Mitigation of Flow-Induced Cylinder Noise Through the Control of Sound Diffraction

The sound emitted by the flow past a circular cylinder can be described by a quadrupole placed at the outbreak location of the shedding instability and diffracted surface into the far field by the body with a dipolar directivity. This mechanism is greatly stabilized for a cylinder coated with a porous material, which features a substantial downstream shift of the onset location of the shed vortices that leads, in turn, to a reduction in the efficiency of the sound scattering and consequent noise mitigation. In this research, a novel design for a porous treatment of the cylinder based on the enhancement of this effect is proposed. Far-field acoustics tests were performed at the Delft University of Technology for Reynolds numbers based on the cylinder diameter ranging in the subcritical regime. The outcomes of the analysis demonstrate that, when the aft part of the flow-permeable coating is modified to make the internal flow more streamlined, an additional sound attenuation of up to 10 dB is achieved in comparison with a uniform porous cover. Moreover, a significant noise decrease of up to 10 dB and potential drag reduction are obtained if these components are connected to the bare cylinder without the use of a porous coating. This result can open up interesting opportunities to design disruptive and more optimized sound-mitigation solution

In-situ poling and structurization of piezoelectric particulate composites

Composites of lead zirconate titanate particles in an epoxy matrix are prepared in the form of 0–3 and quasi 1–3 with different ceramic volume contents from 10% to 50%. Two different processing routes are tested. Firstly a conventional dielectrophoretic structuring is used to induce a chain-like particle configuration, followed by curing the matrix and poling at a high temperature and under a high voltage. Secondly a simultaneous combination of dielectrophoresis and poling is applied at room temperature while the polymer is in the liquid state followed by subsequent curing. This new processing route is practiced in an uncured thermoset system while the polymer matrix still possess a relatively high electrical conductivity. Composites with different degrees of alignment are produced by altering the magnitude of the applied electric field. A significant improvement in piezoelectric properties of quasi 1–3 composites can be achieved by a combination of dielectrophoretic alignment of the ceramic particles and poling process. It has been observed that the degree of structuring as well as the functional properties of the in-situ structured and poled composites enhance significantly compared to those of the conventionally manufactured structured composites. Improving the alignment quality enhances the piezoelectric properties of the particulate composites.Novel Aerospace Material

Социальное благополучие как критерий эффективности неоиндустриализации экономики

Неоиндустриализация предполагает экономику, основанную на знаниях и сетях. В отличие от индустриальной экономики, где ключевыми факторами развития являются добыча и переработка сырья, в новой экономике будет доминировать инженерное творчество, дизайн и программирование. Это коренным образом меняет картину социального благополучия, которое выступает, с одной стороны, критерием, с другой - конечным результатом неоиндустриализации экономики

Modelling of thermal-physical properties of composite material

Article represents theoretical determination of effective heat conductivity of composite materials. Authors describe PC program written with Visual Basic for calculation of heat conductivity of composite materials. There is particular focus on various methods for calculation of heat conductivity of composite materials in accordance with offered models and on comparison between calculated and experimental data