Publication Summary
The sound produced by large‐scale structures in free shear flows is investigated using direct numerical simulations (DNS). Both temporal and spatial DNS approaches are investigated, with special attention given to the former due to its lower computational cost. It is shown that the temporal approach can be used to investigate Mach‐wave generation but not the general sound emitted by large‐scale subsonic sources. Consequently, temporal DNS data of supersonic mixing layers undergoing transition to turbulence are analyzed. Two dominant Mach waves are found, each of which is identified with vortical features in the flow. The spatial DNS approach is then investigated to study the effect of the computational box size on the sound calculation. A large‐scale model is used to show that the low‐subsonic case is more restrictive in that sense than the supersonic one. The first case is further investigated by calculating the basic radiation emitted by axisymmetric jets, using the compact Lighthill and Mohring–Kambe formulations. Boundary corrections are developed and tested to reduce the box size effect and to improve the agreement between the two formulations. Finally, the effect of the retarded‐time variation along the jet is discussed.
CAER Authors
Dr. Eldad Avital
Queen Mary University of London - Reader in Computational (& Experimental) Fluids and Acoustics