Numerical Clarification of Wavy Sand Erosion Phenomena generated by Interaction among Flow, Small Particle and Wall Surface

砂蚀是固体颗粒撞击壁面造成壁面严重机械损伤的现象。这种现象是典型的流场、粒子轨迹和壁面变形相互作用的多物理场问题。众所周知，由于沙蚀，各种机器的性能和寿命都严重下降。我们开发了砂土侵蚀现象的数值计算程序。为了模拟这一现象，反复计算了紊流、颗粒运动轨迹和侵蚀壁面的侵蚀量。采用Neilson-Gilchrist模型对沙蚀造成的重量损失进行估算。2004年，我们将此代码扩展为三维计算，并将其应用于90度弯曲。主要目的是澄清波浪侵蚀模式在弯曲壁上形成的原因。计算了9种不同颗粒直径和壁曲率的情况。墙体材料采用铝，颗粒材料采用碳化硅。结果表明：(1)颗粒一旦撞击壁面，壁面就会产生侵蚀空腔。(2)侵蚀空腔主要沿顺流方向生长；(3)侵蚀空腔的跨向生长主要受弯曲壁面上的纵向垂直运动支配；(4)上述现象在弯曲壁面上形成波浪状侵蚀模式。2005年，我试图阐明压气机叶片通道波浪沙侵蚀的机理。首先，将代码扩展到旋转参照系。在所有计算中使用了大约300万个网格点。结果表明：(A)在转子压力侧前缘和端部附近发生严重的冲沙，(B)由于动能较小，在定子内没有明显的冲沙现象，(C)在转子通道内离心力使颗粒向端部运动，(D)颗粒在定子内加速，因此在下游阶段会再次发生冲沙。然而，由于波浪侵蚀模式尚未清楚地重现，需要进一步的研究。少

Sand erosion is a phenomenon where solid particles impinging to a wall cause serious mechanical damages to the wall surface. This phenomenon is a typical multi-physics problem where the flow field, particle trajectory and wall deformation interact with among others. It is well known that the performance and lifetime of various machines are severely degraded due to sand erosion. We have developed the numerical procedure for sand erosion phenomenon. To simulate the phenomenon, the turbulent flow, the particle trajectory and the amount of erosion on the eroded wall were calculated repeatedly. The Neilson-Gilchrist model was used to estimate the weight loss due to sand erosion.In 2004, we extended this code to a three-dimensional computation, and it was applied to the 90-degree bend. The main objective was to clarify the reason why the wavy erosion pattern is formed over the curved wall. 9 cases with different particle diameters and wall curvatures were computed. The materials for the wall … More and the particle were adopted as aluminum and silicon carbide, respectively. It was found that (1)once a particle hits against a wall, an erosion cavity is generates on the wal,. (2)the erosion cavity mainly grows in the streamwise direction, (3)the spanwise growth of the erosion cavity is dominated by the longitudinal vertical motion over the curved wall, and (4)the above described phenomena produces the wavy erosion pattern over the curved wall.In 2005, I tried to clarify the mechanism of wavy sand erosion in a compressor blade passages. First, the code was extended to the rotational frame of reference. About 3 million grid points were used in all computations. It was confirmed that (A)sand erosion severely occurs around the leading edge and the tip of the rotor pressure side, (B)erosion does not appear remarkably in the stator because of the less kinetic energy, (C)in the rotor passage the centrifugal force makes the particles go toward the tip, and (D)particles are accelerated in the stator and thus sand erosion would take place again in the downstream stages. However, since wavy erosion pattern has not clearly reproduced, further investigations will be needed. Less