Experimental Study of Flow Structure Characteristics for a T-Junction Duct With Horizontal Vanes

2019 ◽  
Vol 141 (11) ◽  
Author(s):  
Shicong Li ◽  
Xiaoyu Wang ◽  
Jing He ◽  
Mei Lin ◽  
Hanbing Ke
Keyword(s):  
Experimental Study ◽  
Flow Field ◽  
Separation Bubble ◽  
Velocity Ratio ◽  
Flow Characteristics ◽  
Vortex Sheet ◽  
Trailing Edge ◽  
Branch Duct ◽  
Instantaneous Flow ◽  
Large Vortex

An experimental study is carried out to investigate the flow characteristics of the trailing edge of the horizontal vanes mounted at the branch entrance of a T-junction duct by means of particle image velocimetry (PIV). The measured region starts at the trailing edge of the vanes and ends at about 1.26D (hydraulic diameter) length at downstream of the branch duct. The velocity field is obtained across a number of vertical height planes (z/D = ±0.2, 0, and −0.4) under different flow conditions (cross velocity: uc = 30–50 m/s; velocity ratio: R = 0.08–0.18). The instantaneous flow results show that Kelvin-like vortices with counter-clockwise direction appear at the heights of z/D = ±0.2 and 0, and that a separation bubble is formed at the upper wall of the branch duct at the same heights, respectively. As for near wall z/D = −0.4, one large vortex is observed at the downstream channel, but the separation bubble vanishes as the branching Reynolds number is increased to 3.6 × 104. The time-average flow field is slightly different from that of instantaneous flow field. In addition, the vorticity distribution indicates that two significant vortex sheet layers with negative and positive values are found at the high velocity ratio or high cross velocity, and the normalized vorticity strength increases with increasing velocity ratio and decreases with increasing cross velocity except at z/D = −0.4.

scholarly journals Effect of the Extended Rigid Flapping Trailing Edge Fringe on an S833 Airfoil

2022 ◽  
Vol 12 (1) ◽  
pp. 444
Author(s):  
Hongtao Yu ◽  
Zifeng Yang
Keyword(s):  
Flow Field ◽  
Flow Characteristics ◽  
Aerodynamic Performance ◽  
Substantial Effect ◽  
Wake Flow ◽  
Trailing Edge ◽  
Large Vortex ◽  
2D Numerical Simulation ◽  
Angular Amplitude ◽  
The Impact

A 2D numerical simulation was conducted to investigate the effect of an extended rigid trailing edge fringe with a flapping motion on the S833 airfoil and its wake flow field, as an analogy of an owl’s wing. This study aims to characterize the influence of the extended flapping fringe on the aerodynamic performance and the wake flow characteristics downstream of the airfoil. The length (Le) and flapping frequencies (fe) of the fringe are the key parameters that dominate the impact on the airfoil and the flow field, given that the oscillation angular amplitude is fixed at 5°. The simulation results demonstrated that the airfoil with an extended fringe of 10% of the chord at a flapping frequency of fe = 110 Hz showed a substantial effect on the pressure distribution on the airfoil and the flow characteristics downstream of the airfoil. An irregular vortex street was predicted downstream, thus causing attenuations of the vorticities, and shorter streamwise gaps between each pair of vortices. The extended flapping fringe at a lower frequency than the natural shedding vortex frequency can effectively break the large vortex structure up into smaller scales, thus leading to an accelerated attenuation of vorticities in the wake.

An Experiment Study of Wall Slot Jets Pertinent to Trailing Edge Cooling of Turbine Blades

2010 ◽  
Author(s):  
Zifeng Yang ◽  
Anand Gopa Kumar ◽  
Hirofumi Igarashi ◽  
Hui Hu
Keyword(s):  
Flow Field ◽  
Turbine Blades ◽  
Flow Characteristics ◽  
Field Measurements ◽  
Main Stream ◽  
Wall Jet ◽  
Ambient Conditions ◽  
Trailing Edge ◽  
Jet Streams ◽  
Cooling Effectiveness

An experimental study was conducted to quantify the flow characteristics of wall jets pertinent to trailing edge cooling of turbine blades. A high-resolution stereoscopic PIV system was used to conduct detailed flow field measurements to quantitatively visualize the evolution of the unsteady vortex and turbulent flow structures in cooling wall jet streams and to quantify the dynamic mixing process between the cooling wall jet streams and the main stream flows. The detailed flow field measurements are correlated with the adiabatic cooling effectiveness maps measured by using pressure sensitive paint (PSP) technique to elucidate underlying physics in order to improve cooling effectiveness to protect the critical portions of turbine blades from the harsh ambient conditions.

An Experimental Study on the Effects of Wake Interference on the Performances of Wind Turbines Over Complex Terrains

2012 ◽  
Author(s):  
Hui Hu ◽  
Ahmet Ozbay ◽  
Wei Tian ◽  
Zifeng Yang
Keyword(s):  
Experimental Study ◽  
Flow Field ◽  
Wind Turbine ◽  
Wind Turbines ◽  
Flow Characteristics ◽  
Field Measurements ◽  
Wake Interference ◽  
Baseline Case ◽  
Power Yield ◽  
Power Outputs

An experimental study was conducted to investigate the interferences of wind turbines sited over hilly terrains in order to elucidate underlying physics to explore/optimize design paradigms of wind turbines sited over complex terrains for higher power yield and better durability. The experiments were conducted in a large wind tunnel with of wind turbine models sited over a flat terrain (baseline case) and a 2D-ridge with non-homogenous atmospheric boundary layer winds. In addition to measuring dynamic wind loads (both forces and moments) and the power outputs of the wind turbine models, a high-resolution digital Particle Image Velocimetry (PIV) system was used to conduct detailed flow field measurements to quantify the flow characteristics of the surface winds and wake interferences among multiple wind turbines over flat (baseline case) and complex terrains. The detailed flow field measurements were correlated with the wind load measurements and power outputs of the wind turbine models to elucidate the underlying physics associated with turbine power generation and fatigue loads acting on the wind turbines.

