Transverse Pulsations Research Articles

Improvement of the calculation method of cyclone dust collectors

The object of research is a method for calculating the efficiency of cyclones using the magnitude of the velocity of transverse pulsations of a turbulent gas flow in the inlet of the cyclone. One of the most problematic issues when creating a new cyclonic technique for gas dust cleaning is the need to carry out a fairly large amount of work – modeling cyclones in laboratory conditions on model cyclones, taking into account the large-scale transition, etc. Therefore, the development of the most accurate analytical method for calculating the efficiency of cyclones is an important problem since it makes it possible to quickly and accurately determine all the necessary cyclone parameters for specific production conditions.During the study, patterns of dust particle deposition in the approximation of the «diffusion boundary layer» were used, which made it possible to calculate with high accuracy the efficiency of cleaning industrial dust in cyclones of various designs. At the same time, the time and the amount of experimental work are also significantly reduced in the development of new types of cyclones or in their modernization or selection.The most accurate dependencies are obtained for evaluating the most important parameters of dust cleaning efficiency in various cyclones. This is due to the fact that the method for calculating cyclones proposed in the work has a number of features, in particular, the development of new dependences for calculating the cut-off diameter «dh=50», the inertial capture coefficient of dust particles «E», and others. It is also proposed to use the average cross section the inlet pipe of the cyclone of the velocity of transverse pulsations of the turbulent gas flow and the new interpolation dependence of the coefficient of inertial capture of dust particles «E» at the potential flow regime in the inlet pipe of the cyclone x machines. Thanks to this, it is possible to obtain accurate values of the indicators of cleaning efficiency in cyclones of various design parameters. Compared with similar well-known calculation methods, this provides such advantages as accuracy of calculations, speed of execution and reliability of the results.

Growth, Coenosarc Pulsations, and Hydroplasm Movement in the Colonial Hydroid Dynamena pumila (L., 1758) Placed in Flow-Through and Nonflow Cuvettes

The coenosarc pulsations of the stolon and hydroplasmic flows (HFs) in the colonial hydroid Dynamena pumila (L., 1758) have been recorded in flow-through and nonflow, shallow cuvettes via time-lapse video microscopy. The water in the flow-through cuvette was refreshed during every 24 s. Each episode was video recorded for 2 h. Eleven indicators were used to compare hydroid reactions to maintenance in flowing and nonflowing water: the period and amplitude of pulsations of the stolon growing tip; the hourly stolon growth; the period and amplitude of transverse coenosarc pulsations; the period of unidirectional HF rate pulsations; the maximum velocity of HFs to and from the stolon tip; the distance of particle transfer per act of unidirectional HF; the volume of displaced hydroplasm per HF; and the percentage of the rest ratio in coenosarc pulsations and hydroplasm movement. On the whole, no significant changes in the coenosarc pulsations or in the growth and displacement of the hydroplasm were detected when they were compared sequentially in the same colonies in nonflowing and flowing water. At the same time, there were no changes in the growth, the frequency and amplitude of the transverse pulsations of the coenosarc, or the activity and extent of the hydroplasm currents. However, it was found that the period of growth pulsations increases by 20% in the regime with water exchange in comparison with the previous regime without flowing water. The period of HFs in the stolon increases by 42%, and the maximum current velocity decreases by 20% in flowing water. As a result, the calculated volume of moved hydroplasm in the stolon for one HF decreased by 30% in flow conditions.

Functional morphology of hydrozoan stolons: stolonal growth, contractility and hydroplasmic movement in Gonothyraea loveni (Allman, 1859)

