常气压辉光放电等离子体对边界层流动的影响

基于Shyy提出的常气压下均匀辉光放电等离子体与空气干扰的物理模型,通过求解电位势方程得到电场分布及作用于流体上的电场力.以NACA0015翼型低速绕流为对象,通过数值求解考虑等离子体作用的流体运动控制方程,研究等离子体位置和个数控制对翼型绕流分离的影响.位于分离点上游的等离子体能够有效地抑制流动分离,而在分离区的等离子体对流动影响很弱,这一结论同实验观察一致,并给出等离子体对翼型壁面压力和气动力影响的规律.     

Link-Wise Artificial Compressibility Method for attached and separated flows past airfoils

The performance of the recently developed Link-Wise Artificial Compressibility Method (LW-ACM) is evaluated for aerodynamic applications and then applied for both attached and separated flows. Numerical flow simulations are performed around NACA-0012 and TSAGI-12 shaped airfoils at low speed and high angle of attack. Results of aerodynamic characteristics of the airfoils were found in good agreements with previous investigations including LBM (PowerFLOW) and FVM (CFL3D). Results also showed that LW-ACM is efficient and rapidly convergent when used to solve both attached and separated flows.     

Reduction of motor fan noise using CFD and CAA simulations

Motor fans used for cooling electric motors have long been recognized as one of the major noise sources. Current paper focuses on design of motor fan for electric motors that are used in submarines for pumping sea water. Noise reduction at source is very important and the critical task, for under water applications. An attempt has been made for reduction of motor fan noise by modification of noise sources. For this purpose computational fluid dynamics and computational aeroacoustics code FLUENT package is used to identify the noise sources and to know the overall sound pressure level of motor fan. From these results it is observed that aerodynamic noise is the dominate fan noise source. Aerodynamic noise of motor fan can be reduced by modifying fan geometry. The aerodynamic noise level of motor fan has been reduced by replacing the straight blades with various digits of NACA (National Advisory Committee for Aeronautics) 65 series airfoil sections. From the numerical results it is observed that the minimum sound pressure level for NACA 65-010 is 65.4 dB(A). These numerical results are compared with measurements in a semi-anechoic chamber. It is found that there is good agreement between numerical and experimental results.     

Incompressible Roe‐like scheme for turbulent flows

In the current study, numerical investigation of incompressible turbulent flow is presented. By the artificial compressibility method, momentum and continuity equations are coupled. Considering Reynolds averaged Navier–Stokes equations, the Spalart–Allmaras turbulence model, which has accurate results in two‐dimensional problems, is used to calculate Reynolds stresses. For convective fluxes a Roe‐like scheme is proposed for the steady Reynolds averaged Navier–Stokes equations. Also, Jameson averaging method was implemented. In comparison, the proposed characteristics‐based upwind incompressible turbulent Roe‐like scheme, demonstrated very accurate results, high stability, and fast convergence. The fifth‐order Runge–Kutta scheme is used for time discretization. The local time stepping and implicit residual smoothing were applied as the convergence acceleration techniques. Suitable boundary conditions have been implemented considering flow behavior. The problem has been studied at high Reynolds numbers for cross flow around the horizontal circular cylinder and NACA0012 hydrofoil. Results were compared with those of others and a good agreement has been observed. Copyright © 2012 John Wiley & Sons, Ltd.     

The 160.44 day Lu as a new gamma calibration standard

Gamma emissions in the decay of 160.44 day isomer ^177mLu were analyzed with a 60 cc, coaxial HPGe detector. The energies and intensities of 50 gamma transition - 40 of which belong to the daughter ¹⁷⁷Hf, that was excited by beta decay of the isomer, and 10 to the isomeric transition in ¹⁷⁷Lu were precisely determined. These precise values have resulted in an internally consistent decay scheme for ^177mLu. These gamma intensity and gamma emission probability measurements will help in making the long lived ^177mLu available as a calibration standard for HPGe detectors and also for other applications.     

振动NACA0012翼型的移动网格数值模拟

利用流体力学方程的积分形式给出非结构移动网格上离散格式,利用自适应移动网格方法移动网格,进而得到网格速度.对振动Naca0012翼型问题,分三种类型确定网格速度,再结合Riemann问题的解法器构造数值通量,得到移动网格单元上新的物理量.数值实验表明这种格式同时具有高效、高分辨率的特点.