Development of LBGK and incompressible LBGK‐based lattice Boltzmann flux solvers for simulation of incompressible flows

This paper presents lattice Boltzmann Bhatnagar–Gross–Krook (LBGK) model and incompressible LBGK model‐based lattice Boltzmann flux solvers (LBFS) for simulation of incompressible flows. LBFS applies the finite volume method to directly discretize the governing differential equations recovered by lattice Boltzmann equations. The fluxes of LBFS at each cell interface are evaluated by local reconstruction of lattice Boltzmann solution. Because LBFS is applied locally at each cell interface independently, it removes the major drawbacks of conventional lattice Boltzmann method such as lattice uniformity, coupling between mesh spacing, and time interval. With LBGK and incompressible LBGK models, LBFS are examined by simulating decaying vortex flow, polar cavity flow, plane Poiseuille flow, Womersley flow, and double shear flows. The obtained numerical results show that both the LBGK and incompressible LBGK‐based LBFS have the second order of accuracy and high computational efficiency on nonuniform grids. Furthermore, LBFS with both LBGK models are also stable for the double shear flows at a high Reynolds number of 10⁵. However, for the pressure‐driven plane Poiseuille flow, when the pressure gradient is increased, the relative error associated with LBGK model grows faster than that associated with incompressible LBGK model. It seems that the incompressible LBGK‐based LBFS is more suitable for simulating incompressible flows with large pressure gradients. Copyright © 2014 John Wiley & Sons, Ltd.     

Computation of hydrodynamic mass and damping coefficients for a cavitating marine propeller flow using a panel method

The present paper deals with the numerical calculation of hydrodynamic mass and damping coefficients under consideration of unsteady sheet cavitation on marine propeller flows. In the first part of the paper, the mathematical and numerical background behind the numerical method is introduced. The numerical calculations carried out in this work are based on a low-order panel method. Panel methods belong to the class of collocation techniques and are applied to obtain a numerical solution of a potential flow based system of boundary integral equations. They are suitable for the present application because of their short computation time which makes them applicable in the design process of marine propellers.Additionally, two different approaches for the determination of hydrodynamic masses and damping are introduced in this work. The hydrodynamic masses and damping are important in studies of the ship motion in seaway and in the analysis of vibrations of a vessel and its appendages. The developed approaches are applied on a propeller flow in heave motion. Hereby, the calculations are performed for a non-rotating and rotating propeller under non-cavitating and cavitating conditions. The results obtained from the simulations are discussed in detail and an outlook is given.     

Novel sulfonated polyimide/ZrO2 composite membrane as a separator of vanadium redox flow battery

Sulfonated polyimide (SPI) and ZrO₂ are blended to prepare a series of novel SPI/ZrO₂ composite membranes for vanadium redox flow battery (VRFB) application. Results of atomic force microscopy and X‐ray diffraction reveal that ZrO₂ is successfully composited with SPI. All SPI/ZrO₂ membranes possess high proton conductivity (2.96–3.72 × 10^?2 S cm^?1) and low VO²⁺ permeability (2.18–4.04 × 10^?7 cm² min^?1). SPI/ZrO₂‐15% membrane is determined as the optimum one on account of its higher proton selectivity and improved chemical stability. The VRFB with SPI/ZrO₂‐15% membrane presents higher coulombic efficiency and energy efficiency than that with Nafion 117 membrane at the current density, which ranged from 20 to 80 mA cm^?2. Cycling tests indicate that the SPI/ZrO₂‐15% membrane has good operation stability in the VRFB system. Copyright © 2014 John Wiley & Sons, Ltd.     

从电子流动观点看催化剂在有机反应中的作用

分析和总结了催化剂催化有机化学反应的4种基本方式,包括建立电子流动通道、改变电子流动属性、加强电子流动能力和稳定电子流动结果。本文旨在揭示有机化学反应中催化剂作用的本质,以便学生更加深刻理解并掌握有机化学反应。     

Continuous‐Flow Microwave Synthesis of Metal–Organic Frameworks: A Highly Efficient Method for Large‐Scale Production

Metal–organic frameworks are having a tremendous impact on novel strategic applications, with prospective employment in industrially relevant processes. The development of such processes is strictly dependent on the ability to generate materials with high yield efficiency and production rate. We report a versatile and highly efficient method for synthesis of metal–organic frameworks in large quantities using continuous flow processing under microwave irradiation. Benchmark materials such as UiO‐66, MIL‐53(Al), and HKUST‐1 were obtained with remarkable mass, space–time yields, and often using stoichiometric amounts of reactants. In the case of UiO‐66 and MIL‐53(Al), we attained unprecedented space–time yields far greater than those reported previously. All of the syntheses were successfully extended to multi‐gram high quality products in a matter of minutes, proving the effectiveness of continuous flow microwave technology for the large scale production of metal–organic frameworks.     

