Vortex Diameter Research Articles

Experimental and numerical study of maximum efficiency vortex finder insertion depth of a Stairmand cyclone

The vortex finder is essential in cyclone separators, significantly affecting separation performance via its diameter and insertion depth. The current study shows that as the insertion depth of the vortex finder increases, the separation efficiency initially increases and then decreases, and there exists a maximum point with which the corresponding insertion depth is the maximum efficiency insertion depth (SMEID). However, there are inconsistent conclusions in the existing literature regarding the maximum efficiency insertion depth and a lack of explanation for the flow field mechanism at the maximum efficiency insertion depth. This study examines the Stairmand type cyclone using 13 μm silicon micro-powder, employing numerical simulation and cold mold experiments to explore the effects of the vortex finder's insertion depth and diameter on separation performance and flow field. The results indicate that the insertion depth has minimal impact on pressure drop. The maximum efficiency insertion depth of the vortex finder decreases as the diameter decreases and is independent of this insertion depth with respect to the inlet velocity. Analysis of the flow field reveals that the maximum efficiency insertion depth is essentially the result of a "competitive and synergistic" mechanism between the annular space separation capability and the separation space separation capability.

Numerical Study on the Design of an Anti-Backflow Injector for Combustion Chambers

The backflow of high-temperature products in an engine’s combustion chamber is a key issue which can significantly reduce combustion efficiency. This is particularly problematic for hypergolic propellants, as the high-temperature products may still contain fuel or an oxidizer. If either the fuel or the oxidizer backflows into the manifold of the other, it can easily lead to micro-explosions, thereby creating a threat. To address this problem, this paper proposes a new design of an anti-backflow injector, aimed at effectively preventing the backflow of combustion products to the propellant manifold. A steady-state, non-reactive Computational Fluid Dynamics (CFD) model is employed to evaluate the steady internal flow characteristics of the proposed anti-backflow injector. Additionally, a complementary transient, multiphase fluid dynamics simulation is carried out to assess the response characteristics of the anti-backflow injector. Our analysis focuses on the response characteristics of the concave valve core. The study also explores the impact of different expansion port angles on the injection effect, finding that the vortex diameter at the injector outlet is positively related to the expansion port angle. It is also shown that the injection angle becomes more stable as the expansion angle increases. When the expansion port angles are 10° and 20°, the injection angles show similar trends. In terms of anti-backflow effect, taking the injection stiffness of 150% and a time range of 300 µs as examples, the response time of the anti-backflow models with expansion ports of 10°, 15°, and 20° is increased by 67 µs, 99 µs, and 213 µs, respectively, compared to the base models with the same expansion angles. Meanwhile, when the injection stiffness is 50%, the response time of the anti-backflow models with expansion ports of 10°, 15°, and 20° is increased by 207 µs, 210 µs, and 207 µs, respectively. When the injection stiffness is 20%, the response recovery speed of the anti-backflow models with expansion ports of 10° and 15° is increased by 41 µs and 96 µs, respectively. However, the performance of the anti-backflow model with a 20° expansion port is 216 µs of the base model. The optimized design of the anti-backflow injector has potential applications in solving the propellant backflow problem and contributes to the advancement of combustors.

An analysis of the influence of a generic building on tornadic flow fields using high-frequency PIV and point velocity measurements

