A simple sliding‐mesh interface procedure and its application to the CFD simulation of a tidal‐stream turbine

An effective way of using computational fluid dynamics (CFD) to simulate flow about a rotating device—for example, a wind or marine turbine—is to embed a rotating region of cells inside a larger, stationary domain, with a sliding interface between. This paper describes a simple but effective method for implementing this as an internal Dirichlet boundary condition, with interfacial values obtained by interpolation from halo nodes. The method is tested in two finite‐volume codes: one using block‐structured meshes and the other unstructured meshes. Validation is performed for flow around simple, isolated, rotating shapes (cylinder, sphere and cube), comparing, where possible, with experiment and the alternative CFD approach of fixed grid with moving walls. Flow variables are shown to vary smoothly across the sliding interface. Simulations of a tidal‐stream turbine, including both rotor and support, are then performed and compared with towing‐tank experiments. Comparison between CFD and experiment is made for thrust and power coefficients as a function of tip‐speed ratio (TSR) using Reynolds‐averaged Navier–Stokes turbulence models and large‐eddy simulation (LES). Performance of most models is good near the optimal TSR, but simulations underestimate mean thrust and power coefficients in off‐design conditions, with the standard k– ? turbulence model performing noticeably worse than shear stress transport k– ω and Reynolds‐stress‐transport closures. LES gave good predictions of mean load coefficients and vital information about wake structures but at substantial computational cost. Grid‐sensitivity studies suggest that Reynolds‐averaged Navier–Stokes models give acceptable predictions of mean power and thrust coefficients on a single device using a mesh of about 4 million cells. Copyright © 2013 John Wiley & Sons, Ltd.     

TWO-GRID ERROR ESTIMATES FOR THE STREAM FUNCTION FORM OF NAVIER-STOKES EQUATIONS

ＩｎｔｒｏｄｕｃｔｉｏｎＷｅｃｏｎｓｉｄｅｒｔｗｏ＿ｇｒｉｄｍｅｔｈｏｄｆｏｒｔｈｅｓｔｒｅａｍｆｕｎｃｔｉｏｎｆｏｒｍｏｆｔｈｅｓｔａｔｉｏｎａｒｙＮａｖｉｅｒ＿Ｓｔｏｋｅｓｅｑｕａｔｉｏｎｓ.Ｔｈｅａｄｖａｎｔａｇｅｓｏｆｔｈｅｓｔｒｅａｍｆｕｎｃｔｉｏｎｆｏｒｍａｒｅｔｈａｔｔｈｅｉｎｃｏｍｐｒｅｓｓｉｂｉｌｉｔｙｃｏｎｄｉｔｉｏｎｉｓｓａｔｉｓｆｉｅｄａｕｔｏｍａｔｉｃａｌｌｙａｎｄｔｈｅｐｒｅｓｓｕｒｅｉｓｎｏｔｐｒｅｓｅｎｔｉｎｔｈｅｗｅａｋｆｏｒｍ .Ｔｈｅｍｅｔｈｏｄｉｓｂａｓｅｄ…     

An experimental investigation of heat transfer characteristics for turbulent flow over staggered ribs in a square duct

An experimental study of developing and fully developed turbulent air flow in a square duct with two opposite rib-roughened walls in which the ribs are attached in a staggered fashion was conducted to determine the heat transfer characteristics. The rib height-to-hydraulic diameter ratio (e/D_H) was 0.19, the rib pitch-to-height ratio (p/e) was 5.31. The streamwise temperature distribution was measured, and a law of the wall for the thermal boundary layer at each free-stream turbulence level was obtained. The effects of free-stream turbulence intensity with variations of 4–11% on heat transfer coefficients were also examined. Finally, the relationship between Nusselt number and Reynolds number was correlated. The results might be used in the design of turbine blade cooling channels.     

