A critical study of laminar-turbulent transition phenomena and its role in aerodynamics and heat transfer in modern and future gas turbine engines is presented. In order to develop a coherent view of the subject, a current look at transition phenomena from both a theoretical and experimental standpoint are provided and a comprehensive state-of-the-art account of transitional phenomena in the engine’s throughflow components given. The impact of transitional flow on engine design is discussed and suggestions for future research and developmental work provided.

Local rates of heat transfer on the endwall, suction, and pressure surfaces of a large scale turbine blade cascade were measured for two inlet boundary layer thicknesses and for a Reynolds number typical of gas turbine engine operation. The accuracy and spatial resolution of the measurements were sufficient to reveal local variations of heat transfer associated with distinct flow regimes and with regions of strong three-dimensional flow. Pertinent results of surface flow visualization and pressure measurements are included. The dominant role of the passage vortex, which develops from the singular separation of the inlet boundary layer, in determining heat transfer at the endwall and at certain regions of the airfoil surface is illustrated. Heat transfer on the passage surfaces is discussed and measurements at airfoil midspan are compared with current finite difference prediction methods.

A critical study of laminar-turbulent transition phenomena and their role in aerodynamics and heat transfer in modern and future gas turbine engines is presented. In order to develop a coherent view of the subject, a current look at transition phenomena from both a theoretical and experimental standpoint are provided and a comprehensive state-of-the-art account of transitional phenomena in the engine’s throughflow components given. The impact of transitional flow on engine design is discussed and suggestions for future research and developmental work provided.

The effect of length scale in free-stream turbulence is considered for heat transfer in laminar boundary layers. A model is proposed which accounts for an “effective” intensity of turbulence based on a dominant frequency for a laminar boundary layer. Assuming a standard turbulence spectral distribution, a new turbulence parameter which accounts for both turbulence level and length scale is obtained and used to correlate heat transfer data for laminar stagnation flows. The result indicates that the heat transfer for these flows is linearly dependent on the “effective” free-stream turbulence intensity.

The purpose of this paper is to discuss the risk factors, prevention strategies, classification, and treatment of intra-operative femur fractures sustained during primary and revision total hip arthroplasty.

Detailed film effectiveness and surface heat transfer measurements were obtained for secondary air injection through rows of holes into the stagnation region of an incident mainstream flow. Tests were performed using a blunt body with a circular leading edge and a flat afterbody. Rows of holes were located at ±15 deg and +44 deg from stagnation. The holes in each row were spaced four hole diameters apart and were angled 30 deg to the surface in the spanwise direction. Measurements were taken for three cooling-to-incident flow mass flux ratios both in the leading edge region within the hole pattern and downstream to a distance of about 85 hole diameters. The results indicate that large spanwise variations in both film effectiveness and heat transfer coefficient exist, and that the highest values of each do not in general correspond. Near the holes, film effectiveness values as high as 0.7–0.8 were found, while heat transfer coefficients with injection were as much as three times those without. Far downstream the film effectiveness decayed to values near 0.1, while the heat transfer coefficient remained about 10 percent above that without injection. Nevertheless, it is shown that for typical turbine temperatures, leading edge injection reduces the surface heat load everywhere for all but the highest mass flux ratio. The exception produces an increase in heat load within the injection region.

A theory is presented for calculating the fluctuations in a laminar boundary layer when the free stream is turbulent. The kinetic energy equation for these fluctuations is derived and a new mechanism is revealed for their production. A methodology is presented for solving the equation using standard boundary layer computer codes. Solutions of the equation show that the fluctuations grow at first almost linearly with distance and then more slowly as viscous dissipation becomes important. Comparisons of calculated growth rates and kinetic energy profiles with data show good agreement. In addition, a hypothesis is advanced for the effective forcing frequency and free-stream turbulence level which produce these fluctuations. Finally, a method to calculate the onset of transition is examined and the results compared to data.

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