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Raymond J. Stalker - One of the best experts on this subject based on the ideXlab platform.

  • Reynolds Analogy in High-Enthalpy and High-Mach-Number Turbulent Flows
    AIAA Journal, 2006
    Co-Authors: Milinda V. Suraweera, David J. Mee, Raymond J. Stalker
    Abstract:

    Te results of a shock-tunnel study in which skin friction, heat transfer rates, and static pressure are measured in hypervelocity turbulent boundary layers. Shock-tunnel measurements of skin friction and heat transfer rates show a trend of decreasing Reynolds analogy factor with increasing skin friction coefficient. Thetrend is apparently independent of Stagnation Enthalpy, unit Reynolds number, and Mach number for the range of conditions examined. The effect of oxygen dissociation within the boundary layer because as the source of the observed trend is discounted as similar Reynolds analogy factors are obtained when either air or nitrogen is used as the test gas.

  • Skin-friction measurements in high-Enthalpy hypersonic boundary layers
    Journal of Fluid Mechanics, 2003
    Co-Authors: Christopher P. Goyne, Raymond J. Stalker, Allan Paull
    Abstract:

    Skin-friction measurements are reported for high-Enthalpy and high-Mach-number laminar, transitional and turbulent boundary layers. The measurements were performed in a free-piston shock tunnel with air-flow Mach number, Stagnation Enthalpy and Reynolds numbers in the ranges of 4.4-6.7, 3-13 MJ kg(-1) and 0.16 x 10(6)-21 x 10(6), respectively. Wall temperatures were near 300 K and this resulted in ratios of wall Enthalpy to flow-Stagnation Enthalpy in the range of 0.1-0.02. The experiments were performed using rectangular ducts. The measurements were accomplished using a new skin-friction gauge that was developed for impulse facility testing. The gauge was an acceleration compensated piezoelectric transducer and had a lowest natural frequency near 40 kHz. Turbulent skin-friction levels were measured to within a typical uncertainty of +/-7%. The systematic uncertainty in measured skin-friction coefficient was high for the tested laminar conditions; however, to within experimental uncertainty, the skin-friction and heat-transfer measurements were in agreement with the laminar theory of van Driest (1952). For predicting turbulent skin-friction coefficient, it was established that, for the range of Mach numbers and Reynolds numbers of the experiments, with cold walls and boundary layers approaching the turbulent equilibrium state, the Spalding & Chi (1964) method was the most suitable of the theories tested. It was also established that if the heat transfer rate to the wall is to be predicted, then the Spalding & Chi (1964) method should be used in conjunction with a Reynolds analogy factor near unity. If more accurate results are required, then an experimentally observed relationship between the Reynolds analogy factor and the skin-friction coefficient may be applied.

  • Skin-Friction Measurements in a Supersonic Combustor with Crossflow Fuel Injection
    Journal of Propulsion and Power, 2001
    Co-Authors: Haruto Tanno, Allan Paull, Raymond J. Stalker
    Abstract:

    Shock-tunnel experiments have been performed to measure the effect on skin-friction drag in a supersonic combustor of flow disturbances induced by hydrogen fuel injection transverse to the airstream. Constant-area, circular cross section combustors of lengths varying up to 0.52 m were employed. The experiments were done at a Stagnation Enthalpy of 7.2 MJ . kg(-1) and a Mach number of 4.3, with a boundary layer that was turbulent downstream of the 0.14-m station in the combustors. Combustor skin-friction drag was measured by a method based on the stress wave force balance, the method being validated by agreement between fuel-off skin-friction drag measurements and predictions using existing skin-friction theories. When fuel was injected, it was found that the drag remained at fuel-off values. Thus, the streamwise vortices and other flow disturbances induced by the fuel injection, mixing, and combustion, which are expected to be present in a scramjet combustor, did not influence the skin-friction drag of the combustors.

  • Species measurements in a hypersonic, hydrogen-air, combustion wake
    Combustion and Flame, 1996
    Co-Authors: K.a. Skinner, Raymond J. Stalker
    Abstract:

    Abstract A continuously sampling, time-of-flight mass spectrometer has been used to measure relative species concentrations in a two-dimensional, hydrogen-air combustion wake at mainstream Mach numbers exceeding 5. The experiments, in a free piston shock tunnel, yielded distributions of hydrogen, oxygen, nitrogen, water, and nitric oxide at Stagnation enthalpies ranging from 5.6 MJ kg −1 to 12.2 MJ kg −1 and at a distance of approximately 100 times the thickness of the initial hydrogen jet. The amount of hydrogen mixed in stoichiometric proportions was approximately independent of the Stagnation Enthalpy, despite the fact that the proportion of hydrogen in the wake was increased with Stagnation Enthalpy. Roughly 50% of the mixed hydrogen underwent combustion at the highest Enthalpy. The proportion of hydrogen reacting to water could be approximately predicted using reaction rates based on mainstream temperatures.

