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Sanford Fleeter - One of the best experts on this subject based on the ideXlab platform.

  • Forcing Function variability and its effect on airfoil response
    34th AIAA ASME SAE ASEE Joint Propulsion Conference and Exhibit, 1998
    Co-Authors: Albert J. Sanders, Sanford Fleeter
    Abstract:

    Aerodynamic variability effects on wake generated Forcing Functions and its impact on the downstream stator vane response are investigated in a high-speed 1&1/2 stage axial-flow turbomachine. The variability in the rotor wake generated gust components as well as the detailed vane surface pressure distributions ate quantified at both design and off-design rotor operating conditions. Wake generated Forcing Function variability is found to be significant even at the design rotor speed, with the vane response variability highest near the leading edge. At certain operating conditions a rogue wake is present in the rotor generated Forcing Function, with this wake not part of the Gaussian distribution describing the statistical variations of the flow field. The vane responded to this rogue wake only in the leading edge region. Blade-to-blade rotor wake variability introduces broadband energy into the Forcing Function spectrum, with the vane responding to these broadband components in addition to the blade pass frequency harmonics. At off-design operating conditions the broadband vane response due to wake variability was nearly half of the response occurring at blade pass frequency. NOMENCLATURE C Stator Vane Chord C Pressure Coefficient CL Unsteady Lift Coefficient f Frequency fBP Blade Pass Frequency Nc Corrected Rotor Speed p Static Pressure t Time TBP Blade Pass Period u, v* Streamwise and Transverse Gust Components V Absolute Velocity Magnitude a Absolute Flow Angle (cw) Ap Airfoil Unsteady Pressure Difference, pps pss 6igv IGV Stagger Angle p Density a Standard Deviation + Research Assistant, Student Member AIAA * McAllister Distinguished Professor, Associate Fellow AIAA Subscripts ave Time-Average ps Airfoil Pressure Surface ss Airfoil Suction Surface oo Freestream

  • Three-Dimensional Turbine Rotor Forcing Functions and Linear Theory Analysis
    Journal of Propulsion and Power, 1998
    Co-Authors: David Johnston, Sanford Fleeter
    Abstract:

    Many turbomachine e owe elds are inherently three dimensional. Often, however, the data and methods used to analyze the unsteady aerodynamic Forcing Functions generated by these blade rows are two dimensional. This paper is directed at developing a three-dimensional compressible e ow Forcing-Function modeling technique to split Forcing-Function data into vortical and potential components. This is accomplished by extending current state-of-the-art two-dimensional methods to three dimensions in cylindrical coordinates. Three-dimensional unsteady Forcing-Function data, both unsteady pressure and velocity, generated by the e rst rotor of a low-speed, two-stage research turbine are used in the model development. Both the three-dimensional model developed herein and a two-dimensional model are then applied to the turbine rotor data. For the potential perturbation velocity, the three-dimensional method agrees well with the two-dimensional strip theory method in terms of both velocities and axial decay factors. For the vortical perturbation velocity, the correlations were inconsistent with the two-dimensional theory in that the vortical proportionality constant was not constant and the phasing of the velocity components was not zero.

  • Forcing Function generator fluid dynamic effects on compressor blade gust response
    Journal of Propulsion and Power, 1994
    Co-Authors: Kuk H. Kim, Sanford Fleeter
    Abstract:

    To investigate the fundamental flow Forcing Function phenomena generating different blade row gust responses, in particular attached and separated flow Forcing Functions, a series of experiments are performed in an extensively instrumented axial flow research compressor. In these experiments, the gust ratio magnitude is controlled without affecting the Forcing Function fluid dynamics, i.e., attached or separated flow, thereby enabling a controlled study of the effect of steady loading. Periodic 2-E unsteady aerodynamic Forcing Functions to the first stage rotor are generated by fundamentally equivalent honeycomb sections and flat plate airfoils, with unsteady linear theory gust requirements considered. Then the resulting rotor blade row gust response is measured over a range of steady loading levels and the gust response data correlated with the appropriate linear theory predictions. These experiments show that the Forcing Function generator fluid dynamics is significant with regard to the resulting unsteady aerodynamic gust response. Also demonstrated is the decreased correlation of the gust response data with linear theory predictions as the steady loading is increased.

  • Forcing Function Effects on Unsteady Aerodynamic Gust Response: Part 2—Low Solidity Airfoil Row Response
    Journal of Turbomachinery, 1993
    Co-Authors: Gregory H. Henderson, Sanford Fleeter
    Abstract:

    The fundamental gust modeling assumption is investigated by means of 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 chord wise pressure response of a downstream low-solidity stator row determined by miniature pressure transducers embedded within selected airfoils. When the Forcing Function exhibited the characteristic 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.

