Complex Flow
Measurements in the INL MIR Facility using PIV
These experiments were performed at
the Idaho National Laboratory (INL) Matched
Index of Refraction (MIR)
flow system in support of the KNERI project "Advanced computational
thermal fluid physics (CTFP) and its assessment for light water
reactors and supercritical reactors." The goal of the
experimental
portion of the study is to answer the scientific needs, guide code
development and assess code capabilities for treating the generic
forced convection problems in ALWRs and SCRs. The data
provides
benchmark velocity and turbulence measurements for the portion of the
study dwelling on forced convection in complex reactor
geometries. For
the representative geometry, the experimental model provides a generic
simulation of flow along fuel rods separated by periodic grid spacers
as in an SCWR concept.
Download the report (MS Word)
Barton L. Smith, PI
The model represents two fuel rods from this core
The model is a two-rod configuration which was selected to include some
flow features of thermal SCWR concepts suggested by Forschungszentrum
Karlsruhe, INL and Prof. Oka of
U. Tokyo. The geometry is scaled to be six to seven times larger
than
typical fuel pins. The rod diameter is 2.50 inches (63.5 mm) and
the
axial pitch of the ring-cell spacers is 17.5 inches (444.5 mm).
The
outer diameter of these spacers is 3.025 inches (76.8 mm) so the
nominal dimensions of the rectangular flow channel containing the
simulated fuel rods are 3.025 by 6.050 in^2 (76.8 X
153.7 mm^2). Consequently, the pitch-to-diameter ratio (p/D) is
about
1.21 for the simulated fuel rods. These spacers have lengths of
1.75
inches (44.5 mm) and inside diameters of 2.85 inches (72.4 mm).
In the
measuring region the rods and side and end walls are fabricated of
quartz to match the refractive index of the light mineral oil employed
as the fluid.
Model Cross Section
Measurements of velocity are made using a state-of-the-art Particle
Image Velocimetry (PIV) system by LaVision Inc.
PIV generates a planar 2-component velocity vector field at an instant
in time. The flow is seeded with 10 micron diameter silver-coated
glass spheres. Each measurement requires a pair of digital images of
these particles. The seeds are chosen to be small and neutrally
buoyant, and are illuminated by a laser sheet. Cross-correlations are
performed on small pieces (interrogation windows) of the image pairs to
determine the most likely velocity vector in the plane for that
sub region. The interrogation window initially consists of 64
pixels in each direction and these may overlap one another by 50%. The
camera is placed perpendicular to the laser sheet. The resolution and
accuracy of the result can be improved by shifting the 2nd window in
the estimated direction of the velocity vector by a known amount. A
first pass with no shift provides the estimate of how much to shift the
window on the second pass. Multiple passes make it possible
to reduce the interrogation windows to 16 pixels, quadrupling the
spatial resolution. Data were acquired at two streamwise (x)
stations
and 33 spanwise (z) planes in between two spacers. Each plane
consists of 400 samples.
Results
The entire set of statistics is a 1.6 million data point, 155 MB ASCII
(TechPlot format) file that you can
download here
if you have the
network muscle.
Some feedback that I've been getting is that no one is interested in
plowing through a file that size. The three files below are y-z
planes at full resolution for four locations and are in the same
format as the large file.
X_32MM.txt
X_80MM.txt
x_200mm.txt
X_320MM.txt
The file
has columns of x, y, z, U, V, u'u', v'v', and u'v'. The
streamwise (x) origin is at the
downstream end of the upstream spacer. The domain extends
slightly upstream of that point. The second spacer is at x = 400
mm. The spanwise (z) origin is
centered on the lower rod. The cross stream (y) axis origin is
centered in the channel. Note that the rods may not be precisely
vertically centered in the channel due to deformation of the rod
spacers. Other known issues
with this data:
1) While acquiring the data, we were able to precisely find the center
of the lower rod. Determining the locations of the spanwise edges
of the channel was not as easy. You will notice that data at the
extreme z values is sketchy, possibly due to the laser sheet being
blocked or refracted.
2) Data taken looking through the cylinders (i.e. large positive values
of z) are distorted.
3) "Masks" were applied to the raw data at the locations of the rods,
spacers, and the channel walls. These regions will have the value
0.
Some jpg images and avi animations
of the mean streamwise (U) and cross-stream (V) velocity as well as the
TKE are shown below. Blue regopms are masked, and are presumably
solid surfaces. The fence furthest right (upstream) is partially
blocked by the upper spacer, which was not made from index-matched
material.
Streamwise Velocity (U)
Cross-Stream
Velocity
TKE
U_spanwise_iso.avi
U_streamwise_iso.avi
U_streamwise.avi
V_spanwise_iso.avi
V_streamwise_iso.avi
V_streamwise.avi
TKE_spanwise_iso.avi
TKE_streamwise_iso.avi
TKE_streamwise.avi
