Supersonic Unstalled Flutter In Fan Rotors; Analytical and Experimental Results

1974 ◽  
Vol 96 (4) ◽  
pp. 379-386 ◽  
Author(s):  
L. E. Snyder ◽  
G. L. Commerford
Keyword(s):  
Wind Tunnel ◽  
High Speed ◽  
Reduced Frequency ◽  
Cascade Analysis ◽  
Blade Shape ◽  
Supersonic Flutter ◽  
Transonic Fan ◽  
Flutter Testing ◽  
Stagger Angle ◽  
Interblade Phase Angle

Supersonic unstalled flutter is predicted using an unsteady supersonic cascade analysis, a cascade wind tunnel and a high speed fan rotor. Since the unsteady analysis assumes thin flat plate airfoils, the effect of thickness and blade shape was examined experimentally by flutter testing two sets of supersonic blading in a cascade wind tunnel. The effects of changes in Mach number, reduced frequency, stagger angle and interblade phase angle were examined from the analysis and tests. Results show that the trends are in agreement, but that blade shape has an effect on the level of reduced velocity at the incipient flutter point. The unsteady aerodynamic analysis is applied to two transonic fan stages. The first rotor was designed as a supersonic flutter test vehicle while the second was designed to be flutter free. Results of the fan tests show that the analysis correctly predicts the susceptibility to flutter of each rotor.

Flutter Limits and Behaviors of Flexible Webs Having a Simplified Basic Configuration in High-Speed Flow

2003 ◽  
Vol 125 (2) ◽  
pp. 345-353 ◽  
Author(s):  
Nobuyuki Yamaguchi ◽  
Keisuke Ito ◽  
Masayuki Ogata
Keyword(s):  
Wind Tunnel ◽  
High Speed ◽  
Bending Stiffness ◽  
High Speed Flow ◽  
Limit Values ◽  
Fluid Force ◽  
Reduced Frequency ◽  
Speed Flow ◽  
Trailing Edges ◽  
Basic Configuration

Fluttering conditions were analyzed for webs with a simplified basic configuration with both leading and trailing edges fixed in a uniform flow. The predicted flutter limits are expressed in terms of a ratio of fluid force to tension (σ*), a ratio of tension to bending stiffness (τ*), and a reduced frequency fR. Three characteristic zones of the behavior are seen to appear depending on the magnitude of τ*. For medium τ* of 1×103 to 1×106, flutter-limit values of σ* and fR remain nearly constant, respectively. For low τ*<1×103 effect of bending stiffness becomes significant and buckling-like instabilities tend to occur preceding the flutter. For high τ*>1×106 ripple-like modes tend to occur and σ* falls drastically and fR scatters much. Experimental flutter limits obtained in the wind tunnel were seen on the average to agree with the expected ones for the tested range of 9×102<τ*<4×104.

Experimental Investigation During Stall and Surge in a Transonic Fan Stage and Rotor-Only Configuration

2006 ◽  
Author(s):  
A. J. Gannon ◽  
G. V. Hobson ◽  
R. P. Shreeve ◽  
I. J. Villescas
Keyword(s):  
High Speed ◽  
Fast Response ◽  
Pressure Measurements ◽  
Post Processing ◽  
Transonic Compressor ◽  
Compressor Rotor ◽  
The Difference ◽  
Data Signal ◽  
Transonic Fan ◽  
Casing Pressure

High-speed pressure measurements of a transonic compressor rotor-stator stage and rotor-only configuration during stall and surge are presented. Rotational speed data showed the difference between the rotor-only case and rotor-stator stage. The rotor-only case stalled and remained stalled until the control throttle was opened. In the rotor-stator stage the compressor surged entering a cyclical stalling and then un-stalling pattern. An array of pressure probes was mounted in the case wall over the rotor for both configurations of the machine. The fast response probes were sampled at 196 608 Hz as the rotor was driven into stall. Inspection of the raw data signal allowed the size and speed of the stall cell during its growth to be investigated. Post-processing of the simultaneous signals of the casing pressure showed the development of the stall cell from the point of inception and allowed the structure of the stall cell to be viewed.