The current practice of implementing tornadic wind actions on structures in building codes is not well established compared to atmospheric boundary layer winds. Given there is a lack of velocity measurements in actual tornados close to the surface, there is a body of research that is currently looking into physical simulations of tornado-like vortices (TLVs). Our study contributes to this field of research by looking into the aerodynamic effects a generic building exerts on TLVs that are stationary and positioned above the building. Our study also investigated the differences among two distinctively different velocity measurement techniques in TLV flows—Cobra probe and particle image velocimetry (PIV). We further examine how different TLV intensities affect the results by considering TLVs that correspond to (Enhanced Fujita) EF1- and EF2-rated tornadoes in the atmosphere. We show that the velocity fluctuations in Cobra probe records are higher than in PIV measurements despite both velocity records being sampled at 200 Hz. The discrepancy is due to the inherent spatial filtering used in PIV data processing. A larger discrepancy between the two measurement techniques was observed in the EF1 TLV. The presence of the building affected EF1 more than EF2 TLV due to the larger core diameter of the latter vortex. The diameter of the circumference of the maximum tangential velocity in EF1 and EF2 TLVs undisturbed by the building was 1.6 and 2.1 times larger than the diagonal length of the building. By comparing our results against prior research on the same TLVs, but without a building in the flow, we concluded that the building had the strongest effect in amplifying vertical velocity in the EF2 TLV. The significance of this result to wind loading and structural responses requires further wind engineering analyses. The circular symmetry of EF1 was more affected than in EF2 TLV due to its smaller size relative to the building.

Complex gravity-acoustic impact on V-flame structure

Development of efficient and safe energy systems for space objects includes ensuring fire safety. This problem requires a deep understanding of influence of gravitational forces on combustion processes, which explains the importance of studying this issue. The paper analyzes the dynamics of inverted conical methane-air flame under conditions of normal and reverse gravitational force with external acoustic excitation. Applied frequencies of acoustic excitation could be parasitic or be produced during proper work of different technical systems of aircraft. High speed recording of flame chemiluminescence and PIV analysis were conducted. Decomposition of flow vector pictures into the modes was calculated using POD method. Energy contribution into the flow was analyzed for its separate elements at the different frequencies of excitation. At the high excitation frequencies vortex generation intensity in the shear layer with reverse gravity is about the same as it was observed in the experiments with normal gravity direction, that could indicate dominance of acoustic mechanism of the vortexes stimulation over the mechanism of shear instability. At external excitation frequency equals 240 Hz significant growth of shear vortex diameters and increasing of perpendicular oscillations amplitude of flame branches were obtained. Thereby in such experiment with 240 Hz external acoustic excitation the most intensive large scale instability of flow was observed.

The impact of cylinder vortex stabilizer on fluctuating turbulence characteristics of a cyclone separator based on Large Eddy Simulation

The main purpose of present study is to comprehensively clarify the impact of cylinder vortex stabilizer on fluctuating turbulence structure of a Stairmand cyclone separator on basis of Large Eddy Simulation. The cylinder vortex stabilizer is easy and could be applied to any existing cyclone model without any major replacement. This novel modification in cyclone body is considered to alleviate the negative effect of entrainment of particles from the ash hopper and swing of the vortex end in swirling flow. The numerical simulations were conducted based on Stairmand cyclone separator and three new models with variation of vortex stabilizer length and diameter. The results showed that the cylinder vortex stabilizer could enhance flow instability and improve fluctuating turbulence structure to some extent. It is confirmed that cylinder vortex stabilizer could significantly reduce the tangential velocity in the inner quasi-forced vortex region of the cyclones. Comparing with Stairmand cyclone, the swirling first and second peak frequency of cyclone model with vortex stabilizer (Length L/D: 6.5, diameter d/D: 0.12) have been confirmed to get considerable reduction of 11.54% and 10.86%, respectively. This modified cyclone model is comparatively better for enhancement of flow stability, providing about 18.4% maximum reduction of normalized flow angle, 24.8% of rotational kinetic energy in dust collector and 14.2% in the main body of cyclone.

Assessment of the Vortex Feature-Based Vorticity Confinement Method Applied to Rotor Aerodynamics and Aeroacoustics

