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翼型在低雷诺数条件下，同时进行低幅度的俯仰和沉浮运动的调查数据。本研究旨在探讨浮力（雷利数）对流动模式、气动系数以及传热速率（努塞尔数）的影响。分析了多个案例，雷诺数设定为Re = 1000，无量纲（缩减）频率为7.86，俯仰幅度为1°，无量纲（以翼型弦长为基准）沉浮幅度为0.0125。考虑了三个平均几何攻角（0°、10°和15°），以及两个运动之间的相位角（0°和90°）和雷利数范围从Ra = 0至Ra = 1,000,000。研究发现，雷利数的增加会降低气动性能，而通过提高平均几何攻角可以减轻这一影响。当平均攻角为0°时，努塞尔数随雷利数的增加而降低；反之，当平均攻角为10°或15°时，随着雷利数的升高，传热速率也会增加。此外，将相位角从0°调整至90°，在所有情况下均会导致努塞尔数的增加。当雷利数达到500,000或更高时，观察到尾流和翼型后流动速度的行为发生了显著变化，这可能表明传热机制的转变，即从强制对流转变为混合对流。

关于数据集中的文件，六点尾流中的瞬时变量（x1和x2速度、压力和温度）被呈现于“hpoints”文件夹中。每个文件名由三部分标识：字母“a”代表平均攻角，“p”代表相位角，“Ra”代表雷利数；“k”代表10^3，“M”代表10^6。例如，“a00p00_Ra001M.txt”是针对平均攻角为0°、相位角为0°、雷利数为1,000,000的案例的文件。文件的第一行是点的数量，接下来六行是流场中点的坐标。然后，第一列是时间（对应一个时间点，有六个行对应每个点），接下来是：x1方向速度、x2方向速度、压力和温度。

此外，瞬时阻力和升力系数在“aero_coeffs”文件夹中呈现，瞬时（轮廓平均）努塞尔数在“nusselt”文件夹中呈现。这些文件夹包含指示相位角（φ）的子文件夹，这些子文件夹中又包含包含平均几何攻角（0deg、10deg和15deg）的子文件夹。每个文件名显示了报告的量（cD（阻力系数）、cL（升力系数）或nusselt）和雷利数（Ra）。文件的第一列是时间，第二列是报告的量。