Vortex Suction Research Articles

The influence of vortex flow generated by spur dikes on the distribution and mixing of dissolved oxygen at a wide-shallow confluence

The inflow of heavy polluted tributaries is one of the main factors that destroy the water quality at the river confluence area and downstream, especially in the wide-shallow river confluence area. In this study, a generalized model of a two-dimensional confluence was established and validated, and dissolved oxygen concentration was used as the water quality indicator. The influence laws and mechanisms of different spur dike layout patterns on the water quality distribution characteristics and the transport and mixing processes at the confluence were explored through numerical simulation. The results show that there is a large area of water pollution at the confluence with the polluted tributary, which is distributed near the outlet of the tributary, and the water quality in this area recovers slowly. The flow ratio is the main factor affecting the distribution of water quality transport at the confluence. Arranging dikes on the opposite bank of the tributary can significantly reduce the area of pollution by adjusting the flow field. Arranging dikes on the tributary side of the confluence can effectively promote water quality mixing through vortex suction between dikes and improve water quality near the tributary side of the river bank. The dissolved oxygen concentration between dikes at the river bank on the tributary side showed an increasing trend along the river direction, and vortex flow velocity showed a decreasing trend, and the increment of dissolved oxygen concentration had a good linear correlation with the interval between dikes and the change in vortex flow velocity between dikes.

Study on suction effect of water jet propulsion pump based on entropy weight theory

Water jet propulsion pumps start at special stages such as mooring and sailing, the ship is in shallow water, and the underwater keen clearance (UKC) is relatively small, which is easy to induce underwater suction vortex near the inlet position and cause violent vibration of the pumping unit. The powerful suction effect of the water-jet propulsion pump can draw in debris from the bottom of the riverbed, causing damage to the propulsion pump. This research investigated the suction effect of water jet propulsion pump under different UKC conditions. A flow field analysis method based on the entropy weight theory was constructed to reveal the flow characteristics of the flow field where the underwater suction vortex occurs. The research found that the suction effect on the flow field tends to stabilize under the condition of UKC greater than 2.5D0. After UKC reaches 4.2D0, suction effects essentially cease to create large-scale shear stresses near the riverbed. In addition, this research analyzes the vorticity field using vorticity and net circulation to elucidate the vortex strength within the flow field under different UKC conditions. The probability of generation of underwater suction vortices will be greatly reduced when the UKC is greater than 0.83D0.

Study on hydraulic characteristics of two-direction flow at the inlet/outlet of a large pumped storage station

Abstract The inlet/outlet is one of the most important parts of a pumped storage power station. Improper designs will cause problems such as suction vortex and increased head loss, which will affect the operation efficiency of the power station. This paper takes the inlet/outlet of a pumped storage power station in Zhejiang Province as an example for research. The upper reservoir inlet/outlet takes itself and the surrounding terrain, gully, and dam as the research object, and conducts physical model tests; the lower reservoir inlet and outlet take itself and the surrounding stone factory and other mountain terrain as the research object, and conduct numerical simulation studies. On this basis, the rationality of the scheme is explored and the optimization scheme is found, which can be used as a reference for similar engineering designers.

Study on the Adsorption Performance of a Vortex Suction Cup under Varying Diameters of Underwater Structure Tubes

Study on the Adsorption Performance of a Vortex Suction Cup under Varying Diameters of Underwater Structure Tubes

Influence of Partition Wall Length on Inlet Flow Regime of a Pumping Station Arranged in Parallel with a Sluice Gate

When a sluice gate is arranged in parallel with pumping station units, biased flow occurs in the forebay when the units are operating. The transverse flow velocity in front of the channel inlet is relatively high, and, in severe cases, it may lead to the formation of suction vortices, impacting the stable operation of pump units. Taking the Liushan Pumping Station project of the Eastern Route of the South-to-North Water Diversion Project as a case study, this paper investigates the effect of the partition wall length on the inlet flow regime of pumping station units arranged in parallel with the sluice gate to reduce the transverse flow velocity in front of the channel inlet. Using numerical simulations, the inlet flow regimes for different partition wall lengths were compared. Moreover, the flow field distributions in the forebay under different operating conditions were analyzed alongside the transverse flow velocity in front of the channel inlet and the uniformity of flow velocity distribution in the section behind the channel inlet. Hydraulic model tests were then conducted to validate the simulation results. The results indicate that in the original design, there existed a vortex zone in the forebay in front of the inlet of the channel where the transverse flow was relatively high. However, the introduction of partition walls significantly reduced the transverse flow velocity in front of the inlet of the channel in the forebay. The optimal effect was achieved when the length of the partition wall was twice the width of the inlet channel. Furthermore, the uniformity of velocity distribution at the inlet of the channel increased by an average of 7.4%, leading to a substantial improvement in the inlet flow regime of the pumping station. The addition of partition walls in the forebay effectively resolved the issues related to the flow regime in the forebay, providing valuable references for similar engineering studies in the future.