The accurate prediction of helicopter rotor aerodynamics and aeroacoustics using Computational Fluid Dynamics (CFD) techniques still remains a challenge, as the over-dissipation of numerical schemes results in a higher diffusive rate of rotor wake and vortices than what can be expected from the fluid governing equations. To alleviate this issue, a vortex feature-based vorticity confinement (FVC2-L2) method that combines the locally normalized λ2 vortex detection method with the standard second vorticity confinement (VC2) scheme is presented to counterbalance the truncation error introduced by the numerical discretization of the convective term while avoiding the over-confinement inside the boundary layer. The FVC2-L2 scheme is adopted for helicopter rotor aerodynamic and aeroacoustic predictions through its implementation in the multi-block structured grid CFD solver ROSITA and coupling with the aeroacoustic code ROCAAP based on the permeable surface Ffowcs Williams–Hawkings (PS-FWH) equation. This approach is assessed in helicopter rotor flows via three databases. Firstly, the well-documented HART-II rotor in the baseline condition is used to evaluate the capability of the presented VC scheme in blade–vortex interaction (BVI) phenomena prediction. Subsequently, the UH-1H non-lifting hovering rotor and the AH-1/OLS low-speed descending flight rotor are adopted for assessment of such a method in aeroacoustics. The benefits of the FVC2-L2 scheme in terms of aerodynamics prediction, wake preservation, and noise signal prediction are well demonstrated by comparison with the experimental data and the results obtained without VC schemes. Particularly, the FVC2-L2 scheme mainly improves the highly unsteady airloads prediction, and results in an improvement of BVI noise prediction by more than 5 dB with respect to the case without VC schemes for AH-1/OLS rotor case. Additionally, some shortcomings of the approach are noticed in engineering applications. On the basis of a simplified convective vortex, some provisional guidelines on the required εo value in terms of number of cells per vortex diameter are provided: an εo value ranging from 0.01 to 0.04 for grids which may represent the vortex core diameter with 6 to 12 cells.

Numerical study of hydrogen jet in methane / air premixed atmosphere

The work presented a numerical study on the transient characteristics of under-expanded hydrogen jets from a cylindrical nozzle. The finite-volume solution was adopted in the two-dimensional simulation of high-pressure chocked hydrogen jets, by solving the Navier-Stokes equations for gas phase flow. Numerical analyses were respectively performed over the micro level to characterize the fine structures, and over macro levels to explore the key global parameters of the gaseous jets. Parameterization work was conducted in terms of the microscopic characteristics of jets, such as, the length of jet core, the diameter of jet vortex, and the key global parameters, i.e. the penetration and the steady fuel injection rate. The effects of the injection parameters on the micro-structure and macro characteristics were hence quantified.

Convective Vortices and Dust Devils Detected and Characterized by Mars 2020

AbstractWe characterize vortex and dust devils (DDs) at Jezero from pressure and winds obtained with the Mars Environmental Dynamics Analyzer (MEDA) instrument on Mars 2020 over 415 Martian days (sols) (Ls = 6°–213°). Vortices are abundant (4.9 per sol with pressure drops >0.5 Pa correcting from gaps in coverage) and they peak at noon. At least one in every five vortices carries dust, and 75% of all vortices with Δp > 2.0 Pa are dusty. Seasonal variability was small but DDs were abundant during a dust storm (Ls = 152°–156°). Vortices are more frequent and intense over terrains with lower thermal inertia favoring high daytime surface‐to‐air temperature gradients. We fit measurements of winds and pressure during DD encounters to models of vortices. We obtain vortex diameters that range from 5 to 135 m with a mean of 20 m, and from the frequency of close encounters we estimate a DD activity of 2.0–3.0 DDs km−2 sol−1. A comparison of MEDA observations with a Large Eddy Simulation of Jezero at Ls = 45° produces a similar result. Three 100‐m size DDs passed within 30 m of the rover from what we estimate that the activity of DDs with diameters >100 m is 0.1 DDs km−2sol−1, implying that dust lifting is dominated by the largest vortices in Jezero. At least one vortex had a central pressure drop of 9.0 Pa and internal winds of 25 ms−1. The MEDA wind sensors were partially damaged during two DD encounters whose characteristics we elaborate in detail.

