Numerical Research on the Change Regularity of S Series Airfoil Tip Vortex

2013 ◽  
Vol 401-403 ◽  
pp. 379-382
Author(s):  
Wei Min Wu ◽  
Yuan Jun Dai
Keyword(s):  
Flow Field ◽  
Tip Vortex ◽  
Gradual Change ◽  
Complex Flow ◽  
Central Vortex ◽  
Tetrahedral Grid ◽  
Numerical Research ◽  
Wall Flow ◽  
Gradient Change ◽  
Grid Based

This paper take the impeller of S series airfoil for instance, in view of the complex flow field which is in the condition for the optimum attack angle of design wind velocity with tip vortex, presents a new generating strategy of grid based on controlling gradient method which takes the non-uniform tetrahedral grid with gradient gradual change in the near blade wall flow field. The transition layer grid which is in the development from body-fitted field to the middle of the domain having relatively high density of grid contrast with the far flow field can well capture the size and location of tip vortex, and find that the decay rate of the vorticity magnitude of tip vortex of S series impeller is more quickly than the tip vortex of traditional airfoil impeller. As well as find a fraction of central vortex and tip vortex shaded into each other in the far field and Doppler effect in the downstream. Because the numerical experiment and analysis showed that through controlling gradient change of grid can get high precision of calculating results, can also get S series impeller had higher efficiency in conversion of wind energy contrast with NACA series impeller, so the generating strategy of grid is reasonable and effective.

Effects of Flue Gas Inlet Structure on the Flow Field Characteristics of Multi-Stage Liquid Column Scrubber

2013 ◽  
Vol 773 ◽  
pp. 749-754
Author(s):  
Zhen Ya Duan ◽  
Fu Lin Zheng ◽  
Hui Ling Shi ◽  
Jun Mei Zhang
Keyword(s):  
Flow Field ◽  
Flue Gas ◽  
Static Pressure ◽  
Liquid Column ◽  
Liquid Distribution ◽  
Multi Stage ◽  
Flow Field Characteristics ◽  
Wall Flow ◽  
Two Peaks ◽  
Saddle Shape

In this paper, the numerical model of multi-stage liquid column scrubber was established. The flow field of liquid column scrubber with different inlet structure was respectively simulated by a commercial CFD code, Fluent. Considering the distribution characteristics of static pressure and velocity in the scrubber, this inlet type, single horizontal gas inlet with a notch at the bottom, is regarded as the most reasonable structure. On one hand, that structure has uniform distribution of static pressure. On the other hand, the velocity profile of its field presents saddle shape, i.e. the low central velocity exists between two peaks, which could contribute to weakening wall-flow phenomenon and obtaining uniform gas-liquid distribution.

Visualization of Internal Flow Field of Propeller Fan

2017 ◽  
Author(s):  
Takaya Onishi ◽  
H. Sato ◽  
M. Hayakawa ◽  
Y. Kawata
Keyword(s):  
Flow Field ◽  
High Performance ◽  
Laser Light ◽  
Internal Flow ◽  
Light Sheet ◽  
Tip Vortex ◽  
Laser Light Sheet ◽  
Blade Surface ◽  
Similar Tendency ◽  
Flow Phenomena

Propeller fans are required not only to have high performance but also to be extremely quiet. The internal flow field of ventilation propeller fans is even more complicated because they usually have a very peculiar configuration with protruding blades upstream. Thus, many kinds of internal vortices yield which cause noise and their cause and countermeasures are needed to be clarified. The purposes of this paper are to visualize the internal flow of the propeller fan from the static and rotating frame of reference. The internal flow visualization measured from the static frame gives approximately the scale of the tip vortex. The visualization from the rotating coordinate system yields a better understanding of the flow phenomena occurring at the specific blade. The experiment is implemented by using a small camera mounted on the shaft of the fan and rotated it to capture the behavior of the vortices using a laser light sheet to irradiate the blade surface. Hence, the flow field of the specific blade could be understood to some extent. The visualized results are compared with the CFD results and these results show a similar tendency about the generation point and developing process of the tip vortex. In addition, it is found that the noise measurement result is relevant to the effect of tip vortex from the visualization result.

scholarly journals Flow Field Investigation in the Exit Region of a Radial Inflow Turbine Using LDV

1994 ◽  
Author(s):  
D. Muthuvel Murugan ◽  
Widen Tabakoff ◽  
Awatef Hamed
Keyword(s):  
Flow Field ◽  
Field Investigation ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Complex Flow ◽  
Tip Clearance Flow ◽  
Exit Region ◽  
Flow Investigation ◽  
Clearance Flow ◽  
Radial Inflow Turbine

Detailed flow investigation in the downstream region of a radial inflow turbine has been performed using a three component Laser Doppler Velocimetry. The flow velocities are measured in the exit region of the turbine at off-design operating conditions. The results are presented as contour and vector plots of mean velocities, flow angles and turbulent stresses. The measured parameters are correlated to the rotor blade rotation to observe any periodic nature of the flow. The measurements reveal a complex flow pattern near the tip region at the rotor exit due to the interaction of the tip clearance flow. The degree of swirl of the flow near the tip region at the rotor exit is observed to be high due to the gross under turning of the flow near the tip region. The effect of the rotor on the exit flow field is observed in the proximity of the rotor exit.

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.