  • Experiments on supersonic combustion ramjet propulsion in a shock tunnel
    Journal of Fluid Mechanics, 1995
    Co-Authors: Allan Paull, Raymond J. Stalker, David J. Mee
    Abstract:

    Measurements have been made of the propulsive effect of supersonic combustion ramjets incorporated into a simple axisymmetric model in a free piston shock tunnel. The nominal Mach number was 6, and the Stagnation Enthalpy varied from 2.8 to 8.5 MJ kg-1. A mixture of 13% silane and 87% hydrogen was used as fuel, and experiments were conducted at equivalence ratios up to approximately 0.8. The measurements involved the axial force on the model, and were made using a stress wave force balance, which is a recently developed technique for measuring forces in shock tunnels. A net thrust was experienced up to a Stagnation Enthalpy of 3.7 MJ kg-1, but as the Stagnation Enthalpy increased, an increasing net drag was recorded. Pitot and static pressure measurements showed that the combustion was supersonic. The results were found to compare satisfactorily with predictions based on established theoretical models, used with some simplifying approximations. The rapid reduction of net thrust with increasing Stagnation Enthalpy was seen to arise from increasing precombustion temperature, showing the need to control this variable if thrust performance was to be maintained over a range of Stagnation enthalpies. Both the inviscid and viscous drag were seen to be relatively insensitive to Stagnation Enthalpy, with the combustion chambers making a particularly significant contribution to drag. The maximum fuel specific impulse achieved in the experiments was only 175 s, but the theory indicates that there is considerable scope for improvement on this through aerodynamic design.

William N. Dawes - One of the best experts on this subject based on the ideXlab platform.

  • On the Interpretation of Measured Profile Losses in Unsteady Wake–Turbine Blade Interaction Studies
    Journal of Turbomachinery-transactions of The Asme, 1998
    Co-Authors: Howard P. Hodson, William N. Dawes
    Abstract:

    The interaction of wakes shed by a moving blade row with a downstream blade row causes unsteady flow. The meaning of the free-stream Stagnation pressure and Stagnation Enthalpy in these circumstances has been examined using simple analyses, measurements, and CFD. The unsteady flow in question arises from the behavior of the wakes as so-called negative jets. The interactions of the negative jets with the downstream blades lead to fluctuations in static pressure, which in turn generate fluctuations in the Stagnation pressure and Stagnation Enthalpy. It is shown that the fluctuations of the Stagnation quantities created by unsteady effects within the blade row are far greater than those within the incoming wake. The time-mean exit profiles of the Stagnation pressure and Stagnation Enthalpy are affected by these large fluctuations. This phenomenon of energy separation is much more significant than the distortion of the time-mean exit profiles that is caused directly by the cross-passage transport associated with the negative jet, as described by Kerrebrock and Mikolajczak. Finally, it is shown that if only time-averaged values of loss are required across a blade row, it is nevertheless sufficient to determine the time-mean exit Stagnation pressure.

  • ON THE INTERPRETATION OF MEASURED PROFILE LOSSES IN UNSTEADY WAKE-TURBINE BLADE INTERACTION STUDIES
    Journal of Turbomachinery, 1998
    Co-Authors: Howard P. Hodson, William N. Dawes
    Abstract:

    The interaction of wakes shed by a moving blade row with a downstream blade row causes unsteady flow. The meaning of the free-stream Stagnation pressure and Stagnation Enthalpy in these circumstances has been examined using simple analyses, measurements, and CFD. The unsteady flow in question arises from the behavior of the wakes as so-called negative jets. The interactions of the negative jets with the downstream blades lead to fluctuations in static pressure, which in turn generate fluctuations in the Stagnation pressure and Stagnation Enthalpy. It is shown that the fluctuations of the Stagnation quantities created by unsteady effects within the blade row are far greater than those within the incoming wake. The time-mean exit profiles of the Stagnation pressure and Stagnation Enthalpy are affected by these large fluctuations. This phenomenon of energy separation is much more significant than the distortion of the time-mean exit profiles that is caused directly by the cross-passage transport associated with the negative jet, as described by Kerrebrock and Mikolajczak. Finally, it is shown that if only time-averaged values of loss are required across a blade row, it is nevertheless sufficient to determine the time-mean exit Stagnation pressure.