Physical modeling of slag carryover in the last stage of ladle teeming during continuous casting with dynamic change of slide gate opening

To investigate slag carryover in the last stage of ladle teeming during continuous casting, a water model system was established. The nozzle flow rate of model ladle was controlled by slide gate, which was automatically governed by a control module. The prototype teeming process can be accurately modelled through the system. However, under the condition that the slide gate is fully opened, the teeming process in water model has a great deviation with the actual. The vortex critical height in the mode of dynamic changing of slide gate is obviously less than that under the condition of 100% opening. Furthermore, under the dynamic changing mode, effects of operating parameters on vortex formation and slag carryover have been investigated. The vortex critical height decreases as the residence time before teeming increases. The effect of initial water level on critical height of vortex is little. As the flow rate increases, the critical height of vortex increases significantly. The variation of vortex diameter experiences developing stage and matured stage. When oil is added into model ladle, an important change is that the critical height of vortex decreases. By contrast, the vortex diameter obviously increases. The vortex critical height decreases while oil is added into ladle, but it increases as the oil layer thickness increases.

Razvojni eksperiment analize formiranja vrtloga

This developed a laboratory vortex apparatus with the aim to perform an experimental analysis of the formation of free and forced vortexes using water as fluid flow process. The experimental observations revealed that the apparatus surface of the vortex adjacent to the inner air core region was level where the radius expanded as the height increased. The orifice of the apparatus was selected for orifice diameters of 5, 10, 15, and 20mm at 30, 45, 60 and 90o angle of inclination were used to determine the diameter of the vortex developed for experimental flow process. The apparatus generated highest vortex diameter of 17mm for the free vortex and 8mm for forced vortex flow process a constant pressure head of 11.2m. Further analysis of the effect of orifice revealed that the larger the orifice diameter of 10, 15 and 20mm at developed a vortex faster for the two flow process as the angle of inclination was increased. The finding of this study will enhance further study to understand turbulent fluid flow process of vortex formation to meet demands of future technologies.

Validation of cardiac index measured by four‐dimensional cardiac magnetic resonance flow against the invasively measured cardiac index in patients with pulmonary hypertension

AbstractThe purpose of this study was to validate cardiac index (CI) measured noninvasively by four‐dimensional (4D) and two‐dimensional (2D) cardiovascular magnetic resonance (CMR) flows against the invasively measured CI by right heart catheterization (RHC) in patients with pulmonary hypertension (PH). Thirty patients with PH (mean age: 32 ± 10 years) were included. 4D and 2D flow measured CI within 24 h from RHC measured CI invasively. Qualitative analysis of 4D pulmonary flow (vortex presence and eccentricity of flow) was performed.All patients had helical right‐sided flow with vortex formation; the mean vortex diameter was 29 ± 7 mm, occupying 69% of the main pulmonary artery (MPA) lumen. MPA was dilated (42 ± 9 mm). Mean CI measured by 4D flow CMR was closer to mean CI measured invasively (indirect Fick method CI = 2.1 ± 0.8 L/min/m2 vs. PA 4D flow = 2.3 ± 0.7 L/min/m2 “bias 0.22 ± 0.25 L/min, p = 0.001,” and Ao 4D flow = 2.3 ± 0.7 L/min/m2 “bias 0.2 ± 0.28 L/min, p = 0.001”), while 2D flow had a higher mean CI (PA 2D flow = 2.5 ± 0.7 L/min/m2 “bias 0.45 ± 0.7 L/min, p = 0.001” and Ao 2D flow = 2.5 ± 0.8 L/min/m2 “bias 0.45 ± 0.67 L/min, p = 0.001”). The correlation coefficients among the different comparisons of CI showed: a low correlation between the 2D flow‐indirect Fick method (Ao r2 = 0.37, PA r2 = 0.32) and a high correlation between the 4D flow‐indirect Fick method (Ao r2 = 0.86, PA r2 = 0.89).There is an excellent agreement between CI measured by 4D flow and CI measured invasively. 4D flow, a noninvasive imaging technique, could accurately measure CI better than the conventional 2D flow in patients with PH.

