Michael Yu. Hrebtov

Kutateladze Institute of Thermophysics, SB RAS · Laboratory of Power Plant Aerodynamics

The large-eddy simulation method was applied to study an isothermal swirled gas flow in a model combustion chamber at Reynolds number Re = 15000. The study identified a coherent vortex structure: this is a precessing vortex core which contributes to pressure pulsations reaching a maximum inside the model device. It is possible to suppress this cohe...

We studied flow dynamics in a model combustion chamber using Large-eddy simulations (LES) and Particle image velocimetry (PIV) at the Reynolds number Re of 15,000. The swirl is produced using a Turbomeca swirler and air flow, while combustion is supported by a central methane/air jet. We compared four flow regimes, assessing the effect of the centr...

Large-eddy simulations are performed to investigate the cavitating flow around two dimensional hydrofoil section with angle of attack of 9° and high Reynolds number of 1.3×10 ⁶ . We use the Schnerr-Sauer model for accurate phase transitions modelling. Instantaneous velocity fields are compared successfully with PIV data using the methodology of con...

We performed Large-eddy simulations of the flow in a model air Francis turbine in a range of low-load regimes with a swirler rotating at fixed frequency. All investigated regimes revealed the presence of coherent helical vortex structure in the draft tube: the precessing vortex core. We identified the frequency of this instability and obtained mean...

The paper presents a simplified numerical model of the hydrogen plasma generation process in a microwave resonant cavity. The model assumes electroneutrality and the prescribed electron temperature of the plasma, thus significantly reducing the computational cost. This allows for the parametric study in a wide range of operating pressures end elect...

We perform Large-eddy simulations of a non-premixed swirling flame in a model of a combustion chamber with a swirling air bulk flow at Re = 15000 and a central pilot low-velocity jet with methane using the Flamelet-generated manifold model. The unsteady behaviour of this regime is well reproduced based on the flame dynamics. The distribution of tur...

The paper presents the results of optimization of the geometric parameters of the simplified wall jet cooling system using a modified Adjoint Shape optimization method for algebraic systems of equations (Discrete Adjoint Optimization). The modification consists in using a linearized discrete system of equations with the replacement of derivatives b...

The article presents a simplified numerical simulation of a vacuum ferroelectric cathode operating in a low-current mode (without surface plasma formation). The field emission from the cathode was simulated for the range of applied electric field magnitudes. The polarization domain growth process during the charging of ferroelectric surface was sim...

We present results of Large-eddy simulations (LES) modeling of steady sheet and unsteady cloud cavitation on a two-dimensional hydrofoil which are validated against Particle image velocimetry (PIV) data. The study is performed for the angle of attack of 9◦ and high Reynolds numbers ReC of the order of 10^6 providing a strong adverse pressure gradie...

We perform Large-eddy simulations to study a cavitating flow over a two-dimensional hydrofoil section using the Schnerr-Sauer cavitation model and the adaptive mesh refinement in intensive phase transition flow areas. The case corresponds to 9 • angle of attack and high Reynolds number 1.32 × 10^6 based on the foil chord length providing a strong a...

Lagrangian particle tracking Shake-the-box (STB) method (Schanz et al., 2016) acquires the 3D positions of tracer particles from the temporal sequences of their 2D projection images even for rather high seeding densities. Approximation of tracks by analytical functions (Gesemann, 2015) provides an accurate evaluation of tracers' local velocity and...

Lagrangian particle tracking Shake-the-box (STB) method (Schanz et al., 2016) acquires the 3D positions of tracer particles from the temporal sequences of their 2D projection images even for rather high seeding densities. Approximation of tracks by analytical functions (Gesemann, 2015) provides an accurate evaluation of tracers’ local velocity and...

We report on a numerical simulation of morning transition in the atmospheric boundary layer above the river Yenisey near the city of Krasnoyarsk. The effect of meandering river promotes complex air circulation patterns leading to the formation of large-scale vertical vortex pair. The current LES results supports previous RANS simulations indicating...

The Lagrangian particle tracking shake-the-box (STB) method provides accurate evaluation of the velocity and acceleration of particles from time-resolved projection images for high seeding densities, giving an opportunity to recover the stress tensor. In particular, their gradients are required to estimate local pressure fluctuations from the Navie...

