This paper deals with the numerical prediction of the aeroacoustic behavior of orifices under grazing flow conditions. A hybrid computational aeroacoustics approach is adopted where the steady, incompressible, mean flow over the orifice is obtained from a RANS simulation. In a next step, the mean flow variables are used to solve the linearized Navier–Stokes equations (LNSE), using a Runge–Kutta...

A perforated plate with stepwise apertures (PPSA) is proposed to improve sound absorption for low frequencies. In contrast an ordinary insufficient acoustic resistance and small mass, the stepped holes could match of air characteristic impedance also moderately increase mass especially at Prototypes made by 3D printing technology are tested in tube. The measured results agree well that predicti...

The loading conditions used in some current in vivo and in vitro blast-induced neurotrauma models may not be representative of real-world blast conditions. To address these limitations, we developed a compressed-gas driven shock tube with different driven lengths that can generate Friedlander-type blasts. The shock tube can generate overpressures up to 650 kPa with durations between 0.3 and 1.1...

We present a numerical investigation of an acoustic sensor based on cylindrical resonator to monitor the properties liquids flowing in tube. The design consists hollow washer surrounding tube, which carries liquid, and can be filled during sensing process. Due impedance mismatch between liquid solid washer, we demonstrate presence high-quality factor resonances associated with (such as velocity...

Measurements of acoustic properties sound absorbing materials in impedance tubes show poor reproducibility, which was demonstrated round robin tests. The tube measurements are standardized but lack precise definitions the actual measurement setup, specimen preparation, and other factors that introduce uncertainty practice. In this paper, machine learning models identify those mostly affect abso...

in this study, a novel variable impedance control for a lower-limb rehabilitation robotic system using voltage control strategy is presented. the majority of existing control approaches are based on control torque strategy, which require the knowledge of robot dynamics as well as dynamic of patients. this requires the controller to overcome complex problems such as uncertainties and nonlinearit...

In this study, biodegradable materials that could be utilized to reduce noise were examined. Sound absorption test was conducted with an impedance tube. Sawdust, coconut fiber, and expansive clay used create samples. Noise reduction coefficient results for sawdust mixture ranged from 0.24 0.62. A of fiber recorded in between 0.31 0.58. Coconut mixed ranging The study findings suggests these hav...

The uncertainty related to measurements is fundamental for qualifying the method applied estimation of quantities derived from an experimental test. In this paper analysis given intrinsic properties fibrous and porous materials, i.e. characteristic impedance wavenumber, measurement data obtained by a four-microphone tube. addition, some other material properties, amongst which flow resistivity....