Numerical Simulation of Flowfield around High Speed Trains Passing by each other at the same Speed

2011 ◽  
Vol 97-98 ◽  
pp. 698-701
Author(s):  
Ming Lu Zhang ◽  
Yi Ren Yang ◽  
Li Lu ◽  
Chen Guang Fan
Keyword(s):  
Numerical Simulation ◽  
Wind Tunnel ◽  
Flow Field ◽  
Point Source ◽  
High Speed ◽  
Stokes Equations ◽  
Field Structure ◽  
Vehicle Speed ◽  
Mesh Method ◽  
High Speed Trains

Large eddy simulation (LES) was made to solve the flow around two simplified CRH2 high speed trains passing by each other at the same speed base on the finite volume method and dynamic layering mesh method and three dimensional incompressible Navier-Stokes equations. Wind tunnel experimental method of resting train with relative flowing air and dynamic mesh method of moving train were compared. The results of numerical simulation show that the flow field structure around train is completely different between wind tunnel experiment and factual running. Two opposite moving couple of point source and point sink constitute the whole flow field structure during the high speed trains passing by each other. All of streamlines originate from point source (nose) and finish with the closer point sink (tail). The flow field structure around train is similar with different vehicle speed.

Sailing Yacht Rig Improvements Through Viscous Computational Fluid Dynamics

2005 ◽  
Author(s):  
Vincent G. Chapin ◽  
Romaric Neyhousser ◽  
Stephane Jamme ◽  
Guillaume Dulliand ◽  
Patrick Chassaing
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Wind Tunnel ◽  
High Speed ◽  
Stokes Equations ◽  
Wind Tunnel Test ◽  
Physical Modelling ◽  
Optimized Design ◽  
Linear Interaction ◽  
Sailing Yacht

In this paper we propose a rational viscous Computational Fluid Dynamics (CFD) methodology applied to sailing yacht rig aerodynamic design and analysis. After an outlook of present challenges in high speed sailing, we emphasized the necessity of innovation and CFD to conceive, validate and optimize new aero-hydrodynamic concepts. Then, we present our CFD methodology through CAD, mesh generation, numerical and physical modelling choices, and their validation on typical rig configurations through wind-tunnel test comparisons. The methodology defined, we illustrate the relevance and wide potential of advanced numerical tools to investigate sailing yacht rig design questions like the relation between sail camber, propulsive force and aerodynamic finesse, and like the mast-mainsail non linear interaction. Through these examples, it is shown how sailing yacht rig improvements may be drawn by using viscous CFD based on Reynolds Averaged Navier-Stokes equations (RANS). Then the extensive use of viscous CFD, rather than wind-tunnel tests on scale models, for the evaluation or ranking of improved designs with increased time savings. Viscous CFD methodology is used on a preliminary study of the complex and largely unknown Yves Parlier Hydraplaneur double rig. We show how it is possible to increase our understanding of his flow physics with strong sail interactions, and we hope this methodology will open new roads toward optimized design. Throughout the paper, the necessary comparison between CFD and wind-tunnel test will be presented to focus on limitations and drawbacks of viscous CFD tools, and to address future improvements.

scholarly journals A Novel Vision-Based Pose Measurement Method Considering the Refraction of Light

Sensors ◽  
2018 ◽  
Vol 18 (12) ◽  
pp. 4348 ◽  
Author(s):  
Wei Liu ◽  
Xin Ma ◽  
Xiao Li ◽  
Yi Pan ◽  
Fuji Wang ◽  
...  
Keyword(s):  
Wind Tunnel ◽  
High Speed ◽  
Measurement Accuracy ◽  
Performance Testing ◽  
Angle Measurement ◽  
Normal Vector ◽  
Calibration Model ◽  
Linear Calibration ◽  
Observation Window ◽  
Vision Measurement

Nowadays, due to the advantages of non-contact and high-speed, vision-based pose measurements have been widely used for aircraft performance testing in a wind tunnel. However, usually glass ports are used to protect cameras against the high-speed airflow influence, which will lead to a big measurement error. In this paper, to further improve the vision-based pose measurement accuracy, an imaging model which considers the refraction light of the observation window was proposed. In this method, a nonlinear camera calibration model considering the refraction brought by the wind tunnel observation window, was established first. What’s more, a new method for the linear calibration of the normal vector of the glass observation window was presented. Then, combining with the proposed matching method based on coplanarity constraint, the six pose parameters of the falling target could be calculated. Finally, the experimental setup was established to conduct the pose measurement study in the laboratory, and the results satisfied the application requirements. Besides, experiments for verifying the vision measurement accuracy were also performed, and the results indicated that the displacement and angle measurement accuracy approximately increased by 57% and 33.6%, respectively, which showed the high accuracy of the proposed method.

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