Backwards wave breaking by flow separation vortices under solitary waves

In this work, the backward wave breaking process by the presence of flow separation vortices under a solitary wave is studied. Based on a set of non-dimensional variables defined from the Buckingham Π theorem, a set of numerical experiments are performed in order to analyze the effect of varying the submerged obstacle geometry on the surrounding flow and free surface by using a RANS-VOF model. Model simulations are tested against available experiments showing a good performance of numerical results. The structure-submergence ratio and the structure-based Reynolds number modulate the type of breaking (collapsing-plunging). The structure aspect ratio defines the location and number of backward breaking points for rectangular structures and the breaking wave direction for triangular structures (either forward or backward). Moreover, when the flow separation vortex diameter is comparable to the local water depth a backward wave breaking process is originated. The vortex behaves as a rigid body that accelerates the flow at the upper side of the vortex, accumulating mass at the downstream side where a very large slope on the free surface makes the water fall backward due to gravity.

Experimental Investigation on Juncture Flow Associated with a Surface-Mounted Circular Cylinder Trailed by a Backward-Facing Step

Juncture flows associated with surface-mounted obstacles can be characterized by a U-shaped tubular vortical flow known as a horseshoe vortex (HSV). Horseshoe vortices are usually detrimental to engineering applications. In order to identify a boundary geometry that may effectively reduce a HSV’s strength for further design of HSV-reduction devices, or otherwise enhance it for further disaster prevention by avoiding such a geometry in design, the characteristics of HSVs influenced by external boundary geometries must first be understood. Thus, we experimentally investigated a juncture flow field associated with a fundamental geometry—a circular cylinder mounted perpendicular to a plane surface—with a trailing backward-facing step (BFS) representing a novel idea of downstream effects on upstream-formed flow structures. This setup is not only one of the simplest nonplanar geometries that generates flow features such as an unsteady separated shear layer that may considerably affect an HSV, but it is also a new attempt without prior knowledge. We used the particle image velocimetry (PIV) and PIV-based flow visualization techniques combined with a vortex-fitting algorithm to measure the juncture flow and identify the HSV and its kinematic modes at the low Reynolds number of 1166. We observed from the flow-visualization results regarding HSV’s kinematic modes and their duration percentages as follows: (1) without the BFS: “oscillation with a small displacement” (98.6%) and “breakaway to roll-up” (1.4%); (2) with the BFS (step height/cylinder diameter = 1.5): “oscillation with a small displacement” (83.3%), “merging” (4.5%), and “mixed” (12.2%). It is clearly evident that the BFS increased the number and complexity of kinematic modes, i.e., the unsteadiness of the HSV. Moreover, the PIV results show that the BFS reduced HSV stretching, which resulted in increased vortex diameter by 8.24% and increased circulation by 6.37%, i.e., the strength of the HSV was enhanced by the BFS.

A global climatology of polar lows investigated for local differences and wind-shear environments

Abstract. Polar lows are intense mesoscale cyclones developing in marine polar air masses. This study presents a new global climatology of polar lows based on the ERA5 reanalysis for the years 1979–2020. Criteria for the detection of polar lows are derived based on a comparison of five polar-low archives with cyclones derived by a mesoscale tracking algorithm. The characteristics associated with polar lows are considered by the following criteria: (i) intense cyclone (large relative vorticity), (ii) mesoscale (small vortex diameter), and (iii) development in the marine polar air masses (a combination of low potential static stability and low potential temperature at the tropopause). Polar lows develop in all marine areas adjacent to sea ice or cold landmasses, mainly in the winter half year. The length and intensity of the season are regionally dependent. The highest density appears in the Nordic Seas. For all ocean sub-basins, forward-shear polar lows are the most common, whereas weak-shear polar lows and those propagating towards warmer environments are second and third most frequent, depending on the area. Reverse-shear polar lows and those propagating towards colder environments are rather seldom, especially in the Southern Ocean. Generally, polar lows share many characteristics across ocean basins and wind-shear categories. The most remarkable difference is that forward-shear polar lows often occur in a stronger vertical wind shear, whereas reverse-shear polar lows feature lower static stability. Hence, the contribution to a fast baroclinic growth rate is slightly different for the shear categories.

