Wake-body interaction Noise Simulations by Coupling CFD and BEM

In many engineering applications, the wake-body interaction or body-vortex interaction (BVI) occurs. In the wake-body interaction, vortices shed from an upstream obstacle interact with downstream obstacle and generate noise, for example blades in a turbomachinery, tubes in a heat exchanger, rotating blades like a helicopter and wind turbine and so on. The rod-airfoil and airfoil-airfoil configurations are typical models for the wake-body interaction. A rod and an airfoil are immersed upstream of the airfoil. In this paper, we reviewed the noise mechanism generated by the wake-body interaction and show the numerical results obtained by the coupling method using commercial CFD and acoustic BEM codes. The results shows that depending on the spacing between the rod or airfoil and the airfoil, the flow patterns and noise radiation vary. With small spacing, the vortex shedding from the upstream obstacle is suppressed and it results in the suppression of the sound generation. With large spacing, the shear layer or the vortices shed from the upstream obstacle impinge on the downstream obstacle and it results in the large sound generation. The dominant peak frequency of the generated sound varies with increasing of the spacing between the two obstacles.

Attenuation and Prediction of the Ground Vibrations Induced by High-Speed Trains Running Over Bridge

This paper aims to study the transfer laws of vibration signals in the free field near a high-speed train line by conducting a field test. The characteristics of ground vibration acceleration were analyzed in the time and frequency domains, and a prediction method in the frequency domain was proposed. The results show: (1) there is a vibration amplification area away from the bottom of the pier under the influence of high-speed trains running over the bridge due to the fluctuation attenuation of the vibration waves; (2) the dominant peak frequency points in the frequency spectrum of the acceleration can be regarded as the resonance frequency induced by periodic loading; and (3) the soil vibration can be effectively predicted by the proposed method with a strong capability to defend the interference of environmental vibrations according to the comparison between the predicted value and the experimental data.

Effect of Different Gamma Dose and Chemical Etching on Pre- and Post-Alpha-Irradiated PM-355 Polymer

This work is based on the effect of different gamma doses with pre- and post-alpha-irradiated PM-355 polymer (polycarbonate of allyl diglycol). The phase crystallinity and structural analysis of the reference and irradiated PM-355 polymer were analyzed using an X-ray diffraction (XRD) study. It is revealed that the irradiation and etching reduce the %crystallinity but increase the crystallite size of the PM-355 polymer. The increase in crystallite size of PM-355 polymer after irradiation is supported by the scanning electron microscopic (SEM) analysis. The etching of the samples results in an increase in its track diameter. The optical band gap energy, measured by ultraviolet-visible (UV-VIS) spectroscopy, shows a decrement trend with the increase of gamma and alpha irradiation doses, and etching for all sets of samples under investigation. The number of carbon atoms per conjugation and per cluster has increased after gamma irradiation and etching. However, the increment is more pronounced for etched samples compared to nonetched ones. This indicates that etching results in a bigger size of cluster. Photoluminescence (PL) for both cases before and after etching has a dominant peak around 430 nm before and after irradiation, and change in peak intensity after irradiation confirmed that particle bombardment induced defects and clusters in the PM-355, which serves as nonradiative centers. The polymer can be used as a detector for gamma irradiation.

Refinement of the velocity section sedimentary stratum by the Nakamura method at new seismic stations of the IDG RAS

In 2017, as part of a project to study the deep structure of the central part of the East Europe-an platform, IDG RAS staff installed a sub latitudinal seismic profile of about 500 km in length, consisting of six stations. To successfully solve the problem of restoring a deep velocity section, the fullest possible information is needed on the velocity characteristics of the sedimentary sequence and, in particular, the first 0.5-1 km. Despite the considerable knowledge of the geological structure of the Moscow syneclise, information about its speed structure is based on interpolation and is fragmentary in nature. The paper presents the results of studies of the upper part of the sedimentary cover of the central part of the East Eu-ropean Platform (EEP) according to the data of the new network of broadband seismic stations IDG RAS. Using seismic noise records for each station, the dominant frequency peaks were obtained by the Nakamura method. For the Mikhnevo and Shatura stations, based on the data of deep drilling, it was established that the dominant peak corresponds to the boundary of the Upper Devonian - Lower Carbonian sediments. The obtained results make it possible to trace the occurrence of the indicated boundary along with all stations of the network along with the sublatitudinal profile through the collision zone of the EEP.

