Berson Arganthaël, Blanc-Benon Philippe, Comte-Bellot Geneviève
Queen's-RMC Fuel Cell Research Centre, Queen's University, 945 Princess Street, Kingston, Ontario K7L 5L9, Canada.
Rev Sci Instrum. 2009 Apr;80(4):045102. doi: 10.1063/1.3103948.
A constant-voltage anemometer is subject to nonlinear effects when the operating hot wire is exposed to large velocity fluctuations in the incident flow. This results in the generation of undesirable higher harmonics, just as in the two classic systems, constant-current and constant-temperature anemometers, for which no attempts are normally made to correct the nonlinearities. The present investigation shows that these undesirable higher harmonics can be suppressed in the case of a constant-voltage anemometer. A new approach to process experimental data is proposed. It is based on three explicit equations established and solved with all terms included, i.e., without linearization. These are (1) the first-order differential equation that describes the electronic circuit of a constant-voltage anemometer-this equation permits to deduce the instantaneous resistance of the hot wire from the output voltage of the anemometer; (2) the first-order differential equation that expresses the thermal lag behavior of the hot wire when used in a constant-voltage mode-this equation permits to restore the instantaneous resistance that an ideal wire would have without thermal inertia in the same flow conditions; and (3) the algebraic relation that expresses the heat-transfer law of an ideal wire, according to King's law, a look-up table, or a polynomial fit-this relation permits to deduce the instantaneous flow velocity from the instantaneous resistance of the ideal wire. The proposed method is easily implemented on a personal computer and permits odd turbulence moments, such as skewness factors, to be obtained satisfactorily.
当工作中的热线暴露在入射流的大速度波动中时，恒压风速仪会受到非线性效应的影响。这会导致产生不良的高次谐波，就像在恒流和恒温风速仪这两种经典系统中一样，通常不会尝试校正这些非线性。目前的研究表明，在恒压风速仪的情况下，可以抑制这些不良的高次谐波。提出了一种处理实验数据的新方法。它基于建立并求解的三个显式方程，所有项都包含在内，即不进行线性化。这三个方程分别是：（1）描述恒压风速仪电子电路的一阶微分方程——该方程允许从风速仪的输出电压推导出热线的瞬时电阻；（2）表示热线在恒压模式下使用时热滞后行为的一阶微分方程——该方程允许恢复在相同流动条件下没有热惯性的理想导线的瞬时电阻；（3）根据金氏定律、查找表或多项式拟合表示理想导线传热规律的代数关系——该关系允许从理想导线的瞬时电阻推导出瞬时流速。所提出的方法很容易在个人计算机上实现，并能令人满意地获得诸如偏度因子等奇数湍流矩。
