Comparing experiment and computation of hypersonic laminar boundary layers with isolated roughness

Brett F. Bathel, Prahladh S. Iyer, Krishnan Mahesh, Paul M. Danehy, Jennifer A. Inman, Stephen B. Jones, Craig T. Johansen

Research output: Chapter in Book/Report/Conference proceedingConference contribution

1 Scopus citations

Abstract

Streamwise velocity profile behavior in a hypersonic laminar boundary layer in the presence of an isolated roughness element is presented for an edge Mach number of 8.2. Two different roughness element types are considered: a 2-mm tall, 4-mm diameter cylinder, and a 2-mm radius hemisphere. Measurements of the streamwise velocity behavior using nitric oxide (NO) planar laser-induced fluorescence (PLIF) molecular tagging velocimetry (MTV) have been performed on a 20-degree wedge model. The top surface of this model acts as a flat-plate and is oriented at 5 degrees with respect to the freestream flow. Computations using direct numerical simulation (DNS) of these flows have been performed and are compared to the measured velocity profiles. Particular attention is given to the characteristics of velocity profiles immediately upstream and downstream of the roughness elements. In these regions, the streamwise flow can experience strong deceleration or acceleration. An analysis in which experimentally measured MTV profile displacements are compared with DNS particle displacements is performed to determine if the assumption of constant velocity over the duration of the MTV measurement is valid. This assumption is typically made when reporting MTV-measured velocity profiles, and may result in significant errors when comparing MTV measurements to computations in regions with strong deceleration or acceleration. The DNS computations with the cylindrical roughness element presented in this paper were performed with and without air injection from a rectangular slot upstream of the cylinder. This was done to determine the extent to which gas seeding in the MTV measurements perturbs the boundary layer flowfield.

Original languageEnglish (US)
Title of host publication52nd AIAA Aerospace Sciences Meeting - AIAA Science and Technology Forum and Exposition, SciTech 2014
PublisherAmerican Institute of Aeronautics and Astronautics Inc.
ISBN (Print)9781624102561
DOIs
StatePublished - 2014
Event52nd AIAA Aerospace Sciences Meeting - AIAA Science and Technology Forum and Exposition, SciTech 2014 - National Harbor, MD, United States
Duration: Jan 13 2014Jan 17 2014

Publication series

Name52nd AIAA Aerospace Sciences Meeting - AIAA Science and Technology Forum and Exposition, SciTech 2014

Other

Other52nd AIAA Aerospace Sciences Meeting - AIAA Science and Technology Forum and Exposition, SciTech 2014
CountryUnited States
CityNational Harbor, MD
Period1/13/141/17/14

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    Bathel, B. F., Iyer, P. S., Mahesh, K., Danehy, P. M., Inman, J. A., Jones, S. B., & Johansen, C. T. (2014). Comparing experiment and computation of hypersonic laminar boundary layers with isolated roughness. In 52nd AIAA Aerospace Sciences Meeting - AIAA Science and Technology Forum and Exposition, SciTech 2014 (52nd AIAA Aerospace Sciences Meeting - AIAA Science and Technology Forum and Exposition, SciTech 2014). American Institute of Aeronautics and Astronautics Inc.. https://doi.org/10.2514/6.2014-0236