Highly resolved experimental results of the separated flow in a channel with streamwise periodic constrictions

2016 ◽  
Vol 796 ◽  
pp. 257-284 ◽  
Author(s):  
Christian J. Kähler ◽  
Sven Scharnowski ◽  
Christian Cierpka
Keyword(s):  
Turbulent Flow ◽  
Flow Separation ◽  
Flow Direction ◽  
Separated Flow ◽  
Mean Flow ◽  
Complex Flow ◽  
Flow Measurements ◽  
Flow Features ◽  
Wall Flow ◽  
Near Wall

The understanding and accurate prediction of turbulent flow separation on smooth surfaces is still a challenging task because the separation and the reattachment locations are not fixed in space and time. Consequently, reliable experimental data are essential for the validation of numerical flow simulations and the characterization and analysis of the complex flow physics. However, the uncertainty of the existing near-wall flow measurements make a precise analysis of the near-wall flow features, such as separation/reattachment locations and other predicted near-wall flow features which are under debate, often impossible. Therefore, the periodic hill experiment at TU Munich (ERCOFTAC test case 81) was repeated using high resolution particle image velocimetry and particle tracking velocimetry. The results confirm the strong effect of the spatial resolution on the near-wall flow statistics. Furthermore, it is shown that statistically stable values of the turbulent flow variables can only be obtained for averaging times which are challenging to realize with highly resolved large eddy simulation and direct numerical simulation techniques. Additionally, the analysis implies that regions of correlated velocity fluctuations with rather uniform streamwise momentum exist in the flow. Their size in the mean flow direction can be larger than the hill spacing. The possible impact of the correlated turbulent motion on the wake region is discussed, as this interaction might be important for the understanding and control of the flow separation dynamics on smooth bodies.

RANS Maneuvering Simulation of Esso Osaka With Rudder and a Body-Force Propeller

2005 ◽  
Vol 49 (02) ◽  
pp. 98-120
Author(s):  
Claus D. Simonsen ◽  
Frederick Stern
Keyword(s):  
Flow Field ◽  
Open Water ◽  
Verification And Validation ◽  
Fair Agreement ◽  
Navier Stokes ◽  
Complex Flow ◽  
Flow Problems ◽  
The Difference ◽  
Propeller Geometry ◽  
Flow Study

A simplified potential theory-based infinite-bladed propeller model is coupled with the Reynolds averaged Navier-Stokes (RANS) code CFDSHIP-IOWA to give a model that interactively determines propeller-hull-rudder interaction without requiring detailed modeling of the propeller geometry. Computations are performed for an open-water propeller, for the Series 60 ship sailing straight ahead and for the appended tanker Esso Osaka in different maneuvering conditions. The results are compared with experimental data, and the tanker data are further used to study the interaction among the propeller, hull, and rudder. A comparison between calculated and measured data for the Series 60 ship shows fair agreement, where the computation captures the trends in the flow, that is, the flow structure and the magnitude of the field quantities together with the integral quantities. For the tanker, the flow study reveals a rather complex flow field in the stern region, where the velocity distribution and propeller loading reflect the flow field changes caused by the different maneuvering conditions. The integral quantities, that is, the propeller, hull, and rudder forces, are in fair agreement with experiments. No formal verification and validation are performed, so the present results are related to previous work with verification and validation of the same model, but without the propeller. For the validated cases, the levels of validation are the same as without the propeller, because the validation uncertainties, that is, the combined experimental and simulation uncertainties, are assumed to be the same for both cases. Based on this, validation is obtained for approximately the same cases as for the without-propeller conditions, but the comparison errors, that is, the difference between experiment and calculation, are different. For instance, the difference between computation and experiment for the ship resistance is generally larger with the propeller than without, whereas the opposite is the case for the rudder drag. Summarizing the results, the method shows encouraging results, and taking the effort related to modeling the propeller into account, the method appears to be useful in connection with studies of rudder-propeller-hull related flow problems, where the real propeller geometry cannot be modeled.

scholarly journals Computational study on the aerodynamics of a long-shrouded contra-rotating rotor in hover

2019 ◽  
Vol 11 ◽  
pp. 175682931983368
Author(s):  
Chao Huo ◽  
Peng Lv ◽  
Anbang Sun
Keyword(s):  
Flow Field ◽  
Opposite Direction ◽  
Computational Study ◽  
Flow Characteristics ◽  
The Other ◽  
Complex Flow ◽  
Sliding Mesh ◽  
Global Performance ◽  
Mesh Method ◽  
Downstream Flow

This paper aims to investigate the aerodynamics including the global performance and flow characteristics of a long-shrouded contra-rotating rotor by developing a full 3D RANS computation. Through validations by current experiments on the same shrouded contra-rotating rotor, the computation using sliding mesh method and the computational zone with an extended nozzle downstream flow field effectively works; the time-averaged solution of the unsteady computation reveals that more uniform flow presents after the downstream rotor, which implies that the rear rotor rotating at opposite direction greatly compensates and reduces the wake; the unsteady computations further explore the flow field throughout the whole system, along the span and around blade tips. Complex flow patterns including the vortices and their interactions are indicated around the blade roots and tips. For further identifying rotor configurations, the rotor–rotor distance and switching two rotor speeds were studied. The computation reveals that setting the second rotor backwards decreases the wake scale but increases its intensity in the downstream nozzle zone. However, for the effect of switching speeds, computations cannot precisely solve the flow when the rear rotor under the windmill because of the upstream rotor rotating much faster than the other one. All the phenomena from computations well implement the experimental observations.

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.

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