Vortex Center Research Articles

Study on the mechanism of vibration signal generation in water supply pipeline leaks

This study addresses water supply network leakage by employing numerical simulations to overcome challenges related to too small orifice hindering sensor deployment. Utilizing computational fluid dynamics and finite element methods, coupled with large eddy simulation, flow field distribution within pipes and at leakage orifice is investigated. The formation of leakage flow fields is categorized into three stages: leakage formation, unstable leakage, and stable leakage. During the leakage stage, the flow field is analyzed, and four regions—bottom central, bottom vortex, upper central, and upper vortex—are identified based on spatial characteristics. Detailed variable distribution patterns (velocity, pressure, vorticity) are provided in various planes. Understanding these distribution characteristics, six excitation sources responsible for generating leakage vibration signals are identified: pulsating velocity, pulsating pressure, bubble rupture, cavity pulsation, vortex-induced vibration, and gas expansion. The relationships among these excitation sources and their intensities concerning pipeline pressure and leak orifice radius are analyzed. Notably, a positive correlation between pressure and the intensity of all excitation sources is observed, while the impact of leak orifice size on these sources is found to be intricate. This research significantly contributes to an enhanced understanding of the physical processes associated with pipeline leakage.

Spatio-temporal dynamics of superstructures and vortices in turbulent Rayleigh–Bénard convection

Understanding turbulent thermal convection is essential for modeling many natural phenomena. This study investigates the spatiotemporal dynamics of the vortical structures in the mid-plane of turbulent Rayleigh–Bénard convection in SF6 via experiments. For this, a Rayleigh–Bénard cell of aspect ratio 10 is placed inside a pressure vessel and pressurized up to 1, 1.5, and 2.5 bar in order to reach Rayleigh numbers of Ra = 9.4×105,2.0×106, and 5.5×106, respectively. For all three cases, the Prandtl number is Pr =0.79 and ΔT≈7 K. Then, stereoscopic particle image velocimetry is conducted to measure the three velocity components in the horizontal-mid-plane for 5.78×103 free fall times. For the given aspect ratio, the flow is no longer dominated by the side walls of the cell and turbulent superstructures that show a two-dimensional repetitive organization form. These superstructures show diverse shapes with faster dissipation rates as Ra increases. Out-of-plane vortices are the main feature of the flow. As Ra increases, the number of these vortices also increases, and their size shrinks. However, their total number is almost constant for each Ra through the measurement period. Furthermore, their occurrence is random and does not depend on whether the flow is upward-heated, downward-cooled, or horizontally directed. Vortex tracking was applied to measure lifetime, displacement, and traveled distance of these structures. The relation between lifetime and traveled distance is rather linear. Interestingly, in the vortex centers, the out-of-plane momentum transport is larger in comparison to the bulk flow. Therefore, these vortices will play a major role in the heat transport in such flows.

Governance of Friedrich-Wintgen bound states in the continuum by tuning the internal coupling of meta-atoms.

Bound state in the continuum (BIC) is a phenomenon that describes the perfect confinement of electromagnetic waves despite their resonant frequencies lying in the continuous radiative spectrum. BICs can be realized by introducing a destructive interference between distinct modes, referred to as Friedrich-Wintgen BICs (FW-BICs). Herein, we demonstrate that FW-BICs can be derived from coupled modes of individual split-ring resonators (SRR) in the terahertz band. The eigenmode results manifest that FW-BICs are in the center of the far-field polarization vortices. Quasi-BIC-I keeps an ultrahigh quality factor (Q factor) in a broad momentum range along the Γ-X direction, while the Q factor of the quasi-BIC-II drops rapidly. Our results can facilitate the design of devices with high-Q factors with extreme robustness against the incident angle.

Numerical investigation the shape of groove on tip leakage vortex suppression of a NACA0009 hydrofoil

To investigate the effect of different bionic grooves on the tip leakage vortex, four bionic grooves with different shapes were designed, which are semicircular, rectangular, triangular and trapezoid. The streamline, pressure, vortex strength and turbulence kinetic energy were analyzed to clarify the suppression mechanism. When the groove is arranged, the velocity of vortex center and the area of high-intensity vortex area decrease. The vortex strength in the triangular groove is higher than other groove shapes. The pressure in the center of the tip leakage vortex core increases. The low pressure area reduces obviously, which is the smallest in the trapezoidal groove condition. The turbulent kinetic energy in the main flow field increases, but decreases in the tip clearance. The high turbulent kinetic energy region is divided into small pieces by the bionic groove, which is the smallest in the rectangular groove condition. The bionic groove leads to the decrease in lift-to-drag ratio, which is the largest in the semicircular groove and smallest in the rectangular groove condition.

