Laboratory modelling of the wind-wave interaction with modified PIV-method

Laboratory experiments on studying the structure of the turbulent air boundary layer over waves were carried out at the Wind-Wave Flume of the Large Thermostratified Tank of the Institute of Applied Physics, Russian Academy of Sciences (IAP RAS), in conditions modeling the near water boundary layer of the atmosphere under strong and hurricane winds and the equivalent wind velocities from 10 to 48 m/s at the standard height of 10 m. A modified technique of Particle Image Velocimetry (PIV) was used to obtain turbulent pulsation averaged velocity fields of the air flow over the water surface curved by a wave and average profiles of the wind velocity. The main modifications are: 1) the use of high-speed video recording (1000-10000 frames/sec) with continuous laser illumination helps to obtain ensemble of the velocity fields in all phases of the wavy surface for subsequent statistical processing; 2) the development and application of special algorithms for obtaining form of the curvilinear wavy surface of the images for the conditions of parasitic images of the particles and the droplets in the air side close to the surface; 3) adaptive cross-correlation image processing to finding the velocity fields on a curved grid, caused by wave boarder; 4) using Hilbert transform to detect the phase of the wave in which the measured velocity field for subsequent appropriate binning within procedure obtaining the average characteristics

Bag-breakup fragmentation as the dominant mechanism of sea-spray production in high winds

Peer reviewe

Dynamics of turbulent jet with positive buoyancy in a stratified fluid

The modeling of flow induced by submerged sewer system was carried out within laborarory physical experiment. Results of experiments perfomed at two expeimental facilities (Large Termostratified Tank LTSB (20*4*2 m) and small ltank (1.2*0.5*0.5 m) with saline stratification) are presented. The theoretical model of Fan &Brooks (1969) was verified within the series of experiments in saline pycnocline–type stratification in wide range of parameters. The conditions of scaling modeling were determined on the basis of this model, and laboratory scale modeling with geometrical scale 1:27 was perfomed in LTSB. Excitation of intencive temperature oscillations in the picnocline was observed. They were interpreted as self-sustained oscillations of the buoayant plume

Laboratory, numerical and theoretical modeling of a far wake flow in a stratified fluid

A laboratory study and direct numerical simulation (DNS) of far wake flow in a stratified fluid are performed. The laboratory study employs the PIV technique to measure the velocity field in a wake behind a towed sphere at high Reynolds and Froude numbers. The DNS parameters and initialization are prescribed in accordance with the experimental data, which allows a direct comparison between numerical and experimental results. The results of the DNS and the laboratory experiment are compared with predictions of a theoretical model, which considers the wake as a quasi-two dimensional turbulent jet flow with the main mechanism of evolution associated with transfer of momentum from the mean flow to quasi-two dimensional sinuous disturbances growing due to hydrodynamic instability. The time evolution of the wake axis velocity and its width obtained within the framework of the model is in good agreement with the experimental and numerical data

MAGIC and H.E.S.S. detect VHE gamma rays from the blazar OT081 for the first time: a deep multiwavelength study

https://pos.sissa.it/395/815/pdfPublished versio

Wind Speed Analysis Method within WRF-ARW Tropical Cyclone Modeling

This paper presents an analysis of a new method for retrieving the parameters of the atmospheric boundary layer in hurricanes. This method is based on the approximation of the upper parabolic part of the wind speed profile and the retrieval of the lower logarithmic part. Based on the logarithmic part, the friction velocity, near-surface wind speed and the aerodynamic drag coefficient are obtained. The obtained data are used for the verification of the modeling data in the WRF-ARW model. The case of the Irma hurricane is studied. Different configurations of the model are tested, which differ in the use of physical parameterizations. The difference of wind profiles in various sectors of the hurricane is studied