Wake-Body Interaction Noise Simulated by the Coupling Method Using CFD and BEM

In many engineering applications, obstacles often appear in the wake of obstacles. Vortices shed from an upstream obstacle interact with downstream obstacle and generate noise, for example blades in a turbomachinery, tubes in a heat exchanger, rotating blades like a helicopter and wind turbine and so on. This phenomenon is called wake-body interaction or body-vortex interaction (BVI). The rod-airfoil and airfoil-airfoil configurations are typical models for the wake-body interaction. A rod and an airfoil are immersed upstream of the airfoil. In this chapter, we review the noise mechanism generated by the wake-body interaction and show the numerical results obtained by the coupling method using commercial CFD and acoustic BEM codes. The results show that depending on the spacing between the rod or airfoil and the airfoil, the flow patterns and noise radiation vary. With small spacing, the vortex shedding from the upstream obstacle is suppressed and it results in the suppression of the sound generation. With large spacing, the shear layer or the vortices shed from the upstream obstacle impinge on the downstream obstacle and it results in the large sound generation. The dominant peak frequency of the generated sound varies with increase in the spacing between the two obstacles.

Universality in spectral condensation

Self-organization is the spontaneous formation of spatial, temporal, or spatiotemporal patterns in complex systems far from equilibrium. During such self-organization, energy distributed in a broadband of frequencies gets condensed into a dominant mode, analogous to a condensation phenomenon. We call this phenomenon spectral condensation and study its occurrence in fluid mechanical, optical and electronic systems. We define a set of spectral measures to quantify this condensation spanning several dynamical systems. Further, we uncover an inverse power law behaviour of spectral measures with the power corresponding to the dominant peak in the power spectrum in all the aforementioned systems.

Palladium Role in Growth of ZnO Nanostructure with Plasmonics Layering by Seed Mediated Hydrothermal Method

The electrical and optical properties of nanomaterials depend on their structural form. As an effort to develop an advanced nanomaterial, zinc oxide (ZnO) is interesting to synthesis for many applications such as active material for solar cells and biosensors. This paper provides the role of palladium and plasmonic materials in growing ZnO nanostructure, with a focus on its structural analysis. Nanomaterial ZnO was grown by seed-mediated hydrothermal method with layering by plasmonic materials, i.e. gold (Au) and platinum (Ag). X-ray diffraction analysis shows the presence of three dominant peak angles, i.e 34.43o, 36.32o, and 47.49o corresponding to crystal orientation of (002), (101) and (102), respectively. Palladium (Pd) treatment plus layering by plasmonic materials give a higher size of the nanostructure, but their electric band gaps are decreasing slightly. These findings also supported by high absorbance in UV-vis spectra. Gold layering on the nanomaterial gives a more significant role than platinum which indicated by higher size in diameter and higher absorption of UV-Vis spectra. The average size of pristine ZnO, ZnO:Pd, ZnO:Pd:Ag, and ZnO:Pd:Ag are 44.13, 45.99, 45.28, and 44.81 nm, respectively.

THE EFFECTS OF r-HDPE/r-PP FORMULATION RATIO INTO MECHANICAL, THERMAL AND MORPHOLOGICAL BEHAVIOR OF r-HDPE/r-PP POLYMERIC BLENDS

This study has reported the effects of different formulation ratio between recycled high density polyethylene (r-HDPE) and recycled polypropylene (r-PP) into the resulted mechanical, thermal and morphological properties of r-HDPE/r-PP polymeric blends. About five (5) different formulation ratio of r-HDPE/r-PP have been prepared and tested. The best combination ratio between r-HDPE and r-PP was determined in this work. It was found that the 70/30 wt.% of r- HDPE/r-PP blend possessed an outstanding mechanical and physical strength. About 59.80% and 2.30% of positive improvement in comparison to 0/100 wt.% of r-HDPE/r-PP was achieved for both of tensile strength and hardness, respectively. Interestingly, for 70/30 wt.% of r-HDPE/r-PP blend had also experienced major increased in their elongation at break up to 473%. The fracture morphological behavior of the tested samples that were observed via SEM observation, had established the interaction between the structure and properties of produced r-HDPE/r-PP blends, especially on the miscibility state between the r-HDPE and r-PP phases. Thermal evaluation by using the DSC had confirmed the partial miscibility state due to dominant peak shifting at 120 - 140°C and obvious melting peak reduction pattern. Overall, from this study, it was found that the blending between r-HDPE and r-PP into r-HDPE/r-PP blends are feasible to improve the properties of primary phase.