Angular Frequency Of Rotation Research Articles

Tunable acoustic vortex generation by a compact rotating disk

Acoustic vortices (AVs) carry orbital angular momentum (OAM), showing great promise in advancing communication, biomedicine, and metrology. An ideal OAM generation method that realizes the tunability of AV topological charge and working frequency in a compact way is strongly desired. Here, we utilize aerodynamic dipole sources from a rotating disk to generate AV. This method generates AVs with different topological charges through the interference of these dipole sources at the angular rotation frequency and its multiples. These AVs exhibit high purity, and their three-dimensional characteristics are explored. Furthermore, our experiment demonstrates that the generated AVs significantly enhance the sound field amplitude at their working frequency, which is the product of the topological charge and angular frequency. The results also verify that this amplitude enhancement effect is positively correlated with the AV’s stability and achieves the contactless detection of disk rotation information. The demonstrated method provides expanded versatility for OAM-based applications.

Algorithm of accurate cargo movement on a physical model of a sorting conveyor

Relevance. It is justified by the necessity to confirm the operability of the algorithm of accurate movement of the selected wood sorting to the corresponding storage bunker in the technological process of roundwood sorting at winter warehouses of timber processing companies to solve scientific and engineering problems both at present and in the future. Aim. To investigate the process of moving piece load on the physical model of longitudinal chain or belt conveyor, providing scaled reduction of positioning error. When sorting roundwood on chain longitudinal conveyors of considerable length, there is an error of movement of the selected roundwood sort to the place of discharge into the accumulator, which increases in proportion to the length of the sorting line. At present, conveyors of limited length are used. The accumulators are located on both sides of the conveyor. This reduces the transport error. Sometimes the sorting yard does not allow placing a short conveyor on it or there is a considerable amount of assortments. In this case, it is necessary to use a conveyor of considerable length. The paper proposes a new method of sorting roundwood on longitudinal chain conveyors of considerable length. This reduces the tracking error of the movement of the assortment. Optoelectronic sensors of angular displacements of the leading and driven shafts of the belt conveyor are used as sensors of angular displacements of the shaft. Methods. Physical modelling, information-static processing methods. Results and conclusions. The authors have carried out the analysis of the structure of the physical similarity stand of the longitudinal conveyor; sensors of the technological process, namely, angular frequency of rotation; software and hardware means of processing the obtained information to minimize the error of transporting piece cargo on the conveyor belt. The results of the study confirm the possibility of practical application of the device for operation on longitudinal conveyors.

Modelling the centrifugal mixing process of minced meat to optimise the production of chopped meat semi-finished products

One of the most important problems in ensuring the quality of mincemeat preparation in the production of sausages is the effective structuring of components and mixing of their ingredients. To solve this problem, researchers added a multifunctional admixture based on whey protein in the process of centrifugal mixing of the components, which determined the composition of the factor space of the investigated process. Based on the results of the research, the effective content of whey protein, sodium alginate, and soy fiber in the developed recipe was proven, which showed high characteristics in terms of fat-retaining and moisture-retaining ability, digestibility, pH level – activity, and other parameters. The developed formulation made it possible to improve the general indicator of the balance of amino acids in the product and increase the functional-technological and quality parameters of the developed products. The physical and mechanical characteristics of the obtained meat product were evaluated based on the results of physical and mathematical modelling. Modelling was carried out using Federman-on-Buckingham's second similarity theory and the "dimension theory" method, which allows the processing of the obtained experimental data in the form of a criterion equation, which was compiled using Froude, Euler, and Sherwood criteria. The purpose of this study was to obtain dependencies between such process factors as product density, the coefficient of dynamic viscosity of the technological medium, the ultimate shear stress, the change in the concentration of the main impurities of lactic acid in the raw material, the value of the diffusion coefficient and the coefficient of mass transfer in the loading mass, the weight of one load of products, the angular frequency of rotation of the screws of the minced meat mixer, the radius of the rotating working bodies, the characteristic size of the products after grinding. Using the complex criterion equation and the developed program, we find a recommended set of operating mode parameters for preparing minced meat under the conditions of centrifugal influence on the mixing process and the action of the specified factors.

