A divergence-conforming hybridized discontinuous Galerkin method for the incompressible Reynolds-averaged Navier-Stokes equations

We present a hybridized discontinuous Galerkin (HDG) method for the incompressible Reynolds-averaged Navier-Stokes equations coupled with the Spalart-Allmaras one-equation turbulence model. The method extends upon an HDG method recently introduced by Rhebergen and Wells for the incompressible Navier-Stokes equations. With a special choice of velocity and pressure spaces for both element and trace degrees of freedom (DOFs), the method returns pointwise divergence-free mean velocity fields and properly balances momentum and energy. We further examine the use of different polynomial degrees and meshes to see how the order of the scalar eddy viscosity affects the convergence of the mean velocity and pressure fields, specifically for the method of manufactured solutions. As is standard with HDG methods, static condensation can be employed to remove the element DOFs and thus dramatically reduce the global number of DOFs. Numerical results illustrate the effectiveness of the proposed methodology.     

Effective Application of Microwave Resonant Cavity System to Flow Chemistry

By applying advanced telecommunication solid state devices to microwave (MW) resonant cavity system for flow chemistry, it becomes possible to heat up low polarity solvents higher than 250 C, that are considered impossible to heat up by MW until now. The resonant cavity system is opening new process windows to production processes of specialty chemicals which require low cost, high yield and high productivity.     

Flow dynamics in the short asymmetric Taylor-Couette cavities at low Reynolds numbers

This paper reports on the numerical investigations of Taylor-Couette flow of radius ratio η = 0.25–0.6 performed at low Reynolds numbers Re = 100–200. The inner cylinder and the bottom end-wall rotate, while the outer cylinder and the top end-wall are held fixed. A fully 3D DNS code based on the spectral Chebyshev – Fourier approximation is used. This study is complementary to those of Mullin and Blohm (Phys. of Fluids 2001, vol 13, 136–140) and Lopez et al. (J. Fluid Mech. 2004, vol 501, 327–354) where investigations have been performed for radius ratio 0.5. The 1-cell and 3-cell structures found by these authors are shown to exist for a wide range of radius ratios, and the transition processes between them are qualitatively similar. These structures show hysteresis, disappearing at saddle-node bifurcations which connect at a cusp point in the (Re, Γ) plane. This cusp exists for the entire range of 0.1 < η < 0.75, and it traces out a parabolic curve in the (Re, Γ) plane, reaching a minimum Re at η = 0.375. The detailed 3D DNS computations provide a lot of new information about such phenomena as the modulated rotating wave, the period doubling cascade and homoclinic collision. The results show that the period doubling bifurcation is important in the flow when the radius ratio is close to η = 0.375.     

Simulating bubble dynamics in a buoyant system

Multiphase flows are critical components of many physical systems; however, numerical models of multiphase flows with large parameter gradients can be challenging. Here, two different numerical methods, volume of fluid (VOF) and smoothed particle hydrodynamics (SPH), are used to model the buoyant rise of isolated gas bubbles through quiescent fluids for a range of Bond and Reynolds numbers. The VOF is an Eulerian grid–based method, whereas the SPH is Lagrangian and mesh free. Each method has unique strengths and weaknesses, and a comparison of the two approaches as applied to multiphase phenomena has not previously been performed. The VOF and SPH simulations are compared, verified, and validated. Results using two-dimensional VOF and SPH simulations are similar to each other and are able to reproduce numerical benchmarks and experimental results for sufficiently large Morton and Reynolds numbers. It is also shown that at low Reynolds numbers, the two methods, SPH and VOF, diverge in the transient regime of the bubble rise. Regimes that require simulations capable of representing three-dimensional drag are identified as well as regimes in which results from VOF and SPH diverge.     

