Aerospace & Defense Technology - April 2021 - 30

Tech Briefs

reaction time) following rehabilitation
(Figure 2) and were within a normative
range (indicated by the orange lines).
Symptoms: Initial results indicated
improvement in symptoms over time
for the participants in the study. Preliminary qualitative assessment of descriptive data also suggests a decrease in the
dizziness handicap inventory (DHI)
total score following rehabilitation.
Preliminary retest-reliability analysis
of wearable sensors measuring head
movement: Eighteen healthy controls
were tested at three different time points
on a series of conditions involved in the
rehabilitation program. A total of eight
different conditions were tested:

* 2 Standing Balance: horizontal and vertical, eyes closed
* 2 Vestibular-Ocular Reflex: horizontal
and vertical, eyes fixated while head
moves
* 2 Visual Motion Sensitivity: horizontal
and vertical, eyes and head move together
* 2 Walking (dynamic) Balance: horizontal and vertical, eyes and head move
together
Participants wore an inertial sensor
on their forehead and sternum, reflecting what is used during the rehabilitation program. One of the research
team's physical therapists instructed
participants which condition to per-

form for 30 seconds. For each trial, the
two measures collected were the rotational velocity and range of motion
(RoM) for the forehead and sternum in
the primary movement axis.
This work was done by Dr. Laurie King
(PI); Dr. Lucy Parrington; Dr.Kody Campbell; and Shelby Martin of Oregon Health
& Science University and the Veteran Affairs Portland Health Care System for the
Army Medical Research and Materiel
Command. For more information,
download the Technical Support
Package (free white paper) at
www.aerodefensetech.com/tsp under
the DAQ, Testing & Sensors category.
ARL-0237

Characterization of Turbulent Unsteady Separation Using
Photonic Micro-Skin Friction and Wall Pressure Sensors
Investigating the structure and dynamics of unsteady/transient separated turbulent boundary layers
using a photonic skin friction and wall pressure sensor.
Army Research Laboratory, Research Triangle Park, North Carolina

T

he goal of this research was to investigate the structure and the dynamics of
unsteady/transient separated turbulent
boundary layers for 4¥103 < Re< 1.4¥104.
Central to the study is the characterization
of the streamwise and spanwise fluctuating skin friction and wall pressure fluctuations in and around the separation zone.
During the initial stage of the project,
a photonic skin friction and wall pres-

sure sensor will be implemented to
measure directly and at the same spatial
location the unsteady skin friction and
wall pressure. The photonic sensor will
be an extension of previous sensor development efforts, which were limited
to low to moderate-frequency wall shear
stress measurements.
The proposed work will be carried out
in the specially designed test section of

a)

b)

Optical
fiber
Photodiode

Photodiode output

δλ

Scanning
laser

λ
Schematic of the WGM sensor and its output

30

www.aerodefensetech.com

Cov

ToC

a low-speed wind tunnel. There is a
need of reliable wall shear stress sensors
to (a) corroborate existing theories and
(b) provide precise two-dimensional,
skin friction data well-resolved in time
and space for the development and validation of models that can predict the
onset and extent of stall in transient
separated turbulent boundary layers.
The main goal is to generate high fidelity data, taking into account the evolution of the boundary layer from its origin, and to identify key issues and
challenges regarding current understating of unsteady separated turbulent
boundary layer flows. Detailed velocity
mapping will be carried out in and
around the separation region using hotwire anemometry, laser doppler velocimetry (LDV) and particle image velocimetry (PIV). These detailed velocity
field measurements, together with the
unsteady skin friction and wall pressure,
will fully characterize the unsteady separated flow region. In addition, the extensive data collected (velocity, turbulence
quantities, wall shear stress, wall pressure, and higher order moments) will be
analyzed in a systematic way to allow for
Aerospace & Defense Technology, April 2021


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Aerospace & Defense Technology - April 2021

Table of Contents for the Digital Edition of Aerospace & Defense Technology - April 2021

Aerospace & Defense Technology - April 2021 - Intro
Aerospace & Defense Technology - April 2021 - Sponsor
Aerospace & Defense Technology - April 2021 - Cov1
Aerospace & Defense Technology - April 2021 - Cov2
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Aerospace & Defense Technology - April 2021 - Cov3
Aerospace & Defense Technology - April 2021 - Cov4
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