Available at: http://digitalcommons.calpoly.edu/theses/1260
Date of Award
MS in Mechanical Engineering
The Stanton gauge technique provides an indirect method for measurement of skin friction on a smooth aerodynamic surface in which a pressure tap is available. This thesis presents the design and evaluation of a new type of skin friction measurement gauge based on the Stanton gauge concept but not requiring a surface pressure tap. This new skin friction measurement gauge, called a "Flow Tab", can therefore be used on an aerodynamic model or aircraft surface without alteration of the surface. The Flow Tab is thus particularly well-suited to use with Cal Poly's Boundary Layer Data System (BLDS), a small, self-contained instrument that can be installed onto a model or aircraft surface without permanent alteration of the surface. A series of preliminary experiments conducted in a low-speed wind tunnel on a flat plate model with mild favorable pressure gradient, with both laminar and turbulent boundary layers, led to selection of three variants of the Flow Tab design. These Flow Tabs had edge heights of 0.002, 0.0035, and 0.005 inches, giving dimensionless heights h+ of 1.4 -16 over the streamwise Reynolds number range of about 0.7 to 2.2 million. Uncertainty analysis and test results demonstrated that better than 10% measurement uncertainty for the Flow Tab results could be achieved with edge heights of 0.0035 and 0.005 inches using the same calibration equations as published for the Stanton gauge. Further investigation of its performance over a wider range of Reynolds numbers, and in more complex conditions including those encountered on swept wings with a variety of pressure gradients, is recommended. Integration of the flow tab with BLDS for flight testing applications presents challenges related to its relatively small pressure signal that may require some special modifications to existing BLDS hardware and software.