Forcing Function Effects on Unsteady Aerodynamic Gust Response: Part 1 — Forcing Functions

1992 ◽  
Author(s):  
Gregory H. Henderson ◽  
Sanford Fleeter
Keyword(s):  
Linear Theory ◽  
Static Pressure ◽  
Pressure Fluctuations ◽  
Perforated Plate ◽  
Flow Angle ◽  
Unsteady Aerodynamic ◽  
Forcing Function ◽  
Forcing Functions ◽  
Relative Flow ◽  
Gust Response

The fundamental gust modeling assumption is investigated by means of a series of experiments performed in the Purdue Annular Cascade Research Facility. The unsteady periodic flow field is generated by rotating rows of perforated plates and airfoil cascades. In this paper, the measured unsteady flow fields are compared to linear-theory gust requirements, with the resulting unsteady gust response of a downstream stator cascade correlated with linear theory predictions in an accompanying paper. The perforated-plate forcing functions closely resemble linear-theory forcing functions, with the static pressure fluctuations small and the periodic velocity vectors parallel to the downstream mean-relative flow angle over the entire periodic cycle. In contrast, the airfoil forcing functions exhibit characteristics far from linear-theory gusts, with the alignment of the velocity vectors and the static pressure fluctuation amplitudes dependent on the rotor-loading condition, rotor solidity and the inlet mean-relative flow angle. Thus, these unique data clearly show that airfoil wakes, both compressor and turbine, are not able to be modeled with the boundary conditions of current state-of-the-art linear unsteady aerodynamic theory.

Forcing Function Effects on Unsteady Aerodynamic Gust Response: Part 1—Forcing Functions

1993 ◽  
Vol 115 (4) ◽  
pp. 741-750 ◽  
Author(s):  
G. H. Henderson ◽  
S. Fleeter
Keyword(s):  
Linear Theory ◽  
Static Pressure ◽  
Pressure Fluctuations ◽  
Perforated Plate ◽  
Flow Angle ◽  
Unsteady Aerodynamic ◽  
Forcing Function ◽  
Forcing Functions ◽  
Relative Flow ◽  
Gust Response

The fundamental gust modeling assumption is investigated by means of a series of experiments performed in the Purdue Annular Cascade Research Facility. The unsteady periodic flow field is generated by rotating rows of perforated plates and airfoil cascades. In this paper, the measured unsteady flow fields are compared to linear-theory vortical gust requirements, with the resulting unsteady gust response of a downstream stator cascade correlated with linear theory predictions in an accompanying paper. The perforated-plate forcing functions closely resemble linear-theory forcing functions, with the static pressure fluctuations small and the periodic velocity vectors parallel to the downstream mean-relative flow angle over the entire periodic cycle. In contrast, the airfoil forcing functions exhibit characteristics far from linear-theory vortical gusts, with the alignment of the velocity vectors and the static pressure fluctuation amplitudes dependent on the rotor-loading condition, rotor solidity, and the inlet mean-relative flow angle. Thus, these unique data clearly show that airfoil wakes, both compressor and turbine, are not able to be modeled with the boundary conditions of current state-of-the-art linear unsteady aerodynamic theory.

Forcing Function Effects on Unsteady Aerodynamic Gust Response: Part 2—Low Solidity Airfoil Row Response

1993 ◽  
Vol 115 (4) ◽  
pp. 751-759 ◽  
Author(s):  
G. H. Henderson ◽  
S. Fleeter
Keyword(s):  
Linear Theory ◽  
Perforated Plate ◽  
Function Generator ◽  
Pressure Transducers ◽  
Response Characteristics ◽  
Unsteady Aerodynamic ◽  
Forcing Function ◽  
Annular Cascade ◽  
Airfoil Cascade ◽  
Gust Response

The fundamental gust modeling assumption is investigated by means of a series of experiments performed in the Purdue Annular Cascade Research Facility. The unsteady periodic flow field is generated by rotating rows of perforated plates and airfoil cascades, with the resulting unsteady periodic chordwise pressure response of a downstream low-solidity stator row determined by miniature pressure transducers embedded within selected airfoils. When the forcing function exhibited the characteristics of a linear-theory vortical gust, as was the case for the perforated-plate wake generators, the resulting response on the downstream stator airfoils was in excellent agreement with the linear-theory models. In contrast, when the forcing function did not exhibit linear-theory vortical gust characteristics, i.e., for the airfoil wake generators, the resulting unsteady aerodynamic responses of the downstream stators were much more complex and correlated poorly with the linear-theory gust predictions. Thus, this investigation has quantitatively shown that the forcing function generator significantly affects the resulting gust response, with the complexity of the response characteristics increasing from the perforated-plate to the airfoil-cascade forcing functions.

