannel T-Junction and Its Micropumping Effect: A Computational Study

We discuss a bifurcation phenomenon of Marangoni flow in a microchannel T-junction and its novel unidirectional pumping effect.The T-junction is formed by a main channel connected with a liquid reservoir and a side channel outlet to the atmosphere.A volatizing meniscus is formed in the side channel and Marangoni convections are generated due to the non-uniform evaporation on the meniscus.It is found for weak evaporations (Ma < 270) the Marangoni convections are symmetrical.However,for intense evaporations (Ma > 270),the initial inward symmetrical Marangoni convection becomes unstable and converted into one single vortex flow.Moreover,the single vortex induces a steady unidirectional flow in the main channel,acting like a pump.

穿河输流管道自埋特性试验研究

针对穿河输流管道易受水流冲刷破坏,导致输运介质泄露的问题,通过试验研究穿河输流管道自埋特性,观测了管道自埋过程和地形剖面特征,分析了管道自埋程度的影响因素。结果表明,在一定水力条件下,当穿河管道具有一定的初始嵌入度时,管道底部河床泥沙不会冲穿,管道反被泥沙掩埋,具有明显的自埋特性,穿河输流管道前后掩埋斜坡坡度均趋于稳定值;管后相对掩埋距离L/D随弗劳德数Fr增大而增大,随初始嵌入度e/D增大而减小。

大直径吸力桶基础水流局部冲刷数值模拟研究

基于福建省某海域项目典型海域水文地质资料,本文采用Flow 3D软件开展大直径吸力桶基础冲刷数值模拟,研究了不同尺寸比、不同桶径、水流流速对吸力桶基础冲刷特性的影响。结果表明:不同工况下吸力桶基础冲刷发展阶段类似,但是受水流影响。当水流流速v<2 m/s时,冲刷发展阶段可分为:快速冲刷-缓慢冲刷-冲刷平衡;当水流流速v≥2 m/s时,冲刷发展阶段可分为:快速冲刷-波动冲刷-冲刷平衡。并且桶基冲刷坑深度跟水流、桶径、尺寸比成正比。在水流作用下不同工况的吸力桶基础冲刷深度与时间具有较强的函数关系,据此可为实际工程提供参考。

Effect of Fluidic Diode on Performance of Unidirectional Impulse Turbine

A pair of unidirectional turbines(UT)can operate in oscillatory airflow without additional units.However,this arrangement suffers from poor flow rectification.A fluidic diode(FD)offers variable hydrodynamic resistance based on the flow direction,and this can be coupled with UT to improve flow rectification.In this work,a numerical investigation on the effect of FD with UT is presented using the commercial fluid dynamics software ANSYS Fluent 16.1 with k-ωSST turbulence closure model.Periodic domains of UT and FD are numerically validated individually with experimental results.Later,both are coupled to obtain the combined effect,and these results are compared with the analytical approach.It was observed that coupling FD with UT improved the unit's performance at the lower flow coefficient(<1),but its performance decreased as the flow coefficient increased.Due to the diode's presence,fluid leaving the turbine experiences higher resistance at a higher flow coefficient,which decreases the overall performance of the combined unit.

基于Crank-Nicolson差分方法的煤层瓦斯渗流解算

煤矿瓦斯抽采和自然放散过程中,瓦斯在煤层中的运移以Darcy渗流为主,吸附作用导致渗流控制方程变得较为复杂,不得不进行大幅简化。基于渗流理论,推导得出各种坐标系下标准形式的煤层中瓦斯Darcy渗流控制方程。针对煤壁突然暴露后瓦斯单向流动的问题,在不进行过多简化的前提下,利用Crank-Nicolson差分方法推导得出无条件稳定的、具有二阶精度的离散化表征的渗流控制有限差分方程。利用Python语言的SciPy包,选择用于非线性方程组求解的Powell混合法的变体,通过编程实现了对所构建差分方程的数值求解。解算得出不同时刻、距煤壁不同位置的瓦斯含量和瓦斯压力与距离都呈反正切函数关系,给出了在任意位置、不同时间的瓦斯含量计算的综合拟合公式;同时得出煤壁瓦斯涌出速率随时间呈幂函数关系下降的表达式。

