scholarly journals Dynamic Analysis of Cavitation Tip Vortex of Pump-Jet Propeller Based on DES

2020 ◽  
Vol 10 (17) ◽  
pp. 5998 ◽  
Author(s):  
Jianping Yuan ◽  
Yang Chen ◽  
Longyan Wang ◽  
Yanxia Fu ◽  
Yunkai Zhou ◽  
...  
Keyword(s):  
Flow Field ◽  
Energy Loss ◽  
Dynamic Characteristics ◽  
Vortex Core ◽  
Tip Clearance ◽  
Tip Vortex ◽  
Detached Eddy Simulation ◽  
High Rotational Speed ◽  
Propulsion Efficiency ◽  
Cavitation Bubbles

When a pump-jet propeller rotates at high speeds, a tip vortex is usually generated in the tip clearance region. This vortex interacts with the main channel fluid flow leading to the main energy loss of the rotor system. Moreover, operating at a high rotational speed can cause cavitation near the blades which may jeopardize the propulsion efficiency and induce noise. In order to effectively improve the propulsion efficiency of the pump-jet propeller, it is mandatory to research more about the energy loss mechanism in the tip clearance area. Due to the complex turbulence characteristics of the blade tip vortex, the widely used Reynolds averaged Navier–Stokes (RANS) method may not be able to accurately predict the multi-scale turbulent flow in the tip clearance. In this paper, an unsteady numerical simulation was conducted on the three-dimensional full flow field of a pump-jet propeller based on the DES (detached-eddy-simulation) turbulence model and the Z-G-B (Zwart–Gerber–Belamri) cavitation model. The simulation yielded the vortex shape and dynamic characteristics of the vortex core and the surrounding flow field in the tip clearance area. After cavitation occurred, the influence of cavitation bubbles on tip vortices was also studied. The results revealed two kinds of vortices in the tip clearance area, namely tip leakage vortex (TLV) and tip separation vortex (TSV). Slight cavitation at J = 1.02 led to low-frequency and high-frequency pulsation in the TLV vortex core. This occurrence of cavitation promotes the expansion and contraction of the tip vortex. Further, when the advance ratio changes into J = 0.73, a third type of vortex located between TLV and TSV appeared at the trailing edge which runs through the entire rotational cycle. This study has presented the dynamic characteristics of tip vortex including the relationship between cavitation bubbles and TLV inside the pump-jet propeller, which may provide a reference for the optimal design of future pump-jet propellers.

Experimental Investigation on the Tip Vortex of a Wind Turbine With and Without a Slotted Tip

2017 ◽  
Author(s):  
Pengyin Liu ◽  
Jinge Chen ◽  
Shen Xin ◽  
Xiaocheng Zhu ◽  
Zhaohui Du
Keyword(s):  
Experimental Data ◽  
Flow Field ◽  
Wind Turbine ◽  
Vortex Core ◽  
Control Method ◽  
Tip Vortex ◽  
Wake Flow ◽  
Core Model ◽  
Near Wake ◽  
Measured Velocity

In this paper, a slotted tip structure is experimentally analyzed. A wind turbine with three blades, of which the radius is 301.74mm, is investigated by the PIV method. Each wind turbine blade is formed with a slots system comprising four internal tube members embedded in the blade. The inlets of the internal tube member are located at the leading edge of the blade and form an inlet array. The outlets are located at the blade tip face and form an outlet array. The near wake flow field of the wind turbine with slotted tip and without slotted tip are both measured. Velocity field of near wake region and clear images of the tip vortex are captured under different wake ages. The experimental results show that the radius of the tip vortex core is enlarged by the slotted tip at any wake age compared with that of original wind turbine. Moreover, the diffusion process of the tip vortex is accelerated by the slotted tip which lead to the disappearance of the tip vortex occurs at smaller wake age. The strength of the tip vortex is also reduced indicating that the flow field in the near wake of wind turbine is improved. The experimental data are further analyzed with the vortex core model to reveal the flow mechanism of this kind of flow control method. The turbulence coefficient of the vortex core model for wind turbine is obtained from the experimental data of the wind turbine with and without slotted tip. It shows that the slotted tip increases the turbulence strength in the tip vortex core by importing airflow into the tip vortex core during its initial generation stage, which leads to the reduction of the tip vortex strength. Therefore, it is promising that the slotted tip can be used to weaken the vorticity and accelerate the diffusion of the tip vortex which would improve the problem caused by the tip vortex.