An in-depth examination of flow structures organization downstream of a delta-winglet pair vortex generator under laminar, transitional, and turbulent flow regimes

In the present study, we experimentally investigate the time-averaged and time-evolving flow structures generated downstream of a delta-winglet pair vortex generator in an airflow channel. The Stereoscopic Particle Image Velocimetry technique is used to measure the velocity fields in the cross-sectional planes at various axial positions along the channel. The analysis of time-averaged flow topology shows that the flow is predominantly composed of two main counter-rotating longitudinal vortices under laminar, transitional, and turbulent regimes. While the time-averaged flow behavior might appear simple, the real-time organization of the instantaneous flow structures presents more complex features. The study of the flow's temporal evolution indicates that the transition from laminar to turbulent regime is controlled by a meandering mechanism referred to the motion of the main vortex centers around their axis and the emergence of secondary structures that evolve periodically over time.

Free flow over and under cylindrical weir-gates with a flow extender

ABSTRACT The complex field of free flow around a cylindrical weir – gate with and without a flow extender is investigated experimentally. The effects of the gap between the channel bed and the cylinder on the discharge characteristics of the cylindrical weir-gate are studied. It is observed that the ratio of the gate to weir discharge increased non-linearly with the normalized opening height. Four triangular downstream extensions of the cylinder oriented at, θ = 0, 10, 20, and 30 degrees were tested, and the minimum underflow to overflow discharge ratio was observed for θ = 10°. The highest improvement in discharge coefficients was 16% ± 6% for extender orientation angles of θ = 10°. The effects of opening height and extender angle on flow streamlines, pressure distribution, vortex strength, turbulent kinetic energy, and Reynolds stresses were investigated. A region of negative pressure was observed near the weir crest and the peak negative pressure increased with the opening height. The size and orientation of downstream wakes were measured, and it was found that the length of wakes varies from 0.30 to 1.06 times the diameter of the cylinder. The experiments showed that for a constant normalized opening height, the vortex center point formed further downstream as the upstream water head increased.

Tachyon Condensation in a Chromomagnetic Center Vortex Background

The chromomagnetic vacuum of SU(2) gluodynamics is considered in the background of a finite radius flux tube (center vortex) with a homogeneous field inside and a zero field outside. In this background, there are tachyonic modes. These modes cause an instability. It is assumed that the self-interaction of these modes stops the creation of gluons, and it is assumed that a condensate will be formed. For constant condensates, the minimum of the effective potential is found at the tree level. In the background of these condensates, all tachyonic modes acquire non-zero real masses, which will result in a real effective potential of this system. Considering only the tachyonic modes and adding the energy of the background field, the total energy is found to have a minimum at some value of the background field, which depends on the coupling of the initial SU(2) model. For small coupling, this dependence is polynomial in distinction from the Savvidy vacuum where it is exponentially suppressed. The minimum of this energy will deepen with a shrinking radius of the flux tube. It can be expected that this process can be stopped by adding quantum effects. Using the high-temperature expansion of the effective potential, it can be expected that the symmetry, which is broken by the condensate, will be restored at sufficiently high temperatures.

THEORETICAL STUDY OF VORTEX-LIKE ATOMIC STRUCTURES WITHIN A CONTINUUM FRAMEWORK

Using regression analysis through a component-wise search for regressors, a computational approach is proposed for estimating the oriented curvature of vortex-like atomic structures. The studied discrete vector fields of atomic displacements of such structural states are obtained based on the results of molecular dynamics simulations of a deformable defect-free crystallite. Within the given approach, a continuous representation of the desired discrete vector field is obtained. The redistribution of the free volume and reorientation of the crystal lattice are analyzed. It is found that the value of oriented curvature outside specific regions (vortex centers and regions of compensation of atomic displacements) is about |K| ≈ 0.286 nm-1. The relationship is shown between vortex-like structures and model concepts of a continuous disclination-type defect.

Impact of activation energy on magneto-bioconvection flow of oxytactic microorganisms with NePCM in complex shaped enclosure considering thermal radiations

This work explores the effect of activation energy on bioconvection flow of oxytactic microorganisms with nano-encapsulated phase change materials in complex shaped enclosure. The inner wavy wall is partially fixed at the constant high temperature. The proposed problem has been modeled first using the conservation laws and then simulated by utilizing finite element method. The discretized system of nonlinear algebraic equation is computed using the Newtons method. The obtained results have been analyzed for the several important controlling parameters. It has been observed that the vortex centers have been established near the adiabatic walls for lower values of Lewis number. The average Sherwood number and density of motile microorganism are the increasing functions of chemical reaction parameter. Moreover, the average Nusselt number declines with rising values of Peclet number.