scholarly journals Forcing Function Effects on Unsteady Aerodynamic Gust Response: Part 2 — Low Solidity Airfoil Row Response

1992 ◽  
Author(s):  
Gregory H. Henderson ◽  
Sanford Fleeter
Keyword(s):  
Linear Theory ◽  
Perforated Plate ◽  
Function Generator ◽  
Pressure Transducers ◽  
Response Characteristics ◽  
Unsteady Aerodynamic ◽  
Forcing Function ◽  
Annular Cascade ◽  
Airfoil Cascade ◽  
Gust Response

The fundamental gust modeling assumption is investigated by means of a series of experiments performed in the Purdue Annular Cascade Research Facility. The unsteady periodic flow field is generated by rotating rows of perforated plates and airfoil cascades, with the resulting unsteady periodic chordwise pressure response of a downstream low solidity stator row determined by miniature pressure transducers embedded within selected airfoils. When the forcing function exhibited the characteristics of a linear-theory gust, as was the case for the perforated-plate wake generators, the resulting response on the downstream stator airfoils was in excellent agreement with the linear-theory models. In contrast, when the forcing function did not exhibit linear-theory gust characteristics, i.e., for the airfoil wake generators, the resulting unsteady aerodynamic response of the downstream stators were much more complex and correlated poorly with the linear-theory gust predictions. Thus, this investigation has quantitatively shown that the forcing function generator significantly affects the resulting gust response, with the complexity of the response characteristics increasing from the perforated-plate to the airfoil-cascade forcing functions.

Unsteady Aerodynamic Forcing Functions: A Comparison Between Linear Theory and Experiment

1994 ◽  
Vol 116 (4) ◽  
pp. 676-685 ◽  
Author(s):  
J. M. Feiereisen ◽  
M. D. Montgomery ◽  
S. Fleeter
Keyword(s):  
Linear Theory ◽  
Static Pressure ◽  
Perforated Plate ◽  
Velocity Data ◽  
Pressure Data ◽  
Perforated Plates ◽  
Unsteady Aerodynamic ◽  
Split Flow ◽  
Potential Component ◽  
Pressure Perturbations

The unsteady flow field generated by rotating rows of perforated plates and airfoil cascades is mathematically split into vortical and potential components using two methods, one relying entirely on velocity data and the other utilizing both velocity and unsteady static pressure data. The propagation and decay of these split flow perturbations are then examined and compared to linear theory predictions. The perforated plate gusts closely resemble linear theory vortical gusts. Both splitting methods indicate that they are dominantly vortical gusts with insignificant unsteady static pressure perturbations. The airfoil gusts resemble linear theory combined vortical and potential gusts. The recombined airfoil gusts using the vortical and potential components calculated by the method using only unsteady velocity data do not necessarily resemble the measured gusts, nor do they behave axially as predicted by linear theory. The recombined airfoil gusts using the linear theory components calculated by the method using both unsteady velocity and unsteady static pressure data do resemble the measured gusts and behave axially as predicted by linear theory, with the vortical component propagating unattenuated and the potential component decaying at the rate predicted by linear theory.

scholarly journals Unsteady Aerodynamic Forcing Functions: A Comparison Between Linear Theory and Experiment

1993 ◽  
Author(s):  
John M. Feiereisen ◽  
Matthew D. Montgomery ◽  
Sanford Fleeter
Keyword(s):  
Linear Theory ◽  
Static Pressure ◽  
Perforated Plate ◽  
Velocity Data ◽  
Pressure Data ◽  
Perforated Plates ◽  
Unsteady Aerodynamic ◽  
Split Flow ◽  
Potential Component ◽  
Pressure Perturbations

The unsteady flow field generated by rotating rows of perforated plates and airfoil cascades are mathematically split into vortical and potential components using two methods, one relying entirely on velocity data and the other utilizing both velocity and unsteady static pressure data. The propagation and decay of these split flow perturbations are then examined and compared to linear theory predictions. The perforated plate gusts closely resemble linear theory vortical gusts. Both splitting methods indicate that they are dominantly vortical gusts with insignificant unsteady static pressure perturbations. The airfoil gusts resemble linear theory combined vortical and potential gusts. The recombined airfoil gusts using the vortical and potential components calculated by the method using only unsteady velocity data do not necessarily resemble the measured gusts, nor do they behave axially as predicted by linear theory. The recombined airfoil gusts using the linear theory components calculated by the method using both unsteady velocity and unsteady static pressure data do resemble the measured gusts and behave axially as predicted by linear theory, with the vortical component propagating unattenuated and the potential component decaying at the rate predicted by linear theory.