Study on the performance of vortex suction cup for an underwater inspection robot

Using robots to detect Marine structures is very important for maintaining the safety of Marine structures. This paper presents an underwater inspection robot specifically engineered for the assessment of underwater structures. The integration of reliable adhesion technology is identified as a critical factor in the development of such robots. The vortex suction cup, employed by the robot as its primary adhesion mechanism, outperforms traditional adhesion methods by enabling non-contact attachment while consuming less power. As the vortex suction cup is the core component of the underwater inspection robot , this study comprehensively investigates how variations in the vortex suction cup’s structural and operational parameters influence its adhesion performance, measured from an energy efficiency ratio perspective. Initially, we delineate the vortex suction cup’s design and succinctly explicate the mechanism underpinning the generation of negative pressure. Subsequently, we establish an evaluative parameter, the energy efficiency ratio (η=F/P), that is, the adsorption force obtained per watt of power consumption of the suction cup, serving as a metric for the adhesion performance. By simulating the structural and operational parameters of the suction cup, we extract the corresponding adhesion force, torque, and energy efficiency ratio. Lastly, we construct an experimental apparatus to measure the suction cup’s adhesion force and output torque, validating the veracity of the simulated outcomes. Our simulation and experimental findings indicate that increasing the height of the suction cup housing enhances the adsorption force, however, this simultaneously diminishes its energy efficiency ratio performance. Likewise, an increase in the chamber inner radius amplifies the adhesion force, and the energy efficiency ratio commensurately increases. Augmenting the radius of the negative pressure effect board improves the adhesion force, decreases the required torque, and consequently amplifies the energy efficiency ratio. The suction cup’s adhesion force and required torque display a direct relationship with its speed, but the energy efficiency ratio is minimally affected by speed. When the distance is close (h ¡ 4 mm), changes in the adhesion gap profoundly impact the suction cup’s torque and energy efficiency ratio. However, when the adhesion gap ranges between 5–15 mm, the energy efficiency ratio exhibits a gradual decline.

Hydraulic performance improvement of a two-way pumping station through bell mouth shape design

A two-way pumping station is a specialized device that facilitates bidirectional water pumping and drainage. The pressure pulsation characteristics of two-way pumping stations have emerged as a prominent research focus in the field of hydraulic engineering. In this work, with the aim of systematically proposing optimization measures to ensure operational stability, a transient numerical simulation is conducted to elucidate the influence mechanism of the suspension height of the bell mouth (SHb) on the internal flow field and pressure pulsation of a two-way pumping station. High-precision experiments are performed to compare time-frequency domain characteristics under different SHb using a continuous wavelet transform (CWT). The findings indicate that an appropriate reduction in SHb effectively reduces unstable flow and pressure pulsation within the inlet conduit, consequently reducing the pressure pulsation of the impeller. With a reduction in SHb, the influx of low-velocity backflow into the bell mouth is prevented and the generation and propagation of suction vortices are suppressed. However, the reduction amplifies the flow impact between the mainstream flow and the bell mouth wall. The spatial distribution of the pressure pulsation is also examined, and it is found that a reduction in SHb increases the pressure pulsation intensity on the side facing the incoming flow and on the rear side, while the mainstream area tends to exhibit stability. In terms of time-frequency domain characteristics, a reasonable reduction in SHb leads to improved circumferential uniformity of the impeller inflow and the effective suppression of low-frequency disturbances.

Research and development of vortex suction dedusting device based on multi-factor horizontal response surface method

The excavation of coal mines generates substantial dust, posing environmental and health risks for underground coal mine workers. To address the dust issue, a novel Vortex Air Flow Negative Pressure Entrainment Dedusting Device was developed. Through numerical simulations and a comprehensive experiment, factors influencing dust removal efficiency, such as the number of air ducts, wind speed, and pressure duct layout angle, were analysed. The result showed that the number of air ducts had the most significant effect on the suppression efficiency, while the pressure duct layout angle had the least significant impact. Six ducts with 25 m/s air velocity and 30° pressure duct angle were determined as the optimum operational parameters for dust removal. Field tests with the optimum setting were also conducted. The results demonstrated the best dust control performance compared to other settings, which resulted in a 90% reduction in coal dust concentrations. The developed device provides underground coal mines with an effective method to control coal dust efficiently during the excavation.

