Direct Numerical Simulation of a Square-Notched Trailing Edge for Jet-Noise Reduction

2008 ◽  
Author(s):  
Andreas Babucke ◽  
Markus Kloker ◽  
Ulrich Rist
Keyword(s):  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Noise Reduction ◽  
Jet Noise ◽  
Trailing Edge

Direct Numerical Simulation of Turbulent Flow over a Rectangular Trailing Edge

2001 ◽  
Vol 14 (5) ◽  
pp. 337-358 ◽  
Author(s):  
Y.F. Yao ◽  
T.G. Thomas ◽  
N.D. Sandham ◽  
J.J.R. Williams
Keyword(s):  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Turbulent Flow ◽  
Trailing Edge

Direct numerical simulation of a puff and a slug in transitional cylindrical pipe flow

1999 ◽  
Vol 387 ◽  
pp. 39-60 ◽  
Author(s):  
H. SHAN ◽  
B. MA ◽  
Z. ZHANG ◽  
F. T. M. NIEUWSTADT
Keyword(s):  
Numerical Simulation ◽  
Reynolds Number ◽  
Direct Numerical Simulation ◽  
Pipe Flow ◽  
Leading Edge ◽  
Transition Process ◽  
Axial Position ◽  
Trailing Edge ◽  
Mean Velocity ◽  
The Mean

A direct numerical simulation of transitional pipe flow is carried out with the help of a spectral element method and used to investigate the localized regions of ‘turbulent’ flow that are observed in experiments. Two types of such regions can be distinguished: the puff and the slug. The puff, which is generally found at low values of the Reynolds numbers, is simulated for Re = 2200 where the Reynolds number Re is based on the mean velocity UB and pipe diameter D. The slug occurs at a higher Reynolds number and it is simulated for Re = 5000. The computations start with a laminar pipe flow to which is added a prescribed velocity disturbance at a given axial position and for a finite time. The disturbance then evolves further into a puff or slug structure.The simulations confirm the experimentally observed fact that for a puff the velocity near the leading edge changes more gradually than for a slug where an almost discontinuous change is observed. The positions of the leading and trailing edges of the puff and slug are computed from the simulations as a function of time. The propagation velocity of the leading edge is found to be constant and equal to 1.56UB and 1.69UB for the puff and slug, respectively. For the trailing edge the velocity is found to be 0.73UB and 0.52UB, respectively. By rescaling the simulation results obtained at various times to a fixed length, we define an ensemble average. This method is used to compute the average characteristics of the puff and slug such as the spatial distribution of the mean velocity, the turbulent velocity fluctuations and also the wall shear stress. By computing particle trajectories we have investigated the entrainment and detrainment of fluid by a puff and slug. We find that the puff detrains through its trailing edge and entrains through its leading edge. The slug entrains fluid through its leading and through most of its trailing edge. As a consequence the fluid inside the puff is constantly exchanged with fluid outside whereas the fluid inside a slug remains there. These entrainment/detrainment properties which are in agreement with the measurements of Wygnanski & Champagne (1973) imply that the puff has the characteristics of a wave phenomenon while the slug can be characterized more as a material property which travels with the flow.Finally, we have investigated in more detail the velocity field within the puff. In a coordinate system that travels with the mean velocity we find recirculation regions both near the trailing and leading edges which agrees at least qualitatively with experimental data. We also find streamwise vortices, predominantly in the trailing-edge region which have been also observed in experiments and which are believed to play an important role in the dynamics of the transition process.

Supersonic jet noise reduction and mixing enhancement through nozzle trailing edge modifications

1997 ◽  
Author(s):  
Mo Samimy ◽  
Jin-Hwa Kim ◽  
Pamela Clancy ◽  
Mo Samimy ◽  
Jin-Hwa Kim ◽  
...  
Keyword(s):  
Noise Reduction ◽  
Supersonic Jet ◽  
Jet Noise ◽  
Mixing Enhancement ◽  
Trailing Edge ◽  
Supersonic Jet Noise

scholarly journals Experimental Study of Vapor Supercavitation Suppression of Capillary Outlet Jet Noise

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Qianxu Wang ◽  
Yicai Liu ◽  
Yao Yao ◽  
Yu Zhang
Keyword(s):  
Numerical Simulation ◽  
Experimental Study ◽  
Noise Reduction ◽  
Jet Noise ◽  
Bubble Bursting ◽  
Key Factor ◽  
Capillary Outlet

The degree of bubble bursting at the inlet of an evaporator is the key factor to determine the size of the injection noise at the capillary outlet. In this study, by using the theory of cavitation dynamics, the transition tube between the capillary and evaporator is improved to suppress the bubble bursting at the entrance of the evaporator, so as to reduce the jet noise at the outlet of the capillary. The influence of aeration structure on noise reduction of a refrigerator (Haier BCD-520) was studied by numerical simulation, and experiments were carried out. The results show that the admixture structure significantly inhibits the bubble bursting and reduces the injection noise by 1.5 dB(A).

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