Aeroelastic Stability Analysis of Supersonic Cascades

1979 ◽  
Vol 101 (4) ◽  
pp. 533-541 ◽  
Author(s):  
J. A. Strada ◽  
W. R. Chadwick ◽  
M. F. Platzer
Keyword(s):  
Flat Plate ◽  
Leading Edge ◽  
Experimental Information ◽  
Nonlinear Method ◽  
Three Solutions ◽  
Blade Loading ◽  
Pressure Distributions ◽  
Blade Thickness ◽  
Analytical Expressions ◽  
Good Agreement

This paper presents three solutions for the analysis of supersonic flow past oscillating cascades with subsonic leading-edge locus. A quite elementary solution is first developed for the case of slowly oscillating finite and infinite flat plate cascades which provides simple analytical expressions for the unsteady pressure distributions. Comparisons with other solutions show generally excellent agreement. Furthermore, a previously developed linearized characteristics solution for finite flat plate cascades is applied to the case of superresonant blade motions. Again, the unsteady blade loading distributions are found to be in good agreement with Verdon’s recent infinite cascade solution for this case. Finally, a nonlinear method of characteristics solution for finite cascades is described which permits the analysis of blade thickness effects on flutter. At this time, only the inlet and passage flow computations have been completed which are compared with the available experimental information.

Application of a Two-Dimensional Supersonic Passage Analysis to the Design of Compressor Rotors

1974 ◽  
Author(s):  
R. G. Hantman ◽  
A. A. Mikolajczak ◽  
F. J. Camarata
Keyword(s):  
Leading Edge ◽  
Inviscid Flow ◽  
Two Dimensional ◽  
Compressor Rotor ◽  
Pressure Distributions ◽  
Displacement Thickness ◽  
Blade Section ◽  
Comparison Of The Results ◽  
Rotational Method ◽  
Good Agreement

A description of a two-dimensional supersonic cascade passage analysis and its application to the design of a high hub-to-tip ratio supersonic compressor rotor is presented. The analysis, applicable to the case in which the inviscid flow is everywhere supersonic, includes an entrance region calculation which accounts for blade leading edge bluntness effects, and a passage and wake region calculation. The inviscid part of the analysis is solved using a rotational method of characteristics. The effect of the blade boundary layer displacement thickness is taken into consideration. Comparison of the results of the analysis with supersonic cascade data is made, showing good agreement in overall performance prediction, in blade surface static pressure distributions, and in achievement of the desired shock wave patterns. A comparison of the results of the analysis is made also with the performance of a blade section of a high hub-to-tip ratio supersonic compressor and acceptable agreement obtained.

Wind-Related Heat Transfer Coefficient for Flat-Plate Solar Collectors

1987 ◽  
Vol 109 (2) ◽  
pp. 108-110 ◽  
Author(s):  
S. Shakerin
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Flat Plate ◽  
Separation Bubble ◽  
Convective Heat Transfer Coefficient ◽  
Leading Edge ◽  
The Heat Transfer Coefficient ◽  
Good Agreement

Experiments were performed to evaluate the convective heat transfer coefficient for a flat plate mounted in a wooden model of a roof of a building. The experiments were carried out in a closed-circuit wind tunnel and included parametric adjustments of the roof tilt and Reynolds number, based on the length of the plate. The roof tilt was set at 0, 30, 45, 60, and 90 degrees and the Reynolds number ranged from 58,000 to 250,000. A transient, one lump, thermal approach was used for heat transfer calculations. Due to a separation bubble at the leading edge of the model, i.e., the roof, at angles of attack of less than 40 degrees, the flow became turbulent after reattachment. This resulted in a higher heat transfer than previously reported in the literature. At higher angles of attack, the flow was not separated at the leading edge and remained laminar. The heat transfer coefficient for higher angles of attack, i.e., α > 40 deg, was found to be approximately independent of the angle of attack and in good agreement with the previously published results.

On the steady separated flow around an inclined flat plate

1997 ◽  
Vol 333 ◽  
pp. 403-413 ◽  
Author(s):  
W. W. H. YEUNG ◽  
G. V. PARKINSON
Keyword(s):  
Flat Plate ◽  
Bluff Body ◽  
Separation Bubble ◽  
Separated Flow ◽  
Leading Edge ◽  
Source Model ◽  
Pressure Distributions ◽  
Wide Range ◽  
Trailing Edges ◽  
Edge Separation

An inviscid analytic model is proposed for the steady separated flow around an inclined flat plate. With the plate normal to the stream, the model reduces to the wake-source model of Parkinson & Jandali originally developed for flow external to a symmetrical two-dimensional bluff body and its wake. At any other inclination, the Kutta condition is satisfied at both leading and trailing edges of the plate, and, in the limit that the angle of attack approaches zero, classical airfoil theory is recovered. A boundary condition is formulated based on some experimental results of Abernathy, but no additional empirical information is required. The predicted pressure distributions on the wetted surface for a wide range of angle attack are found to be in good agreement with experimental data, especially at smaller angles of attack. An extension to include a leading-edge separation bubble is explored and results are satisfactory.

