Experimental and Numerical Investigation of Near-field Rotor Aeroacoustics

This work presents comparisons between experimental and numerical estimates of near-field rotor aeroacoustics in hover. The experiments took place at the Kazan National Research Technical University named after A. N. Tupolev (Kazan Aviation Institute). A set of rotor blades with NACA-0012 aerofoil sections was used to obtain the sound pressure distribution using a linear array of microphones. It is shown that CFD and experimental results are in good agreement suggesting that the obtained test data can be useful as a validation case for development of CFD tools

Experimental and numerical study of rotor aeroacoustics

The work documents recent experiments at the Kazan National Research Technical University named after A.N. Tupolev (Kazan Aviation Institute), related to helicopter acoustics. The objective is to measure nar-field acoustics of rotors in hover and provide data suitable for computational fluid dynamics validation. The obtained set of data corresponds to a scaled rotor of known planform and the results are of high resolution. An advantage of the current dataset is that direct near-field acoustic data is made available and this allows for easy and direct comparisons with computational fluid dynamics predictions, without the need to use far-field aeroacoustic methods

Relativistic theory of the double photoionization of helium-like atoms

A fully relativistic calculation of the double photoionization of helium-like atoms is presented. The approach is based on the partial-wave representation of the Dirac continuum states and accounts for the retardation in the electron-electron interaction as well as the higher-order multipoles of the absorbed photon. The electron-electron interaction is taken into account to the leading order of perturbation theory. The relativistic effects are shown to become prominent already for the medium-Z ions, changing the shape and the asymptotic behaviour of the photon energy dependence of the ratio of the double-to-single photoionization cross section

Thermospheric parameters' long-term variations over the period including the 24/25 solar cycle minimum. Whether the CO2 increase effects are seen?

Abstract The CO2 concentration has been increasing for more than five decades reaching ~29 % at present with respect to the pre-industrial era. The largest CO2 cooling effects in the thermosphere are predicted for solar minimum conditions. A comparison of solar minima in 1954/1964 to the recent one in 2019 was used to check at the quantitative level the theoretical predictions and the validity of the CO2 cooling hypothesis. June monthly median noontime ionospheric observations at Moscow, Rome, and Slough/Chilton were used to infer neutral gas density ρ, exospheric temperature Tex, height of the F2-layer maximum hmF2, and total solar EUV flux for the (1954–2020) period. Solar and geomagnetic activity was shown to explain ~99 % of the whole variability in the retrieved neutral gas density and Tex during the (1958–2020) period resulting in statistically insignificant residual linear trends. A comparison of 1954/1964 to 2019 solar minima does not confirm the theoretically predicted decrease of ~21 % in ρ, ~15 K in Tex, and ~7 km in hmF2 related to a 29 % increase of the CO2 abundance. The main conclusion: despite continuous CO2 increase in the Earth's atmosphere long-term variations of thermospheric parameters are controlled by solar and geomagnetic activity

CAA Modeling of Helicopter Main Rotor in Hover

In this work rotor aeroacoustics in hover is considered. Farfield observers are used and the nearfield flow parameters are obtained using the in house HMB and commercial Fluent CFD codes (identical hexa-grids are used for both solvers). Farfield noise at a remote observer position is calculated at post processing stage using FW–H solver implemented in Fluent and HMB. The main rotor of the UH-1H helicopter is considered as a test case for comparison to experimental data. The sound pressure level is estimated for different rotor blade collectives and observation angles

Remote sensing technology in mapping socio-economic divergence of Europe

Marine and ocean coasts traditionally act as natural growth poles for the humankind. Recent studies conducted by scholars from both natural and social sciences suggest that coastal zones accumulate population, agglomerate industries, attract entrepreneurs, and pull investments. The coastalization effect remains to be one of the defining factors of regional development around the globe and is projected to strengthen within a quarter of a century. Deepening socio-economic inequality and polarization between countries and regions despite of efforts taken with the convergence policies puts the ‘marine factor’ on research agenda. The study holds a comparative evaluation of the coastalization processes across the regions of Europe using the remote sensing technology and the statistical multivariate analysis for testing the correlation level of the results obtained. The research is based on a dataset for 413 regions of Europe featuring indicators for population density and Gross Regional Product (GRP) in Purchasing Power Parity (PPP) per sq.km. The regions are grouped into clusters depending on their socio-economic indicators and the intensity of nocturnal illumination. Results suggest that coastal and inland region types evenly distribute between clusters, with an average of 40% coastal. Observations over nocturnal illumination clearly indicate an extensive anthropogenic impact on European coasts, both northern and southern. However, their overall luminosity is inferior to inland territories. The study concludes with four patterns derived from a combined methodology of socio-economic indicators and remote sensing

The "Quasar" Network Observations in e-VLBI Mode Within the Russian Domestic VLBI Programs

The purpose of the Russian VLBI "Quasar" Network is to carry out astrometrical and geodynamical investigations. Since 2006 purely domestic observational programs with data processing at the IAA correlator have been carried out. To maintain these geodynamical programs e-VLBI technology is being developed and tested. This paper describes the IAA activity of developing a real-time VLBI system using high-speed digital communication links

Mapping long-term spatial trends of the Taimyr wild reindeer population

This report presents preliminary results of mapping and analyzing wild reindeer spatial dynamics in Taimyr, Russia. We collected, spatially referenced, and systematized comprehensive aerial and land survey information spanning from 1969 to 2003, which is the most complete long-term data available about a wild reindeer herd in Eurasia. The report introduces some of the mapping products and presents a summary of our observations on spatiotemporal changes in reindeer distribution and migration. Using these data and new digital products in the GIS (Geographic Information Systems) environment, we were able to observe the long-term shift of the Taimyr Reindeer Herd's summer, winter, and calving areas to the east and south with a simultaneous expansion of the habitat. We identified and confirmed locations of large reindeer concentrations (herds) seasonally formed throughout the study period. Using the most recent summer survey data (2009) we also were able to confirm the existence of two major migration flows in the fall: eastern (most reindeer) and western