Low Reynolds number flow with thermal convection over an airfoil with simultaneous pitching and plunging motions: aerodynamic coefficients, heat transfer rate and history points data.

This dataset contains the data of the investigation on the low Reynolds number flow over a NACA0012 airfoil with simultaneous, low amplitude, pitching and plunging motions. In this work, the influence of the buoyancy force (the Rayleigh number) on the flow patterns, the aerodynamic coefficients and the heat transfer rate (the Nusselt number) is studied. Several cases were analyzed with a Reynolds number of Re = 1000, a non-dimensional (reduced) frequency of 7.86, a pitching amplitude of 1° and a non-dimensional (scaled with the chord of the airfoil) plunging amplitude of 0.0125. Three mean geometric angle of attacks were considered (0°, 10°, and 15°), as well as two phase angles between motions (0° and 90°) and Rayleigh numbers ranging from Ra = 0 to Ra = 1 000 000. We found that an increase in the Rayleigh number decreases the aerodynamic performance, and that this effect is reduced by increasing the mean geometric angle of attack. If the mean angle of attack is of 0°, the Nusselt number decreases with an increase of the Rayleigh number; in contrast, if the mean angle of attack is 10° or 15°, the heat transfer rate increases as the Rayleigh number gets higher values. Also, changing the phase angle from 0° to 90° increases the Nusselt number in all cases. A noticeable change in the wake and in the behaviour of the flow velocity behind the airfoil is observed when the Rayleigh number is 500 000 or higher, which may be indicative of a transition in the heat transfer mechanism, changing from a forced convection to a mixed convection.

With respect to the files in the dataset, the instantaneous variables (x1 and x2 velocities, pressure and temperature) of the flow at six points in the wake are presented in the folder "hpoints". Each file name is identificated with three parts: the letter "a" is the mean angle of attack, "p" is the phase angle, and "Ra" is the Rayleigh number; the letter "k" means 10^3, and "M" means 10^6. For example, "a00p00_Ra001M.txt" is the file for the case with a 0° mean angle of attack, 0° phase angle and Ra = 1 000 000. In the file, the first line is the number of points, and the following six lines are the coordinates of the points in the flow field. Then, the first column is the time (for a time, there are six rows corresponding to each point), an the following are: velocity in x1, velocity in x2, pressure, and temperature.

Furthermore, the instantaneous drag and lift coefficients are presented in the folder "aero_coeffs", and the instantaneous (contour-average) Nusselt numbers are presented in the folder "nusselt". These folders contain sub-folders indicating the phase angle (phi), which also contain sub-folders with the mean angle geometric of attack (0deg, 10deg, and 15deg). Each file name shows the reported quantity (cD (drag coefficient), cL (lift coefficient), or nusselt) and the Rayleigh number (Ra). In the file, the first column is the time and the second is the reported quantity.

本数据集涵盖了针对NACA0012翼型（NACA0012 airfoil）开展的低雷诺数（Reynolds number, Re）流动研究数据，该翼型带有同步低幅值俯仰与垂荡运动。本研究聚焦于浮力（buoyancy force）、瑞利数（Rayleigh number, Ra）对流动形态、气动系数及传热速率（努塞尔数，Nusselt number, Nu）的影响规律。本次分析共设置如下工况参数：雷诺数Re=1000，无量纲（折合）频率7.86，俯仰幅值1°，无量纲垂荡幅值（以翼型弦长为基准缩放）0.0125；平均几何攻角取0°、10°、15°三种工况，运动相位角取0°与90°两种，瑞利数Ra范围为0至1000000。研究结果表明：瑞利数升高会降低气动性能，而该削弱效应可通过提升平均几何攻角得以缓解。当平均攻角为0°时，努塞尔数随瑞利数升高而降低；与之相反，当平均攻角为10°或15°时，传热速率随瑞利数增大而提升。此外，将相位角从0°调整至90°可在所有工况下提升努塞尔数。当瑞利数达到500000及以上时，翼型尾流及尾流流速特性会出现显著变化，这表明传热机制可能发生了从强制对流（forced convection）到混合对流（mixed convection）的转变。

针对数据集内的文件，尾流6个测点的流动瞬时变量（x1方向速度、x2方向速度、压强及温度）存储于"hpoints"文件夹中。文件名由三部分组成：前缀"a"代表平均攻角，"p"代表相位角，"Ra"代表瑞利数；"k"表示10³，"M"表示10⁶。例如，"a00p00_Ra001M.txt"对应平均攻角0°、相位角0°且瑞利数为1000000的工况文件。该文件首行为测点总数，后续6行依次为流场中各测点的坐标。后续数据的首列为时间（每一时刻对应6行数据，分别对应6个测点），其余列依次为x1方向速度、x2方向速度、压强及温度。

此外，瞬时阻力系数、升力系数存储于"aero_coeffs"文件夹，瞬时（面平均）努塞尔数存储于"nusselt"文件夹。这两个文件夹均包含以相位角命名的子文件夹，每个相位角子文件夹下又包含对应平均几何攻角（0°、10°、15°）的子文件夹。文件名包含所记录的物理量（cD为阻力系数、cL为升力系数，或nusselt代表努塞尔数）以及瑞利数Ra。文件中首列为时间，第二列为对应物理量的数值。