Inlet Condition Effects on the Tip Clearance Flow With Zonal Detached Eddy Simulation

2013 ◽  
Vol 136 (4) ◽  
Author(s):  
William Riéra ◽  
Lionel Castillon ◽  
Julien Marty ◽  
Francis Leboeuf
Keyword(s):  
Guide Vane ◽  
Tip Clearance ◽  
Tip Vortex ◽  
Inlet Guide Vane ◽  
Detached Eddy Simulation ◽  
Tip Leakage Vortex ◽  
Tip Clearance Flow ◽  
Tip Leakage ◽  
Inlet Condition ◽  
Clearance Flow

In the present study, the influence of the inlet condition on the tip clearance flow of an axial compressor is investigated. Two different zonal detached eddy simulations (ZDES) computations are carried out and compared to Reynolds-averaged Navier–Stokes (RANS) and unsteady RANS (URANS) computations as well as to experimental data. A rotating distortion map of the flow cartography is set as inlet condition for the first ZDES computation. An azimuthally averaged inlet condition is used for the second one and uncouples the rotor tip-leakage vortex flutter phenomenon, which stems from the arrival of the inlet guide vane wake from the behavior inherent to the rotor tip-leakage vortex. In the studied configuration, the inlet guide vane tip vortex reveals to lower the effects from double leakage on the rotor. The topology of the rotor tip-leakage vortex is described, and its development is analyzed.

Physics of Tip Clearance Flow in Turbomachinery (Keynote Paper)

2002 ◽  
Author(s):  
Masahiro Inoue ◽  
Masato Furukawa
Keyword(s):  
Flow Field ◽  
Physical Interpretation ◽  
Vortex Core ◽  
Vortical Structure ◽  
Three Dimensional ◽  
Axial Flow ◽  
Tip Clearance ◽  
Tip Clearance Flow ◽  
Clearance Flow ◽  
Flow Phenomena

In a recent advanced aerodynamic design of turbomachinery, the physical interpretation of three-dimensional flow field obtained by a numerical simulation is important for iterative modifications of the blade or impeller geometry. This paper describes an approach to the physical interpretation of the tip clearance flow in turbomachinery. First, typical flow phenomena of the tip clearance flow are outlined for axial and radial compressors, pumps and turbines to help comprehensive understanding of the tip clearance flow. Then, a vortex-core identification method which enables to extract the vortical structure from the complicated flow field is introduced, since elucidation of the vortical structure is essential to the physical interpretation of the tip clearance flow. By use of the vortex-core identification, some interesting phenomena of the tip clearance flows are interpreted, especially focussing on axial flow compressors.

Investigation of Tip Clearance Phenomena in an Axial Compressor Cascade Using Euler and Navier–Stokes Procedures

1993 ◽  
Vol 115 (3) ◽  
pp. 453-467 ◽  
Author(s):  
R. F. Kunz ◽  
B. Lakshminarayana ◽  
A. H. Basson
Keyword(s):  
Flow Field ◽  
Axial Compressor ◽  
Numerical Procedure ◽  
Tip Clearance ◽  
Tip Vortex ◽  
Navier Stokes ◽  
Experimental Investigations ◽  
Compressor Cascade ◽  
Flow Angle ◽  
Physical Phenomena

Three-dimensional Euler and full Navier–Stokes computational procedures have been utilized to simulate the flow field in an axial compressor cascade with tip clearance. An embedded H-grid topology was utilized to resolve the flow physics in the tip gap region. The numerical procedure employed is a finite difference Runge-Kutta scheme. Available measurements of blade static pressure distributions along the blade span, dynamic pressure and flow angle in the cascade outlet region, and spanwise distributions of blade normal force coefficient and circumferentially averaged flow angle are used for comparison. Several parameters that were varied in the experimental investigations were also varied in the computational studies. Specifically, measurements were taken and computations were performed on the configuration with and without: tip clearance, the presence of an endwall, inlet endwall total pressure profiles and simulated relative casing rotation. Additionally, both Euler and Navier–Stokes computations were performed to investigate the relative performance of these approaches in reconciling the physical phenomena considered. Results indicate that the Navier–Stokes procedure, which utilizes a low Reynolds number k–ε model, captures a variety of important physical phenomena associated with tip clearance flows with good accuracy. These include tip vortex strength and trajectory, blade loading near the tip, the interaction of the tip clearance flow with passage secondary flow, and the effects of relative endwall motion. The Euler computation provides good but somewhat diminished accuracy in resolution of some of these clearance phenomena. It is concluded that the level of modeling embodied in the present approach is sufficient to extract much of the tip region flow field information useful to designers of turbomachinery.