ABSTRACTIn many hydroids the movement of hydroplasm inside the colony is generated by the pulsation of coenosarc walls. We hypothesized that the stolon coenosarc is not only morphologically but also functionally non-homogeneous, and tested this hypothesis using time-lapse video microscopy to study rhythmic patterns – transverse pulsations, longitudinal pulsations and hydroplasmic flows – in the five distal internodes of the stolon in Gonothyraea loveni, which is commonly used in laboratories to study growth and morphogenesis. Growth (apical) and transverse (lateral) pulsations of the coenosarc are rhythmic to varying degrees. Growth pulsations and longitudinal oscillations of the distal part of the growing tip (GT) have the most regular rhythm. In the proximal part of the GT and in the coenosarc of the terminal internode behind the GT, transverse pulsations have a different period, about double that of growth pulsations. The highest amplitude of transverse pulsations is observed in the terminal segment of the stolon and the following segment between the 1st and 2nd upright stems. Longitudinal oscillations of the coenosarc tube are clearly discernible throughout all five internodes, even though they subside with distance from the GT. Thus, the zone of intercalary growth spreads over several internodes of the stolon and is not limited to its distal segment. Hydroplasmic flows are rhythmical. Their velocity generally increases with distance from the GT, but can differ significantly between adjacent internodes, which points to the important role of local subcurrents. There are six morphofunctional zones in the hydroid stolon.

Flow rate in a channel with small-amplitude pulsating walls

The influence of wall transverse pulsation on the viscous incompressible fluid flow in a channel under the action of pressure and gravity is studied under approximation of the small amplitudes. It is found that for the large values of the Womersley numbers the pulsations decrease the flow rate, rather than increase it, as it was found in the previous studies for the small Womersley numbers.

Mechanism of turbulent pulsation in channels

The space-time pulsation field of hydrodynamic parameters for channel turbulent flow is derived from the wave model of turbulence. Conditions for pulsation field randomization are analyzed. Calculations of the longitudinal and transverse pulsations are compared with the Reichardt’s measurements.

The spatiotemporal field of turbulent flow pulsation

Relations describing the spatiotemporal field of pulsation of the hydrodynamic parameters of a turbulent flow have been derived based on the wave model of turbulence. The process of chaotization of the pulsation field is analyzed. The results of calculations of the longitudinal and transverse velocity pulsation components are compared to the results of measurements reported by H. Reichardt.

Turbulent Characteristics of Curved Wall Jets

Results of the experimental and numerical studies into the turbulent characteristics of a semirestricted jet near a curved surface are given. A comparative analysis of the longitudinal and transverse velocity pulsations, the correlation between the longitudinal and transverse pulsations, the coefficient of one-point correlation, the mixing path length of the jet near flat and concave surfaces is carried out. The curvature significantly affects the characteristics. The results of the study are generalized by empirical dependences.

Theoretical and experimental investigation of combustion to detonation transition in chemically active gas mixtures in closed vessels

This paper presents the results of numerical and experimental investigations of the process of deflagration to detonation transition. It is shown that both regimes of combustion to detonation transition and regimes including deflagration waves lagging behind the shock waves are possible. Several types of flow patterns of deflagration to detonation transitions are determined theoretically and experimentally. Stability of one- and two-dimensional detonation waves is investigated. It is shown that one-dimensional pulsations in the symmetrical case with free boundaries cause strong transverse pulsations.

Particles Heat Treating in a Pulsating Gas Stream

The subject of the paper is the application of pulsating flow to the particles heat treating. Pulsation influence mechanisms are segregated by the author into two groups: quasi – steady – state (when, at every point in time, an instantaneous value of the heat transfer rate may be calculated with the equations obtained for steady-state conditions) and unsteady – state which includes the remainder. It is shown that, depending on the process parameters, pulsations can increase, not influence, or even reduce heat transfer. Resonance phenomena and large size particles, for which the influence of gravity is substantial, receive special attention. The heat transfer intensification may be achieved due to increases in both heat transfer coefficient and particle residence time. Longitudinal pulsations (when the pulsation and main flow velocities have the same direction) may be preferable in the unsteady-state range of parameters. Transverse pulsations (when the pulsation velocity is perpendicular to the main flow) can be more effective in the quasi – steady – state range. Nonuniformity of heat treating in pulsating flow, influence of the main flow turbulence, trigger effects, and different methods of pulsation generation, including pulsating combustion, are discussed. In conclusion some recommendations are given for designing practical processes.