Theory based recommendations to the resistive wall mode stability studies in tokamaks

The problem of the plasma stability against the resistive wall modes is considered from two sides, theoretical and experimental. The main subject is the dispersion relation and its verification, which is commonly understood as a comparison of the predicted and observed stability thresholds. As in the conventional magnetohydrodynamics, the growth rate γ and the angular rotation frequency ω of the mode are found from the energy balance with account of some dissipation in the plasma, additional to the resistive losses in the vacuum vessel wall. The resulting relations are integral, which allows the same γ and ω with different integrands. It is shown explicitly that only two fitting parameters are needed for getting a perfect agreement of such results with measured γ and ω. This explains why all attempts with so-called kinetic relations have been good in that. This also reveals the reason for the earlier finding [A. M. Garofalo, Fusion Sci. Technol. 48, 918 (2005)] that a number of models provided the stability regardless of the type of dissipation as long as the dissipation was sufficiently large. It is shown here that such “degeneracy” is a general property. One consequence is that a similar success with any model cannot guarantee its validity, and none of them can be recommended to ITER immediately. It is also explained that the edge harmonic oscillations can be a promising candidate for testing the dissipation channels missing in the kinetic dispersion relations.

Rotating Alfvén waves in rotating plasmas

Angular momentum coupling between a rotating magnetized plasma and torsional Alfvén waves carrying orbital angular momentum (OAM) is examined. It is demonstrated not only that rotation is the source of Fresnel–Faraday rotation – or orbital Faraday rotation effects – for OAM-carrying Alfvén waves, but also that angular momentum from an OAM-carrying Alfvén wave can be transferred to a rotating plasma through the inverse process. For the direct process, the transverse structure angular rotation frequency is derived by considering the dispersion relation for modes with opposite OAM content. For the inverse process, the torque exerted on the plasma is derived as a function of wave and plasma parameters.