Numerical Method to Determine the Inception of Propeller Tip Vortex Cavitation Based on Bubble Dynamics

Due to the scale effect, tip vortex cavitation (TVC) is the earliest type of cavitation that occurs on real ship propellers. As a result, experts in the ship field have been paying close attention to the accurate prediction of propeller TVC inception for a long time. The motion and growth of the microscopic nuclei in the water have a significant influence on TVC inception. However, the minimum pressure coefficient method—a common method at present—based on the traditional Eulerian framework, neglects the influence of microscopic nuclei and therefore cannot accurately predict the cavitation inception. Moreover, the numerical prediction method for cavitation inception, which is based on bubble dynamics models and considers the influence of nuclei, has not established a set of unified and specific discrimination criteria applicable to propeller cavitation inception. In order to make up for the shortcomings of traditional prediction models and the existing methods based on bubble dynamics in the prediction of TVC inception, we propose a new discrimination method for propeller TVC inception based on bubble dynamics in this paper. The comparison with experimental results demonstrates that our proposed method allows us to predict propeller TVC inception more accurately. In addition, the effect mechanism of tip vortex flow characteristics on nuclei evolution is further investigated, and it is found that when approaching the low-pressure region at a vortex core under the influence of tip vortex suction, nuclei grow explosively under the continuous action of the low pressure at the vortex core until they reach their maximum sizes and then collapse rapidly.

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.

Performance analysis of a novel flat lay-type synthetic jet pump with Y-shaped jet chamber.

Recently, synthetic jet pumps have been expected to be used in electronic heat dissipation devices due to the vortex suction phenomenon for transporting fluids. Aiming to improve the delivery ability of the jet pump to output fluid continuously, a novel flat lay-type synthetic jet pump (FLTSJP) with a Y-shaped jet chamber is proposed in this paper. Based on the synthetic jet effect, the pump chamber continuously outputs fluid in one cycle. The output performance of FLTSJP is theoretically analyzed to be affected by the outlet cone angle. The one-cycle flow mechanism of the fluid in the Y-shaped jet chamber is simulated. FLTSJP is manufactured, and a test system is built. Experiments show that the Y-shaped jet chamber effectively improves the output performance. The optimum flow rate and outlet pressure were both reached at 160V and 40Hz, which were 20.63 ml/min and 333.43Pa, respectively. This FLTSJP effectively improves the output performance of synthetic jet pumps and provides a new research concept of water-cooled devices for electronic heat dissipation.

A study on the dynamic characteristics of surface suction vortices in an open inlet pool

The surface suction vortices in the open pump intakes were systematically investigated by using numerical and experimental methods. A 3D open inlet pool model has been applied to numerically simulate the flow pattern in the sump based on the shear stress transfer k–ω model, and the volume of fluid method was used to analyze flow fluctuations in the free surface in order to capture and identify the developing status and the evolution process of surface suction vortices as well. The results show that the surface suction vortices easily occur at large flow rates, and the suction ability of these vortices has a positive linear relationship with the flow rate, submerged depth, and the Froude constant. Moreover, it can be observed that the extended direction of the dynamic vorticity is determined by the vortex component along the Z axis (ωz), which played a major role in the stretching effect during the vortex deformation.

Cooling fan aerodynamic noise reduction with short inlet duct and its applicability

This paper presents experimental and numerical analyses of the noise-reduction method of applying short inlet ducts to axial-flow cooling fans. Far-field noise tests of three different-sized cooling fans with tip Mach numbers of 0.143, 0.156, and 0.174 demonstrated that tonal noise was the primary source of aerodynamic noise. Through the installation of short inlet ducts on these fans, the upstream propagation of tonal noise was reduced. The average total sound pressure levels were decreased by up to 3.5, 4.8, and 7.1 dBA, respectively. At the blade passing frequency, the dominant upstream-propagating azimuthal acoustic modes were suppressed. Full-passage unsteady computational fluid dynamics calculations revealed that the duct transforms multiple suction vortices into a single annular vortex structure and weakens the interaction with the rotor blades. In addition, the acoustic analogy was used to compute the reduction of far-field noise and the variations in the major acoustic modes. This revealed a noise-reduction trend similar to that seen in the experiments. Essentially, the duct restrains the non-uniform inlet flow to influence the various inlet–rotor–stator interaction modes. The application of this approach to various fan configurations confirmed that a duct with a parameter of L/D (duct length/duct inner diameter) equal to 0.08 can be recommended as a compact and efficient way to reduce noise.