Flow at the Centrifugal Pump Impeller Exit With Circumferential Distortion of the Outlet Static Pressure

2004 ◽  
Vol 126 (1) ◽  
pp. 81-86 ◽  
Author(s):  
Soon-Sam Hong ◽  
Shin-Hyoung Kang
Keyword(s):  
Centrifugal Pump ◽  
Flow Rate ◽  
Total Pressure ◽  
Static Pressure ◽  
Mean Flow ◽  
Simple Method ◽  
Local Flow ◽  
Flow Angle ◽  
Flow Parameters ◽  
Relative Flow

The effects of circumferential outlet distortion of a centrifugal pump diffuser on the impeller exit flow were investigated. A fence with sinusoidal width variation was installed at the vaneless diffuser exit. The flow field was measured at the impeller exit with and without the fence, using a hot film probe and an unsteady pressure sensor. Flow parameters varied with the circumferential position and the mean flow parameters plotted against the local flow rate at each circumferential position showed loops along the quasi-steady curves, which were obtained from the result without the fence. Simple theoretical calculations were used to predict the velocity components at the impeller exit with the relative flow angle or total pressure assumed. Good result was obtained when the relative flow angle was assumed to vary quasi-steadily, not constant with the local flow rate. The radial velocity was also reasonably predicted when the total pressure was assumed to vary quasi-steadily. A simple method is proposed to predict the impeller exit flow with downstream blockage in two-step sequence: the first step deals with the diffuser alone to obtain static pressure distribution at the diffuser inlet, while the second step deals with the impeller alone to obtain velocity components distribution at the impeller exit.

Combined-Simultaneous Gust and Oscillating Compressor Blade Unsteady Aerodynamics

1999 ◽  
Author(s):  
Kuk Kim Frey ◽  
Sanford Fleeter
Keyword(s):  
Superposition Principle ◽  
Oscillation Amplitude ◽  
Unsteady Aerodynamics ◽  
Forced Response ◽  
Influence Coefficient ◽  
Torsion Mode ◽  
Unsteady Aerodynamic ◽  
Forcing Function ◽  
Blade Row ◽  
Gust Response

Experiments are performed in a 3-stage axial flow research compressor to investigate and quantify the simultaneous-combined gust and motion induced unsteady aerodynamic response of compressor 1st stage rotor blades. The gust response unsteady aerodynamics are experimentally modeled with a 2/rev forcing function. The torsion mode unsteady aerodynamics are investigated utilizing an experimental influence coefficient technique in conjunction with a unique drive system. Combined gust and oscillating unsteady aerodynamics are obtained by superposition of the separate oscillating blade row and the gust response unsteady aerodynamics. Simultaneous gust and motion induced unsteady aerodynamic response are obtained by driving the torsion mode oscillation in the presence of the 2/Rev forcing function. The effects of steady loading are quantified, with airfoil oscillation amplitude effects also studied. The combined unsteady aerodynamics establish the applicability limitations of the superposition principle at high oscillation amplitudes and high loading. In addition, the gust-blade motion phase angle is identified as a key parameter, with the accuracy of forced response prediction and the alteration of blade row stability due to gust interaction dependent on the gust-blade motion phase.

Multi-Blade Row Interactions in a Transonic Axial Compressor: Part II — Rotor Wake Forcing Function and Stator Unsteady Aerodynamic Response

2001 ◽  
Author(s):  
A. J. Sanders ◽  
S. Fleeter
Keyword(s):  
Pressure Fluctuations ◽  
Axial Compressor ◽  
Axial Flow ◽  
Operating Conditions ◽  
Rotor Speed ◽  
Rotor Wake ◽  
Transonic Compressor ◽  
Response Characteristics ◽  
Unsteady Aerodynamic ◽  
Forcing Function

The unsteady aerodynamic flow field of the downstream stator in an advanced design 1&1/2 stage axial-flow compressor is experimentally investigated at both subsonic and transonic compressor operating conditions. The stator response at the subsonic rotor speed is mainly due to changes in the airfoil circulation distribution resulting from the incidence fluctuations generated by the passing of the rotor wakes. This is not the case for the transonic rotor speed in which phenomena associated with the intra-stator transport of the chopped rotor wake segments through the vane passage dominate the stator unsteady aerodynamic response characteristics. Rotor-IGV and rotor-stator interactions also generate static pressure fluctuations that act as an additional unsteady aerodynamic forcing function to the downstream stator. The spatial periodicity of these acoustic interactions is over the entire annulus of the machine due the unequal number of blades and vanes in the compressor, with the amplitude of the acoustic excitation to the downstream stator varying from vane-to-vane around the compressor annulus.

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