Reduced systolic flow efficacy in left ventricular dyssynchrony evident by blood speckle imaging

Abstract Introduction Intraventricular vortices facilitate efficient blood flow in a healthy heart. Changes in the blood flow pattern can cause energy loss and inefficient filling or ejection. Thus changes, or reduction in vorticity may therefore be of importance for cardiac function. Blood speckle imaging (BSI) is a novel blood flow visualization tool based on echocardiography, partially overcoming the angel dependency of conventional colour Doppler. BSI tracks speckles generated by the moving blood cells, similar to myocardial speckle tracking, but requires a very high frame rate limiting penetration. Dyssynchrony in left bundle branch block (LBBB) affects the systolic functions but there is limited insight into how LBBB alters the blood flow vorticity. Purpose We investigated the effect of dyssynchrony on blood flow hemodynamics using blood speckle imaging. Methods In eight anesthetized canine mongrels, left ventricular flow was visualized using BSI. A qualitative visual assessment of vortices during the cardiac cycle, together with a quantitative assessment based on kinetic energy loss and vorticity were made. Regional myocardial function parameters were measured by sonomicrometry. Peak septal flash strain in isovolumetric contraction (IVC) was measured by sonomicrometry (figure) as an indicator of dyssynchrony. Assessments were made at baseline, under right ventricular free wall pacing (RV pacing) mimicking LBBB, after induced LBBB by ablation and under cardiac resynchronization therapy (CRT). Results During IVC at baseline all animals had a central ventricular vortex. However during RV pacing and LBBB it was distorted in various patterns. RV pacing significantly reduced the number of vortices in systole and disrupted the central vortex in IVC (1.0±0.0 vs 0.4±0.5, p=0.01). Energy loss (EL) in systole increased (40.2±12.5 vs 55.3±23.3 mW/m, p<.05). Septal end systolic strain was significantly reduced (-8.8±5.1 vs -1.9±7.3 %, p<0.01) and septal flash strain was significantly increased (1.0±1.4 vs 7.7±3.6 and 6.6±3.8 [ER1] [ER2] %, p<0.01) in RV pacing and LBBB. CRT caused a realignment of the central vortex (0.8±0.5 vs0.3±0.5, p=0.03). The change in energy loss was not significant, but numerically reduced (55.4±38.8 vs 76.4±48.9 mW/m, p=0.06). See table and figure 1. Conclusions The main systolic vortex in IVC was disrupted during septal flash by RV pacing and LBBB, altering the flow pattern compared to baseline. The resultant unstructured flow pattern had increased energy loss in systole, indicating a less efficient flow pattern and less preservation of energy. It should be further explored if this is of importance to understand the reduced LV function and LV remodelling during dyssynchrony.Figure 1Table 1

Application of FY Satellite Data in Precipitation of Eastward-Moving Southwest China Vortex: A Case Study of Precipitation in Zhejiang Province

Based on the high-resolution data from April to October (the warm season) during the 2010 to 2020 timeframe provided by the FY-2F geostationary meteorological satellite, the classification and application evaluation of the eastward-moving southwest vortex cloud system affecting Zhejiang Province was conducted using cloud classification (CLC) and black body temperature (TBB) products. The results show that: (1) when the intensity of the eastward-moving southwest vortex is strong, the formed precipitation is predominantly regional convective precipitation. The cloud system in the center and southeast quadrant of the southwest vortex is dominated by cumulonimbus and dense cirrus clouds with convective precipitation, while the other quadrants are mainly composed of stratiform clouds, resulting in stable precipitation; (2) The original text is modified as follows: By using the TBB threshold method to identify stratiform and mixed cloud rainfall, we observed a deviation of one order of magnitude. This deviation is advantageous for moderate rain. However, the precipitation results from mixed clouds identified by the TBB threshold method are being overestimated; By means of the application of stratiform and mixed cloud rainfall identified by the TBB threshold method, an order of magnitude deviation was identified (3) The TBB can be consulted to estimate the precipitation, above which there is a large error. Moreover, the dispersion of precipitation produced by deep convective clouds is the largest, while the dispersion of precipitation produced by stratiform clouds is the smallest and has better predictability. Compared to CLC products, cloud type results based on TBB identification are better for convective cloud precipitation application.

