Michael Cutbirth - Academia.edu (original) (raw)

Papers by Michael Cutbirth

Bulletin of the American Physical Society, Nov 20, 2006

Bulletin of the American Physical Society, Nov 22, 2010

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An extensive experimental effort was undertaken to document the performance of a lowaspect ratio ... more An extensive experimental effort was undertaken to document the performance of a lowaspect ratio hydrofoil with trailing edge blowing across a Coanda surface in a large water tunnel facility. This facility was the William B. Morgan Large Cavitation Channel in Memphis, TN. The hydrofoil model with a taper ratio of 0.76 was mounted through a load balance. A reflection plane provided for an effective aspect ratio of 2. The dual-slot configuration allowed for an investigation of thrust vectoring, and also presented an unexpected opportunity to offset the negative impact of excessive turning of the wall jet onto the underside of the foil. This report serves to document the experimental details of that effort for future experiments and document the types of data collected for validation of computational fluid dynamics (CFD) codes. The performance of the selected hydrofoil section shape is documented with six-component load measurements and detailed laser Doppler velocimetry measurements (LDV) taken in the wake of the foil.

Film cooling performance was studied on a simulated turbine vane model with an objective of deter... more Film cooling performance was studied on a simulated turbine vane model with an objective of determining how much the coolant density ratio affects this performance. Experiments were conducted using coolant density ratios of 1.8 and 1.2. The purpose of the study was to determine if tests done at small density ratios (which is often more viable in a laboratory) can give reasonable predictions of performance at more realistic large density ratios. Furthermore, appropriate scaling parameters were determined. The mainstream flow was operated with low and high turbulence levels. Adiabatic effectiveness was measured in the showerhead region of the vane, and following the first row of coolant holes on the pressure side. Adiabatic effectiveness performance using small density ratio coolant gave performance trends similar to the large density ratio coolant, but quantitative values differed by varying amount depending on operating conditions.

Journal of turbomachinery, Feb 1, 2000

An experimental study was conducted to investigate the film cooling performance on the suction si... more An experimental study was conducted to investigate the film cooling performance on the suction side of a first-stage turbine vane. Tests were conducted on a nine times scale vane model at density ratios of DR=1.1 and 1.6 over a range of blowing conditions, 0.2⩽M⩽1.5 and 0.05⩽I⩽1.2. Two different mainstream turbulence intensity levels, Tu∞=0.5 and 20 percent, were also investigated. The row of coolant holes studied was located in a position of both strong curvature and strong favorable pressure gradient. In addition, its performance was isolated by blocking the leading edge showerhead coolant holes. Adiabatic effectiveness measurements were made using an infrared camera to map the surface temperature distribution. The results indicate that film cooling performance was greatly enhanced over holes with a similar 50 deg injection angle on a flat plate. Overall, adiabatic effectiveness scaled with mass flux ratio for low blowing conditions and with momentum flux ratio for high blowing conditions. However, for M<0.5, there was a higher rate of decay for the low density ratio data. High mainstream turbulence had little effect at low blowing ratios, but degraded performance at higher blowing ratios.

Journal of turbomachinery, Jul 1, 2002

The showerhead region of a film-cooled turbine vane in a gas turbine engine involves a complex in... more The showerhead region of a film-cooled turbine vane in a gas turbine engine involves a complex interaction between mainstream flow and coolant jets. This flow field was studied using three component laser Doppler velocimeter measurements in a simulated turbine vane test facility. Measurements were focused around the stagnation row of holes. Low and high mainstream turbulence conditions were used. The spanwise orientation of the coolant jets, typical for showerhead coolant holes, had a dominating effect. Very high levels of turbulence were generated by the mainstream interaction with the coolant jets. Furthermore, this turbulence was highly anisotropic, with the spanwise component of the turbulent fluctuations being twice as large as the other components. Finally, there was an interaction of the high mainstream turbulence with the coolant injection resulting in increased turbulence levels for the spanwise velocity component, but had little effect on the other velocity components.