We report on a numerical study of diurnal cycle in the atmospheric boundary layer above a meandering river. The topography and the river shape are taken from the satellite data near Krasnoyarsk (Russia). Convective patterns developing during the early morning and the daytime lead to the formation of horizontal circulation and the jet-like flow acro...

We present a set of LES results for transitional sheet and unsteady cloud cavitation flow regimes around a two-dimensional hydrofoil section and use our previous visual and PIV data for validation. The study is performed for the angle of attack of 9 and high Reynolds numbers of the order of 10^6 based on the foil chord length providing a strong adv...

The paper presents a numerical simulation of the hydrogen plasma generation process in a cylindrical microwave resonant cavity at moderate pressures (10 Torr). We introduce a modification to the chamber by placing several spherical dielectrics with a high permittivity at the central axis. The radii of the spheres are chosen for the Mie resonance fo...

Large-eddy simulations of the swirling annular jet flow are performed in a model of a combustion chamber at two different flow regimes with and without the central jet at Re = 5000. The mesh convergence study provides well-described time-averaged statistics even for a coarse mesh, while small-scale features are only resolved after a proper refineme...

We present a numerical simulation of the flat plate film cooling setup with an elliptical nozzle with a 35° inclination angle. The baseline simulation mimics an experimental setup from [1]. We introduce a modification to the nozzle channel shape by including a backward step with a fixed width, while keeping the nozzle outlet shape fixed. The modifi...

We present a numerical simulation of the simplified ferroelectric plasma source operating in a gas discharge mode. The plasma source contains two electrodes separated by a ferroelectric. High voltage pulse applied to the cathode leads to formation of a dielectric barrier discharge in gas (argon at 1 Torr pressure). The main point of the study is to...

Conversion of waste heat into usable electricity is a strategic technology for saving natural resources and an important option for powering autonomous devices. Current developments in micro- and nanotechnology open new horizons and require revisiting the process of energy conversion with a focus on low-dimensional micro- and nano-scale generators....

The paper presents the results of Large eddy simulation of a free swirling jet with Reynolds number Re = 104 for different swirl numbers. Rotating nozzle was chosen as the swirl configuration. The additional case that simulated the rotating tube with a honeycomb section using the dynamic mesh was chosen as the initial conditions generator. In the s...

With advances in nanotechnology, ferroelectric switching by individual domain walls (DWs) has become a subject of broad interest. Conventional models consider DW motion in a fixed homogeneous or inhomogeneous electric field. However, it is clear that the electric field commonly evolves in time due to the redistribution of bound charges and screenin...

We present the results of optimization of microwave plasma generation in a prototypical diamond film deposition device by means of numerical simulation. The modification of the device was done by changing the shape of microwave resonant chamber, where the plasma generation occurs, in a way to focus the discharge near the outlet nozzle. The best res...

We present the results of LES modelling and PIV experiment of heat exchange between a flow in a wake of a heated bluff body and an array of thin plates. The efficiency of thermal fluctuations generation was investigated with potential applications to waste heat storing by pyroelectric effect. The effect of periodic attachment of wake vortices to th...

The article presents the results of direct numerical simulation of a turbulent vortex ring with a moderate Reynolds number, interacting with the field of external turbulent fluctuations. The ring is formed by buoyancy forces from a spherically-shaped volume of elevated temperature. We consider the interaction of the ring with the field of turbulent...

Supersonic gas flows activated by microwave discharge are commonly used to obtain thrust for spacecraft. When using a mixture of hydrocarbons and hydrogen as a working gas, the proposed method generates high-speed plasma streams with a high concentration of radicals, allowing it to be used for efficient deposition of diamond films . To optimize dia...

Seasonal variation of air quality in a city with a large river was investigated by means of numerical simulations of air movement and pollutant dispersion over inversion-capped diurnal cycles using a Reynolds-averaged Navier–Stokes (RANS) approach with algebraic turbulent flux model. The study accounts for the effects of urban heat island (UHI), te...

