Abstract Two rotating blade models with different half-flat tip trailing edge serrations were proposed. The flow characteristics and aerodynamic noise simulated using the large-eddy simulation model Ffowcs Williams Hawking’s acoustic analogy, respectively. effect of in reducing was investigated. Results showed that proposed serration designs can effectively reduce broadband noise, effectiveness...

To explore the complex flow field and noise characteristics of underwater high-speed gas jets, mixture multiphase model, large eddy simulation method, Ffowcs Williams–Hawking (FW–H) acoustic model were used for simulations, numerical methods validated by jet experimental results. The results revealed that during initial stages, collided with water surface created low-pressure high-temperature b...

For a single-component perfect gas, entropy perturbations are associated with the difference between overall density fluctuation and that coming from acoustic perturbation. Entropy can generate sound when accelerated/decelerated by non-uniform flow this is highly relevant to thermoacoustic instabilities for gas turbines rocket engines, noise emission aero-engines. Widely used theories model ent...

A Large-Eddy Simulation (LES) solver together with a Ffowcs-Williams and Hawking (FW-H) solver are coupled with a non-intrusive stochastic collocation method to propagate the geometric uncertainty observed in a rod-airfoil experiment. The LES are performed for several displacements of the rod with respect to its nominal position in the cross-wise direction. The positions are chosen to match the...

introduction: knowledge management is one of the most interesting and challenging issues of management in the new millennium. educational and research institutions such as libraries and information centers are the most suitable places for the implementation of knowledge management programs. this study aimed to identify and rank the factors affecting the implementation of knowledge management in...

The moving bullet out of a rifle barrel is propelled by a fired explosive charge. Subsequently, a disturbed muzzle blast wave is initiated which lasts several milliseconds. In this study, axially symmetric, unsteady, Large Eddy Simulation LES , and Ffowcs Williams and Hawkins FWH equations were solved by the implicit-time formulation. For the spatial discretization, second order upwind scheme w...

Huang, Lixi, and John E. Ffowcs Williams. Neuromechanical interaction in human snoring and upper airway obstruction. J. Appl. Physiol. 86(6): 1759–1763, 1999.—The fact that snoring and obstructive apnea only occur during sleep means that effective neuromuscular functioning of the upper airway during sleep is vital for the maintenance of unimpeded breathing. Recent clinical studies in humans hav...

A noise footprint prediction framework for propeller-driven aircraft which couples an aerodynamic model and several aeroacoustic models is presented in this study. The based on the blade element momentum theory, while are a time-domain compact dipole/monopole Ffowcs-Williams Hawking's acoustic analogy, trailing edge model, hemisphere database approach including straight-ray propagation respecti...