Left atrial haemodynamic evaluation using 4D flow cardiac magnetic resonance imaging: application to hypertension and hypertrophic cardiomyopathy

Abstract Introduction Changes in left atrial (LA) hemodynamics have been suggested reflective of left ventricular (LV) disease progression. Kinetic energy (KE), viscous energy loss, and vorticity could be promising indices for the assessment of left atrial dynamics by time resolved four-dimensional cardiac magnetic resonance (4D flow CMR). Hypertrophic cardiomyopathy (HCM) patients are at risk of developing mitral regurgitation and left ventricular outflow tract obstruction, with poor outcome (1). Hypertensive myocardial remodelling has been suggested to be due to complex flow and tissue interactions leading to hypertrophy and diastolic dysfunction (2). Early detection of altered LA hemodynamic abnormalities may help non-invasive assessment, improving their long-term outcome (3). Purpose Quantitative and qualitative evaluation of left atrial hemodynamic metrics by 4D flow CMR in a cohort of HCM patients, hypertensive patients, and healthy controls with no known cardiovascular disease. Methods Eighteen HCM patients (50.0 [±18.2] years, 8 females), twenty-one hypertensive patients (55.2 [±6.2] years, 11 females), and seventeen controls (36.7 [±12.8] years, 1 female) underwent 4D flow CMR. Both patient groups had significantly higher LV-indexed mass, end-diastolic volume, and end-systolic volumes (P < 0.05). A semi-automated pipeline was used to segment the LA including pulmonary inflow and mitral outflow tracts using phase contrast magnetic resonance images derived from the 4D flow acquisition's phase and magnitude images. LA KE, viscous energy loss and vorticity were computed throughout the cardiac cycle. Results The HCM and hypertensive groups demonstrated significantly higher average KE integrated across the cardiac cycle (1.58 ± 0.79 and 1.32 ± 0.50 mJ respectively) compared to controls (1.20 ± 0.47 mJ) (P < 0.05), with the systolic curve in HCM showing the highest peak KE. Qualitatively, KE in the diastolic portion of the cardiac cycle appeared less variable between groups (Figure 1). Vorticity in HCM showed different configurations with loss of the central atrial vortex core (Figure 2). Viscous energy loss was also significantly higher in HCM patients confirming the increase in energy loss (Figure 2). Average KE across the cardiac cycle highly correlated with LA volume and pulmonary capillary wedge pressure calculated by a previously published regression method (4) (Pearson correlation: r= 0.76 and 0.71 respectively P < 0.05). There were also significant correlations with cardiac metrics such as indexed end-diastolic and indexed end-systolic volumes (Pearson correlation: r= 0.54 and 0.52 respectively P < 0.05) as well as indexed LV mass (r= 0.59 P < 0.05). Conclusion Hemodynamic metrics derived from 4D flow CMR may be valuable in establishing valuable predictive metrics of ventricular function. Integration of 4D flow MRI in clinical workflows could provide information that may be indicative of pathological onset before abnormal remodelling.Kinetic energy and viscous energy lossParticle pathlines and vorticity

Structure of the streaming flow generated by a sphere in a fluid undergoing rectilinear oscillation

A solid body in a viscous fluid undergoing oscillatory motion naturally produces a steady secondary flow due to convective inertia. This phenomenon is embodied in the streaming flow generated by a sphere in an unbounded fluid executing rectilinear oscillations. We review the considerable literature on this canonical problem and summarise exact and asymptotic formulas in the small-amplitude limit. These analytical formulas are used to explore the characteristic flow structure of this problem and clarify previously unreported features. A single, toroidal-shaped vortex exists in each hemisphere regardless of the oscillation frequency, which can drive a counter-flow away from the sphere. The vortex centre moves monotonically away from the sphere with decreasing oscillation frequency, and engulfs the entire flow domain for $\beta \equiv \omega R^2/\nu < 16.317$ , where $\omega$ is the angular oscillation frequency, $R$ the sphere radius, and $\nu$ the fluid kinematic viscosity. This seemingly abrupt change in flow structure at the critical frequency $\beta _{critical} =16.317$ , and its quantification, appear to have not been reported previously. We perform a direct numerical simulation of the Navier–Stokes equations, to (1) confirm existence of this critical frequency at finite amplitude, and (2) examine its variation with amplitude. This reveals a universal relationship between the critical frequency and oscillation amplitude, clarifying previous reports on the structure of this streaming flow. The critical frequency is shown to be identical for the streaming flow and the cycle-averaged particle paths, establishing that the critical frequency is accessible directly using standard measurements.