Numerical study on aerodynamic characteristics of two-dimensional propulsive wing in cruise and hover

The propulsive wing vehicle is a new concept vehicle, which is driven by a cross-flow fan (CFF) embedded in the trailing edge of the wing. The propulsive wing vehicle is capable of cruising and hovering at high angles of attack with very high aerodynamic force coefficients, and has the potential to become a new type of vertical take-off and landing (VTOL) vehicle. The cruise and hover states of the propulsive wing vehicle are defined, and a numerical model of the two-dimensional propulsive wing is established. Based on the computational fluid dynamics (CFD) method, the rotation of the CFF is simulated by using the sliding mesh technique. The effects of cruise speed, angle of attack and CFF rotation speed on the aerodynamics of the two-dimensional propulsive wing are evaluated, and the mechanism of the propulsive wing flow field changes is revealed. The results show that the propulsive wing has a very high lift coefficient of up to 60 at low speed and high angle of attack cruise, and a high thrust coefficient of up to 40 at low speed and small angle of attack cruise. The aerodynamic force of the propulsive wing fluctuates periodically with the rotation of the CFF, and the amplitude of the fluctuation is related to the vorticity of the CFF blade shedding vortex. In hover, the flow field of the propulsive wing is affected by the geometry and wake deflection into an asymmetric distribution, forming a vortex on each side of the airfoil, and the vortex diameter varies with the CFF rotation speed, which in turn has an impact on the hovering performance of the propulsive wing.

Study of the vortex chamber and its application for the development of novel measurement and control devices

Abstract Based on studies of the flow structure in a short cylindrical vortex chamber, the dependence of the flow rate coefficient on its geometric parameters is proposed. It is shown that the liquid flow form in the chamber’s axial vortex the pressure on which surface is corresponds to the pressure of the outflow cavity. These results are used to measure pressure in high-temperature cavities, using a sleeve with a diameter equal to or slightly larger than the diameter of the axial vortex. The sleeve is installed in the vortex chamber, and connects the pressure on its surface to the pressure sensor. The possibility of using a vortex chamber as a damper of pressure fluctuations has been substantiated. The design of the vortex damper and its tests results are presented; these show the possibility of increasing the stabilization time of the outlet pressure more than three-fold. Variants of regulating devices with a vortex chamber, functioning without changing the flow cross-sections, are proposed and the results of their tests are presented. This is achieved either by introducing an obstacle into the chamber cavity or by displacing the axis of the outlet nozzle position.

Temporal Evolution of Scour at Submerged Circular Cylinders

Temporal evolutions of scour at submerged circular cylinders were investigated. Flow visualization was carried out around the cylinders over plane, under developed and equilibrium scour holes. Video analysis technique was used to formulate the equations for determining the diameter of the horseshoe vortex around the submerged cylinders, which is also verified from the vector diagrams drawn using the velocity measurements. The scour process similar to live bed scour was noticed around the downstream cylinder. The diameter of the horseshoe vortex is found to depend on the diameter of respective cylinder, submergence ratio, spacing between the cylinders and skew angle. This formulation along with the dislodgement and transportation of a single sediment particle is further incorporated in the proposed model for determining the time variation of scour around the submerged cylinders. It is evident from the results that the upstream cylinder shelters the downstream cylinder and thereby reduces the scour at the downstream cylinder. Proposed model is further extended to incorporate the effect of non-uniformity of the sediment particles on the time variation of scour depth. The results indicate significant reduction of scour depth of around 6% and 35% for upstream and downstream cylinders respectively due to the formation of the armor layer. The model is also compared with the local scour component of field data around cylindrical bridge piers to establish the differences in the scour process around a partially submerged cylinder and fully submerged tandem and skewed cylinders.