Experimental Study on the Three-Dimensional Flow Within a Compressor Cascade With Tip Clearance: Part II—The Tip Leakage Vortex

1993 ◽  
Vol 115 (3) ◽  
pp. 444-450 ◽  
Author(s):  
S. Kang ◽  
C. Hirsch
Keyword(s):  
Vortex Core ◽  
Three Dimensional ◽  
Leading Edge ◽  
Tip Clearance ◽  
Tip Vortex ◽  
Vortex Center ◽  
Compressor Cascade ◽  
Suction Surface ◽  
Tip Leakage Vortex ◽  
Tip Leakage

An analysis of the experimental data of a linear compressor cascade with tip clearance is presented with special attention to the development of the tip leakage vortex. A method for determining the tip vortex core size, center position, and vorticity or circulation from the measured data is proposed, based on the assumption of a circular tip vortex core. It is observed that the axial velocity profile passing through the tip vortex center is wavelike. The vorticity of the tip vortex increases rapidly near the leading edge and reaches its highest values at a short distance downstream, from which it gradually decreases. In the whole evolution, its size is growing and its center is moving away from both the suction surface and the endwall, approximately in a linear way.

Detached Eddy Simulation of Unsteady Flow Field and Prediction of Aerodynamic Sound in a Half-Ducted Propeller Fan

2011 ◽  
Author(s):  
K. Kusano ◽  
J. H. Jeong ◽  
K. Yamada ◽  
M. Furukawa
Keyword(s):  
Flow Field ◽  
Three Dimensional ◽  
Tip Vortex ◽  
Vortical Flow ◽  
Detached Eddy Simulation ◽  
Acoustic Analogy ◽  
Aerodynamic Sound ◽  
Pressure Surface ◽  
Eddy Simulation ◽  
Ducted Propeller

Three-dimensional structures and unsteady nature of vortical flow fields in a half ducted propeller fan have been investigated by a detached eddy simulation (DES) based on k-ω two-equation turbulence model. The validity of the numerical simulation performed in the present study was demonstrated by the comparison to LDV measurement results. The simulation shows the tip vortex is so strong that it dominates the flow field near the rotor tip. The tip vortex does not impinge on the pressure surface of the adjacent blade directly, however it interacts with the shroud surface and induces a separation vortex on the shroud. Furthermore, this separation vortex interacts with the pressure surface of the adjacent blade. These flow structures cause high pressure fluctuation on the shroud surface and the blade pressure surface. Besides, sound pressure levels were predicted by Ffowcs William-Hawkings equation based on Lighthill’s acoustic analogy using the unsteady surface pressure data obtained by DES. As a result, the degree of contribution by each flow structure to overall sound has been estimated quantitatively.

Detached Eddy Simulation of Unsteady Stall Flows of a Full Annulus Transonic Rotor

2010 ◽  
Author(s):  
Hong-Sik Im ◽  
Xiangying Chen ◽  
Ge-Cheng Zha
Keyword(s):  
Pressure Ratio ◽  
Axial Flow ◽  
Leading Edge ◽  
Rotating Stall ◽  
Tip Clearance ◽  
Tip Vortex ◽  
Detached Eddy Simulation ◽  
Stall Inception ◽  
Tip Clearance Flow ◽  
Eddy Simulation

This paper uses the advanced Delayed-Detached Eddy Simulation (DDES) of turbulence to simulate rotating stall inception of NASA Rotor 67. The rotor is a low-aspect-ratio transonic axial-flow fan with a tip speed of 429 m/s and a pressure ratio of 1.63. A full annulus simulation was employed with the time accurate compressible Navier-Stokes code in order to accurately capture the the formation of long-length disturbance and a short-length inception (spike). The validation for all numerical methods used in this study was accomplished by the comparisons of the CFD solutions with the test data in advance of unsteady simulations. Self-induced rotating stall development is simulated holding the same back pressure at the near stall experiment without any throttling. Spike type rotating stall occurs and rotates at roughly 50% of rotor speed counter to the rotation. After spike onset, rotating stall fully develops approximately within 2 rotor revolutions. Two distinct characteristics that can advance the mechanism of spike type rotating stall are observed. First, the passage shock is fully detached from rotor and decays during the spike inception. Consequently the shifted sonic line at the upstream of rotor allows stalling flow to propagate to the neighboring passage. Second, the trailing edge back flow contributes to the build up of a fully developed stall cell by pushing tip clearance flow toward blade leading edge and inducing tip spillage flow. Tip vortex originated from the leading edge dies out during spike inception as the swirl angle of incoming tip flow decreases, while in the unstalled passages it develops without breakdown. DDES challenge for the complete blade row reflects well the sequence of rotating stall and its unsteady behavior.