Nonlinear dynamic characteristics of suction-vortex-induced pressure fluctuations based on chaos theory for a water jet pump unit

To improve the effective use of ocean energy by water jet propulsion pump, it is necessary to study the underwater suction vortex (USV), which affects the propulsion and stealth performance of water jet propulsion pump. This paper analyses the time-frequency and nonlinear dynamic characteristics of the pressure fluctuation induced by USV through high-speed photography and high-frequency pressure fluctuation tests. The nonlinear characteristics of pressure fluctuations under the conditions with and without USV are compared and analyzed based on the chaotic time series analysis theory. The results show that the chaotic characteristics of the pressure fluctuation signal are unaffected by the occurrence of USV. However, the singular attractor structure of the pressure fluctuation signals induced by USV is highly complex, and the largest Lyapunov exponent increases. Therefore, the pressure fluctuation signals induced by USV have stronger chaotic characteristics. Note that the saturation correlation dimension of the pressure fluctuation signal in the period without USV is larger than that with USV, mainly because the influence factor of the pressure fluctuation signal in the USV period is relatively single, which is primarily induced by USV. The nonlinear characteristics analysis of the pressure fluctuation signal can effectively identify the presence of USV.

Increasing the rate of capture of pollutants by local suction due to the use of an external swirling jet. Part 1. Research methods

To capture pollutants in many buildings and structures, it is necessary to use local suction systems. One of the criteria for the effectiveness of local suction ― the rate of capture of pollutants ― it is proposed to increase due to the impact of a swirling annular jet and the occurrence of a reverse air flow. The circular suction is placed coaxially in an external cylindrical casing, in which the air flow is twisted due to the tangential supply of two supply jets into the casing. A vortex dome is formed, which helps to increase the efficiency of such a vortex suction. The change in the axial velocity of air at a distance from the vortex suction was experimentally and numerically investigated for 11 structures, in each of which 4 different ratios of intake and supply air flow rates were set. In the investigated applications of the proposed suction systems, the speed increases significantly at a certain range of distance from them. A combination of designmode parameters that contribute to the highest rate of capture by vortex suction is determined. The results obtained are useful in designing effective suction systems for capturing pollutants.

Capturing wake capture: a 2D numerical investigation into wing–wake interaction aerodynamics

A wing generating lift leaves behind a region of disturbed air in the form of a wake. For a hovering insect, the wings must return through the wake produced by the previous half-stroke and this can have significant effects on the aerodynamic performance. This paper numerically investigates 2D wings interacting with their own wake at Reynolds numbers of 102 and 103, enabling an improved understanding of the underlying physics of the ‘wake capture’ aerodynamic mechanism of insect flight. We adopt a simple kinematic motion pattern comprised of a translational stroke motion followed by a complete stop to expose wake interaction effects. Representative stroke distance to chord ratios between 1.5 and 6.0 are considered, enabling different leading-edge vortex (LEV) attachment states. We also allow pitching rotation towards the end of stroke, leading to wake intercepting angles of 135°, 90°, and 45°, analogous to delayed, symmetric, and advanced pitching rotations of insect wings. It is shown that both vortex suction and jet flow impingement mechanisms can lead to either positive or negative effects depending on the LEV attachment state, and that stroke distances resulting in a detached/attached LEV lead to beneficial/detrimental wake interaction lift. Pitching rotation at the end of the stroke motion is found to induce a strong rotational trailing-edge vortex (RTEV). For advanced pitching, this RTEV serves to enable either a stronger flow impingement effect leading to positive wake interaction lift if the LEV is detached, or a less favourable vortex suction effect leading to negative wake interaction lift if the LEV is closely attached. The higher Reynolds number led to faster development of the wake vortices, but the primary wake interaction mechanisms remained the same for both Reynolds numbers.

