85 



CONCLUSIONS 



REFERENCES 



The flow tube experiment has already demonstrated 

 that wall heating can have a significant effect 

 upon transition Reynolds numbers in water boundary 

 layers. Although the maximum transition Reynolds 

 number of 42 x 10 is well below the predicted 

 maximum, this value has been obtained with only 

 7°C wall overheat. The unheated transition Reynolds 

 number of 10 shows that disturbances are well 

 controlled in the experiment. 



Possible causes for the differences between the 

 predicted and realized transition Reynolds numbers 

 at higher overheats are still under investigation. 

 Preliminary results from the instrumented section 

 indicate that buoyancy-driven instabilities are 

 not a significant factor. However, major deviations 

 from boundary layer axisyrometry have been observed 

 even with no wall heat. These perturbations of the 

 unheated flow could themselves have an effect upon 

 transition Reynolds numbers. This is particularly 

 true if the actual disturbances are Goertler vortices, 

 because these vortices would increase in strength 

 with increasing flow velocity. Since the transition 

 length is fixed at the end of the tube in this 

 experiment, transition Reynolds number will be 

 directly proportional to velocity. Thus the 

 Goertler vortices could impose a limit in transition 

 Reynolds number if they begin to dominate the 

 transition process above some critical flow velocity. 

 This hypothesis will be tested by the installation 

 of the new contraction section, which eliminates 

 the possibility of Goertler vortex formation. 



ACKNOWLEDGMENT 



The author wishes to acknowledge the participation 

 and support of the Marine Systems Division of Rock- 

 well International, and in particular Mr. Douglas 

 Gile. In addition, the author acknowledges the 

 Defense Advanced Research Projects Agency, who 

 sponsored this research. 



Back, L. H., R. F. Cuffel, and P. F. Massier (1969). 

 RIAA Journal, 7, 4; 730. 



Barker, S. J., and C. Jennings (1977). The effect 

 of wall heating on transition in water boundary 

 layers. Proc . of NATO-AGARD Symposium on 

 Laminar-Turbulent Transition, Copenhagen, 19-1. 



Barker, S. J. (1978) . Turbulence Management in a 

 High Speed Water Flow Facility. Submitted to 

 ASME. 



Bradshaw, P. (1965). J. Fluid Mech., 22 pt. 4, 679. 



Chmielewski, G. E. (1974). J. Aircraft, 11, 8; 435. 



Corrsin, S. (1963). Turbulence: Experimental 



methods, in Handbuch der Physik, 8, pt. 2, 523. 



Kaups, K. , and A. M. O. Smith (1967). The laminar 

 boundary layer in water with variable properties. 

 Proc. ASME-AIChE Heat Transfer Conf . , Seattle, 

 Wash. 



Launder, B. E. (1964). Laminarization of the 



Turbulent Boundary Layer by Acceleration, M. I. T. 

 Gas Turbine Lab Report 77. Cambridge, Mass. 



Loehrke , R. I., and H. M. Nagib (1972). Experiments 

 on Management of Free-Stream Turbulence. NATO- 

 AGARD Report 598. 



Lumley, J. L. , and J. F. McMahon (1967). Trans. 

 ASME, D, 89, 764. 



Schlichting, H. (1968) . Boundary Layer Theory, 

 McGraw-Hill, New York. 



Smith, A. M. O. (1957) . Transition, pressure gra- 

 dient, and stability theory, Proc. 9th Int. Con- 

 gress on Appl . Mech., 4, 234, Brussels. 



Spangler, J. G., and C. S. Wells (1968). AIAA 

 Journal, 6, 3; 543. 



Strasizar, A., J. M. Prahl, and E. Reshotko (1975). 

 Experimental Study of Heated Laminar Boundary 

 Layers in Water, Case Western Reserve Univ., 

 Dept. of Fluid, Thermal, and Aerospace Science 

 Report FT AS/TR-75-113 . 



Wazzan, A. R. , T. T. Okamura, and A. M. 0. Smith 

 (1968). Trans. ASME, C, 90, 109. 



Wazzan, A. R. , T. T. Okamura, and A. M. 0. Smith 

 (1970) . The stability and transition of heated 

 and cooled incompressible boundary layers. Proc. 

 4th Int. Heat Transfer Conf., Paris. 