ABOUT ONE PROPERTY OF THE DISPERSION EQUATION FOR LATITUDINAL ACOUSTIC-GRAVITATIONAL WAVES

Acoustic-gravity waves are an example of processes that largely determine the dynamics of the Earth’s atmosphere. This is due to the fact that the sources of these waves are located throughout the height of the atmosphere, from the very “bottom”, where earthquakes, volcanic emissions, tsunamis, tornadoes, etc., occur, and to the very “top”, where perturbations of the solar wind, magnetic storms, and precipitation of particles in high latitudes are active. All these phenomena lead to the active energy exchange between all layers of the Earth’s atmosphere and the interaction of wave disturbances of significantly different scales — from several thousand kilometers to several hundred meters, and this — to the appearance and development of processes of convection and turbulence in the environment. It seems that only nonlinear processes should dominate under such conditions. To a large extent, it is true, but at the same time, observations indicate that in many cases in the process of propagation of acoustic-gravity waves (AGW), the effects can be comprehensively described within the framework of the linear approximation of perturbation theory and well-developed theory of oscillations. At the same time, when creating models of the process, it turned out to be appropriate to use sufficiently justified physical approximations, such as isothermality of the atmosphere, its unlimitedness in the horizontal direction and compressibility in the vertical direction. Taking into account the real scales of the AGW, it is possible to neglect the curvature of the Earth’s surface and consider it locally flat at any point of the surface and use the Cartesian coordinate system X, Y, Z in the calculations. To describe the environment, it makes sense to use non-dissipative hydrodynamics and in an equilibrium state — the hydrostatic equilibrium equation and barometric equation. The above-mentioned approximations and the mathematical apparatus of the theory of oscillations and the theory of differential equations allow when studying the initial system of equations describing the dynamics of AGW, to obtain a dispersion equation in the form of a polynomial of the fourth degree relative to the angular frequency of rotation as a function of the normalized wave vector of disturbance k  (AGW). AGW spectrum is a spectrum of the atmosphere’s own oscillations in the form ( ) k  , and its obtaining can be considered as the final solution to the initial problem if we ignore the obvious influence on the AGW spectrum of the angular frequency of rotation of the atmosphere , which must necessarily be present in the dispersion equation due to the influence of the Coriolis force. The formal reason for the absence of the components of the vector  in the dispersion equation (DE) is the fact that the | |   is a minimum of two orders of magnitude smaller than the characteristic rotation frequency of the atmosphere 0 , which is equal to the acoustic cutoff frequency. At the same time, the improvement of modern atmospheric observation equipment places increases the requirements for the accuracy of DE model solutions. In this sense, the resolution of DE in the work [Cheremnykh O. K. et al. Kinematics and Phys. Celestial Bodies. 2020. 36, № 2. P. 64—78] can be considered as a “zero-order” solution with a small parameter 0    | |/  . In addition, according to the method of obtaining, this solution is approximate. By definition, the solution obtained in the work [Cheremnykh O. K. et al. Kinematics and Phys. Celestial Bodies, 2022. 38, № 3. P. 121—131] by taking into account terms   0 in the modified DE is more accurate. But it is also approximate, although more accurate. In this work, we study in detail the dispersion equation for latitudinal AGW. The need for such consideration, as will be shown, is a consequence of the structure of this equation, namely the presence of a linear frequency term in it. Preliminary analysis showed that existing mathematical methods do not provide an unambiguous solution to this equation. This suggests the need to study possible solutions of the equation in terms of their coincidence with previously obtained ones for some partial cases. Such research allows us to choose the right decision. In the proposed study, we have shown that the Euler-Lagrange method allows, under certain additional conditions, to obtain an exact solution of the modified equation for AGW in closed analytical form.

Using microwave refraction to determine local inhomogeneities of a rotating plasma

Abstract To determine the local inhomogeneities of a rotating plasma, the method based on microwave refraction was used. The method is based on spectral and correlation analysis of the reflected signals from the rotating plasma layer at normal and inclined microwave incidence. This method allowed us to determine local inhomogeneities of plasma electron density, angles of azimuthal displacement of grooves, and its angular frequency of rotation. Using an additional 4th horn antenna, in contrast to previous works, it was possible to find and analyze two regions with azimuthal inhomogeneities in the rotating plasma. Analysis of the reflected signals shows the presence of four grooves, and the angular frequency of rotation ω = 1.16 × 104 rad/s was also determined.

Rossby waves on stellar equatorial β planes: Uniformly rotating radiative stars

Context. Rossby waves arise due to the conservation of total vorticity in rotating fluids and may govern the large-scale dynamics of stellar interiors. Recent space missions have collected a lot of information about the light curves and activity of many stars, which triggered observations of Rossby waves in the stellar surface and interiors. Aims. We aim to study the theoretical properties of Rossby waves in stratified interiors of uniformly rotating radiative stars with a sub-adiabatic vertical temperature gradient. Methods. We used the equatorial β plane approximation and linear vertical gradient of temperature to study the linear dynamics of equatorially trapped Rossby and inertia-gravity waves in interiors of radiative stars. The governing equation was solved by the method of separation of variables in the vertical and latitudinal directions. Results. Vertical and latitudinal solutions of the waves are found to be governed by Bessel functions and Hermite polynomials, respectively. Appropriate boundary conditions at the stellar surface and poles define analytical dispersion relations for Rossby, Rossby-gravity, and inertia-gravity waves. The waves are confined in surface layers of 30–50 H0, where H0 is the surface density scale height, and they are trapped between the latitudes of ±600. Observable frequencies (normalised by the angular frequency of the stellar rotation) of Rossby waves with m = 1 (m = 2), where m is the toroidal wavenumber, are in the interval of 0.65–1 (1.4–2), depending on the stellar rotation, radius, and surface temperature. Conclusions. Rossby-type waves can be systematically observed using light curves of Kepler and TESS (Transiting Exoplanet Survey Satellite) stars. Observations and theory then can be used for the sounding of stellar interiors.