  • Forcing Function Effects on Unsteady Aerodynamic Gust Response: Part 1—Forcing Functions
    Journal of Turbomachinery, 1993
    Co-Authors: Gregory H. Henderson, Sanford Fleeter
    Abstract:

    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

W. E. Asher - One of the best experts on this subject based on the ideXlab platform.

  • The effects of experimental uncertainty in parameterizing air-sea gas exchange using tracer experiment data
    Atmospheric Chemistry and Physics, 2009
    Co-Authors: W. E. Asher
    Abstract:

    It is not practical to measure air-sea gas fluxes in the open ocean for all conditions and areas of interest. Therefore, in many cases fluxes are estimated from measurements of air-phase and water-phase gas concentrations, a measured environmental Forcing Function such as wind speed, and a parameterization of the air-sea transfer velocity in terms of the environmental Forcing Function. One problem with this approach is that when direct measurements of the transfer velocity are plotted versus the most commonly used Forcing Function, wind speed, there is considerable scatter, leading to a relatively large uncertainty in the flux. Because it is known that multiple processes can affect gas transfer, it is commonly assumed that this scatter is caused by single-Forcing Function parameterizations being incomplete in a physical sense. However, scatter in the experimental data can also result from experimental uncertainty (i.e., measurement error). Here, results from field and laboratory results are used to estimate how experimental uncertainty contributes to the observed scatter in the measured fluxes and transfer velocities as a Function of environmental Forcing. The results show that experimental uncertainty could explain half of the observed scatter in field and laboratory measurements of air-sea gas transfer velocity.

  • The effects of experimental uncertainty in parameterizing air-sea gas exchange using tracer experiment data
    Atmospheric Chemistry and Physics Discussions, 2008
    Co-Authors: W. E. Asher
    Abstract:

    Abstract. It is not practical to measure air-sea gas fluxes in the open ocean for all conditions and areas of interest. Therefore, in many cases fluxes are estimated from measurements of air-phase and water-phase gas concentrations, a measured environmental Forcing Function such as wind speed, and a parameterization of the air-sea transfer velocity in terms of the environmental Forcing Function. One problem with this approach is that when direct measurements of the transfer velocity are plotted versus the most commonly used Forcing Function, wind speed, there is considerable scatter, leading to a relatively large uncertainty in the flux. Because it is known that multiple processes can affect gas transfer, it is commonly assumed that this scatter is caused by single-Forcing Function parameterizations being incomplete in a physical sense. However, scatter in the experimental data can also result from experimental uncertainty (i.e., measurement error). Here, results from field and laboratory results are used to estimate how experimental uncertainty contributes to the observed scatter in the measured fluxes and transfer velocities as a Function of environmental Forcing. The results show that experimental uncertainty could explain a major portion of the observed scatter in field and laboratory measurements of the air-sea gas transfer velocity.

Gregory H. Henderson - One of the best experts on this subject based on the ideXlab platform.

  • Forcing Function Effects on Unsteady Aerodynamic Gust Response: Part 2—Low Solidity Airfoil Row Response
    Journal of Turbomachinery, 1993
    Co-Authors: Gregory H. Henderson, Sanford Fleeter
    Abstract:

    The fundamental gust modeling assumption is investigated by means of 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 chord wise pressure response of a downstream low-solidity stator row determined by miniature pressure transducers embedded within selected airfoils. When the Forcing Function exhibited the characteristic 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.

  • Forcing Function Effects on Unsteady Aerodynamic Gust Response: Part 1—Forcing Functions
    Journal of Turbomachinery, 1993
    Co-Authors: Gregory H. Henderson, Sanford Fleeter
    Abstract:

    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

  • Forcing Function effects on unsteady aerodynamic gust response part 2 low solidity airfoil row response
    Volume 5: Manufacturing Materials and Metallurgy; Ceramics; Structures and Dynamics; Controls Diagnostics and Instrumentation; Education, 1992
    Co-Authors: Gregory H. Henderson, Sanford Fleeter
    Abstract:

    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.Copyright © 1992 by ASME

  • Forcing Function Effects on Unsteady Aerodynamic Gust Response: Part 1 — Forcing Functions
    Volume 5: Manufacturing Materials and Metallurgy; Ceramics; Structures and Dynamics; Controls Diagnostics and Instrumentation; Education, 1992
    Co-Authors: Gregory H. Henderson, Sanford Fleeter
    Abstract:

    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.Copyright © 1992 by ASME

  • Forcing Function effects on unsteady aerodynamic gust response part 1 Forcing Functions
    Volume 5: Manufacturing Materials and Metallurgy; Ceramics; Structures and Dynamics; Controls Diagnostics and Instrumentation; Education, 1992
    Co-Authors: Gregory H. Henderson, Sanford Fleeter
    Abstract:

    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.Copyright © 1992 by ASME

Alok Sinha - One of the best experts on this subject based on the ideXlab platform.