Time-Averaged Heat-Flux Distributions and Comparison With Prediction for the Teledyne 702 HP Turbine Stage

1988 ◽  
Vol 110 (1) ◽  
pp. 51-56 ◽  
Author(s):  
M. G. Dunn ◽  
R. E. Chupp
Keyword(s):  
Thin Film ◽  
Heat Flux ◽  
Shock Tube ◽  
Flat Plate ◽  
Leading Edge ◽  
Turbine Stage ◽  
Heated Air ◽  
Edge Distribution ◽  
Flux Measurements ◽  
Good Agreement

Time-averaged heat-flux distributions are reported for the vane and blade of the Teledyne CAE 702 HP full-stage rotating turbine. A shock tube is used as a short-duration source of heated air to which the turbine is subjected and thin-film gages are used to obtain the heat-flux measurements. The thin-film gages were concentrated on the midspan region from the leading edge to near the trailing edge. The blade contained two contoured inserts wtih gages spaced very close together so that the leading edge distribution could be resolved. The NGV and blade results are compared with predictions obtained using a flat-plate technique, an eddy-diffusing model (STAN 5), and a k–ε model. The results of the comparison between data and prediction suggest that: (a) first, the vane data are bounded by the turbulent flat plate and the fully turbulent STAN 5 prediction. For the vane, the k–ε prediction is in relatively good agreement with the STAN 5 prediction and (b) secondly, the blade data are acceptably predicted by the k–ε prediction on both the pressure and the suction surfaces. The STAN 5 fully turbulent calculation for the blade falls above the data (essentially in agreement with the turbulent flat-plate calculation) and the STAN 5 fully laminar falls substantially below the data. With the exception of the pressure loadings and the geometry, the code inputs used for these predictions were identical to those previously used to predict the Garrett TFE 731-2 HP turbine and the Garrett LART HP turbine.

Experimental Study on the Effect of Freestream Turbulence on the Development of an Inflectional Boundary Layer From the Semi-Circular Leading Edge of a Flat Plate

2013 ◽  
Author(s):  
A. Samson ◽  
S. Sarkar
Keyword(s):  
Boundary Layer ◽  
Shear Layer ◽  
Flat Plate ◽  
Leading Edge ◽  
Separated Shear Layer ◽  
Bubble Length ◽  
Shedding Frequency ◽  
Velocity Spectra ◽  
Low Speed Wind Tunnel ◽  
Good Agreement

The characteristics of a boundary layer from the semi-circular leading edge of a flat plate has been investigated for two levels of stream turbulence (Tu = 0.5% and 7.7%) in a low-speed wind tunnel. Measurements of velocity and surface pressure were made along with a planar PIV to visualize flow structures for varying turbulence levels at a Reynolds number of 25000 (based on the leading edge diameter). At low stream turbulence the measurements reveal flow undergoes separation in the vicinity of leading-edge with reattachment in the downstream. Velocity spectra illustrates that the separated shear layer is laminar up to 20% of separation length and then the perturbations are amplified in the second half attributing to breakdown and reattachment. It is also evident that the shear layer is inviscidly unstable and the predominant shedding frequency when normalised with respect to the momentum thickness at separation shows a good agreement with previous studies. The bubble length is highly susceptible to change in Tu depicting an attached layer which grows into a fully turbulent profile at high Tu. Here, the spectra for an attached layer depicts a turbulent-like flow with band of frequencies from the beginning.

The Mechanisms of Noise Generation in a Compressor Model

1967 ◽  
Vol 89 (2) ◽  
pp. 191-197 ◽  
Author(s):  
B. T. Hulse ◽  
J. B. Large
Keyword(s):  
Vortex Shedding ◽  
Mathematical Analysis ◽  
Axial Flow ◽  
Noise Generation ◽  
Compressor Blades ◽  
Rotor Noise ◽  
Blade Thickness ◽  
Flow Compressor ◽  
Analytical Expressions ◽  
Good Agreement

A study is being undertaken in order to gain a better understanding of how compressor noise is produced. To facilitate mathematical analysis, the noise-generating mechanisms of axial-flow compressor blades have been investigated using flat blades. Analytical expressions are given for calculating the compressor noise due to blade thickness, loading, and vortex shedding. Measured values of compressor noise show good agreement with analytical predictions. It has been found that the lift, or loading noise, dominates the blade thickness noise. Rotor-stator spacing is an important parameter in rotor noise generation.

scholarly journals Research of Noise in the Unmanned Aerial Vehicle’s Propeller using CFD

2019 ◽  
Vol 8 (6S) ◽  
pp. 145-150 ◽  
Keyword(s):  
Acoustic Analysis ◽  
Leading Edge ◽  
Low Noise ◽  
Probability Of Detection ◽  
Blade Loading ◽  
Blade Thickness ◽  
High Drive ◽  
Activity Factor ◽  
Military Applications ◽  
Line Noise

