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Review of mass (heat) — transfer measurements using naphthalene sublimation
PLENARY LECTURE The Changing Roles of Experimental and Computational Fluid Mechanics A. J. Strazisar
NASA Lewis Research Center Cleveland, Ohio When computational fluid mechanics was in its infancy, experiments and theoretical analysis were often the primary approaches used to study flow physics. Numerical simulations were performed after an experiment was complete, and the measured, theoretical, and numerical resuits were compared to assess the accuracy of the numerical results. As numerical simulation techniques have matured, computational, analytic, and experimental efforts have become equal partners in fluid mechanics research. Today numerical simulations are being used to guide the design of experimental hardware, to determine those areas of the flow field in which to concentrate the measurement effort, and to complement measurements in studying flow physics. The changing roles of experimental, analytical, and computational research will be traced by reviewing several investigations in which these approaches were used in varying degrees. A case will be made for maintaining a high degree of interaction between these approaches throughout the course of an investigation. The development of prototype computing systems designed to enhance the integration of numerical simulations and flow physics experiments will also be described.
KEYNOTE LECTURES Measurement Techniques in High Enthalpy Hypersonic Facilities J. M. Simmons
Faculty of Engineering The University of Queensland Brisbane, Australia Interest in hypersonic aerodynamic braking and aerospace planes has led to the development of new high enthalpy, hypersonic test facilities. This paper describes the available techniques and future developments for making measurements in these facilities. The emphasis is on instrumentation for use with short-duration flows, in particular, in free-piston shock tunnels. Issues of free-stream calibration, surface measurements on models, flow visualization, laser diagnostics, and accuracy are addressed, with references made to representative experimental studies. The paper concludes with a summary of future research needs.
NUSSELT-REYNOLDS PRIZE LECTURE Review of Mass (Heat) -Transfer Measurements Using Naphthalene Sublimation R. J. Goldstein H. H. Cho
Department of Mechanical Engineering University of Minnesota Minneapolis, Minnesota The naphthalene sublimation method can be used to study mass/heat transfer with confidence for a variety of applications, but with certain restrictions. This method is particularly useful in complex flows and geometries and for flows with large gradients in wall-transport rate. Mass-transfer boundary conditions analogous to isothermal and adiabatic walls in convective heat transfer can be easily imposed. Furthermore, the nature of mass transfer allows one to impose these boundary conditions such that errors analogous to conductive losses in a wall are not present. The test specimen can be easily prepared by several methods, including dipping, machining, spraying, and casting. The local transfer coefficients can be determined with high accuracy and in detail by automated measurement systems that eliminate most human errors and reduce extraneous sublimation losses during the measurement process. The heat-transfer coefficient, which is often desired, can be readily determined from the measured mass-transfer results with good confidence via a heat/mass-transfer analogy. However, this method cannot generally be used in certain flow situations such as high-velocity flows due to recovery temperature effects and natural convection due to the thermal buoyancy effects of sublimation latent heat.
Density-Sensitive Whole-Field Flow Measurement by Optical Speckle Photography W. Merzkirch
Lehrstuhl Fiir Stri~mungslehre Universitiit Essen Essen, Germany An optical whole-field, line-of-sight method is surveyed that allows the measurement of the deflection angles of light transmitted through a flow with density changes. The method uses the principles of speckle photography. In comparison to classic optical methods, eg, interferometry, a much higher number of data values can be obtained from one record. This high signal density is particularly advantageous for analyzing turbulent flows with density fluctuations. Such an analysis is, so far, restricted to the existence of axisymmetric turbulence. A number of applications to this type of turbulent flow are reported, and proposals are made for future developments so that this speckle technique could be applied to the study of turbulent shear flow.
Experimental Thermaland Fluid Science 1993; 7:125-175 © 1993by Elsevier SciencePublishing Co., Inc., 655 Avenue of the Americas, New York, NY 10010
0894-1777/93/$6.00 125
NASA Lewis Research Center Cleveland, Ohio When computational fluid mechanics was in its infancy, experiments and theoretical analysis were often the primary approaches used to study flow physics. Numerical simulations were performed after an experiment was complete, and the measured, theoretical, and numerical resuits were compared to assess the accuracy of the numerical results. As numerical simulation techniques have matured, computational, analytic, and experimental efforts have become equal partners in fluid mechanics research. Today numerical simulations are being used to guide the design of experimental hardware, to determine those areas of the flow field in which to concentrate the measurement effort, and to complement measurements in studying flow physics. The changing roles of experimental, analytical, and computational research will be traced by reviewing several investigations in which these approaches were used in varying degrees. A case will be made for maintaining a high degree of interaction between these approaches throughout the course of an investigation. The development of prototype computing systems designed to enhance the integration of numerical simulations and flow physics experiments will also be described.
KEYNOTE LECTURES Measurement Techniques in High Enthalpy Hypersonic Facilities J. M. Simmons
Faculty of Engineering The University of Queensland Brisbane, Australia Interest in hypersonic aerodynamic braking and aerospace planes has led to the development of new high enthalpy, hypersonic test facilities. This paper describes the available techniques and future developments for making measurements in these facilities. The emphasis is on instrumentation for use with short-duration flows, in particular, in free-piston shock tunnels. Issues of free-stream calibration, surface measurements on models, flow visualization, laser diagnostics, and accuracy are addressed, with references made to representative experimental studies. The paper concludes with a summary of future research needs.
NUSSELT-REYNOLDS PRIZE LECTURE Review of Mass (Heat) -Transfer Measurements Using Naphthalene Sublimation R. J. Goldstein H. H. Cho
Department of Mechanical Engineering University of Minnesota Minneapolis, Minnesota The naphthalene sublimation method can be used to study mass/heat transfer with confidence for a variety of applications, but with certain restrictions. This method is particularly useful in complex flows and geometries and for flows with large gradients in wall-transport rate. Mass-transfer boundary conditions analogous to isothermal and adiabatic walls in convective heat transfer can be easily imposed. Furthermore, the nature of mass transfer allows one to impose these boundary conditions such that errors analogous to conductive losses in a wall are not present. The test specimen can be easily prepared by several methods, including dipping, machining, spraying, and casting. The local transfer coefficients can be determined with high accuracy and in detail by automated measurement systems that eliminate most human errors and reduce extraneous sublimation losses during the measurement process. The heat-transfer coefficient, which is often desired, can be readily determined from the measured mass-transfer results with good confidence via a heat/mass-transfer analogy. However, this method cannot generally be used in certain flow situations such as high-velocity flows due to recovery temperature effects and natural convection due to the thermal buoyancy effects of sublimation latent heat.
Density-Sensitive Whole-Field Flow Measurement by Optical Speckle Photography W. Merzkirch
Lehrstuhl Fiir Stri~mungslehre Universitiit Essen Essen, Germany An optical whole-field, line-of-sight method is surveyed that allows the measurement of the deflection angles of light transmitted through a flow with density changes. The method uses the principles of speckle photography. In comparison to classic optical methods, eg, interferometry, a much higher number of data values can be obtained from one record. This high signal density is particularly advantageous for analyzing turbulent flows with density fluctuations. Such an analysis is, so far, restricted to the existence of axisymmetric turbulence. A number of applications to this type of turbulent flow are reported, and proposals are made for future developments so that this speckle technique could be applied to the study of turbulent shear flow.
Experimental Thermaland Fluid Science 1993; 7:125-175 © 1993by Elsevier SciencePublishing Co., Inc., 655 Avenue of the Americas, New York, NY 10010
0894-1777/93/$6.00 125