Interdiffusion can be a major cause of failure in coated parts that see service at elevated temperatures. Ways to measure the extent of interdiffusion and mathematical equations for predicting these measures are given...Interdiffusion can be a major cause of failure in coated parts that see service at elevated temperatures. Ways to measure the extent of interdiffusion and mathematical equations for predicting these measures are given. The equations are based on the error function solution to the diffusion equation and do not take into account variations of the diffusivity with composition. Also, when the substrate of the coating is multiphase, the equations do not take into account the precipitate morphology, but do take into account that precipitates can act as sinks or sources of solute as the average composition of the substrate varies. The equations are meant to be alloy design tools that indicate how changing substrate or coating chemistry will reduce the extent of interdiffusion.展开更多
In this paper, we investigate flows with moving contact lines on curved solid walls on a dual-resolution grid using a diffuse-interface immersed-boundary（DIIB） method. The dual-resolution grid, on which the flows ar...In this paper, we investigate flows with moving contact lines on curved solid walls on a dual-resolution grid using a diffuse-interface immersed-boundary（DIIB） method. The dual-resolution grid, on which the flows are solved on a coarse mesh while the interface is resolved on a fine mesh, was shown to significantly improve the computational efficiency when simulating multiphase flows. On the other hand, the DIIB method is able to resolve dynamic wetting on curved substrates on a Cartesian grid, but it usually requires a mesh of high resolution in the vicinity of a moving contact line to resolve the local flow. In the present study, we couple the DIIB method with the dual-resolution grid, to improve the interface resolution for flows with moving contact lines on curved solid walls at an affordable cost. The dynamic behavior of moving contact lines is validated by studying drop spreading, and the numerical results suggest that the effective slip length λ_n can be approximated by 1.9Cn, where Cn is a dimensionless measure of the thickness of the diffuse interface. We also apply the method to drop impact onto a convex substrate, and the results on the dual-resolution grid are in good agreement with those on a single-resolution grid. It shows that the axisymmetric simulations using the DIIB method on the dual-resolution grid saves nearly 60% of the computational time compared with that on a single-resolution grid.展开更多
文摘Interdiffusion can be a major cause of failure in coated parts that see service at elevated temperatures. Ways to measure the extent of interdiffusion and mathematical equations for predicting these measures are given. The equations are based on the error function solution to the diffusion equation and do not take into account variations of the diffusivity with composition. Also, when the substrate of the coating is multiphase, the equations do not take into account the precipitate morphology, but do take into account that precipitates can act as sinks or sources of solute as the average composition of the substrate varies. The equations are meant to be alloy design tools that indicate how changing substrate or coating chemistry will reduce the extent of interdiffusion.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11425210,11621202 and 11672288)
文摘In this paper, we investigate flows with moving contact lines on curved solid walls on a dual-resolution grid using a diffuse-interface immersed-boundary（DIIB） method. The dual-resolution grid, on which the flows are solved on a coarse mesh while the interface is resolved on a fine mesh, was shown to significantly improve the computational efficiency when simulating multiphase flows. On the other hand, the DIIB method is able to resolve dynamic wetting on curved substrates on a Cartesian grid, but it usually requires a mesh of high resolution in the vicinity of a moving contact line to resolve the local flow. In the present study, we couple the DIIB method with the dual-resolution grid, to improve the interface resolution for flows with moving contact lines on curved solid walls at an affordable cost. The dynamic behavior of moving contact lines is validated by studying drop spreading, and the numerical results suggest that the effective slip length λ_n can be approximated by 1.9Cn, where Cn is a dimensionless measure of the thickness of the diffuse interface. We also apply the method to drop impact onto a convex substrate, and the results on the dual-resolution grid are in good agreement with those on a single-resolution grid. It shows that the axisymmetric simulations using the DIIB method on the dual-resolution grid saves nearly 60% of the computational time compared with that on a single-resolution grid.