Application of the finite point method to high‐Reynolds number compressible flow problems

In this work, the finite point method is applied to the solution of high‐Reynolds compressible viscous flows. The aim is to explore this important field of applications focusing on two main aspects: the easiness and automation of the meshless discretization of viscous layers and the construction of a robust numerical approximation in the highly stretched clouds of points resulting in such domain areas. The flow solution scheme adopts an upwind‐biased scheme to solve the averaged Navier–Stokes equations in conjunction with an algebraic turbulence model. The numerical applications presented involve different attached boundary layer flows and are intended to show the performance of the numerical technique. The results obtained are satisfactory and indicative of the possibilities to extend the present meshless technique to more complex flow problems. Copyright © 2014 John Wiley & Sons, Ltd.     

Investigation of the effect of nozzle shape on supersonic/hypersonic impactors designed for size discrimination of nanoparticles

In this study the flow field and the nanoparticle collection efficiency of supersonic/hypersonic impactors with different nozzle shapes were studied using a computational modeling approach. The aim of this study was to develop a nozzle design for supersonic/hypersonic impactors with the smallest possible cut-off size d₅₀ and rather sharp collection efficiency curves. The simulation results show that the changes in the angle and width of a converging nozzle do not alter the cut-off size of the impactor; however, using a conical Laval nozzle with an L/D_n ratio less than or equal to 2 reduced d₅₀. The effect of using a cap as a focuser in the nozzle of a supersonic/hypersonic impactor was also investigated. The results show that adding a cap in front of the nozzle had a noticeable effect on decreasing the cut-off size of the impactor. Both flat disks and conical caps were examined, and it was observed that the nozzle with the conical cap had a lower cut-off size.     

Linearized viscoelastic Oldroyd fluid motion in an almost periodic environment

In most of the linear homogenization problems involving convolution terms so far studied, the main tool used to derive the homogenized problem is the Laplace transform. Here we propose a direct approach enabling one to tackle both linear and nonlinear homogenization problems that involve convolution sequences without using Laplace transform. To illustrate this, we investigate in this paper the asymptotic behavior of the solutions of a Stokes–Volterra problem with rapidly oscillating coefficients describing the viscoelastic fluid flow in a fixed domain. Under the almost periodicity assumption on the coefficients of the problem, we prove that the sequence of solutions of our ?‐problem converges in L² to a solution of a rather classical Stokes system. One important fact is that the memory disappears in the limit. To achieve our goal, we use some very recent results about the sigma‐convergence of convolution sequences. Copyright © 2013 John Wiley & Sons, Ltd.     

Numerical simulation of transpiration cooling through porous material

Transpiration cooling using ceramic matrix composite materials is an innovative concept for cooling rocket thrust chambers. The coolant (air) is driven through the porous material by a pressure difference between the coolant reservoir and the turbulent hot gas flow. The effectiveness of such cooling strategies relies on a proper choice of the involved process parameters such as injection pressure, blowing ratios, and material structure parameters, to name only a few. In view of the limited experimental access to the subtle processes occurring at the interface between hot gas flow and porous medium, reliable and accurate simulations become an increasingly important design tool. In order to facilitate such numerical simulations for a carbon/carbon material mounted in the side wall of a hot gas channel that are able to capture a spatially varying interplay between the hot gas flow and the coolant at the interface, we formulate a model for the porous medium flow of Darcy–Forchheimer type. A finite‐element solver for the corresponding porous medium flow is presented and coupled with a finite‐volume solver for the compressible Reynolds‐averaged Navier–Stokes equations. The two‐dimensional and three‐dimensional results at Mach number Ma = 0.5 and hot gas temperature T_HG=540 K for different blowing ratios are compared with experimental data. Copyright © 2014 John Wiley & Sons, Ltd.     

Current Advances in Highly Multiplexed Antibody‐Based Single‐Cell Proteomic Measurements

Single‐cell measurements have played a critical role in revealing the complex signaling dynamics and heterogeneity present in cells, but there is still much to learn. Measuring samples from bulk populations of cells often masks the information and dynamics present in subsets of cells. Common single‐cell protein studies rely on fluorescent microscopy and flow cytometry but are limited in multiplexing ability owing to spectral overlap. Recently, technology advancements in single‐cell proteomics have allowed highly multiplexed measurement of multiple parameters simultaneously by using barcoded microfluidic enzyme‐linked immunosorbent assays and mass cytometry techniques. In this review, we will describe recent work around multiparameter single‐cell protein measurements and critically analyze the techniques.