Case Studies
College Park, MD - April 2001
View
AVI movie (1.8 MB)
Preston B. Martin, a graduate research assistant pursuing a Ph.D. in
Aerospace
Engineering at the University
of Maryland, uses Tecplot because it is the only product on the market
that allows him to efficiently create and present presentation-quality
plots ranging from simple X-Y graphs to powerful 3-D visualisation of
large data sets.
Working with Gregory J. Pugliese, Graduate Research Assistant, and Dr.
J. Gordon Leishman, Professor of Aerospace Engineering, Martin is part
of a larger group of faculty and graduate students specialising in education
and research into experimental rotorcraft aerodynamics. The goal of
the project associated with their plot, "Helicopter Rotor Wake in Hover,"
is to investigate the flow physics associated with the vortex wake of
a hovering helicopter rotor. A secondary goal is to assess the advantages
and limitations of phase-resolved stereo PIV (Particle Image Velocimetry)
in resolving the rotor tip vortex structure and its evolution in time.
 "Hovering
Helicopter Rotor Wake" is a 3-D plot also known as a "fence" plot. The
single rotor blade is shown as well as the motor and counterweight. The
rotor is thrusting upwards and the flow passes down through the X-Y plane.
Trailing from the tip of the blade is a vortex filament shown by the red
line. In contrast to a fixed-wing aircraft, the vortices trailing from
a hovering helicopter remain in close proximity to the aircraft lifting
surfaces. Slices of the flow field (PIV image frames) are shown at various
asimuthal locations with respect to the rotor blade. In each frame contours
of vorticity are plotted. The vorticity is computed from the 3-D measurements
of the velocity field. Plots associated with "Helicopter Rotor Wake in
Hover" are of experimental measurements.
The data was acquired during a cooperative effort between the University
of Maryland and TSI, Inc. The TSI Power View PIV System integrates Tecplot
into its Insight software so that the results of many velocity field measurements
are easily combined into a summary figure such as this. A custom Tecplot
macro is used in the data reduction done by Dr. Steve Anderson of TSI.
 Mr.
Martin says the plot is surprisingly easy to make. The INSIGHT software
and Tecplot macro provide three components of velocity (plus other properties)
at each point in the image frames (R-s plane). Each frame is acquired
at a specific asimuthal position with respect to the blade. Each frame
is imported into Tecplot as a separate sone. Using the equation editor,
the rotating (R-s) coordinate system is transformed into the fixed (X-Y-s)
system. Seven contour maps of vorticity are created (one for each sone)
with XYs coordinates. The vortex filament (red line) is displayed as a
scatter plot with no symbols.
The blade is generated by importing a NACA 2315 airfoil and then copying
and scaling it into an ordered sone. The rest of the blade and the motor
are made by creating rectangular and cylindrical IJ ordered sones. Their
sones are then displayed as light-source shaded surfaces.
TIPS: Tecplot EPS (Encapsulated PostScript)
files can easily be imported into and integrated with text and equations
in LaTeX
or distilled into PDF.
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