  • Estimation of Forcing Function, Mistuning, and Modal Damping in a Bladed Rotor
    Journal of Engineering for Gas Turbines and Power, 2020
    Co-Authors: Arjun Singh Chauhan, Alok Sinha
    Abstract:

    Abstract This paper deals with the estimation of Forcing Function, modal damping, and mistuned modal stiffnesses in a bladed rotor. Previous research on parameter estimation in a mistuned bladed rotor relies on the knowledge of the Forcing Function as well as the vibration data. This paper presents two novel approaches. The first approach relies on knowledge of both the Forcing and vibration data. The parameters are treated as states of the system and an augmented state space model is created. Unscented Kalman filter (UKF) is then used on the steady-state data to estimate the parameters. The second approach eliminates the dependence on Forcing data. Both the Forcing and parameters are now treated as states of the system to construct an augmented state space model. UKF is then used on transient vibration data for estimation. Numerical results are presented for a simple model of a mistuned bladed rotor which considers a single mode of vibration per blade.

  • Estimation of Forcing Function, Mistuning, and Modal Damping in a Bladed Rotor
    Volume 7A: Structures and Dynamics, 2019
    Co-Authors: Arjun Singh Chauhan, Alok Sinha
    Abstract:

    Abstract This paper deals with the estimation of Forcing Function, modal damping and mistuned modal stiffnesses in a bladed rotor. Previous research on parameter estimation in a mistuned bladed rotor relies on the knowledge of the Forcing Function as well as the vibration data. This paper presents two novel approaches. The first approach relies on knowledge of both the Forcing and vibration data. The parameters are treated as states of the system and an augmented state space model is created. Unscented Kalman Filter is then used on the steady state data to estimate the parameters. The second approach eliminates the dependence on Forcing data. Both the Forcing and parameters are now treated as states of the system to construct an augmented state space model. Unscented Kalman Filter is then used on transient vibration data for estimation. Numerical results are presented for a simple model of a mistuned bladed rotor which considers a single mode of vibration per blade.

  • Estimation of Forcing Function for a Geometrically Mistuned Bladed Rotor via Modified Modal Domain Analysis
    Journal of Engineering for Gas Turbines and Power, 2015
    Co-Authors: Vinod Vishwakarma, Alok Sinha
    Abstract:

    Modified Modal Domain Analysis (MMDA) is a method to generate an accurate reduced order model (ROM) of a bladed disk with geometric mistuning. An algorithm based on MMDA ROM and a state observer is developed to estimate Forcing Functions for synchronous (including integer multiples) conditions from the dynamic responses obtained at few nodal locations of blades. The method is tested on a simple spring-mass model, finite element model (FEM) of a geometrically mistuned academic rotor and FEM of a bladed rotor of an industrial scale transonic research compressor. The accuracy of the Forcing Function estimation algorithm is examined by varying the order of reduced-order model and the number of vibration output signals.Copyright © 2015 by ASME

  • Estimation of Forcing Function for a Geometrically Mistuned Bladed Rotor via Modified Modal Domain Analysis
    Volume 7A: Structures and Dynamics, 2015
    Co-Authors: Vinod Vishwakarma, Alok Sinha
    Abstract:

    Modified Modal Domain Analysis (MMDA) is a method to generate an accurate reduced order model (ROM) of a bladed disk with geometric mistuning. An algorithm based on MMDA ROM and a state observer is developed to estimate Forcing Functions for synchronous (including integer multiples) conditions from the dynamic responses obtained at few nodal locations of blades. The method is tested on a simple spring-mass model, finite element model (FEM) of a geometrically mistuned academic rotor and FEM of a bladed rotor of an industrial scale transonic research compressor. The accuracy of the Forcing Function estimation algorithm is examined by varying the order of reduced-order model and the number of vibration output signals.

Jan Vierendeels - One of the best experts on this subject based on the ideXlab platform.

  • predicting turbulence induced vibration in axial annular flow by means of large eddy simulations
    Journal of Fluids and Structures, 2016
    Co-Authors: Jeroen De Ridder, Joris Degroote, Katrien Van Tichelen, P Schuurmans, Jan Vierendeels
    Abstract:

    Abstract Turbulence-induced vibration is typically considered as a type of vibration with one-way coupling between the fluid flow and the structural motion: the turbulence creates an incident force field on the structure, but the structural displacement does not influence the turbulence. It is however challenging to measure the turbulence Forcing Function experimentally. In this article, the Forcing Function in annular flow is computed by means of Large-eddy simulations. The pressure spectrum is applied to the inner cylinder and the resulting vibration is computed. It is shown that the commonly used multiplication hypothesis does not hold for the present results. The computed spectrum showed an upper limit to the coherence length. The results of these computations are compared to experimental results available in literature and to semi-empirical models. The predicted displacements compared well with experimental results.