Spatial Variation of Currents Generated in the
FloWave Ocean Energy Research Facility
Donald Noble∗1, Thomas Davey∗2, Helen Smith†3, Panagiotis Kaklis‡4, Adam Robinson§5, and Tom Bruce§6
∗FloWave Ocean Energy Research Facility, University of Edinburgh, UK
†College of Engineering, Mathematics and Physical Sciences, University of Exeter, Penryn Campus, UK
‡Naval Architecture, Ocean and Marine Engineering, University of Strathclyde, UK
§Institute for Energy Systems, School of Engineering, University of Edinburgh, UK
1D.Noble@ed.ac.uk 2Tom.Davey@ed.ac.uk 3H.C.M.Smith@exeter.ac.uk
4Panagiotis.Kaklis@strath.ac.uk 5Adam.Robinson@ed.ac.uk 6Tom.Bruce@ed.ac.uk
Abstract—FloWave is a state of the art test facility which can
produce combined waves and currents from any direction in a
circular tank. Characterisation of this new facility is ongoing,
with initial results from the ﬂow generation measurements
presented. This is a complex problem, considering different input
velocities, 3D spatial variability of the ﬂow in the X, Y, &
Z directions, as well as temporal stability of the ﬂow. In a
circular tank, production of uniform ﬂow is a non-trivial problem,
however this has been achieved across a large test area using
precise control of the individual drive units and specially designed
turning vanes. This allows the testing of device models and small
arrays, in controlled realistic sea conditions, prior to deployment
Index Terms—Tank testing, tidal current, vertical ﬂow proﬁle,
spatial variation, measurement, characterisation
Physical scale model testing is an essential element in
the development of marine renewable technologies and tech-
niques. Laboratory testing provides a repeatable, controlled,
low-risk environment where technological concepts and oper-
ational techniques may be developed .
FloWave is a state of the art ocean energy research facility,
designed to provide large scale physical modelling services to
the tidal and wave energy sector. It has the unique ability
to provide complex multi-directional waves combined with
currents from any direction in the 25 m diameter circular tank.
As part of the commissioning and characterisation process
for this new facility it is important to investigate the per-
formance characteristics of the waves and current generation
capability, both individually and in combination. It is also
important to understand the shape and size of the usable test
area. The focus of this paper is on the generation of currents,
and speciﬁcally looking at spatial variation thereof.
A. About the facility
FloWave is a circular combined wave and current test
tank. Wavemakers are located around the entire circumference,
with impellers to drive the current recirculation mounted in a
plenum chamber below the test area, as shown in Fig. 1.
The tank is optimised for waves of around 2 s period, and is
capable of generating currents upwards of 1.6 m/s. This offers
15m Ø ﬂoor
25m Ø tank
Fig. 1. Schematic of FloWave in plan and oblique section showing:
(A) Wavemaker paddles around circumference (168 Nr)
(B) Turning vanes and ﬂow conditioning ﬁlters
(C) Current drive impeller units (28 Nr)
(D) Buoyant raisable ﬂoor (15 mØ) below test area
(E) Idealised streamlines of ﬂow across tank ﬂoor
the ability to model metocean conditions for most renewable
energy devices at a typical scale of between 1:20 and 1:40 .
There is a 15 m diameter buoyant ﬂoor in the centre of the
tank, which notionally represents the test area. This ﬂoor can
be raised above the water level to facilitate model installation
and reconﬁguration as required, then submerged to the 2 m
Around the circumference of the tank there are 168 active-
absorbing hinged wavemakers. These are able to generate
regular and irregular waves, both long-crested and multi-
directional, as well as complex multi-modal sea states with
waves from multiple directions.
Currents are generated by 28 impeller units mounted in the
plenum chamber below the test ﬂoor. Each of these contains
a single 1.7 m diameter low-solidity 5-bladed symmetrical
impeller, driven by a 48 kW motor. Turning vanes mounted
below and in front of the wavemakers direct the current
across the tank , as shown in Fig. 1. These turning vanes
incorporate porous screens to provide ﬂow conditioning and
prevent debris ingress to the plenum chamber.
Creating a horizontally uniform current in a circular tank is
a non-trivial matter, requiring precise control of the individual
impellers . In summary, the impeller units on either side
of the required current direction on both the upstream and
downstream side of the tank are driven at varying speeds to
produce the required current corresponding to the desired test
velocity. The control system for the impellers includes the
facility to change the direction of the current during the test,
either to an arbitrary angle or rotating by a set angle every
minute. This capability allows for the simulation of cross-
currents, or a tidal ellipse, without having to reposition the
B. Device Testing and Scales
The development of new technologies generally follows an
iterative process, reﬁning and developing the initial concept,
towards the goal of producing a viable product. A ﬁve-stage
structured development plan has been developed for for wave
energy systems , and this can be related to the Technology
Readiness Level (TRL) concept developed by NASA . With
appropriate modiﬁcations, this process is also applicable for
other marine renewable energy devices plus the supporting
infrastructure, as captured by the EquiMar Protocols . The
development stages are reproduced in Table I, together with
typical scales for marine renewable energy device testing. It
is important to note that development is not a linear ‘once-
through’ process, and that multiple loops through the different
stages are typical.