НАСТРОЙКА И ИССЛЕДОВАНИЕ РЕЖИМОВ РАБОТЫ НАБЛЮДАТЕЛЯ УГЛОВОЙ ЧАСТОТЫ ВРАЩЕНИЯ РЕГУЛИРУЕМОГО ЭЛЕКТРОПРИВОДА ПОСТОЯННОГО ТОКА

In modern closed-loop controlled electric drives used in manufacturing, the use of speed, current, torque, and other technological variable sensors is required. In some cases, indirect estimation of the electric drive state vector is required, when the use of technological parameter sensors (primarily speed sensors) is difficult or impossible. One of the problems is the length of the information cable in the feedback channel from the actuator to the power converter, which makes it difficult to use direct measurement methods. There are also difficulties in using sensors in an aggressive environment. For example, in the coal mining industry, electric motors or the entire electric drive are often located in an explosion-proof enclosure, and installing additional sensors will require expensive modernization of the entire system. State observers in sensorless electric drives allow restoring unmeasurable state vector components based on measured electrical signals in the power converters of the electric drive. From the perspective of a closed-loop controlled electric drive system, the main feedback is the feedback on the angular rotation frequency. Electric drives based on separately excited DC motors (SEDC) are simpler to investigate and implement such systems. The linearized mathematical model of an SEDC contains a relatively smaller number of differential equations compared to variable frequency drives due to the presence of independent channels for forming magnetic flux in the air gap and electromagnetic torque, which simplifies the analysis and synthesis of sensorless control systems using speed observers. Researching the observer of angular rotation for DC electric drives allows for developing design skills on a simpler system before moving on to variable frequency drives. Research in this area for both DC and AC electric drives is promising because it allows for an increased range of regulation and accuracy of the output coordinate in sensorless electric drives at the required level. This article is dedicated to the study of the properties of speed observers for DC electric drives with independent excitation of various structures. Aim of research Analysis of rotation frequency observer structure in DC motor drives with error reduction based on the proportional principle. Research methods Theoretical and experimental research methods were used in this study. Theoretical methods included the theory of automatic control, state observer theory, theory of electric drives, theory of electric machines, mathematical modeling, systems of differential equations, Laplace transforms, and numerical methods for solving differential equations. Experimental studies were conducted on a software-hardware complex, where the genetic algorithm method was used to identify the parameters of the electric machine equivalent circuit. Results Analytical expression for the characteristic equation roots for the investigated structure of the DC motor drive's speed observer was obtained. Based on this expression, stability criteria and trends in changes of the quality indicators for the angular velocity estimation were determined with varying observer coefficients.

A three-dimensional numerical study of laminar buoyancy-driven columnar vortices

This study deals with the development of a low momentum whirling laminar plume that results from the interaction between a plume and a circulating flow imposed by a cylindrical rotating screen. Numerical simulations were performed by direct simulation of the fully three-dimensional flow governed by the compressible Navier-Stokes and energy equations. The rotating thermal plume forms a columnar vortex governed by the Grashof (GR) and nondimensional rotation velocity (Reynolds number (ReR)), based on the cylindrical domain’s radius and the angular frequency of rotation of the permeable lateral surface. Numerical solutions were obtained in the range 102<Gr<106 and 10<ReR<150. The vortex generated bifurcates into a pair of steady co-rotating vortices within the range 104<Gr<2×105 and 30<ReR<100. The steady state configuration of the flow is described and analysed, showing the evolution of the vorticity contours in cross-sections that start out as circlets, gradually turn into an ellipse and end up bifurcating into a pair of co-rotating vortices. The role of the boundary layer is also described, showing an increase in the distance between the co-rotating vortex pair for a given Gr and ReR numbers but in the absence of a boundary layer. At last, the temporal evolution of the vortex splitting process is compared to measurements of merging of two co-rotating vortices available in the literature, uncovering that the two phenomena take similar timescales to occur.

