Wind-Tunnel Investigations of Blunt-Body Drag Reduction ... Blunt-Body Drag Reduction Using Forebody

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  • NASA/TM-2001-210390

    Wind-Tunnel Investigations of

    Blunt-Body Drag Reduction Using

    Forebody Surface Roughness

    Stephen A. Whitmore

    NASA Dryden Flight Research Center

    Edwards, California

    Stephanie Sprague

    University of Kansas

    Lawrence, Kansas

    Jonathan W. Naughton

    University of Wyoming

    Laramie, Wyoming

    January 2001

    https://ntrs.nasa.gov/search.jsp?R=20010014167 2020-06-09T22:34:08+00:00Z

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  • NAS A/TM-2001-210390

    Wind-Tunnel Investigations of

    Blunt-Body Drag Reduction Using

    Forebody Surface Roughness

    Stephen A. Whitmore

    NASA Dryden Flight Research Center

    Edwards, California

    Stephanie Sprague

    University of Kansas

    Lawrence, Kansas

    Jonathan W. Naughton

    Universi_' of Wyoming

    Laramie Wyoming

    National Aeronautics and

    Space Administration

    Dryden Flight Research Center

    Edwards, California 93523-0273

    January 2001

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    Springfield, VA 22161-2171 (703) 487-4650

  • WIND-TUNNEL INVESTIGATIONS OF BLUNT-BODY

    DRAG REDUCTION USING FOREBODY SURFACE ROUGHNESS

    Stephen A. Whitmore*

    NASA Dryden Flight Research Center

    Edwards, California

    Stephanie Sprague t

    University of Kansas

    Lawrence, Kansas

    Jonathan W. Naughton ¢

    University of Wyoming

    Laramie, Wyoming

    Abstract

    This paper presents results of wind-tunnel tests that

    demonstrate a novel drag reduction technique for blunt-

    based vehicles. For these tests, the forebody roughness

    of a blunt-based mcxlel was modified using

    micromachined surface overlays. As forebody

    roughness increases, txmndary layer at the model aft

    thickens and reduces the shearing effect of external flow

    on the separated flow behind the base region, resulting

    in reduced base drag. For vehicle configurations with

    large base drag, existing data predict that a small

    increment in foreN_dy friction drag will result in a

    relatively large decrease in base drag. If the added

    increment in forebody skin drag is optimized with

    respect to base drag. reducing the total drag of the

    configuration is i:x_ssible. The wind-tunnel tests results

    conclusively demtmstrate the existence of a forebody

    drag-base drag t_plimal point. The data demonstrate that

    the base drag coefficient corresponding to the drag

    minimum lies betv, een 0225 and 0.275, referenced to

    the base area. Most importantly, the data show a drag

    _Aerospace Engineer. As_,oclate Fellow. AIAA. 'Student Intern. Department of Aerospace Engineering, Student

    Member. AIAA.

    :IProfessor. Department of Mechanical Engineering. Senior

    Member. AIAA

    Copyright © 2001 bv the American Institute of Aeronautics and Astronautics. Inc. No copyright is asserted in the United Stales under

    Title 17. tIS Code The [IS Government has a royalty-free license to exercise all rights under the copyright claimed herein for Governmental purposcs All other rights are reserved by the copyright owner.

    reduction of approximately 15 percent when the drag

    optimum is reached. When this drag reduction is scaled

    to the X-33 base area, drag savings approaching

    45,000 N (10,000 lbf) can be realized.

    Acronyms

    CFD

    LASRE

    Symbols

    A

    ao, al,a2, a3

    B

    b

    b O, b 2. b 4

    C

    CD

    C D t,,,,,,

    COl,,, rl,¢,,l_

    CD o

    CF

    c f,

    Nomenclature

    computational fluid dynamics

    Linear Aerospike SR-71 Experiment

    slope parameter

    forebody pressure distribution curve-fit

    coefficients

    law-of-the-wake bias parameter

    model span, cm

    base pressure distribution curve-fit

    coefficients

    intercept parameter

    drag coefficient

    base pressure drag coefficient

    forebody pressure drag coefficient

    zero-lift free-stream total drag coefficient

    "viscous" forebody drag coefficient

    local skin-friction coefficient

    American Institute of Aeronautics and Astronautics

  • Cp

    C P fl, rebt, d_

    D'

    dP e

    dx

    dO

    dx

    E[.]

    H

    h base

    i

    L

    N trial_

    I!

    P

    p,, ......(x)

    P_

    _]ratio( X )

    Re L

    Re_

    t"

    U_,

    Uoo

    Ilmm

    .(>9

    +

    II

    X

    pressure coefficient

    average base pressure coefficient

    average forebody pressure coefficient

    section drag, N/m

    longitudinal pressure gradient on model, kPa/m

    longitudinal gradient of the boundary-

    layer momentum thickness

    expectation operator

    wake or boundary-layer shape parameter, H = 8/0

    base height, cm

    measurement index

    model length, cm

    number of repeated pressure scans

    number of data points

    local static pressure, kPa

    free-stream static pressure ratio in wind tunnel

    free-stream static pressure ahead of wind-tunnel model, kPa

    dynamic pressure, kPa

    dynamic pressure ratio in wind tunnel

    free-stream dynamic pressure ahead of wind-tunnel model, kPa

    Reynolds number based on model

    length L

    Reynolds number based on local axial coordinate x

    leading-edge radius, cm

    velocity at the edge of the wake or

    boundary layer, m/sec

    free-stream velocity ahead of the wind-tunnel model, m/see

    minimum velocity in wake velocity

    profile, m/see

    local velocity distribution (in wake or

    boundary layer), m/see

    nondimensional boundary-layer velocity

    independent variable vector

    x

    x i

    Y

    +