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The purpose of the paper is to disclose the effect of the relative position (d) between the impeller and non-vane cavity on the hydraulic performance and unsteady characteristics of vortex pump.

Three groups of vortex pump models with different impeller installation positions were analyzed and studied by combining experimental and CFD (Computational Fluid Dynamics) numerical calculations.

The steady numerical results show that as the width (d) of the impeller moves into the non-vane cavity increases, the proportion of circulation flow in the non-vane cavity is reduced and both the pump head and efficiency are on the rise. The unsteady numerical results and the Enstrophy analysis show that the dynamic and static interference between the circulation flow and the volute tongue is the main reason for the pressure pulsation with a frequency of 2fn in the vortex pump. With the increase of the d value, the dynamic and static interference between the circulation flow and the volute tongue is enhanced. The pulsation amplitude at the volute tongue of the d = 16.5 mm model increases about six times compared with the d = 0 mm model; the distribution of the vortex core in the non-vane cavity is closely related to the position of the impeller, and the peak of the Enstrophy of the circulation flow vortex belt always appears at the top of the impeller.

The research results provide a theoretical foundation for the optimization and improvement of the vortex pump.

The special structure of the vortex pump contributes to its complex internal flow pattern. A type of horizontal 150WX-200-20 vortex pump is taken as a research subject to deeply study the progression and distribution of flow pattern in its channel. To explain the mechanism of flow in this pump, numerical analysis of the whole flow and experiment have been conducted.

The authors studied and analyzed the distribution and evolution of flow pattern under different flow, such as circulating-flow, through-flow and other forms. Finally, a model of flow pattern in the vortex pump has been built, which has more perfectly fit the reality.

They are through-flow affected by circulating-flow, main and subsidiary circulating-flow, vortices between vanes and other vortices (or liquid impingement) in volute. Entering the pump, part of the flow stays in vanes and turn into vortices while the other goes into the front chamber. The flow that runs into the front chamber will be divided into two parts. One part will be collected by viscosity into a vortex rope when it passing through the interface between the impeller and the vaneless chamber, which closely relates to the circulating-flow, and the rest directly goes out of the field through the diffuser. Besides, a fraction of circulating-flow joins the through-flow when it goes through the section V and leaves the pump.

The research results build a theoretical foundation for working out the flow mechanism of the vortex pump, improving its efficiency and optimizing its hydraulic design.

Vortex grippers use tangential nozzles to form vortex flow and are able to grip a workpiece without any physical contact, thus avoiding any unintentional workpiece damage. This study aims to use experimental and theoretical methods to investigate the effects of nozzle diameter on the performance.

First, various suction force-distance curves were developed to analyze the effects of nozzle diameter on the maximum suction force. This study determines the tangential velocity distribution on the workpiece surface by substituting the experimental pressure distribution data into simplified Navier-Stokes equations and then used these equations to analyze the effects on the flow field. Subsequent theoretical analysis of the distribution of pressure and circumferential velocity further validated the experimental results. Next, by rearranging these relationships, the study considered the effects of nozzle diameter on the inherent vortex gripper characteristics. In addition, this study developed various suction force-energy consumption curves to analyze the effects of nozzle diameter.

The results of this study indicated that the vortex gripper’s circumferential velocity and maximum suction force decrease with increasing nozzle diameter. Nozzle diameter did not significantly affect the inherent frequency of the vortex gripper-workpiece inertial system or the corresponding suspension stability of the workpiece. However, an increase in nozzle diameter did effectively increase the vortex gripper’s suspension region. Finally, as the nozzle diameter increased, the energy required to achieve the same maximum suction force decreased.

This study’s findings can enable optimization of nozzle design in emerging vortex gripper designs and facilitate informed selection among existing vortex grippers.

The purpose of this paper is to develop a Vortex-In-Cell (VIC) method with the semi-Lagrangian scheme and apply it to the high-Re lid-driven cavity flow.

The VIC method is developed for simulating high Reynolds number incompressible flow. A semi-Lagrangian scheme is incorporated in the convection term to produce unconditional stability, which gets rid of the constraint of the convection Courant-Friedrichs-Lewy (CFL) condition; the adaptive time step is used to maintain the numerical stability of the diffusion term; and the velocity boundary condition is readily converted to the vorticity formulation to suit discontinuous boundary treatment. The VIC simulation results are compared with those produced by other gird methods reported in open literature studies.