scholarly journals Experimental Study on the Flow Characteristics of Streamwise Inclined Jets in Crossflow on Flat Plate

1992 ◽  
Author(s):  
Sang Woo Lee ◽  
Joon Sik Lee ◽  
Sung Tack Ro
Keyword(s):  
Experimental Study ◽  
Flat Plate ◽  
Flow Structure ◽  
Velocity Ratio ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Slight Variation ◽  
Injection Angle ◽  
Large Velocity ◽  
Vorticity Dynamics

Experimental study has been conducted to investigate the flow characteristics of streamwise 35° inclined jets, injected into a turbulent crossflow boundary layer on a flat plate. Flow is visualized by schlieren photographs for both normal and inclined jets to determine the overall flow structure with the variation of the velocity ratio. Three-dimensional velocity field is measured for two velocity ratios of 1.0 and 2.0 by using a five-hole directional probe. The visualization study shows that a slight variation of the injection angle produces a significant change in the flow structure. It is recognized that the jet flow is mainly dominated by the turbulence for a small velocity ratio, but it is likely to be influenced by an inviscid vorticity dynamics for a large velocity ratio. Such a trend prevails in the streamwise inclined injection, compared with the normal injection. A pair of bound vortices accompanied with a complex three-dimensional flow is present in the downstream region of the jet exit as in the case of the normal injection, although its magnitude and range are different, and the strength of the bound vortex is strongly dependent on the velocity ratio. The interface between the jet and the crossflow is identified from the vorticity distribution.

scholarly journals Effects of roof configuration on natural ventilation for an isolated building

2021 ◽  
Vol 15 (3) ◽  
pp. 8379-8389
Author(s):  
Lip Kean Moey ◽  
Man Fai Kong ◽  
Vin Cent Tai ◽  
Tze Fong Go ◽  
Nor Mariah Adam
Keyword(s):  
Kinetic Energy ◽  
Natural Ventilation ◽  
Velocity Ratio ◽  
Mixing Layer ◽  
Flow Characteristics ◽  
Mean Velocity ◽  
Gable Roof ◽  
Building Models ◽  
Large Vortex ◽  
Field Information

Numerical analyses based on CFD steady RANS were conducted to investigate the effects of roof configuration on wind-induced natural ventilation for an isolated roofed building. Gable roof and saltbox roof building models were tested with 15˚, 25˚, 35˚ and 45˚ roof pitch in present study. The flow field information and flow characteristics were obtained from the contours and plots generated by CFD. In accordance to the increment of roof pitch, the turbulence kinetic energy and mean velocity ratio show vigorous response. The flow separated at the windward corner do not reattach onto the roof, thus induced higher velocity gradient and form a large vortex at the roof ridge. The vortices behind then building caused by the flow separation at the roof ridge extend along the mixing layer and spread up to the roof. The pressure differences mainly rely on the roof shapes. Greater pressure differences between the upstream, interior and downstream was observed in saltbox roof cases. This is due to the extended roof height which boosted the impinging effect caused by the incoming wind. Generally, the saltbox roof configuration exhibit better performance than gable roof in terms of the measured parameters.

scholarly journals Experimental Study of Plasma Actuator Effects on Flow Field Separation Bubble around Blunt Flat Plate

2016 ◽  
Vol 9 (1) ◽  
pp. 397-406 ◽  
Author(s):  
Saeed Kavousfar ◽  
Esmaeil Esmaeilzadeh ◽  
hossein mahdavy moghaddam ◽  
Sohrab Gholamhosein Pouryoussefi ◽  
Masoud Mirzaei ◽  
...  
Keyword(s):  
Experimental Study ◽  
Flow Field ◽  
Flat Plate ◽  
Separation Bubble ◽  
Plasma Actuator ◽  
Field Separation

Experimental Study on the Flow Characteristics of Streamwise Inclined Jets in Crossflow on Flat Plate

1994 ◽  
Vol 116 (1) ◽  
pp. 97-105 ◽  
Author(s):  
Sang Woo Lee ◽  
Joon Sik Lee ◽  
Sung Tack Ro
Keyword(s):  
Experimental Study ◽  
Flat Plate ◽  
Flow Structure ◽  
Velocity Ratio ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Three Dimensional Flow ◽  
Injection Angle ◽  
Large Velocity ◽  
Vorticity Dynamics

Experimental study has been conducted to investigate the flow characteristics of streamwise 35 deg inclined jets, injected into a turbulent crossflow boundary layer on a flat plate. Flow is visualized by schlieren photographs for both normal and inclined jets to determine the overall flow structure with the variation of the velocity ratio. A three-dimensional velocity field is measured for two velocity ratios of 1.0 and 2.0 by using a five-hole directional probe. The visualization study shows that the variation of the injection angle produces a significant change in the flow structure. It is recognized that the jet flow is mainly dominated by the turbulence for a small velocity ratio, but it is likely to be influenced by an inviscid vorticity dynamics for a large velocity ratio. Such a trend prevails in the streamwise inclined injection, compared with the normal injection. A pair of bound vortices accompanied with a complex three-dimensional flow is present in the downstream region of the jet exit as in the case of the normal injection, although its magnitude and range are different, and the strength of the bound vortex is strongly dependent on the velocity ratio. The interface between the jet and the crossflow is identified from the vorticity distribution.

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