Radio Emission of Pulsars. I. Slow Tearing of a Quantizing Magnetic Field

The pulsed radio emission of rotating neutron stars is connected to slow tearing instabilities feeding off an inhomogeneous twist profile within the open circuit. This paper considers the stability of a weakly sheared, quantizing magnetic field in which the current is supported by a relativistic particle flow. The electromagnetic field is almost perfectly force free, and particles are confined to the lowest Landau state, experiencing no appreciable curvature drift. In a charge-neutral plasma, we find multiple branches of slowly growing tearing modes, relativistic analogs of the double-tearing mode, with peak growth rate . Here, B z is the strong (nearly potential) guide magnetic field, J z the field-aligned current density, and is the mode wavenumber normalized by the current gradient scale. These modes are overstable when the plasma carries a net charge, with the real frequency proportional to the imbalance in the densities of positive and negative charges. An isolated current sheet thinner than the skin depth supports localized tearing modes with growth rate scaling as (sheet thickness/skin depth)−1/2. In a pulsar, the peak growth rate is comparable to the angular frequency of rotation, , slow compared with the longitudinal oscillations of particles and fields in a polar gap. The tearing modes experience azimuthal drift reminiscent of subpulse drift and are a promising driver of pulse-to-pulse flux variations. A companion paper demonstrates a Cerenkov-like instability of current-carrying Alfvén waves in thin current sheets with relativistic particle flow and proposes coherent curvature emission by these waves as a source of pulsar radio emission.

Vortices in quantum droplets of heteronuclear Bose mixtures

We have theoretically investigated the structure of spinning self-bound droplets made of $^{41}$K-$^{87}$Rb Bose mixture by solving the Gross-Pitaevskii equation including beyond-mean-field correction in the Lee-Huang-Yang form. The structure and energetics of vortex formation in the self-bound mixture have been elucidated, showing that the formation of linear vortices in the heavier species is energetically favoured over other configurations. A fake (partially filled) core develops as a consequence in the other species, resulting in a hole which might be imaged in experiments. The interplay between vortices and capillary waves, which are the two ways angular momentum can be stored in a swirling superfluid, is studied in detail by computing the relation between angular momentum and rotational frequency. The results show intriguing similarities with the case of a prototypical superfluid, i.e. $^4$He droplets when set into rotation. A two-branches curve in the stability diagram, qualitatively similar to the one expected for classical (incompressible and viscous) rotating liquid droplets, is obtained when vortices are present in the droplets, while prolate (i.e. non axi-symmetric) shapes are only permitted in vortex-free droplets.

The Influence of the Earth’s Atmosphere Rotation on the Spectrum of Acoustic-Gravity Waves

It was shown in a recent study [11] that taking into account the rotation of the Earth’s atmosphere leads to the appearance of a new region of evanescent waves with a continuous frequency spectrum on the diagnostic diagram of acoustic-gravity waves. The region is located below the lower limit of gravity waves, which is equal to $$2\Omega $$ for all wavelengths, where $$\Omega $$ is the angular frequency of the atmospheric rotation. This result was obtained for high-latitude regions of the atmosphere in which one can be limited to considering only the vertical component of the Earth’s rotation frequency. This paper shows that taking into account both components of the vector $$\vec {\Omega }$$ of the atmospheric rotation frequency $$\vec {\Omega }$$ —horizontal, $$\Omega \cos \varphi ,$$ where $$\varphi $$ is the local latitude, and vertical, $$\Omega \sin \varphi $$ —the dominant role in the acoustic-gravity wave propagation is played by the vertical component. It is shown that the horizontal component leads to a negligible modification of the boundaries of the regions of acoustic and gravity waves on the diagnostic diagram. It is also shown that the vertical component of the frequency affects most strongly the lower limit of gravity waves, which depends on the latitude of the observation site for all wavelengths and is equal to 2 $$\Omega \sin \varphi $$ .