The lid-driven cavity flow is simulated from Re = 100 to 100,000. Similar vortex birth mechanisms are exhibited though, but distinct flow characteristics are revealed. At Re = 100 to 7,500, the cavity flow is confirmed steady. At Re = 10,000, 15,000 and 20,000, the cavity flow is periodical with a primary vortex held spatially at the center. In particular, at Re = 100,000 highly turbulent characteristics is first revealed and an analogous primary vortex is formed but in motion rather than stationary, which is caused by the considerable flow separation at all the boundaries.

In the lid-driven cavity, the flow becomes extremely complex and highly turbulent at Re = 100,000, and the analogous primary vortex structure is observed. Boundary layer separation is observed at all walls, producing small vortices and causing the displacement of the analogous primary vortex. Such a finding original and has not yet been reported by other investigators. It may provide a basis for conducting in-depth studies of the lid-driven cavity flow.

A numerical study is performed to investigate flow instability phenomena in a square channel with steady, laminar throughflow. The channel rotates around an axis perpendicular to the channel longitudinal axis. The flow field extends from the channel entrance to a distance of 120 to 600Dh. The range of Reynolds number is Re = 300−2000. The inlet flow velocity is assumed uniform. Surface vorticity intensity is introduced to indicate the variation of vortices. It is revealed that at intermediate Reynolds numbers (680 > Re > 300), the flow is characterized by three vortex patterns: at slow rotation there is one vortex pair; at intermediate rotation a secondary vortex, in addition to the original vortex, emerges near the trailing wall and then breaks down downstream; and at rapid rotation the secondary vortex does not exist with the flow being restabilized to form a single‐pair vortex pattern. At low Reynolds numbers (Re ≤ 300), the flow exhibits a single‐pair vortex pattern, while at high Reynolds numbers (Re ≥ 680), the flow experiences the emergence and breakdown of a secondary vortex, but no restabilization is found with an increase in the rotational speed. It is also disclosed that the variation of the vortices is related to the distance from the inlet.

Having read previous literature about vortex pump, we noticed that mechanisms of circulating flow and its relationship with energy transition remain unclear yet. However, this mechanism, which should be clarified, significantly influences the pump’s efficiency. To comply with the aim of investigating it, the 150WX-200-20 type pump is selected as study object in our present work.

Numerical simulation is conducted to formulate interactions between flow rate and geometric parameters of circulating flow with certain types of blade while experiments on inner flow are served as a witness to provide experimental confirmation of numerical results. Based on these, we coupled some parameters with the pump’s external performance to study their internal connections.

It is concluded that separatrix between circulating flow and other turbulent forms is not that clear under low flow rate. With flow increases, hydraulic losses coming of it will be dominant within the front chamber. Besides, we analogized circulating flow to vortices so as to make a quantitative analysis on its progressive evolution with changing flow, and vortices speaking for circulating flow can be divided into two groups. One is called main circulating flow vortex (hereinafter referred to as MCFV), which occurs all the time while subsidiary circulating flow vortices (hereinafter referred to as SCFV) appear in certain conditions. This context discusses the primary phase of our work with intent to follow up further with circulating flow characterized by vortices (hereinafter referred to as CFV). We confirmed that MCFV Vortex 1 (Vor1) directly influences the efficiency while SCFVs only play helping. As the flow goes to the given working condition, fluids in this pump tend to be steady with the size of CFVs getting larger and their shape being regular. Meanwhile, for MCFV Vor2 and Vor4, their geometric parameters are the key factors for efficiency. When CFVs become steady, they absorb other vortices nearby, as they have higher viscosity with the efficiency reaching its maximum.

The research results explore a new way to measure the circulating flow and help work out the causation of this flow pattern, which may be used to improve the vortex pump’s efficiency.

