A hybrid artificial boundary condition (HABC) that combines the volume-based acoustic damping layer (ADL) and local face-based characteristic (CBC) is presented to enhance absorption of waves near computational boundaries. This method applied prediction aerodynamic noise from a circular cylinder immersed in uniform compressible viscous flow. Different ADLs are designed assess their effectivenes...

in this paper, an approximate axisymmetric method is developed which can reliably calculate fully viscous hypersonic flow over blunt-nosed bodies. in this method, a maslen’s second-order pressure expression is used instead of the normal momentum equation. the combination of maslen’s second-order pressure expression and viscous shock layer equations is developed to accurately and efficiently com...

The purpose of this paper is to present a fast, economical and practical method for mathematical modeling of aerodynamic characteristics of rectangular wing-in-ground effect (WIG). Reynolds averaged Navier-Stokes (RANS) equations were converted to Bernoulli equation by reasonable assumptions. Also Helmbold's equation was developed for calculation of the slope of wing lift coefficient in ground ...

A fuzzy predictive pursuit guidance is proposed as an alternative to the conventional methods. The purpose of this scheme is to obtain a stable and fast guidance. The noise effects must be reduced in homing missile guidance to get an accurate control. An aerodynamic missile model is simulated first and a fuzzy predictive pursuit control algorithm is applied to reduce the noise effects. The perf...

An acoustic analysis of the uvular unvoiced fricative in intervocalic sequences, as spoken in Arabic, is presented. Properties of both the noise region and voiced boundaries are examined, and several attributes are discovered: the glottal waveform changes considerably during its transition between the vowels and the fricative boundaries, with the open quotient becoming 100% at the boundaries co...

Vibrations of blade and tower have important impact for wind turbine. This paper presents a active controller design to suppress blade edgewise vibrations under aerodynamic load and gravitational load.Treating the sum of aerodynamic load input in edgewise direction and gravitational load as unknown disturbance input,a stochastic disturbance accommodating control(SDAC) approach is proposed to de...

Hybrid CAA-approaches are commonly used for aeroacoustic engineering applications. In this kind of computational techniques, the numerical domain is split into a noise generating region, where an aerodynamic field generates the acoustic sources, and an acoustic propagation region. Nowadays a large variety of hybrid approaches exist differing from each other in the way the source region is model...

Motor vibration and noise is an important index to measure motor performance. How reduce one of the topics in field design. Analysis, calculation, reduction have attracted more attention from designers. Based on three main types sources motors, this paper firstly analyzes their causes mechanisms secondly introduces research methods. Although there are many summary articles noise, most theories ...

Broadband noise produced by the trailing-edge of a controlled diffusion (CD) airfoil is directly simulated using a Lattice-Boltzmann method (PowerFlow) which resolves both the aerodynamic and acoustic field around the airfoil. A proper DNS resolution is achieved in the vicinity of the airfoil for quasi-2D slice of the mock-up. Two numerical setups of the anechoic open-jet facility where both ae...

The NASA goal of reducing external aircraft noise by 10 dB in the near-term presents the acoustics community with an enormous challenge. This report identifies technologies with the greatest potential to reduce airframe noise. Acoustic and aerodynamic effects will be discussed, along with the likelihood of industry accepting and implementing the different technologies. We investigate the lower ...