Evaluation of an innovative supersonic boundary layer transition device - Phase I results

Abstract

A combined experimental and computational investigation was initiated to improve upon the design and implementation of roughness boundary layer trips to increase the simulation fidelity of wind tunnel tests of supersonic inlets. Focused on developing the technique prior to rigorously measuring transition, Phase I of this experiment addressed the need for trips and evaluated the performance effects of a new type of epoxy cylinder roughness as well as the widely-used carborundum grit. New design (GRTTCALC) and established boundary layer (SSCBL) codes were used to configure the grit and qualitatively predict its performance effects. Tests with and without grit were conducted on a Mach 2.5 boundary layer that develops over a zero incidence angle flat plate to characterize these effects and assess any impact on the core flow. Both design and test data indicate that a properly chosen grit configuration can be effective across a useful range of test conditions without adversely affecting the core flow. The epoxy cylinder grit was practical to install and more uniform, repeatable and durable than the carborundum trip. Predictions of the emergence of the grit into the core flow with increasing test section unit Reynolds number agreed with the experimentally measured data. Copyright © 1998 by the American Institute of Aeronautics and Astronautics, Inc. No copyright is asserted in the United States under Tide 17, U.S. Code. The U.S. Government has a royalty-free license to exercise all rights under the copyright claimed herein for Governmental purposes. All other rights are reserved by the copyright owner. Nomenclature 8 = Boundary layer thickness d = Grit diameter F = Test section static pressure correction factor, the ratio of the corrected test section to average nozzle block exit static pressures H = Shape factor k = Grit height N = Number density of grit particles p = Static pressure Re = Reynolds number T = Temperature u = Axial boundary layer velocity component U = Axial velocity of the core flow w = Width of grit strip x = Axial plate coordinate z = Vertical coordinate above the plate Subscripts 1 = Displacement boundary layer thickness 2 = Momentum boundary layer thickness c = Compressible inf = Core flow conditions k = Conditions that pertain to the grit height, at the grit height lam= Laminar flow conditions le = Conditions at the leading edge of the grit strip max= maximum conditions t = Total conditions tr = Transformed (refers to the transformed shape factor) u = Conditions per unit length scale wall= Conditions at the wall x = Conditions that pertain to the axial distance from the leading edge of the model height Aerospace Engineer, Inlet Branch, Senior Member 1 American Institute of Aeronautics and Astronautics