Influence of the Earth’s atmosphere rotation on the spectrum of acoustic-gravity waves

It was shown in a recent paper by Cheremnykh et al. (Advances in Space Research, 2022) that taking into account the rotation of the Earth's atmosphere leads to the appearance of a new region of evanescent waves with a continuous frequency spectrum on the diagnostic diagram of acoustic-gravity waves. The region is located below the lower limit of gravity waves, which is equal $2\Omega$ at all wavelengths, where $\Omega$ is the angular frequency of the atmosphere rotation. This result was obtained for high-latitude regions of the atmosphere, in which we can limit ourselves to considering only the vertical component of the Earth's rotation frequency. In the proposed paper we show that taking into account both components of the vector of the atmosphere rotation frequency $\overrightarrow{\Omega}$ - horizontal, $\Omega\cos\varphi$ , and vertical, $\Omega\sin\varphi$, where $\varphi$ is the Earth`s latitude, the dominant role in the acoustic-gravity waves propagation is played by the vertical component. It is shown that the horizontal component leads to an insignificant modification on the diagnostic diagram of the boundaries of the areas of acoustic and gravity waves, which can be neglected. Also shown that the strongest vertical component of the frequency affects the lower limit of gravity waves, which depends at all wavelengths on the latitude of the observation site and is equal to $2\Omega\sin\varphi$.

О форме брахистохроны, вращающейся в вертикальной плоскости

The paper aims to study the influence of the brachistochrone rotating in its own plane on the gutter shape along which a body moves. The problem is solved with a moving basis, which allows one to account for all forces exerted on the body. Introduction of the moving basis yields a compact system of dynamical equations, whose validity was proven in previous author's papers. In limiting cases, such an approach is used to solve analytically the obtained equations of motion and to determine the shape of curves depending on the parameters in the equations by tabular integration. The latter is illustrated in the figures presented. According to the energy conservation law, which accounts for the rotation of the entire system as a whole, the resulting equations also include the angular frequency of rotation as an additional parameter. In this paper, the case of steady rotation is studied. Such conditions have a significant impact on the brachistochrone. In the limiting case of low rotational speeds, the curve, as it should be, degenerates smoothly into a classical brachistochrone, which is justified by the numerical methods used.

Detecting the Figure Rotation of Dark Matter Halos with Tidal Streams

Abstract The dark matter halos that surround Milky Way–like galaxies in cosmological simulations are, to first order, triaxial. Nearly 30 yr ago it was predicted that such triaxial dark matter halos should exhibit steady figure rotation or tumbling motions for durations of several gigayears. The angular frequency of figure rotation predicted by cosmological simulations is described by a log-normal distribution of pattern speed Ω p with a median value 0.15 h km s−1 kpc−1 (∼0.15 h rad Gyr−1 ∼ 9° h Gyr−1) and a width of 0.83h km s−1 kpc−1. These pattern speeds are so small that they have generally been considered both unimportant and undetectable. In this work we show that even extremely slow figure rotation can significantly alter the structure of extended stellar streams produced by the tidal disruption of satellites in the Milky Way halo. We simulate the behavior of a Sagittarius-like polar tidal stream in triaxial dark matter halos with different shapes, when the halos are rotated about the three principal axes. For pattern speeds typical of cosmological halos, we demonstrate, for the first time, that a Sagittarius-like tidal stream would be altered to a degree that is detectable even with current observations. This discovery will potentially allow for a future measurement of figure rotation of the Milky Way’s dark matter halo, perhaps enabling the first evidence of this relatively unexplored prediction of cold dark matter.