Efficient numerical model for sediment transport on vortex ripple bed in wave-induced oscillatory flow

Sediment motion on rippled bed under wave action plays an important role in coastal landforms, but the application of traditional numerical model is limited by large computational work or bottom sediment condition due to unsteady effects. A single-phase model is proposed to maintain low computation and high accuracy for the vortex structure development and suspended sediment motion on vortex rippled bed in wave-induced oscillatory flow. The 2D bottom sediment condition takes into account the acceleration effect and asymmetric boundary layer development under nonlinear waves as well as the sediment phase-lag. The particle inertia and wake flow around sediment particle are considered in sediment turbulence, and the SST k-ω turbulence model which is suitable for inverse pressure gradient flow on rippled bed is selected to close the Reynolds stress. The single-phase model well predicts the velocity on vortex ripples, periodic concentration at fixed points and vertical distribution of averaged sediment concentration. The results show qualitative formation, development and ejection of vortex, and demonstrate quantitative development of vortex center, radius and strength in symmetric and asymmetric flows. In addition, the model well performs the development of sediment cloud referring to vortex structure.

Experimental investigation of characteristics and influence of tip leakage vortex wandering in an axial compressor cascade

Vortex wandering is one of the most basic unsteady flow characteristics of the tip leakage vortex (TLV) in compressors. In this study, stereo particle image velocimetry (stereo-PIV) has been conducted in compressor cascades with various tip clearances to investigate the characteristics and influence of TLV wandering. The most effective vortex identification method for stereo-PIV data has been clarified. The wandering characteristics of the TLV are statistically analyzed, and the relationship between the vortex wandering and the dominant proper orthogonal decomposition mode is identified. The results reveal that TLV preferentially wanders along the pitchwise direction in the blade channel and gradually loses the dominant wandering direction downstream of the blade. The large displacement of the vortex center around its mean location is characterized by higher probabilities at small tip clearance size (1% chord length C). The spatial distribution characteristics demonstrate similarly concentric isocontour around the mean vortex center location for large tip clearances (3% and 5% chord length C). The effect of TLV wandering on the secondary velocity distribution, the tip flow blockage, and the distribution of Reynolds stress is explored using the vortex wandering corrected technique. The analysis verifies that the elevated turbulence kinetic energy in the core of the time-averaged uncorrected TLV is caused by vortex wandering rather than vortex deformation. The discussions of the current paper will enhance our knowledge of TLV wandering. Regardless of the reference to TLV, the interpretation of other swirling flows can benefit from the discussions presented here.

The Effect of Blade Coning on the Flow Field of Wind Turbines under Yaw Conditions

Most wind turbines operate under yaw conditions, which can reduce the output power of wind turbines. In order to improve the power of wind turbines under yaw conditions, this paper adopts a method of blade taper to study its impact on the wind turbine flow field. A 2000W wind turbine is chosen as the research object and SOILDWORKS software is employed to establish a model of blade taper. Three cone angles of 4 °, 8 °, and 12 ° were used, and numerical simulations were conducted using STARCCM+. It is found that under 30 ° yaw conditions, the blade with a cone angle of 12 ° had the highest output power, followed by 8 ° and 4 °. Compared to 4 °, the output power of 12 ° and 8 ° increased by 2.32% and 5.99%, respectively. At the same time, appropriately increasing the blade cone angle can also reduce the dissipation of tip vortices and center vortices in the flow field. By analyzing the limit streamline diagram, it can be concluded that the vorticity at an 8 ° cone angle is less than the other two cone angles under 30 ° operating conditions. Therefore, in this simulation, the comprehensive performance of the 8 ° cone angle is better, which not only improves the output power under 30 ° yaw, but also makes the operation of the wind turbine more stable.

Morphology of Silver Particles and Films Arising from Particle‐Free Silver Ink Droplet Evaporation

AbstractThe evaporation of particle‐free silver ink droplets on heated substrates directly impacts the morphology of the resultant silver particles and electrically conductive inkjet‐printed films. In this work, COMSOL Multiphysics simulations of the droplet evaporation process are used to help explain the fluidic processes responsible for the experimental observations. The results show that the silver particle morphology depends on its location within the evaporating droplet where large particles (3 to 5 µm) accumulate at the center and smaller ones (1 to 2 µm) in the area beyond the central region. The smallest particles (≈500 nm) are near the contact line. Without the fluoro‐surfactant FS‐31, an inner ring with 3 µm particles also appears within the evaporating droplet. The large particles at the central region originate from the fluid near the droplet's apex due to the accumulation of polyacrylamide in the concentrated ethylene glycol solvent near the flow‐abundant apex. Furthermore, the capillary flow along the fluid–air interface transports silver ions and particles throughout the droplet, causing the larger particles to fall onto the substrate at the central vortex, forming the inner ring. The simulations also demonstrate that the evaporating droplet heterogeneously accumulates ethylene glycol in a sandhill formation at the bottom center.