A computational procedure based on a hybrid Lagrangian‐Eulerian discrete‐vortical element formulation and conformal transformation schemes are employed in this study to simulate the interaction of an air jet with swirling air flow inside a two‐dimensional cylinder. Such an investigation is of importance to many flow‐related industrial and environmental problems, such as mixing, cooling, combustion and dispersion of air‐borne or water‐borne contaminants because of the role of vortices in the global transport of matter and heat. The basis for the simulation is discussed and numerical results compared with theoretical results for the velocity field and streamfunction obtained by the method of images. The swirling air motion and the features of a real jet are well simulated and numerical results are validated by predictions of theory to within 20 per cent. To illustrate the merging and interaction processes of vortices and the formation of large eddies, velocity vectors, particle trajectories and streamline contours are presented.

Aging of the oil wells leads to a decrease in reservoir pressure and also to an increase in the water, gas and abrasive particles content. Therefore, there is a need for the oil pumps exploitation characteristics improvements. This paper aims to generate a valuable numerical model which will provide a useful tool to study various cases.

Computational fluid dynamics (CFD) analysis of the generation of so-called coherent structures of eddies and turbulence in the peripheral area of the vortex rotor mounted at the back side of centrifugal rotor was undertaken. After detailed analysis of the influence of the used turbulence models on the results, a hybrid turbulent model Detached Eddies Simulation (DES) was chosen as the most suitable.

Numerical control volume method with unsteady solver and DES turbulence model was proven to be valuable tool for flow analysis in the centrifugal pumps. Having in mind that DES turbulence model consumes much less computational time than large eddies turbulence model, this is a very useful fact that resulted from this research.

The proven numerical model is robust and reliable enough to become a standard method in simulating flow and other physical phenomena occurring in centrifugal pumps and similar turbo machines. This makes it possible to easily research different factors that influence their performances.

Comprehensive experimental and CFD study was performed which made it possible to conduct detailed validation and verification of described CFD model.

This paper aims to propose a precise turbulence model for automobile aerodynamics simulation, which can predict flow separation and reattachment phenomena more accurately.

As the results of wake flow simulation with commonly used turbulence models are unsatisfactory, by introducing a nonlinear Reynolds stress term and combining the detached Eddy simulation (DES) model, this paper proposes a nonlinear-low-Reynolds number (LRN)/DES turbulence model. The turbulence model is verified in a backward-facing step case and applied in the flow field analysis of the Ahmed model. Several widely applied turbulence models are compared with the nonlinear-LRN/DES model and the experimental data of the above cases.

Compared with the experimental data and several turbulence models, the nonlinear-LRN/DES model gives better agreement with the experiment and can predict the automobile wake flow structures and aerodynamic characteristics more accurately.

The nonlinear-LRN/DES model proposed in this paper suffers from separation delays when simulating the separation flows above the rear slant of the Ahmed body. Therefore, more factors need to be considered to further improve the accuracy of the model.

This paper proposes a turbulence model that can more accurately simulate the wake flow field structure of automobiles, which is valuable for improving the calculation accuracy of the aerodynamic characteristics of automobiles.

Based on the nonlinear eddy viscosity method and the scale resolved simulation, a nonlinear-LRN/DES turbulence model including the nonlinear Reynolds stress terms for separation and reattachment prediction, as well as the wake vortex structure prediction is first proposed.

This study aims to provide discussions of the numerical method and the bubbly flow characteristics of an annular bubble plume.

The bubbles, released from the annulus located at the bottom of the domain, rise owing to buoyant force. These released bubbles have diameters of 0.15–0.25 mm and satisfy the bubble flow rate of 4.1 mm³/s. The evolution of the three-dimensional annular bubble plume is numerically simulated using the semi-Lagrangian–Lagrangian (semi-L–L) approach. The approach is composed of a vortex-in-cell method for the liquid phase and a Lagrangian description of the gas phase.

First, a new phenomenon of fluid dynamics was discovered. The bubbly flow enters a transition state with the meandering motion of the bubble plume after the early stable stage. A vortex structure in the form of vortex rings is formed because of the inhomogeneous bubble distribution and the fluid-surface effects. The vortex structure of the flow deforms as three-dimensionality appears in the flow before the flow fully develops. Second, the superior abilities of the semi-L–L approach to analyze the vortex structure of the flow and supply physical details of bubble dynamics were demonstrated in this investigation.

The semi-L–L approach is applied to the simulation of the gas–liquid two-phase flows.