Wave and plasma observations during a compressional Pc 5 wave event August 10, 1982

Magnetometer and thermal plasma instruments on the polar‐orbiting Dynamics Explorer 1 satellite observed a small‐amplitude ultralow frequency (ULF) pulsation event at the outer edge of the plasmapause near the geomagnetic equator in the midafternoon sector on August 10, 1982, during the recovery phase of a magnetic storm. Transverse pulsations of 30–50 s period were observed throughout the event, and a 270‐s period, purely compressional Pc 5 pulsation with several shifts in phase occurred within ±5° of the geomagnetic equator. Electric fields and the motion of thermal ions appeared to be in quadrature with pulsations in magnetic field magnitude throughout the event. This suggests that the net Poynting flux for the compressional waves was zero, consistent with their being standing waves. Large fluxes of trapped 90° pitch angle 10‐eV protons, also symmetric about the geomagnetic equator, were observed in conjunction with the waves. These may serve as a source of free energy for the pulsations. Our observations lend support to recent studies suggesting that many dayside compressional wave events are related to localized field line resonance near plasmapauselike boundaries, but also include features that cannot be explained by existing theories.

Particle deposition on a channel wall in a turbulent disperse flow with gradient

Kinetic ideas about the motion of a set of particles (droplets) in a turbulent gas flow with gradient are used to derive a Fokker-Planck equation for the case of sufficiently large particles (more than few microns). This equation describes the process in which they are deposited on the wall of a channel. Satisfactory agreement has been obtained between the numerical solution to this equation for the deposition rate and the experimental data published in the literature. Under the assumption that the parameters of the carrier gaseous flow vary fairly slowly, a generalized equation is derived for particle diffusion in turbulent flow. This takes into account the intensity gradient of transverse pulsations in the velocity of the carrier gaseous flow.

Observation of an oscillating magnetic field shell at three locations

On July 14, 1982, 1830–1930 UT, a complex magnetic pulsation event was observed near the magnetic shell L ∼4.5 in the local afternoon. A large magnetic storm was in progress and had proceeded to the early recovery phase. The event began, at 1832 UT, with a sudden decrease in |B| and a brief, 120‐s compressional pulsation. A transverse pulsation then developed with period near 180‐s and amplitude about 5 nT. Near 1850 UT this pulsation decreased abruptly and was replaced by a 44‐s transverse pulsation. By 1858 UT the 44‐s pulsation was fading and a 240‐s azimuthal pulsation developed rapidly. It slowly decreased in amplitude after 1910 UT and was gone by 1930 UT. The event was observed at the DE‐1 satellite near the equator in both electric and magnetic field components and at the ground magnetic observatories Siple, Antarctica, and Roberval, Quebec, 15° to 30° west of DE‐1 and at opposite ends of an L = 4.2 field line. The 180‐s and 240‐s pulsations were fundamental, toroidal, resonant oscillations of a magnetic field shell. Since the first 180‐s pulsation started and stopped simultaneously at all three locations and the corresponding magnetic pulsations remained in phase at all three locations, this is interpreted to be a large‐scale toroidal oscillation of one resonant field shell. In the 240‐s pulsation, DE‐1 was on one resonant shell and the ground stations, oscillating at 220 s period, were on another lower L value shell. The 44 s pulsation, also transverse at DE‐1, was weaker on the ground and poorly correlated with the DE‐1 measurements, suggesting that it was more localized in azimuth.

Relation of compressional HM waves at Goes 2 to low‐latitude Pc 3 magnetic pulsations