水流损失和热补偿共同作用对增强型地热系统(EGS)产能影响的研究

基于青海共和盆地-3705m地热田实测数据,结合流固耦合传热理论并运用Comsol软件,建立了离散型裂隙岩体流体传热模型。考虑水流损失和热补偿共同作用,模拟得到了开采过程中上、下岩层(盖层和垫层)为绝热不渗透、传热不渗透、渗透传热时,储层(上、下岩层和压裂层)温度场的变化特征,分析了产出流量、水流损失、产出温度、产热速率的变化规律。研究结果表明:采热过程中产出流量始终小于注入流量;产出流量增幅速率先增大后减小,最后趋于稳定,前3a产出流量增幅超过总增幅量的3/4;忽略水流损失,将高估产热速率,采热初期甚至达到考虑水流损失时产热速率的3倍以上;考虑水流损失,产热速率呈先快速上升再趋于稳定后逐渐下降的趋势,最优开采时间为3a^11a;研究上、下岩层对产出温度的影响,仅考虑传热,采热寿命延长5.43%,同时考虑渗流传热时,采热寿命延长2.71%;采热前9a,水流损失占主导作用,即流入上、下岩层水流损失对产热速率的影响高于热补偿效应,开采10a后,热补偿效应占主导作用;同时考虑水流损失和热补偿效应得到的产热速率变化规律与实际工程更为符合,建议选择低渗透能力的上、下岩层延长增强型地热系统(EGS)运行时间。     

An estimated quantitative lateral flow immunoassay for determination of artesunate using monoclonal antibody

There have been reports of fake artesunate (ART), which has led to deaths from untreated malaria in South East Asia. To rapidly screen for fake and adulterated ART products in the drug market, a lateral flow immunoassay (LFIA) based on a colloidal gold–monoclonal antibody probe for detection of ART within samples was developed. With this method, the calibration curve for ART was determined by the intensity ratio of the test and control bands at various ART concentrations. The linearity range was 12.5–200 μg/ml of ART. Samples were tested by the developed LFIA and can be calculated for ART contents. The levels of ART in the samples were also confirmed by enzyme-linked immunosorbent assay. The results of the two methods were in good conformance. The proposed LFIA was demonstrated to be a simple and rapid analytical method for detecting ART in the pharmaceutical formulation.     

Experimental and numerical study on instability structure of the supersonic mixing layer (Mc = 0.5)

The parameters of instability wave of supersonic mixing layer(Mc=0.5,M1=3.5/M2=1.4) are measured by flow visualization and calculated by means of two-dimensional direct numerical simulaitons of the compressible Navier-Stokes equations.In both cases of the mixing layer with harmonic disturbance or not,the comparative results indicate that the wavelength of the two-dimensional wave is equal to the vortex spacing in the streamwise direction because the difference between them is less than 1%.However,the measur...     

Metastable state and macroscopic quantum tunneling of binary mixtures

We provide a mixing model to explore the metastable state and the macroscopic quantum tunneling (MQT) of binary mixtures. For , we first observe the two condensates form the symmetry-breaking state (SBS) and then suddenly transfer to the symmetry-preserving state (SPS) through the MQT. The SBS is shown to be the metastable state in our system. We find the MQT does not spontaneously arise. The inducement mechanism is the damping but not the excitations. The damping mechanism can also control the lifetime and the tunneling decay rate of the SBS. Finally, we further present the origin of these phenomena by examining the energy of the system.     

板翅式换热器物流分配研究综述

板翅式换热器由于具有紧凑高效等突出优点,在航空、化工、HVAC等领域具有重要地位。由多种因素引起换热器内部流动的不均匀分配,是造成换热效能的下降最主要原因之一。文中总结了国内外学者对于板翅式换热器物流分配不均匀的研究,详细阐述了各种流动分配模型及其对换热器效能的影响。     

动脉中血液脉动流的一种分析方法

动脉中的血液流动被分解为平衡状态(相当于平均压定常流状态)和叠加在平衡状态上的周期脉动流,利用Fung的血管应变能密度函数分析血管壁在平衡状态下的应力-应变关系,确定相对于平衡状态血管作微小变形所对应的周向弹性模量和轴向弹性模量,并建立在脉动压力作用下相应的管壁运动方程,与线性化Navier-Stokes方程联立,求得血液流动速度和血管壁位移的分析表达式,详细讨论血管壁周向和轴向弹性性质差异对脉博波、血液脉动流特性以及血管壁运动的影响.