Effective techniques and crucial problems of numerical study on flue instruments

Abstract

In the last several decades, there have been many important proposals for study on flue instruments from theoretical and experimental points of view. Analyses based on aerodynamic sound theory are crucial for understanding the sounding mechanism of flue instruments. According to the growth of computer power and the improvement of numerical schemes, numerical simulations based on fluid dynamics now become important tools for the study of aerodynamics sound. In this talk, we will discuss accuracy, efficiency and reliability of numerical calculations with Large-Eddy- Simulation (LES) of compressible flow and we will show to what extent LES can reproduce the fluid and acoustic behavior of flue instruments observed experimentally. In comparison between the 2D and 3D models, we find that the 2D model is more unstable due to the characteristic of 2D fluid, that is, existence of long-life vortex tubes, whose irregular behavior disturbs the jet motion as well as the acoustic field. Therefore, a 3D simulation is important to reproduce realistic oscillations of flue instruments avoiding spurious jet instabilities. Furthermore, we will point out the possibility of estimation of the energy transfer between the acoustic field and the hydro-dynamic field, namely how to numerically calculate Howe's energy corollary.