Experimental investigation of inflow-outflow asymmetry in induced-charge electro-osmosis

Induced-charge electro-osmosis (ICEO) is a research hotspot in bioengineering and analytical chemistry. Inflow-outflow asymmetry of ICEO was reported in the existing literatures, but systematic study on this phenomenon is insufficient. In this experimental study, we found that in strong electric fields, not only the velocity magnitude but also the vortex positions of ICEO are asymmetrical along the inflow and outflow directions because of the pronounced non-uniform surface electrokinetic transport. On the inflow and outflow directions, the amplitudes of velocities are unequal, ICEO maximum velocity positions change depending on the electric field intensity and sodium chloride (NaCl) concentration. Additionally, the distances between vortex centers are different. At NaCl solution concentration of 0.001 mol·L–1, the outflow velocity almost vanishes. The asymmetry rises with the increasing electric field intensity. The new discoveries can direct the application of microscale devices.

Dynamics of several point vortices for the lake equations

The global asymptotic dynamics of point vortices for the lake equations is rigorously derived. Vorticity that is initially sharply concentrated around N N distinct vortex centers is proven to remain concentrated for all times. Specifically, we prove weak concentration of the vorticity and in addition strong concentration in the direction of the steepest ascent of the depth function. As a consequence, we obtain the motion law of point vortices following at leading order the level lines of the depth function. The lack of strong localization in the second direction is linked to the vortex filamentation phenomena. The main result allows for any fixed number of vortices and general assumptions on the concentration property of the initial data to be considered. No further properties such as a specific profile or symmetry of the data are required. Vanishing topographies on the boundary are included in our analysis. Our method is inspired by recent results on the evolution of vortex rings in 3D axisymmetric incompressible fluids.

Subvortices within a Numerically Simulated Tornado: The Role of Unstable Vortex Rossby Waves

Abstract Multiple subvortices corresponding to suction vortices in observations are obtained within a simulated tornado for the EF4 tornado case of Funing, China, on 23 June 2016. Within the simulation, the tornado evolves from a one-cell structure with vorticity maximum at its center to a two-cell structure with a ring of vorticity maximum. Five well-defined subvortices develop along the ring. The radial profile of tangential wind across the vorticity ring satisfies the necessary condition of barotropic instability associated with phase-locked, counterpropagating vortex Rossby waves (VRWs) along the ring edges. The phased-locked waves revolve around the parent vortex at a speed less than the maximum azimuthal-mean tangential velocity, agreeing with theoretically predicted VRW phase speed. The radii within which the wave activities are confined are also correctly predicted by the VRW theory where radial group velocity approaches zero. Several other characteristics related to the simulated subvortices agree with VRW theories also. The most unstable azimuthal wavenumber depends on the width and the relative magnitude of vorticity of the vortex ring. Their values estimated from the simulation prior to subvortex formation correctly predict wavenumber 5 as the most unstable. The largest contribution to wave kinetic energy is diagnosed to be from the radial shear of azimuthal wind term, consistent with barotropic instability. Vorticity diagnostics show that vertical vorticity stretching is the primary vorticity source for the intensification and maintenance of the simulated subvortices. Significance Statement Multiple subvortices or suction vortices in tornadoes can produce extreme damage but their cause is not well understood. An intense tornado from China that developed five strong subvortices, along a vorticity ring a distance from the tornado vortex center, was successfully simulated. By examining the propagation and other characteristics of these subvortices and comparing them with theoretical models of vortex Rossby waves (VRWs) that have been studied mostly in the context of typhoons/hurricanes, it is believed that nonlinear growth of unstable VRWs associated with barotropic instability is the primary reason for the development of subvortices within the tornado. The conclusion is further supported by analyses of the primary source of wave growth energy. Vertical vorticity stretching is the main vorticity source for intensifying and maintaining the subvortices at their development and mature stages. The unstable growth of VRWs as the cause of tornado suction vortices has not been analyzed in detail for realistic tornadoes until now.