Scaling of the translational velocity of vortex rings behind conical objects

Ring vortices are efficient at transporting fluid. They are often produced by ejecting a volume of fluid through a circular orifice. The impulse given to the vortex rings results in a propulsive force on the generator. Propulsive vortex rings have been widely studied and characterised. After four convective times, the vortex moves faster than the shear layer it originates from, and separates. This separation corresponds to a maximum in circulation and a maximal spread of the vorticity, quantified by the non-dimensional energy. The simultaneity of these three events obfuscates the causality between them. To analyse the temporal evolution of the non-dimensional energy of ring vortices independent of their separation, we analyse the development of vortices generated in the wake of cones. Cones with different apertures and diameters were accelerated from rest to produce a wide variety of vortex rings and their energy, circulation, and velocity were extracted based on time-resolved velocity field measurements. The rings that form behind the cones have a self-induced velocity that causes them to follow the cone and they continue to grow as the cone travels well beyond the limiting vortex formation times scales observed for propulsive vortices. The non-dimensional circulation, based on the vortex diameter, and the non-dimensional energy of the drag vortex rings converge after three convective times to values comparable to their propulsive counterparts. This result proves that vortex pinch-off does not cause the non-dimensional energy to reach a minimum value. The limiting values of the non-dimensional circulation and energy are mostly independent of the cone geometry and translational velocity and fall within an interval of 10% around the mean value. With only 6% of variation, the velocity of the vortex is the most unifying quantity that governs the formation of vortex rings behind cones.

The Performance Prediction Model of W-Shaped Hydrocyclone Based on Experimental Research

Fine particles misclassification in the underflow (UF) of grinding-classification hydrocyclones might result in ore over-grinding, leading to both reduced ball mill throughput and metal recovery. In the current research, a W-shaped hydrocyclone is proposed, to efficiently decrease the misclassification of fine particles in UF. The effects of the following parameters (including cross-effects) on W-shaped hydrocyclone classification performance were studied experimentally—inlet pressure, apex diameter, and vortex finder insertion depth and diameter. A mathematical model on the basis of the response surface method was established for the prediction of W-shaped hydrocyclone separation performance. The significance of the effects of the factors on the fine particle content in UF decreased in the following order—vortex finder diameter > inlet pressure > vortex finder insertion depth > apex diameter. The significance of influences of different factors on quality effectively decreased in the following order—inlet pressure > vortex finder insertion depth > vortex finder diameter > apex diameter. The significance of factor effects on the quantity efficiency decreased in the following order—inlet pressure > vortex finder insertion depth > apex diameter > vortex finder diameter. All influence factors were considered to obtain the optimal parameter configuration—an apex diameter of 0.14 D, a vortex finder diameter of 0.31 D, an insertion depth of 1.87 D, and an inlet pressure of 0.18 MPa. The corresponding optimal result was a −25 μm particle content (C−25) in UF of 11.92%, a quality efficiency of 42.48%, and a quantity efficiency of 98.99%.

Sub-Mesoscale Vortex Streets in the Region of the Shantar Islands (Sea of Okhotsk), According to Satellite Remote Sensing Data

Images in the visible range of the MODIS Terra/Aqua and ETM+ Landsat 7/OLI Landsat 8 satellites are used to study vortex streets (VSes) in the region of the Shantar Islands (Sea of Okhotsk​​). Two stable VSes are observed in the Northeast Strait separating Large and Small Shantar Islands. The northern VS forms near Diomede Stones Island, while the southern VS arises near a nameless group of rocks. The northern VS is 9–11 km long and consists of 4–5 pairs of cyclone-anticyclone vortices. The average diameter of a northern vortex is 0.73 ± 0.09 km. Vortices in the southern street are traced at distances of 6–7 km, with 3–5 vortex pairs recorded. The average diameter of a southern vortex is 0.47 ± 0.07 km. Vortices in the chain propagate mainly in the easterly direction at low tide and in the westerly direction at high tide. The spatial and temporal scales of the phenomenon show that both the vortices and VSes in the Northeast Strait are of a sub-mesoscale nature. The remote sensing data allow geometric parameters characterizing the stability of the oceanic VSes to be determined. The results from measurements and calculations can be used as tests demonstrating the possibility of applying the existing theory of similarity to VSes under real oceanic conditions. The parameters of oceanic VSes are compared to the results obtained in laboratory experiments and the characteristics of atmospheric VSes.