Sideways force due to coupled rotating kink modes in tokamaks

The possibility of generation of the rotating sideways force on the wall by the kink modes is analytically investigated. The approach is basically the same as that developed earlier in (Mironov and Pustovitov 2017 Phys. Plasmas 24 092508) for the locked modes, but now their rotation is allowed. Its main elements are ∂b/∂t ≠ 0 (described by the growth rate γ and angular rotation frequency ω of the magnetic perturbation b), resistive dissipation in the wall, and the requirement of zero sideways force on the plasma. These make the approach greatly different from those resulting in the so-called Noll’s formula. The result is also different; it predicts a force an order of magnitude smaller. Nevertheless, such a force can be dangerous at the resonance frequency of the vacuum vessel. The derived relations show that the rotating force must be maximal at ωτ w = O(1), where τ w is the resistive wall time. For the faster modes it decreases roughly as ∼1/ω.

Physics of a Particle on a Rotating Hoop

The simple textbook problem of a particle on a vertical, rotating hoop is analysed both in theory and through experiments. We begin by detailing out a somewhat generalised theory, where the effect of dry friction as well as the possibility of a shift in the vertical axis of rotation are incorporated. The bifurcation curves (plots of the angular position of stability versus the angular frequency of rotation) are obtained for all cases (i.e. with and without friction and a shift of the axis). Thereafter we present the experimental set-up fabricated by us and elaborate on the various measurements performed. Finally, we demonstrate through our experiments how well the theoretical results on the bifurcation curves tally with the experimental findings. The match between theory and experiment is found to be reasonably satisfactory. We conclude by mentioning how various aspects of this simple problem as well as its generalisations and extensions, are linked with different advanced areas of physics.

Rotary dryer for thermo sensitive products

To achieve the desired drying objectives in thermal sensitive products, such as medicinal plants, the process chosen should happen under minimally controlled conditions, such as, uniformity of temperature and air velocity, minimizing heat loss and with energy viability and efficiency. If possible, the process must occur using equipment with industrial implementation where the evaporation rate can be controlled. The intermittent drying process, which consist of cycles of exposure of the material to heated air (period of effective drying) and tempering (period of no exposure to heated air), is a great option to preserve the product’s quality during the drying process. We propose a new configuration of rotary dryer intended for intermittent drying; observing the configurations of widely applied rotary dryers, the relationship between angular velocity, period and frequency of rotation and laboratory experiments of manufacturing process in intermittent drying. The proposed dryer is efficient for the application of intermittent drying in products with high thermal sensitivity, such as medicinal plants. Making possible uniformity of temperature and air velocity distribution, minimizing heat loss and with energy viability and efficiency, guarantying the product quality.

Acoustic $\alpha $-disk

It is shown that the turbulent flow of acoustic waves propagating outward from the inner edge of the disk causes the accretion of the matter onto the center. The exponential amplification of waves takes place in the resonance region, $\omega = (n\pm 1)\Omega $. Here $\omega $ is the frequency of the acoustic wave, $n $ is its azimuthal wave number, $\Omega (r) $ is the angular frequency of rotation of the disk. The effect is similar to the inverse Landau damping in a collisionless plasma. Energy comes from the energy of rotation of the disk. That leads to decrease of the disk angular momentum and to accretion of the matter. The value of the accretion rate $dM/dt$ is ${\dot{M}} = \pi rc_{s} \Sigma _{0} (c_{s} / v_{\phi 0})^{2} W $. Here $c_{s} $ is the speed of sound of the disk gas, $v_{\phi 0} $ is the Keplerian rotation velocity, $\Sigma _{0} $ is the surface density of the disk, $W $ is total power of the acoustic turbulence, $W \simeq \int _{0}^{\infty }d \omega \sum_{n\geq 0} | \frac{\Sigma'}{\Sigma _{0}} |^{2} (\omega , n) $, $|\Sigma'|^{2} (\omega , n) $ is the spectral power of turbulence. The presented picture of accretion is consistent with the observed variations of X-ray and optical radiation from objects whose activity is associated with accretion of gas onto them.