Investigating the Effects of Using Synthetic Jet on Wing Tip Vortex at Low Reynolds Number

2017 ◽  
Author(s):  
Djavad Kamari ◽  
Mehran Tadjfar
Keyword(s):  
Reynolds Number ◽  
Vortex Core ◽  
Synthetic Jet ◽  
Tip Vortex ◽  
Detached Eddy Simulation ◽  
Wing Model ◽  
Velocity Magnitude ◽  
Study Results ◽  
Wing Tip Vortex ◽  
Wing Tip

Evolution of wing tip vortex has been widely studied by many researchers. Winglet, jet, and suction devices have been implemented close to the wing tip to passively or actively mitigate the tip vortex effects. This study aims to investigate the effects of employing a synthetic jet at the tip of a half wing model. The flow was assumed to be incompressible, low speed and the Reynolds number based on chord length with aspect ratio equal to two for half wing was 1.8 × 105. Different reduced frequencies and momentum coefficients were applied. A Detached Eddy Simulation by considering Spalart-Allmaras as the turbulence model for subgrid scale zone and near the walls was employed to simulate the flow field study. Results showed large diffusivity in vortex core. Also, a reduction in longitudinal and total velocity magnitude has observed at vortex core region in the near wake.

scholarly journals Experimental Study on the Three Dimensional Flow Within a Compressor Cascade With Tip Clearance: Part II — The Tip Leakage Vortex

1992 ◽  
Author(s):  
Shun Kang ◽  
Ch. Hirsch
Keyword(s):  
Vortex Core ◽  
Three Dimensional ◽  
Leading Edge ◽  
Tip Clearance ◽  
Tip Vortex ◽  
Compressor Cascade ◽  
Suction Surface ◽  
Tip Leakage Vortex ◽  
Tip Leakage ◽  
Vortex Centre

An analysis of the experimental data of a linear compressor cascade with tip clearance is presented with special attention to the development of the tip leakage vortex. A method for determining the tip vortex core size, centre position and vorticity or circulation from the measured data is proposed, based on the assumption of a circular tip vortex core. It is observed that the axial velocity profile passing through the tip vortex centre is wake-like. The vorticity of the tip vortex increases rapidly near the leading edge and reaches its highest values at a short distance downstream, from which it gradually decreases. In the whole evolution, its size is growing and its centre is moving away from both the suction surface and the endwall, approximately in a linear way.

Inlet Condition Effects on the Tip Clearance Flow With Zonal Detached Eddy Simulation

2013 ◽  
Author(s):  
William Riéra ◽  
Lionel Castillon ◽  
Julien Marty ◽  
Francis Leboeuf
Keyword(s):  
Guide Vane ◽  
Tip Clearance ◽  
Tip Vortex ◽  
Inlet Guide Vane ◽  
Detached Eddy Simulation ◽  
Tip Leakage Vortex ◽  
Tip Clearance Flow ◽  
Tip Leakage ◽  
Inlet Condition ◽  
Clearance Flow

In the present study, the influence of the inlet condition on the tip clearance flow of an axial compressor is investigated. Two different ZDES computations are carried out and compared to RANS and URANS computations as well as to experimental data. A rotating distortion map of the flow cartography is set as inlet condition for the first ZDES computation. An azimuthally averaged inlet condition is used for the second one and uncouples the rotor tip-leakage vortex flutter phenomenon, which stems from the arrival of the Inlet Guide Vane wake, from the behaviour inherent to the rotor tip-leakage vortex. In the studied configuration, the Inlet Guide Vane tip vortex reveals to lower the effects from double leakage on the rotor. The topology of the rotor tip-leakage vortex is described and its development is analysed.

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