Daytime magnetic pulsations observed at synchronous orbit by GOES 2 are analyzed to determine whether there is a candidate for the source of low‐latitude Pc 3's in the outer magnetosphere. Compressional, radially transverse and azimuthally transverse modes of magnetic pulsations in a wide frequency range exist simultaneously in the outer daytime magnetosphere. The compressional and the transverse modes of the daytime magnetic pulsations observed at GOES 2 are statistically dominant in the Pc 3 and in the Pc 4 frequency ranges, respectively. Some 70% of the compressional Pc 3 pulsations at GOES 2 have periods similar to the low‐latitude Pc 3's observed at San Gabriel Canyon, which is located ∼11° west of GOES 2's longitude at L = 1.8. Amplitudes of the compressional. Pc 3 pulsations at GOES 2 (L = 6.67) are relatively larger than those of the low‐latitude Pc 3's at SGC (L = 1.8). The transverse pulsations with larger amplitude (δB ≳ 1.0 nT) at GOES 2 can propagate only into the high‐latitude ionosphere. The compressional Pc 3 pulsations with smaller amplitude (δB∼ 0.5 nT) at GOES 2 are theoretically expected to propagate across the ambient magnetic field to very low latitudes to couple with one or more the following: (1) a surface wave at the plasmapause (Lpp); (2) a trapped oscillation of the fast magnetosonic wave in the plasmasphere (L = 1.7 ‐ Lpp); (3) a higher‐harmonic standing oscillation of a local field line at mid‐latitude (L = 2.0 ‐ Lpp); or (4) a fundamental standing oscillation at very low‐latitudes (L = 1.1 and 1.7–2.6). Although further research is needed to clarify the wave and propagation characteristics of the low‐latitude Pc 3 pulsations, we believe that the compressional Pc 3 magnetic pulsation in the outer magnetosphere is one candidate for the source of the low‐latitude Pc 3 magnetic pulsation.

Operation of gas-burner devices with increased jet aperture angle for heating rotary furnaces

An increase in the aperture angle of high-velocity gas jets intensifies the mixing of fuel with oxidizer in the accompanying flow as a result of the growth in the transverse pulsation constituent of the velocity and the surface of the flame front.

Stability of magnetopause boundary and generation of long period geomagnetic pulsations

The effect of irrotational electric field and tensorial plasma conductivity on the growth rate of Kelvin-Helmholtz instability has been investigated. It is shown that the presence of irrotational electric field alters the growth rate. The dependence of Pedersen conductivity on the growth rate has been shown. The Kelvin-Helmholtz perturbations generate a surface wave in the frozen-in plasma. The propagation of these waves gives rise to polarization of the transverse hydromagnetic pulsations. It is shown that the modified K-H spectrum would result in a corresponding change in polarization features of the hydromagnetic pulsations.

Pulsating motions of a solid particle in turbulent flow

The relations governing the transverse pulsations of a spherical particle in a turbulent flow are examined. On the basis of the resulting relations an estimate is made of the effect of several factors on the intensity of the velocity pulsations of the solid component in dispersed flow through a conduit.

DETONATION WAVES IN GASES

1. Introduction 523 2. Structure of detonation wave 524 2.1. Stationary zone of chemical reaction 524 2.2. Rarefaction wave 525 2.3. The Chapman-Jouguet condition 526 2.4. Diverging and converging detonation waves 526 3. Experimental methods for the study of the state of the gas behind the detonation front 527 3.1. Measurement of pressure (pulsed piezoelectric transducers) 527 3.2. Measurement of gas density 528 3.3. Measurement of gas temperature (generalized method of spectral line inversion) 528 3.4. Determination of the chemical composition and concentrations of individual mixture components 529 4. Features of ignition of gas behind a shock wave 529 4.1. The induction period 529 4.2. Determination of kinetic reaction parameters 531 4.3. Formation of detonation front 531 5. Transition from combustion to detonation in gases 532 5.1. Gas dynamic scheme of formation of detonation in a tube 532 5.2. Calculation of the state of the mixture ahead of the flame front 532 5.3. Compression wave and adiabatic self-ignition 533 5.4. Interaction of flame with shock wave 533 6. Oscillations of gas behind the detonation front 534 6.1. Causes of oscillating combustion mode 534 6.2. Properties of transverse waves 535 6.3. Acoustic theory of spin detonation 536 6.4. Structure of spin detonation front 536 6.5. State of gas in a detonation wave with account of transverse pulsations 537 7. Detonation in stationary gas stream 537 7.1. Combustion of gas behind a stationary shock wave 537 7.2. Stationary spin detonation 538 7.3. Pulsating combustion behind a Shockwave in a supersonic stream 538 8. Conclusion 538 9. Literature 539