  • On the Interpretation of Measured Profile Losses in Unsteady Wake-Turbine Blade Interaction Studies
    Volume 1: Turbomachinery, 1996
    Co-Authors: Howard P. Hodson, William N. Dawes
    Abstract:

    The interaction of wakes shed by a moving bladerow with a downstream bladerow causes unsteady flow. The meaning of the freestream Stagnation pressure and Stagnation Enthalpy in these circumstances has been examined using simple analyses, measurements and CFD. The unsteady flow in question arises from the behaviour of the wakes as so-called negative-jets. The interactions of the negative-jets with the downstream blades lead to fluctuations in static pressure which in turn generate fluctuations in the Stagnation pressure and Stagnation Enthalpy. It is shown that the fluctuations of the Stagnation quantities created by unsteady effects within the bladerow are far greater than those within the incoming wake. The time-mean exit profiles of the Stagnation pressure and Stagnation Enthalpy are affected by these large fluctuations. This phenomenon of energy separation is much more significant than the distortion of the time-mean exit profiles that is caused directly by the cross-passage transport associated with the negative-jet, as described by Kerrebrock and Mikolajczak. Finally, it is shown that if only time-averaged values of loss are required across a bladerow, it is nevertheless sufficient to determine the time-mean exit Stagnation pressure.Copyright © 1996 by ASME

Howard P. Hodson - One of the best experts on this subject based on the ideXlab platform.

  • a physical interpretation of Stagnation pressure and Enthalpy changes in unsteady flow
    Journal of Turbomachinery-transactions of The Asme, 2012
    Co-Authors: Howard P. Hodson, T P Hynes, Edward M. Greitzer
    Abstract:

    This paper provides a physical interpretation of the mechanism of Stagnation Enthalpy and Stagnation pressure changes in turbomachines due to unsteady flow, the agency for all work transfer between a turbomachine and an inviscid fluid. Examples are first given to illustrate the direct link between the time variation of static pressure seen by a given fluid particle and the rate of change of Stagnation Enthalpy for that particle. These include absolute Stagnation temperature rises in turbine rotor tip leakage flow, wake transport through downstream blade rows, and effects of wake phasing on compressor work input. Fluid dynamic situations are then constructed to explain the effect of unsteadiness, including a physical interpretation of how Stagnation pressure variations are created by temporal variations in static pressure; in this it is shown that the unsteady static pressure plays the role of a time-dependent body force potential. It is further shown that when the unsteadiness is due to a spatial nonuniformity translating at constant speed, as in a turbomachine, the unsteady pressure variation can be viewed as a local power input per unit mass from this body force to the fluid particle instantaneously at that point. © 2012 American Society of Mechanical Engineers.

  • a physical interpretation of Stagnation pressure and Enthalpy changes in unsteady flow
    ASME Turbo Expo 2009: Power for Land Sea and Air, 2009
    Co-Authors: Howard P. Hodson, T P Hynes, Edward M. Greitzer
    Abstract:

    This paper provides a physical interpretation of the mechanism of Stagnation Enthalpy and Stagnation pressure changes in turbomachines due to unsteady flow, the agency for all work transfer between a turbomachine and an inviscid fluid. Examples are first given to illustrate the direct link between the time variation of static pressure seen by a given fluid particle and the rate of change of Stagnation Enthalpy for that particle. These include absolute Stagnation temperature rises in turbine rotor tip leakage flow, wake transport through downstream blade rows, the influence on mixing losses of turbine wake behavior in downstream blade rows, and effects of wake phasing on compressor work input. Fluid dynamic situations are then constructed to explain the effect of unsteadiness, including a physical interpretation of how Stagnation pressure variations are created by temporal variations in static pressure; in this it is shown that the unsteady static pressure plays the role of a time-dependent body force potential. It is further shown that when the unsteadiness is due to a spatial nonuniformity translating at constant speed, as in a turbomachine, the unsteady pressure variation can be viewed as a local power input per unit mass from this body force to the fluid particle at that point.Copyright © 2009 by ASME

  • On the Interpretation of Measured Profile Losses in Unsteady Wake–Turbine Blade Interaction Studies
    Journal of Turbomachinery-transactions of The Asme, 1998
    Co-Authors: Howard P. Hodson, William N. Dawes
    Abstract:

    The interaction of wakes shed by a moving blade row with a downstream blade row causes unsteady flow. The meaning of the free-stream Stagnation pressure and Stagnation Enthalpy in these circumstances has been examined using simple analyses, measurements, and CFD. The unsteady flow in question arises from the behavior of the wakes as so-called negative jets. The interactions of the negative jets with the downstream blades lead to fluctuations in static pressure, which in turn generate fluctuations in the Stagnation pressure and Stagnation Enthalpy. It is shown that the fluctuations of the Stagnation quantities created by unsteady effects within the blade row are far greater than those within the incoming wake. The time-mean exit profiles of the Stagnation pressure and Stagnation Enthalpy are affected by these large fluctuations. This phenomenon of energy separation is much more significant than the distortion of the time-mean exit profiles that is caused directly by the cross-passage transport associated with the negative jet, as described by Kerrebrock and Mikolajczak. Finally, it is shown that if only time-averaged values of loss are required across a blade row, it is nevertheless sufficient to determine the time-mean exit Stagnation pressure.

  • ON THE INTERPRETATION OF MEASURED PROFILE LOSSES IN UNSTEADY WAKE-TURBINE BLADE INTERACTION STUDIES
    Journal of Turbomachinery, 1998
    Co-Authors: Howard P. Hodson, William N. Dawes
    Abstract:

    The interaction of wakes shed by a moving blade row with a downstream blade row causes unsteady flow. The meaning of the free-stream Stagnation pressure and Stagnation Enthalpy in these circumstances has been examined using simple analyses, measurements, and CFD. The unsteady flow in question arises from the behavior of the wakes as so-called negative jets. The interactions of the negative jets with the downstream blades lead to fluctuations in static pressure, which in turn generate fluctuations in the Stagnation pressure and Stagnation Enthalpy. It is shown that the fluctuations of the Stagnation quantities created by unsteady effects within the blade row are far greater than those within the incoming wake. The time-mean exit profiles of the Stagnation pressure and Stagnation Enthalpy are affected by these large fluctuations. This phenomenon of energy separation is much more significant than the distortion of the time-mean exit profiles that is caused directly by the cross-passage transport associated with the negative jet, as described by Kerrebrock and Mikolajczak. Finally, it is shown that if only time-averaged values of loss are required across a blade row, it is nevertheless sufficient to determine the time-mean exit Stagnation pressure.

  • On the Interpretation of Measured Profile Losses in Unsteady Wake-Turbine Blade Interaction Studies
    Volume 1: Turbomachinery, 1996
    Co-Authors: Howard P. Hodson, William N. Dawes
    Abstract:

    The interaction of wakes shed by a moving bladerow with a downstream bladerow causes unsteady flow. The meaning of the freestream Stagnation pressure and Stagnation Enthalpy in these circumstances has been examined using simple analyses, measurements and CFD. The unsteady flow in question arises from the behaviour of the wakes as so-called negative-jets. The interactions of the negative-jets with the downstream blades lead to fluctuations in static pressure which in turn generate fluctuations in the Stagnation pressure and Stagnation Enthalpy. It is shown that the fluctuations of the Stagnation quantities created by unsteady effects within the bladerow are far greater than those within the incoming wake. The time-mean exit profiles of the Stagnation pressure and Stagnation Enthalpy are affected by these large fluctuations. This phenomenon of energy separation is much more significant than the distortion of the time-mean exit profiles that is caused directly by the cross-passage transport associated with the negative-jet, as described by Kerrebrock and Mikolajczak. Finally, it is shown that if only time-averaged values of loss are required across a bladerow, it is nevertheless sufficient to determine the time-mean exit Stagnation pressure.Copyright © 1996 by ASME

Allan Paull - One of the best experts on this subject based on the ideXlab platform.

  • Skin-friction measurements in high-Enthalpy hypersonic boundary layers
    Journal of Fluid Mechanics, 2003
    Co-Authors: Christopher P. Goyne, Raymond J. Stalker, Allan Paull
    Abstract:

    Skin-friction measurements are reported for high-Enthalpy and high-Mach-number laminar, transitional and turbulent boundary layers. The measurements were performed in a free-piston shock tunnel with air-flow Mach number, Stagnation Enthalpy and Reynolds numbers in the ranges of 4.4-6.7, 3-13 MJ kg(-1) and 0.16 x 10(6)-21 x 10(6), respectively. Wall temperatures were near 300 K and this resulted in ratios of wall Enthalpy to flow-Stagnation Enthalpy in the range of 0.1-0.02. The experiments were performed using rectangular ducts. The measurements were accomplished using a new skin-friction gauge that was developed for impulse facility testing. The gauge was an acceleration compensated piezoelectric transducer and had a lowest natural frequency near 40 kHz. Turbulent skin-friction levels were measured to within a typical uncertainty of +/-7%. The systematic uncertainty in measured skin-friction coefficient was high for the tested laminar conditions; however, to within experimental uncertainty, the skin-friction and heat-transfer measurements were in agreement with the laminar theory of van Driest (1952). For predicting turbulent skin-friction coefficient, it was established that, for the range of Mach numbers and Reynolds numbers of the experiments, with cold walls and boundary layers approaching the turbulent equilibrium state, the Spalding & Chi (1964) method was the most suitable of the theories tested. It was also established that if the heat transfer rate to the wall is to be predicted, then the Spalding & Chi (1964) method should be used in conjunction with a Reynolds analogy factor near unity. If more accurate results are required, then an experimentally observed relationship between the Reynolds analogy factor and the skin-friction coefficient may be applied.

  • Skin-Friction Measurements in a Supersonic Combustor with Crossflow Fuel Injection
    Journal of Propulsion and Power, 2001
    Co-Authors: Haruto Tanno, Allan Paull, Raymond J. Stalker
    Abstract:

    Shock-tunnel experiments have been performed to measure the effect on skin-friction drag in a supersonic combustor of flow disturbances induced by hydrogen fuel injection transverse to the airstream. Constant-area, circular cross section combustors of lengths varying up to 0.52 m were employed. The experiments were done at a Stagnation Enthalpy of 7.2 MJ . kg(-1) and a Mach number of 4.3, with a boundary layer that was turbulent downstream of the 0.14-m station in the combustors. Combustor skin-friction drag was measured by a method based on the stress wave force balance, the method being validated by agreement between fuel-off skin-friction drag measurements and predictions using existing skin-friction theories. When fuel was injected, it was found that the drag remained at fuel-off values. Thus, the streamwise vortices and other flow disturbances induced by the fuel injection, mixing, and combustion, which are expected to be present in a scramjet combustor, did not influence the skin-friction drag of the combustors.

  • Experiments on supersonic combustion ramjet propulsion in a shock tunnel
    Journal of Fluid Mechanics, 1995
    Co-Authors: Allan Paull, Raymond J. Stalker, David J. Mee
    Abstract:

    Measurements have been made of the propulsive effect of supersonic combustion ramjets incorporated into a simple axisymmetric model in a free piston shock tunnel. The nominal Mach number was 6, and the Stagnation Enthalpy varied from 2.8 to 8.5 MJ kg-1. A mixture of 13% silane and 87% hydrogen was used as fuel, and experiments were conducted at equivalence ratios up to approximately 0.8. The measurements involved the axial force on the model, and were made using a stress wave force balance, which is a recently developed technique for measuring forces in shock tunnels. A net thrust was experienced up to a Stagnation Enthalpy of 3.7 MJ kg-1, but as the Stagnation Enthalpy increased, an increasing net drag was recorded. Pitot and static pressure measurements showed that the combustion was supersonic. The results were found to compare satisfactorily with predictions based on established theoretical models, used with some simplifying approximations. The rapid reduction of net thrust with increasing Stagnation Enthalpy was seen to arise from increasing precombustion temperature, showing the need to control this variable if thrust performance was to be maintained over a range of Stagnation enthalpies. Both the inviscid and viscous drag were seen to be relatively insensitive to Stagnation Enthalpy, with the combustion chambers making a particularly significant contribution to drag. The maximum fuel specific impulse achieved in the experiments was only 175 s, but the theory indicates that there is considerable scope for improvement on this through aerodynamic design.

  • A skin friction gauge for impulsive flows
    31st Joint Propulsion Conference and Exhibit, 1995
    Co-Authors: Christopher P. Goyne, Allan Paull, Raymond J. Stalker
    Abstract:

    A new skin friction gauge has been designed for use in impulsive facilities. The gauge was tested in the T4 free piston shock tunnel, at The University of Queensland, using a 1.5 m long plate that formed one of the inner walls of a rectangular duct. The test gas was air and the test section free stream flow had a Stagnation Enthalpy of 4.7 MJ/kg. Measurements were conducted in a laminar and turbulent boundary layer. The measurements compared well with laminar and turbulent analytical theory.