Experimental study on flow evolution and pressure fluctuation characteristics of the underwater suction vortex of water jet propulsion pump unit in shallow water

The occurrence of the underwater suction vortex will cause the ship to vibrate violently and even lose thrust. The evolution process of the underwater suction vortex was obtained by high-speed photography. According to the characteristics of vortex in different phases, its diachronic process can be divided into five phases: premonitory, nascent, developing, weakening, and disappearing. The underwater suction vortex is a vertical axis vortex below the intake, and its shape is similar to a tornado, showing a form of thick at the top and thin at the bottom. The pressure fluctuation test studied the time-frequency characteristics of pressure fluctuation induced by the underwater suction vortex. The results show that the underwater suction vortex can cause the pressure fluctuation amplitude to recover after a sudden drop. The frequency of characteristic low frequency induced by the underwater suction vortex is 0.28 Hz, which is easy to be ignored. The corresponding amplitude of this frequency is much larger than that of other frequencies, and the low-frequency pressure fluctuation induced by the underwater suction vortex is dominant. The results can provide a theoretical basis for the mechanism and prevention of suction vortex of water jet propulsion pump unit.

A 15-m resolution numerical simulation of a tornado in South China: Structure and vorticity budget of the suction vortices

An EF3 tornado occurred in the spiral cloud belt surrounding Typhoon Rainbow on October 4, 2015. We performed six nested numerical simulations with horizontal resolutions of 4050, 1350, 450, 150, 50 and 15 m to analyze the structure and mechanisms of formation of the tornado. The typical structure of the tornadic supercell was simulated at a resolution of 444 m. The tornado-like vortex system developed until the grid spacing was ≤148 m. The suction vortex inside the tornado were captured at a resolution of 15 m. These suction vortices developed and rotated rapidly before being organized into the main vortex of the tornado. We used the vorticity equation to analyze the vorticity budget of the suction vortex. The main contribution to the vorticity was the solenoidal term. The horizontal convergence term mainly influenced the high-level outflow, whereas the tilting term affected the mid-level updraft. The frictional term mainly affected the lower levels where the suction vortex developed. We propose a conceptual model based on our results. Influenced by the frictional force, the suction vortex generated, developed and merged into the tornado vortex near the surface. The vertical circulation of the strong spiral region was influenced by convergence at higher levels and inflow at the lower rear of the tornado. Tilting of the vorticity tube and merging of the suction vortex caused the hydrometeors to aggregate and fall at the location where the tornado was generated.

The Dodge City Tornadoes on 24 May 2016: Understanding Cycloidal Marks in Surface Damage Tracks and Further Analysis of the Debris Cloud

Abstract Mobile, polarimetric radar data were collected on a series of tornadoes that occurred near Dodge City, Kansas. A poststorm survey revealed a series of tornadic debris swaths in several dirt fields and high-resolution pictures of the tornado documented the visual characteristics of the tornado and the lofted debris cloud. The main rotational couplet associated with the tornado was identified in the single-Doppler velocities; however, no secondary rotational couplets were resolved in the low-level data performed during two consecutive volume scans. Numerical simulations have suggested that cycloidal damage swaths can result when debris is deposited as the low-level inflow turns upward in the corner region of the updraft annulus of the tornado core. This mechanism can dominate even when suction vortices are present in the simulations and can produce these swaths in the absence of these smaller-scale vortices. It is hypothesized that the observed cycloidal damage swaths were a result of the low-level inflow in the corner region of the tornado and not by the existence of suction vortices. Polarimetric data were combined with photographs of the tornado in order to document the lofted debris cloud and its relationship with the funnel. This analysis provided an opportunity to investigate whether recent findings describing the cross-correlation coefficient ρhv and differential reflectivity ZDR signatures of the lofted debris cloud could be replicated. Regions of low ρhv at the periphery of the funnel cloud suggesting high debris loading and a column of negative ZDR centered on the tornado believed to be produced by common debris alignment were noted. Significance Statement It is well known that some tornadoes produce smaller-scale vortices that rotate around the central axis of the main circulation. In addition, numerous aerial photographs have documented cycloidal debris marks within tornado damage tracks that traverse open fields. The prevailing theory shown in numerous textbooks is that these marks are produced by these vortices. The current study suggests that this widely accepted model for producing these marks may be incorrect. It is suggested that these cycloidal marks are produced by the main tornado circulation and not by the smaller-scale vortices in this case.

Circulation of Superfluid Suction Vortex

Circulation of Superfluid Suction Vortex