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

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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