This paper presents an experimental study of the heat transfer on the leading edge of a simulated... more This paper presents an experimental study of the heat transfer on the leading edge of a simulated film cooled turbine airfoil. Previous studies have shown that use of film cooling on the leading edge of an airfoil can significantly increase the heat transfer coefficients around the leading edge which counteracts the benefits of the adiabatic effectiveness provided by the coolant film. These heat transfer results complement our earlier study of the adiabatic effectiveness for this leading edge and film cooling hole geometry. Heat transfer and adiabatic effectiveness results were combined to determine the overall performance of the film cooling in terms of the net heat flux reduction. Heat transfer coefficients were found to be significantly increased by the film cooling flow in a narrow region which followed the path of the coolant flow. However, heat transfer coefficients were maximum to one side of the coolant jet, consistent with a streamwise vortex flow which is believed to be generated by the interaction of the mainstream with the coolant jet. Overall performance in terms of the net heat flux reduction was found to be unaffected by the large heat transfer coefficients in the vicinity of the holes, but was significantly diminished farther downstream.

Experimental Thermal and Fluid Science, Jul 1, 2012

Much is known about smooth-flat-plate turbulent boundary layers (TBLs) at laboratory-scale Reynol... more Much is known about smooth-flat-plate turbulent boundary layers (TBLs) at laboratory-scale Reynolds numbers because of a wealth of experimental data. However, smooth-flat-plate TBL data are much less common at the high Reynolds numbers typical of aerodynamic and hydrodynamic applications (Re x $ 10 8-10 10), and at the even higher Reynolds numbers of many geophysical flows. This paper presents new LDV-measured profiles of the stream-wise velocity variance, the wall-normal velocity variance, and the Reynolds shear stress from the TBL that formed on a smooth flat plate at Karman numbers from 15,000 to 60,000 (Re x from 75 million to 220 million). The experiments were conducted in the William B. Morgan Large Cavitation Channel on a polished (k + < 0.2) flat-plate test model 12.9 m long and 3.05 m wide at water flow speeds up to 20 m s À1. The TBL on the model developed in a mild favorable pressure gradient having an acceleration parameter K $ 10 À10. When plotted with the usual inner and outer scalings, the stream-wise velocity variance profiles display a Reynolds number dependence that is consistent with prior lower Reynolds-number zero-pressure-gradient TBL measurements. However, using the same normalizations, the profiles of wall-normal velocity variance and Reynolds shear stress are found to be Reynolds number independent, or nearly so, when experimental uncertainties are considered.

Measurement Science and Technology, Jul 25, 2005

The William B Morgan Large Cavitation Channel (LCC) is a large variable-pressure closed-loop wate... more The William B Morgan Large Cavitation Channel (LCC) is a large variable-pressure closed-loop water tunnel that has been operated by the US Navy in Memphis, TN, USA, since 1991. This facility is well designed for a wide variety of hydrodynamic and hydroacoustic tests. Its overall size and capabilities allow test-model Reynolds numbers to approach, or even achieve, those of full-scale air-or water-borne transportation systems. This paper describes the facility along with some novel implementations of measurement techniques that have been successfully utilized there. In addition, highlights are presented from past test programmes involving (i) cavitation, (ii) near-zero pressure-gradient turbulent boundary layers, (iii) the near-wake flow characteristics of a two-dimensional hydrofoil and (iv) a full-scale research torpedo.

The process of film cooling is known to severely disturb the boundary layer around a turbine airf... more The process of film cooling is known to severely disturb the boundary layer around a turbine airfoil. Since most film-cooled airfoils have more than one injection station, the flow field approaching a row of film cooling holes could be altered by the presence of an upstream cooling station. To investigate this possibility, an experimental investigation was conducted on the suction side of a scaled-up turbine vane. Adiabatic effectiveness measurements were made downstream of a single row of cooling holes both with and without the upstream showerhead holes operating. A range of suction side blowing ratios, 0.3 ≤ M ≤ 1.3, were investigated with large-scale mainstream turbulence intensities of Tu∞ = 0.5% and Tu∞ = 21%. The effects of the showerhead coolant were evaluated at an engine-typical showerhead blowing ratio of Msh = 1.6, with three of the six rows of cooling holes in the showerhead directed towards the suction side of the airfoil. Experiments were conducted with a coolant-to-mainstream density ratio of DR = 1.6. An infrared camera was used to obtain spatially-resolved surface temperature measurements, which were corrected for conduction effects and converted to adiabatic effectiveness. The results showed that showerhead coolant had a strong impact on suction side adiabatic effectiveness levels under low mainstream turbulence. Although effectiveness levels increased with the showerhead operating, the suction side coolant jets increased dispersion of the showerhead coolant. Under high mainstream turbulence conditions, there was very little interaction between the showerhead coolant and the suction side coolant jets. Adiabatic effectiveness levels were considerably lower than those for the low turbulence case, which was partially due to increased dispersion of the showerhead coolant upstream of the suction side holes. The superposition model over-predicted adiabatic effectiveness levels under low mainstream turbulence conditions, but was very effective in predicting the combined performance of the showerhead and the suction side cooling holes under high mainstream turbulence conditions.