基于海洋捕食者算法的波浪能转换装置模型预测控制

该文提出一种基于智能海洋捕食者算法的模型预测控制策略,实现了波浪能转换装置的动态最大能量捕获。提出的模型预测控制策略利用海洋捕食者算法来获取最优控制力,并采用非线性限制来控制功率的单向流动。通过相应的对比分析验证了海洋捕食者算法的优化准确性和快速收敛性。该方法还利用控制域来处理最优控制变量以便在算法的计算负担和优化准确度之间进行平衡。所提出的方法证明在处理多维的波浪能转换系统方面,特别是系统的非凸和非线性限制问题,具有较好的利用价值。仿真与实验结果证明提出的方法能较好地提高波浪能转换装置的输出功率,并满足典型海域工况下的实时需求。

药厂孵化室的设计与施工

讲述药厂孵化室的两种设计方案,着重的解析非常规设计的原因和观点以及此方案的安装施工,希望可以为以后类似项目提供参考。

Mechanical stirring for highly efficient gas injection refining

In gas injection refining processes,wide dispersion of small bubbles in the bath is indispensable for high refining efficiency.Eccentric mechanical stirring with unidirectional impeller rotation was tested using a water model for pursuing better bubble disintegration and dispersion.Effects of various factors on bubble disintegration and dispersion were investigated.These factors were stirring mode,eccentricity and rotation speed,nozzle structure,nozzle immersion depth,and gas flow rate.Gas injection from a nozzle at the end of the impeller shaft and from an immersed lance was studied.Under eccentric stirring,a vortex was formed away from the shaft.Small bubbles were produced in the strong turbulence or high shear stress field near the rotating impeller and moved in the direction to the vortex keeping up with the macroscopic flow induced by the mechanical stirring.Thus small bubbles could disperse widely in the bath under eccentric stirring with unidirectional rotation.

不同纤维堆积状态下饱和渗透率实验研究

通过调节压力控制纤维体积分数,用单向饱和流动法对纤维层厚度方向的饱和渗透率进行了测定。考察了纤维体积分数随压力的变化规律,并分别研究了纤维体积分数、纤维层数、铺层方式和纤维种类对渗透率的影响。结果表明,当纤维体积分数超过某临界值后其值随压力增大的幅度减小。单向和正交铺层时层数变化对渗透率没有影响,而平纹布渗透率随着纤维层数的增加而减小。此外,纤维种类的改变对渗透率有明显影响。

Study on Various Rectifiers for Fan-Filter Units

The face velocities of the high efficiency particulate air filters and the ultra low penetration airfilters in fan filter units (FFUs) have large relative standard deviation and turbulivity. It seriously affects the unidirectivity of the flow in the unidirectional flow clean zone and cleanroom. The cross contamination in this kind of unidirectional flow area is hardly controlled. It is significant to find optional method for keeping the face velocity uniformity of FFU and reducing the face velocity turbulivity of FFU, furthermore, to keep the cleanliness level under FFUs. The normal and easy method is to add flow rectifiers under filters. FFUs with various flow rectifiers have been tested. The uniformity and turbulivity of facevelocity under the FFU are presented in this paper. The influence of the facevelocity uniformity and turbulivity on the contamination boundary of the unidirectional flow is studiedas well.

感潮河段丁坝局部冲刷三维数值模拟

针对局部冲刷和一般冲刷的不同,建立了考虑垂向水流作用的局部冲刷三维紊流泥沙数学模型,并对往复流和单向流作用下的丁坝局部冲刷进行了验证计算和数值模拟。结果表明,往复流作用下丁坝局部冲刷在冲刷过程和冲淤形态上与单向流有明显不同,若采用单向流作用下的局部冲刷模型试验结果来指导往复流作用下丁坝头防护工程的设计和施工是不利的。

树脂传递模塑工艺中渗透率的测定

对树脂传递模塑工艺中纤维增强材料的渗透率测量方法进行了综述和评价 ,讨论了毛细压力、流动速度和试验流体等因素对渗透率测量结果的影响 .

RTM二维径向流动模型的理论概况及研究

综述了牛顿流体在放置了各向同性和各向异性预制件的RTM平板模具中二维径向恒流和恒压渗流的流动模型。对各个模型的可测量物理量之间的关系通过求解其解析解进行了必要的拓展补充推导和研究分析 ,对传统的二维解析方程进行了拓展和改进 ,提供了在不透明模具中测定渗透率的方法。即在恒流条件下利用压力传感器和恒流泵测定预制件的二维渗透率 ;或者在恒压条件下利用数字流量计和压力表测得二维渗透率。