TY - JOUR
T1 - Numerical investigation of roughness effects on transition on spherical capsules
AU - Hein, Stefan
AU - Theiss, Alexander
AU - Di Giovanni, Antonio
AU - Stemmer, Christian
AU - Schilden, Thomas
AU - Schröder, Wolfgang
AU - Paredes, Pedro
AU - Choudhari, Meelan M.
AU - Li, Fei
AU - Reshotko, Eli
N1 - Publisher Copyright:
Copyright © 2018 by S. Hein, A. Theiss, A. Di Giovanni, C. Stemmer, T. Schilden, W. Schröder, and E. Reshotko, and their affiliations, and the United States Government as represented by the Administrator of the National Aeronautics and Space Administration. Published by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.
PY - 2019
Y1 - 2019
N2 - To address the hitherto unknown mechanism of boundary-layer transition on blunt reentry capsules, the role of roughness-induced disturbance growth on a spherical-section forebody is assessed via optimal transient growth theory and direct numerical simulations (DNS). Optimal transient-growth studies have been performed for the blunt capsule experiments at Mach 5.9 in the Hypersonic Ludwieg tube at the Technische Universität Braunschweig (HLB), which included measurements behind a patch of controlled, distributed micron-sized surface roughness. Transient-growth results for the HLB capsule indicate similar trends as the corresponding numerical data for a Mach 6 experiment in the Actively Controlled Expansion (ACE) facility of the Texas A&M University (TAMU) at a lower Reynolds number. Both configurations indicate a similar dependence on surface temperature ratio and, more important, rather low values of maximum energy gain. DNS are performed for the conditions of the HLB experiment to understand the generation of stationary disturbances by the roughness patch and the accompanying evolution of unsteady perturbations. However, no evidence of either modal or nonmodal disturbance growth in the wake of the roughness patch is found in the DNS data; thus, the physical mechanism underlying the observed onset of transition still remains unknown.
AB - To address the hitherto unknown mechanism of boundary-layer transition on blunt reentry capsules, the role of roughness-induced disturbance growth on a spherical-section forebody is assessed via optimal transient growth theory and direct numerical simulations (DNS). Optimal transient-growth studies have been performed for the blunt capsule experiments at Mach 5.9 in the Hypersonic Ludwieg tube at the Technische Universität Braunschweig (HLB), which included measurements behind a patch of controlled, distributed micron-sized surface roughness. Transient-growth results for the HLB capsule indicate similar trends as the corresponding numerical data for a Mach 6 experiment in the Actively Controlled Expansion (ACE) facility of the Texas A&M University (TAMU) at a lower Reynolds number. Both configurations indicate a similar dependence on surface temperature ratio and, more important, rather low values of maximum energy gain. DNS are performed for the conditions of the HLB experiment to understand the generation of stationary disturbances by the roughness patch and the accompanying evolution of unsteady perturbations. However, no evidence of either modal or nonmodal disturbance growth in the wake of the roughness patch is found in the DNS data; thus, the physical mechanism underlying the observed onset of transition still remains unknown.
UR - http://www.scopus.com/inward/record.url?scp=85063948196&partnerID=8YFLogxK
U2 - 10.2514/1.A34247
DO - 10.2514/1.A34247
M3 - Article
AN - SCOPUS:85063948196
SN - 0022-4650
VL - 56
SP - 388
EP - 404
JO - Journal of Spacecraft and Rockets
JF - Journal of Spacecraft and Rockets
IS - 2
ER -