The major use and need of the multi-rotor UAV in various fields has increased the importance to study the aerodynamics of multi-rotor Unmanned Aerial Vehicles such as the secondary flow over the blade, reduction of noise due to the propeller of the UAV, and the optimization of the design on the propeller with more blades to increase efficiency of the UAV. This paper mainly deals with the reduction of noise which is induced by the propeller. Since there is a demand for compact multi-rotor quite UAV as it has a low probability of detection using radar and infrared but as it generates high drive-line noise caused by propeller it cannot be implemented for some critical applications. As a result, an idea is launched to design a propeller with low drive-line noise levels. A methodology is developed to design a low noise as well as efficient propellers for multi-rotor UAVs. The important parameters like blade thickness, tip loss and blade loading are considered in this research. Also, the effects of propeller important parameters such as activity factor, advance ratio are considered. After the finalization of design consideration of UAV’s propeller and the furthermore noise reduction methodologies also studied such as leading-edge comb, trailing edge tuft, and upper surface porosity in order to generate a perfect UAV for military applications. In order to minimize the noise produced by the propeller the idea of modifying the leading-edges is finalized. Computer-AidedDesign of base propeller and propeller with leading-edge modifications has been generated with the help of CATIA V5 and the acoustic analysis for the static base and propellers with leading-edge modifications with different velocities has been simulated using ANSYS Workbench Fluent 16.2. Finally, a propeller with the leading-edge modification has been found to induce low noise.

Computer Modeling of a Tire under Cornering Loads

1989 ◽  
Vol 17 (2) ◽  
pp. 86-99 ◽  
Author(s):  
I. Gardner ◽  
M. Theves
Keyword(s):  
Finite Element Analysis ◽  
Geometric Approach ◽  
Lateral Force ◽  
Slip Angle ◽  
Element Analysis ◽  
Pressure Distributions ◽  
Slip Effects ◽  
Improved Accuracy ◽  
Nonlinear Geometric ◽  
Good Agreement

Abstract During a cornering maneuver by a vehicle, high forces are exerted on the tire's footprint and in the contact zone between the tire and the rim. To optimize the design of these components, a method is presented whereby the forces at the tire-rim interface and between the tire and roadway may be predicted using finite element analysis. The cornering tire is modeled quasi-statically using a nonlinear geometric approach, with a lateral force and a slip angle applied to the spindle of the wheel to simulate the cornering loads. These values were obtained experimentally from a force and moment machine. This procedure avoids the need for a costly dynamic analysis. Good agreement was obtained with experimental results for self-aligning torque, giving confidence in the results obtained in the tire footprint and at the rim. The model allows prediction of the geometry and of the pressure distributions in the footprint, since friction and slip effects in this area were considered. The model lends itself to further refinement for improved accuracy and additional applications.

Experimental study of heat transfer in the boundary layer of a flat plate with the impact of weak shock waves on the leading edge

2020 ◽  
Author(s):  
V. L. Kocharin ◽  
A. A. Yatskikh ◽  
D. S. Prishchepova ◽  
A. V. Panina ◽  
Yu. G. Yermolaev ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Experimental Study ◽  
Shock Waves ◽  
Flat Plate ◽  
Leading Edge ◽  
Weak Shock ◽  
The Impact

scholarly journals Reduction of Unsteady Blade Loading by Beneficial Use of Vortical and Potential Disturbances in an Axial Compressor With Rotor Clocking

1998 ◽  
Vol 120 (4) ◽  
pp. 705-713 ◽  
Author(s):  
S. T. Hsu ◽  
A. M. Wo
Keyword(s):  
Large Scale ◽  
Axial Compressor ◽  
Leading Edge ◽  
Forced Response ◽  
Suction Surface ◽  
Blade Loading ◽  
Beneficial Use ◽  
Unsteady Loading ◽  
Vortical Disturbance ◽  
First Time

This paper demonstrates reduction of stator unsteady loading due to forced response in a large-scale, low-speed, rotor/stator/rotor axial compressor rig by clocking the downstream rotor. Data from the rotor/stator configuration showed that the stator response due to the upstream vortical disturbance reaches a maximum when the wake impinges against the suction surface immediately downstream of the leading edge. Results from the stator/rotor configuration revealed that the stator response due to the downstream potential disturbance reaches a minimum with a slight time delay after the rotor sweeps pass the stator trailing edge. For the rotor/stator/rotor configuration, with Gap1 = 10 percent chord and Gap2 = 30 percent chord, results showed a 60 percent reduction in the stator force amplitude by clocking the downstream rotor so that the time occurrence of the maximum force due to the upstream vortical disturbance coincides with that of the minimum force due to the downstream potential disturbance. This is the first time, the authors believe, that beneficial use of flow unsteadiness is definitively demonstrated to reduce the blade unsteady loading.

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