Built-Environment
Pressure Scanning - Validating Structural Integrity measurement
THE CHALLENGE
APPLICATION: BUILT ENVIRONMENT WIND TUNNEL TESTING
The Application:
In the development of taller and ever-more complex buildings,
a blend of CFD (Computational Fluid Dynamics) and Wind Tunnel
testing is used to ensure that buildings are structurally safe,
unlikely to cause discomfort or be susceptible to fatigue and
failure. Often theoretical calculations will not be representative
of reality, especially in a highly complex structure. In addition
to the integrity of the structure itself, consideration must
be given to the effects on buildings in the surrounding vicinity.
An initial desk study may determine the necessity for use of
a powerful simulation tool, the Wind Tunnel.
Where wind tunnel testing is required, a highly-detailed scale
model (usually 1/200th or 1/400th, depending on available wind
tunnel constraints) is constructed representing the structure
under test and the buildings and landscape nearby. This is constructed
in a model shop from detailed architectural plans, either by
assembly of sectional fabrications or by 3D printing of models,
which are often mounted on a rotating platform. This platform
can usually be rotated through 360o to assess directional wind
actions that would otherwise be difficult to visualise. The model
is installed in the wind tunnel and subjected to extended testing
over a wide range of wind directions and velocities, often up
to 60 m/s. Data is gathered from numerous locations on the model
to identify any areas that require further analysis or evaluation.
The Measurement
Challenge:
Models vary considerably in design and diversity and may represent
a building, bridge, chimney, sports stadium, offshore platform
or wind turbine tower, where use criteria are being considered.
These models are fitted with numerous sub-1mm pressure tappings
that allow the localised pressure to be accurately measured at,
often, 300-500 measurement points. The model and platform are
usually supported on a multi-directional force balance. The data
is used to determine whether the structure will perform as expected
over a spectrum of wind conditions. Testing can be expensive
and time-consuming, so ensuring efficient gathering of high quality,
valid data - every time - is vital.
Accurate and consistent data from a proven and reliable measurement
device ensures that measurement effects are minimised and the
data truly represents the effects of wind and turbulence on a
full-size structure. Based upon the analysis of the multitude
of data gathered, decisions can be taken as to whether the structure
is acceptable or needs design modifications, such as the addition
of aerofoil sections, vortex disruptors, dampers or other such
devices.
Challenges in the measurement of so many local pressures can
be addressed with the use of pressure scanners which gather vast
amounts of synchronous data very quickly and accurately, transferring
this to a data acquisition system. Self-zeroing scanners with
purge facilities are used to ensure that the data is consistently
and accurately measured with minimal downtime or intervention.
Often the pressure sensors will be regularly checked, calibrated
and zeroed to ensure accuracy and repeatability of the scanned
pressure data in-situ between test points and data frames. Usually
multiple pressure scanners are multiplexed to gather data from
many models and often space constraints may prove to be an issue
in the wind tunnel environment.
Typical
Users:
Government, Commercial and University research establishments
own and operate the wind tunnels. They are usually contracted
to gather appropriate data to present to the structures architectural
team. Some built-environment consultants operate their own wind
tunnels and offer a comprehensive turnkey consultancy for their
clients, providing data and solutions.
THE SOLUTION
SCANIVALVE MPS 4264 PRESSURE SCANNER EXCELS IN THIS APPLICATION
Compact, high performance Pressure Scanner
· Dedicated sensor for each channel (up to 64 channels)
· High Accuracy temperature compensated sensors
· Network-ready Ethernet for quick system integration
· Fast data collection up to 2500 samples/channel/second
· Dynamic Zero Correction for unmatched sensor stability
· IEEE1588-2008v2 PTP compatibility
· Removable headers for installation flexibility
· Integral web-server
· Simple LabVIEW integration
The Scanivalve MPS 4264 pressure scanners are mounted within
the model or under the rotating platform to collect the huge
amount of data being generated under test. Ethernet outputs and
power supplies can be multiplexed through local Scanivalve hubs,
further adding to the compactness of the solution, with one hub
handling real-time synchronous data of over 500 live pressure
measurements.
Often very low wind speeds need to be detected in this application
and this requires scanners with very low range calibrations,
combined with high accuracy, repeatability and sensitivity. Scanivalve
MPS is suitable for use as low as full scale ranges of 4"
H2O, with other custom ranges possible to suit all applications.
High-speed Ethernet data rates of up to 2500Hz/channel, in "Fast
Mode" maximise the amount of valuable data that can be gathered
during a single test run. This data is collected in any common
Engineering Unit, presenting the test engineers with meaningful
data for analysis. Shortening test runs can save the user considerable
time and cost.
Removable headers on the scanner mean that 64 tubes be conveniently
connected before the scanner is installed in the tunnel and adds
to the versatility of using one scanner on multiple models, avoiding
unnecessary downtime during test periods. The headers can remain
fitted to the model for later use.
Integration of the Scanivalve MPS is quick and simple. The integral
web-server allows the scanner to be set up from a PC and further
integrated into a LabVIEW package, avoiding the need for any
separate signal converters or marshalling cabinets.
Where low channel counts are required and space is not an issue,
users look to the Scanivalve DSA, where 16 channels of data can
synchronously be measured and transferred via Ethernet. Again,
these can be "daisy chained" via Ethernet and time-stamped
allowing highly accurate synchronisation of data from many compatible
measurement sources.
In addition to a versatile range of high performance pressure
scanners, Evolution Measurement offer the widest range of accessories
including pressure tubulations, tubing and connectors that enable
the test model to be commissioned very quickly and efficiently.
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October 2017