Journal of turbomachinery, Oct 1, 2002

The goal of this study was to determine how showerhead blowing on a turbine vane leading edge aff... more The goal of this study was to determine how showerhead blowing on a turbine vane leading edge affects of the performance of film cooling jets farther downstream. An emphasis was placed on measurements above the surface, i.e., flow visualization, thermal field, and velocity field measurements. The film cooling performance on the pressure side of a simulated turbine vane, with and without showerhead blowing, was examined. Results presented in this paper are for low mainstream turbulence; high mainstream turbulence effects are presented in the companion paper. At the location of the pressure side row of holes, the showerhead coolant extended a distance of about 3d from the surface (d is the coolant hole diameter). The pressure side was found to be subjected to high turbulence levels caused by the showerhead injection. Results indicate a greater dispersion of the pressure side coolant jets with showerhead flow due to the elevated turbulence levels.

Public reporting burden for this collection of information is estimated to average i hour per res... more Public reporting burden for this collection of information is estimated to average i hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to

Volume 3: Heat Transfer; Electric Power; Industrial and Cogeneration, May 8, 2000

There have been numerous studies of film cooling performance for the downstream coolant holes on ... more There have been numerous studies of film cooling performance for the downstream coolant holes on a turbine airfoil using test geometries ranging from flat plates to airfoils. Most of these studies simulate a relatively unperturbed boundary layer flow approaching the coolant holes. This stimulated the current inquiry into the effects of realistic upstream conditions for downstream coolant holes. To investigate this, a series of experiments were performed focussing on the first downstream row of holes on the pressure side of a typical turbine vane. The film cooling effectiveness for this pressure side row of holes was determined subject to no showerhead blowing, and to showerhead blowing with varying blowing rates. Furthermore, tests were conducted with low and high freestream turbulence levels. For this investigation, a leading edge showerhead array of six film cooling rows was utilized, with coolant from three of these rows being directed towards the pressure side of the vane. For all experiments a coolant to freestream density ratio of nominally DR = 1.8 was used. Adiabatic effectiveness was determined from surface temperature measurements for a nominally adiabatic surface using an infrared camera for spatially resolved mapping of the surface temperature. This study showed that showerhead injection had a dominant influence on the adiabatic effectiveness performance of downstream cooling. Showerhead injection appeared to cause a significant increase in coolant jet dispersion, presumably by increased levels of turbulence. Even when the freestream turbulence level at the pressure side coolant holes was increased to 17%, showerhead injection caused a significant degradation in the film cooling performance of the pressure side row of holes. Because of the increased dispersion caused by the showerhead injection for the pressure side coolant jets, the superposition model failed to correctly predict adiabatic effectiveness levels for combined showerhead and pressure side coolant injection.

Oklahoma State University, May 1, 1996

An constant in the wall temperature curve fit, n=0,l,2,3 absolute viscosity of the coolant fluid,... more An constant in the wall temperature curve fit, n=0,l,2,3 absolute viscosity of the coolant fluid, N-s/m 2 v kinematic viscosity of the coolant fluid, m 2 /s en constant in the surface temperature curve fit, n=l,2,3 p density of the coolant fluid, kg/m) xvi dummy variable to express the direction of the radial heat flow, cm temporary coefficient for the wall temperature, dimensionless