¡¤ Elucidate the hydrodynamic effects of lid on the flow-induced noise
- Direct numerical simulation
¡¤ L=2R, H=R, Le=0.5R, He=0.023R, Lin=Lout=4.54R
¡¤ Inflow : Fully-developed turbulent pipe flow at Ret=186.
¡¤ Outflow : Convective boundary condition.
¡¤ Periodic boundary conditions in the q direction.
¡¤ Grid resolution : Dz+min=1.45, Dz+max=17.97, (RDq)+=9.13, D r+min=0.13, Dr+max=4.9
- Mean velocity
¡¤ Relatively strong recirculation in case of the cavity without lid.
¡¤ Secondary recirculation is not seen for the cavity with lid.
- Radial mean velocity profiles
¡¤ Mass exchange at the cavity mouth is weakened in case of the cavity with lid
- Flow-induced noise
¡¤ Lighthill¡¯s equation for acoustic density fluctuations
¡¤ From the Lighthill acoustic analogy, acoustic source can be obtained from DNS of incompressible flow.
¡¤ Lighthill stress tensor
- Noise Source Term vs. Pressure Fluctuations
¡¤ Distributions of Srms are very similar those of p¡¯rms
¡¤ Flow-induced noise near the downstream edge is significantly reduced by lid
- 3D View of Instantaneous Flow Field
¡¤ Vortex identification by -l2 (Jeong and Hussain, 1995).
¡¤ Reduced turbulent structure in case of the cavity with lid