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.

本数据集收录了针对NACA0012翼型在低雷诺数（Reynolds number, Re）条件下，伴随同步小幅俯仰与垂荡运动的绕流流场的调查数据。本研究聚焦于浮力（以瑞利数（Rayleigh number, Ra）表征）对流场形态、气动系数及传热速率（以努塞尔数（Nusselt number, Nu）表征）的影响规律。本次分析共设置多组工况：雷诺数固定为Re=1000，无量纲（约化）频率为7.86，俯仰幅值为1°，垂荡幅值经翼型弦长无量纲化后为0.0125。工况参数涵盖3种平均几何攻角（0°、10°与15°）、2种运动相位角（0°与90°），以及范围为Ra=0至Ra=1000000的瑞利数。

研究结果表明：瑞利数升高会降低气动性能，而增大平均几何攻角可削弱这一负面影响。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，在所有工况中，将运动相位角从0°调整至90°均可提升努塞尔数。当瑞利数达到500000及以上时，翼型后方尾流结构与流速特性会出现显著变化，这可能预示着传热机制发生转变——从强制对流过渡至混合对流。

关于数据集内的文件，尾流六个测点的流场瞬时变量（x1、x2方向速度、压强与温度）存储于"hpoints"文件夹。文件名由三部分构成：字母"a"代表平均几何攻角，"p"代表运动相位角，"Ra"代表瑞利数；字母"k"表示10^3，"M"表示10^6。例如，"a00p00_Ra001M.txt"对应平均攻角0°、相位角0°且Ra=1000000的工况。文件首行为测点数量，后续六行依次为流场内六个测点的坐标。随后的数据中，第一列为时间（每个时间步对应六行数据，分别对应六个测点），后续各列依次为x1方向速度、x2方向速度、压强与温度。

此外，瞬时阻力系数与升力系数存储于"aero_coeffs"文件夹，瞬时（轮廓平均）努塞尔数存储于"nusselt"文件夹。两类文件夹均按运动相位角（phi）划分二级子文件夹，二级子文件夹下再按平均几何攻角（0deg、10deg与15deg）划分三级子文件夹。文件名包含所记录的物理量（cD，即阻力系数；cL，即升力系数；或nusselt）与瑞利数（Ra）。文件首列为时间，次列为对应物理量的数值。