Some Solvable Stochastic Control Problems With Delay

We consider optimal harvesting of systems described by stochastic differential equations with delay. We focus on those situations where the value function of the harvesting problem depends on the initial path of the process in a simple way, namely through its value at 0 and through some weighted averages

A verification theorem of variational inequality type is proved. This is applied to solve explicitly some classes of optimal harvesting delay problems     

电子束与等离子体相互作用中的反常效应

本文对强流相对论性电子束与靶等离子体相互作用的反常吸收效应进行了理论研究。从符拉索夫方程出发,导出了强流相对论性电子束双流不稳定性效应解,并进行了弱碰撞修正,得到了相应的等离子体波增长率,对不同情况下出现反常效应的条件及机制进行了研究和讨论。     

Dy和Y掺杂改性对CuO/CeZrO_2催化剂在富氢气氛中CO优先氧化催化性能的影响

采用水热-浸渍法制备了系列Dy和Y掺杂改性的CuO/CeZrO_2催化剂,使用X射线粉末衍射(XRD)、N_2吸附脱附和程序升温还原(H_2-TPR)等手段对催化剂进行了表征,研究了Dy和Y掺杂改性对CuO/CeZrO_2在富氢气氛中CO优先氧化催化性能的影响。结果表明,所制备的CuO-CeZrO_2催化剂均为萤石结构;添加适当比例的Dy_2O_3和Y_2O_3能增强活性组分与载体间的相互作用,有利于CuO活性组分的分散和低温还原能力的提高,从而改善了CuO/CeZrO_2用于CO优先氧化的催化活性。同时,掺杂Dy和Y能够提高CuO/CeZrO_2催化剂的抗CO_2抑制作用的能力,改善其催化稳定性。     

A uniformly valid asymptotic solution of the Navier-Stokes equations

ＡＵＮＩＦＯＲＭＬＹＶＡＬＩＤＡＳＹＭＰＴＯＴＩＣＳＯＬＵＴＩＯＮＯＦＴＨＥＮＡＶＩＥＲ－ＳＴＯＫＥＳＥＱＵＡＴＩＯＮＳＱｉｎＳｈｅｎｇ－ｌｉ（秦圣立）ＺｈａｎｇＡｉ－ｓｈｕ（张爱淑）（Ｄｅｐｔ．ＯｆＰｈｙｓｉｃｓ,ＱｕｆｕＴｅａｃｈｅｒｓＵｎｉｖｅ...     

Opportunities and challenges of thin-film boron-doped diamond electrochemistry for valuable resources recovery from waste: Organic,inorganic, and volatile product electrosynthesis

Thin-film boron-doped diamond (BDD) electrochemistry has made a tremendous progress in electrochemical synthesis/recovery of high-added value products from aqueous and gaseous waste streams. The distinguished electrochemical characteristic of this electrode has made this material emerging and successfully used in electrosynthetic transformations, besides its destructive and powerful performance in disinfection and detoxification of wastewaters. Organic electrosynthesis is achieved by the oxyl radical oxidation formed at BDD, peroxo compounds electrosynthesis is attained by oxidation of corresponding anions at the BDD surface, whereas electrochemical conversion of SO₂, CO₂, NO₃^?, and NH₃ to value-added products occurs by BDD cathodic reduction process. There are still some challenges needed to address for seamless scale-up and translation into application of this future technology.     

Investigation of Plasma Parameters in a Magnetoplasma Compressor

The article presents the results of experimental investigations that were carried out at the Center for Science and Technology Development in Belgrade (Yugoslavia) and pertained to the plasma streams generated by a gasdischarge magnetoplasma compressor (MPC). The integral characteristics of the discharge, the dynamic parameters of a compression flux, and the concentration of the plasma electrons in the magnetoplasma compressor have been determined. The distinguishing features of the discharge afterglow from the volume of a vacuum chamber for a long time after the termination of the discharge current have been investigated.     

自动消解仪—ICP法测定水系沉积物中6种重金属元素

建立了自动消解仪-电感耦合等离子体发射光谱法(ICP-OES)同时测定水系沉积物中Cu、Zn、Ni、Cr、Pb、Co六种元素含量的方法。该方法的相关系数好、检出限低。方法经国家标准物质(GBW07361)验证,准确度和精密度均能达到环境监测分析的要求,为水系沉积物中重金属元素含量的测定提供了简单可靠的分析方法。