We report on numerical simulation of windless diurnal cycle of pollutant spreading over an urban terrain with a river running through the city, using a RANS algebraic flux model. The case mimics the real environment of Krasnoyarsk region (Russia). Two sets of conditions were considered: "winter" and "summer". In both cases the simulation starts wit...

Pyroelectric energy harvesting is an important option for powering autonomous electronic devices. For the technology to be efficient high-frequency thermal oscillations are needed. Here we suggest a method of creation of thermal oscillations in a pyroelectric plate, based on Karman instability. Vortices, shedding alternatively from the two sides of...

We report on Large Eddy Simulation of a stably stratified atmospheric boundary layer with a simplified river flow at the bottom boundary. The shear generated by the friction of water surface leads to creation of the air flow in a thin layer above water surface. Stratification prevents vertical motion due to negative buoyancy effects, and the flow e...

The paper presents the results of Large Eddy Simulation of a swirling impinging jet with moderate Reynolds number (10⁴), where the swirl is organized via the rotation of a convergent nozzle. The results show that the effect of the swirl in this configuration leads to an increase of axial velocity, compared to the non-swirling case. It is shown that...

The present paper reports on high-speed tomographic particle image velocimetry measurements of large-scale coherent structures in the near field of swirling turbulent jets. Three flow cases are considered: a jet without superimposed swirl; a jet with low swirl; and a high-swirl jet with bubble-type vortex breakdown and a central recirculation zone....

Conversion of waste heat into usable electricity is now one of the important strategies for saving natural resources and minimizing impact on the environment. In contrast to Seebeck devices, utilizing a temperature gradient, pyroelectric scavengers use temporal temperature oscillations. Here, optimal strategies for pyroelectric energy harvesting ar...

We present the results of Large Eddy Simulation of a turbulent jet discharging into a confined slot with the wall spacing to jet inlet width ratio = 0.1 and Re = 10⁴. The jet exhibits a meandering motion accompanied by formation of checkerboard pattern of large vortices in the mixing layer. A passive scalar transport was simulated with uniform inle...

We performed a numerical simulation of penetrative convection of an inversion-topped weakly stratified atmospheric boundary layer over urban terrain with a strong localized source of heat and moisture. With some simplifications, the case mimics the real environment of the Krasnoyarsk region in Russia where the non-freezing river Yenisei acts as a t...

We present the results of direct numerical simulation of stably stratified open channel flow. The simulation was conducted in a frame of reference moving with the mean flow. The chosen setup allowed us to apply temporal filtering without affecting the long-living large-scale laminar and turbulent patches to see the dynamics of the processes on thei...

We present the results of numerical simulation of conjugate heat transfer between thin (100-1000 nm) solid plates and periodically heated air flow. Several air inflow conditions were studied with different turbulence intensity and integral scale. The thermal response in the plate was calculated showing that inflow turbulence interacting with the pl...

We present the results of direct numerical simulation of stably stratified open channel flow. The main goal of the paper is to check the effect of thermal stratification on the dynamics of vortex interactions. By comparing the vortex stretching in neutral and stratified cases we show that imposing the stratification leads to an increase of the rati...

We present the results of simulation of conjugate heat transfer between the grid of barium titanate plates and the hot air flow. The air temperature undergoes rapid change and the thermal front propagation and heat exchange with the solid plates have been studied for several plate configurations. The results show that the air heat could be effectiv...

We present “wall functions” for treating the ground boundary conditions in the computation of thermal convection over horizontal surfaces at high Rayleigh numbers using coarse numerical grids. The functions are formulated for an algebraic-flux model closed by transport equations for the turbulence kinetic energy, its dissipation rate and scalar var...

We present a numerical simulation of penetrative convection of weakly stratified atmospheric boundary layer over a urban terrain with a strong localized source of heat and moisture. The case mimics the real environment of Krasnoyarsk region (Russia) where the non-freezing river Yenisei acts as a source of heat and moisture during winter. We simulat...

Large eddy simulation of turbulent free round jet has been performed to study statistical properties of turbulence, including third-order structure functions. It has been shown the presence of a zone within the jet initial region where the spectral flux of turbulent energy is directed from smaller scales toward larger ones and the longitudinal thir...