Rigid vorticity transport equation and its application to vortical structure evolution analysis in hydro-energy machinery

Wang, Chaoyue; Zeng, Yi; Yao, Zhifeng; Wang, Fujun

doi:10.1080/19942060.2021.1938685

Cited by 22 publications

(15 citation statements)

References 48 publications

(59 reference statements)

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“…3(b), where the total loss (TL) was calculated by Eqs. (18) and (19). The maximum total loss error in different methods is 5% in pump mode and error of 4% in turbine mode.…”

Section: Simulation Validationmentioning

confidence: 96%

“…Liu et al [14][15][16] proposed the rigid vorticity vector (also named as Liutex) to depict the rigid rotation of the fluid parcel, and a vorticity binary decomposition 17 was further presented to evaluate the local shear and rigid rotational strength. Since this method has been validated in many studies, [18][19][20] it could provide a special perspective to analyze the relationship between irreversible loss and local vortex strength.…”

Section: Introductionmentioning

confidence: 99%

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Hydraulic loss analysis in a pump-turbine with special emphasis on local rigid vortex and shear

2022

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Since the pump as turbine (PAT) is increasingly employed in energy storage, improving efficiency in both pump and turbine modes is required for economic benefits. This study aims to analyze the vortex flow characteristics and vortex control methods in both modes to reduce hydraulic loss. In this paper, a delayed detached eddy simulation (DDES) was applied in a low specific speed pump-turbine. Based on the entropy production analysis and vorticity binary decomposition in the local vortices, the results show that the local shear is the leading cause of hydraulic loss instead of the existence of vortices. The average wake loss can be 1.6 times higher than the loss in jet regions in pump mode, but there is little difference in the distribution of shear and vortices in the wake flow in turbine mode. The local loss caused by rotor-stator interaction with tongue effect at blade passing frequency is up to threefold over the loss without tongue effect in both modes. Reducing shear and RSL (ratio of shear to rigid vorticity) of the local vortices via modification in volute tongue angle to suppress tongue effect can be an effective way to decrease hydraulic loss in both modes.

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“…3(b), where the total loss (TL) was calculated by Eqs. (18) and (19). The maximum total loss error in different methods is 5% in pump mode and error of 4% in turbine mode.…”

Section: Simulation Validationmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

Hydraulic loss analysis in a pump-turbine with special emphasis on local rigid vortex and shear

2022

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show abstract

“…To analysis the contribution of interphase force curl to rigid vorticity transport, the classical vorticity transport equation is equivalently transformed into a new form that explicitly emphasizes the rigid vorticity transport process. The rigid vorticity transport equation is expressed is given by [3] ( )…”

Section: Rigid Vorticity Transport Equation In Water-sand Two-phase Flowmentioning

confidence: 99%

“…It captures the basic characteristics of vorticity and has been successfully used for vorticity identification and visualization under the Euler framework. Rigid vorticity transport equation is an effective tool to describe the intuitive evolution characteristics of vortices [3]. Moreover, water-sand two-phase flows are widely existed in hydraulic engineering and chemical engineering.…”

Section: Introductionmentioning

confidence: 99%

Contribution of interphase force curl to rigid vorticity transport in water-sand two-phase flow with fine particles

Chen,

Wang,

Wang

et al. 2024

J. Phys.: Conf. Ser.

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Rigid vorticity transport equation is an effective tool for describing the intuitive vortex evolution characteristics. Compared to single-phase flows, the curl of the interphase force appears as a new source term of this equation under the condition of multiphase flows, which may cause additional contributions. However, the effects of the interaction force on rigid vorticity transport in water-sand two-phase flows with fine particles are still unclear. In this article, taking the Karman vortices induced by a hydrofoil as a typical case, the distributions of rigid vorticity in single-phase flows and two-phase flows were compared, and the dynamics mechanism of the dominant interaction force was analyzed. The following notable results are obtained. Firstly, the drag force can be regarded as the dominant interaction force. Secondly, the effect of the drag force on a vortex tube is mainly manifested as inducing normal strain and the contribution is relatively low. Thirdly, there are only slight differences in the waveform, amplitude, frequency of rigid vorticity and apparent vortical structures between the single-phase flows and the fine-particle two-phase flows. These new findings are helpful for understanding the vortex evolution in water-sand two-phase flows with fine particles.

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“…Based on the proposed model, a code has been developed which can be applied to any two-and three-dimensional water tank with an arbitrarily shaped elastic underwater structure. Wang et al [21] proposed a rigid vortex transport equation based on vorticity decomposition, which can be used to distinguish rigid rotation from shear motion of a local fluid. This equation provides a practical method for the analysis and control of interstitial vortex flow.…”

Section: Introductionmentioning

confidence: 99%

Effect of Rotational Speed Variation on the Flow Characteristics in the Rotor-Stator System Cavity

et al. 2021

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In this paper, to study the effect of dynamic and static interference of clearance flow in fluid machinery caused by changes in rotational speed, the model was simplified to a rotor-stator system cavity flow. Investigating the flow characteristics in the cavity by changing the rotor speed of the rotor-stator system is of considerable significance. ANSYS-CFX was applied to numerically simulate the test model and the results were compared with the experimental results of the windage torque of the rotor-stator system. The inlet flow rate and geometric model remained unchanged. With an increase in the rotating Reynolds number, the shear stress on the rotor wall gradually increased, and the maximum gradient was within l* < 0.15. In addition to the shear stress, the tangential Reynolds stress Rrθ contributed partly to the torque on the rotor wall. The swirling vortex formed by entrainment in the cavity of the rotor-stator system tended to separate at ReΦ= 3.53 × 106. As the rotating Reynolds number continued to increase, the secondary vortex finally separated completely. The strength of the vortex in the rotor turbulent boundary layer decreased with an increase in the rotating speed, but the number of vortex cores increased with the increase of speed. Depending on the application of the fluid machine, controlling the rotating speed within a reasonable range can effectively improve the characteristics of the clearance flow.

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Rigid vorticity transport equation and its application to vortical structure evolution analysis in hydro-energy machinery

Cited by 22 publications

References 48 publications

Hydraulic loss analysis in a pump-turbine with special emphasis on local rigid vortex and shear

Hydraulic loss analysis in a pump-turbine with special emphasis on local rigid vortex and shear

Contribution of interphase force curl to rigid vorticity transport in water-sand two-phase flow with fine particles

Effect of Rotational Speed Variation on the Flow Characteristics in the Rotor-Stator System Cavity

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