Investigating the effect of non-dimensional distances on the calculation of sound intensity in large eddy simulation method

The accuracy of the large eddy simulation method near the wall depends on the non-dimensional distances y ^ +, x ^ + and z ^ + of the grid in the boundary layer. Study on these non-dimensional distances have been made in various research. But these values ​​can vary depending on the physics of the problem and the phenomena being studied. In this article, the effect of these parameters is investigated on sound estimation. For this purpose two types of grids with different setting have been used. The results obtained from both grids have been validated using experimental data in the one-third octave band . In the study of vortices, using flow lines and Q-criteria, it was observed that the use of larger non-dimensional distances on the wall surface increases the longitudinal scale and strength of vortices and as a result the strength of acoustic waves is estimated to be higher than the actual value. This issue was studied from different directions and it was observed that the differences between the two grids varies at different angles. The maximum difference between the total average sound pressure level obtained by the two meshes is about eleven decibels at an angle of 135 degrees. Considering that the two-dimensional distances used in the both grids were within the suitable ranges suggested in the previous study, it can be said that more stringent requirements for non-dimensional distances are needed to accurately predict the strength of acoustic waves.