15-inch Low Velocity Water Flow Facility
Background Information
This facility was acquired from the Naval Surface Weapons Center-Carderock Div.
(David Taylor Model Basin) in 1997. Prior to 1983 it was a National Oceanic and
Atmospheric Administration (NOAA) calibration facility. The 15-Inch Low Velocity
Flow Facility was designed, built, and tested by Saint Anthony Falls Hydraulic
Laboratory, University of Minnesota, in 1967 for the primary purpose of calibrating
ocean current meters and other ocean instrumentation in laminar flow over the velocity
range between 0.01 to 4.5 knots. After being moved to NOAA, it was subsequently
upgraded to reduce large scale speed fluctuations, improve the flow uniformity
across the jet, and improve the flow measurement accuracy and was recalibrated
(1975-76). Ocean current meters evaluated by NOAA in this flow facility were
reportedly calibrated against a secondary standard meter which previously had
been calibrated with Towing Carriage No. 1 at David Taylor Model Basin.
Description of Facility
The recirculating 15-Inch Low Velocity Flow Facility (Figure 0-1) consists of a
rectangular 2100 gallon, type 304 stainless steel, tank with a surface open to the
atmosphere and a submerged open jet working section. The tank is divided into three
sections - the upstream stilling chamber, the working section, and the downstream
receiving chamber (Figures 0-2a and 0-2b). Water is recirculated through three independent
parallel closed pumping systems. The water is discharged into the upstream stilling chamber
of the tank through vertical perforated standpipes and then through the submerged jet
entrance nozzle into the working section. The water leaves the working section through
an exit nozzle and passes into the receiving diffuser chamber. It then flows out of the
tank through a second set of perforated standpipes, into the pumps, and back to the
upstream still chamber.
To provide adequate velocity control throughout the full range of 0.01 to 4.5 knots (450 to velocity ratio) three different capacity pumps are used with the following ratings:
| Pump Horsepower | Velocity Range |
|---|
| 3/4 HP | 0.01 to 0.2 knots |
| 5 HP | 0.2 to 1.0 knots |
| 20 HP | 1.0 to 4.0 knots |
These pumps can be operated individually or in any combination. The flow through
each of the three piping systems is measured by turbine-type flow meters which have
an accuracy of +0.2 percent over their linear flow range. If more than one pump is
used, the total flow through the nozzle is the sum of the flow through each piping system.
The two small pumps are operated at fixed speeds. When these pumps are used the water
velocity is controlled by the use of variable aperture valves. The pump can be operated
at three different fixed speeds with various preset valve openings to give water velocities
in the range between 1 and 4 knots. For the highest (4.5 knot) water velocity, all three
pumps run at their highest speeds with the control valve set at their maximum openings.
Test Section Dimensions
- Entrance Nozzle Diameter = 15 in. (381 mm)
- Exit Nozzle Diameter = 24 in. (610 mm)
- Distance Between Entrance and Exit Nozzles = 24 in. (610 mm)
- Overall width = 48 in. (1219 mm)
- Overall depth = 60 in. (1524 mm)
- Overall length = 51 in. (1295 mm)
SPEED FLUCTUATION AT TEST SECTION CENTERLINE
Over the velocity range between 0.487 to 4.31 knots the centerline speed can be expected to fluctuate +1 percent.
Over the lower speed range between 0.15 and 0.487 knots, fluctuations are less that 3% except at 0.437 knots where variations up to 3.7% have been found.
 |
 |
 |
| Photograph of the 15 inch Water Flow Facility in the Aerospace and Ocean Engineering Department. |
 |
| Photograph of an airplane model in the 15 inch Water Flow Facility. |
|
|
|
|
AOE Research
|