Edward M. Greitzer - One of the best experts on this subject based on the ideXlab platform.

  • Analysis of Fan Stage Conceptual Design Attributes for Boundary Layer Ingestion
    Journal of Turbomachinery, 2017
    Co-Authors: David K. Hall, Edward M. Greitzer, Choon S. Tan
    Abstract:

    This paper describes a new conceptual framework for three-dimensional turbomachinery flow analysis and its use to assess fan stage attributes for mitigating adverse effects of inlet distortion due to boundary layer ingestion (BLI). A nonaxisymmetric throughflow analysis has been developed to define fan flow with inlet distortion. The turbomachinery is modeled using momentum and energy source distributions that are determined as a function of local flow conditions and specified blade camber surface geometry. Comparison with higher-fidelity computational and experimental results shows the analysis captures the principal flow redistribution and distortion transfer effects associated with BLI. Distortion response is assessed for a range of (i) design flow and Stagnation Enthalpy rise coefficients, (ii) rotor spanwise work profiles, (iii) rotor–stator spacings, and (iv) nonaxisymmetric stator geometries. Of the approaches examined, nonaxisymmetric stator geometry and increased stage flow and Stagnation Enthalpy rise coefficients provide the greatest reductions in rotor flow nonuniformity, and may offer the most potential for mitigating performance loss due to BLI inlet distortion.

  • a physical interpretation of Stagnation pressure and Enthalpy changes in unsteady flow
    Journal of Turbomachinery-transactions of The Asme, 2012
    Co-Authors: Howard P. Hodson, T P Hynes, Edward M. Greitzer
    Abstract:

    This paper provides a physical interpretation of the mechanism of Stagnation Enthalpy and Stagnation pressure changes in turbomachines due to unsteady flow, the agency for all work transfer between a turbomachine and an inviscid fluid. Examples are first given to illustrate the direct link between the time variation of static pressure seen by a given fluid particle and the rate of change of Stagnation Enthalpy for that particle. These include absolute Stagnation temperature rises in turbine rotor tip leakage flow, wake transport through downstream blade rows, and effects of wake phasing on compressor work input. Fluid dynamic situations are then constructed to explain the effect of unsteadiness, including a physical interpretation of how Stagnation pressure variations are created by temporal variations in static pressure; in this it is shown that the unsteady static pressure plays the role of a time-dependent body force potential. It is further shown that when the unsteadiness is due to a spatial nonuniformity translating at constant speed, as in a turbomachine, the unsteady pressure variation can be viewed as a local power input per unit mass from this body force to the fluid particle instantaneously at that point. © 2012 American Society of Mechanical Engineers.

  • a physical interpretation of Stagnation pressure and Enthalpy changes in unsteady flow
    ASME Turbo Expo 2009: Power for Land Sea and Air, 2009
    Co-Authors: Howard P. Hodson, T P Hynes, Edward M. Greitzer
    Abstract:

    This paper provides a physical interpretation of the mechanism of Stagnation Enthalpy and Stagnation pressure changes in turbomachines due to unsteady flow, the agency for all work transfer between a turbomachine and an inviscid fluid. Examples are first given to illustrate the direct link between the time variation of static pressure seen by a given fluid particle and the rate of change of Stagnation Enthalpy for that particle. These include absolute Stagnation temperature rises in turbine rotor tip leakage flow, wake transport through downstream blade rows, the influence on mixing losses of turbine wake behavior in downstream blade rows, and effects of wake phasing on compressor work input. Fluid dynamic situations are then constructed to explain the effect of unsteadiness, including a physical interpretation of how Stagnation pressure variations are created by temporal variations in static pressure; in this it is shown that the unsteady static pressure plays the role of a time-dependent body force potential. It is further shown that when the unsteadiness is due to a spatial nonuniformity translating at constant speed, as in a turbomachine, the unsteady pressure variation can be viewed as a local power input per unit mass from this body force to the fluid particle at that point.Copyright © 2009 by ASME

  • A note on irrotational viscous flow
    Physics of Fluids, 2005
    Co-Authors: B. T. Sirakov, Edward M. Greitzer
    Abstract:

    This Brief Communication describes features of steady irrotational flow in a viscous fluid. The aim is to illustrate, in a simple manner, the different roles played by viscous forces (which are identically zero) and viscous stresses (which are not), the differences in behavior of Stagnation pressure (which is constant along a streamline even in the presence of viscous dissipation) and Stagnation Enthalpy (which changes through the flow), and the role of viscous stresses on the boundary in creating these behaviors.