Tank testing usually ﬁts into the early development stages,
proving preliminary concepts with small scale models and
reﬁning designs with larger models that are more detailed or
more representative, before moving onto open water testing.
As noted above, the FloWave facility is optimised for models
around 1:40 to 1:20 scale, and so can be used for both concept
and design validation. Depending on the speciﬁcs of the device
and the constraints of the tank, both physical as well as the
wave and current generation, it is possible to test at a broader
range of scales.
It is not possible to accurately scale all physical phenomena
by the same factor when undertaking physical model testing
at a scale other than unity . Given that gravitational forces
are likely to be dominant in problems involving a free surface
with waves, Froude scaling is used for most of the testing at
FloWave. This is one of two dimensionless scaling factors
commonly used in tank testing, the Froude and Reynolds
numbers, respectively the ratios between inertia/gravity forces
and inertia/viscous forces. In tank testing, both the small scale
model and full scale prototype are immersed in the same ﬂuid
and are subject to the same gravitational force, therefore it is
not possible to satisfy both relationships simultaneously.
Testing closer to full scale reduces the impact of these
scaling effects, resulting in more accurate and representative
testing. It is also difﬁcult to include power take off and control
systems in small models. Therefore testing physical models at
a larger scale is a valuable stage in the development process
between small scale models and open water testing.
Most marine renewable energy devices are intended to be
installed in arrays, with multiple devices in close proximity.
Therefore modelling inter-array effects is an important part of
the design process, e.g. assessing the impact on power capture.
The physical size of the facilities used to test marine renewable
energy devices will place limits the number of individual units
that can be tested in an array conﬁguration. This is typically
in the region of 2 to 7, but will depend on the shape and size
of both the device and the test facility.
The results from physical model testing can then be used to
validated computer numerical models. These computer models
are typically used to simulate either performance at the level
of an individual component or device, or the interactions
between multiple devices which can be extended to cover large
arrays of devices in a variety of different conditions, subject
to sufﬁcient computational resource.
II. EX PE RI ME NTAL ME TH OD
A series of tests were conducted to characterise the per-
formance of currents generated in the facility. These were
conducted with only the required measurement equipment in
the tank, to avoid potential distortion of ﬂow around a device
FIV E STAGE S OF DE VE LOP ME NT,FO R WAVE AN D TI DAL E NER GY D EVI CE S
Stage TRL Nominal scale Typical infrastructure
1. Concept Validation 1-3 Small scale (c. 1:100-1:25) University laboratory
2. Design Validation 3-5 Larger scale (c. 1:25-1:10) Industrial scale laboratory
3. Systems Validation 5-6 Sub-prototype size (c. 1:4) Benign test site
4. Device Validation 7-8 Approaching full size (c. 1:1) Exposed test site
5. Economics Validation 9 Full size, small arrays Commercial site
SIX DIMENSIONS OF VARIABILITY IN VELOCITY WITHIN THE FACILITY
Dimension of velocity variability Symbol
Reference velocity magnitude U0
Spatial variation across the test area X, Y
Vertical (shear) proﬁle of velocity Z
Different current directions θ
Temporal variations in current t
For effective testing, controlled steady ﬂows need to be
provided in the tank, with a vertical proﬁle representative of
real sites. It is also important to understand any variation in
velocity throughout the test volume, so that the correct velocity
can be speciﬁed for any model position.
As part of previous commissioning work, a calibration of
velocity in the tank against primary control motor rpm was
undertaken. This showed a linear relationship, and was used
to set input velocities for these tests.
A. Test Plan
An initial measurement and characterisation program focus-
ing on the performance of generating currents in the tank was
developed, concentrating on the test volume at the tank centre.
Characterisation of the FloWave facility is a complex multi-
dimensional problem, as illustrated in Table II.
The ﬁrst phase of testing, presented here, considers the
spatial variability of the generated current over a range of
baseline velocities. Measurements were made of the vertical
proﬁles of velocity, and of the spatial variation of velocity
across the plan area of the tank. These cover the horizontal
components of velocity for the vertical plane (X−Z) and
horizontal plane (X−Y) for different input velocities (U0).
The tank is designed to be rotationally symmetrical, and there-
fore current direction is not discussed here. Measurement of
temporal variation and turbulence is ongoing, but initial results
showing the temporal stability of the facility are presented.
1) Tank Coordinates and Terminology: The tank co-
ordinate system is Cartesian, as shown in Fig. 2, with the
origin at the centre of the tank on the test ﬂoor, and Z
positive upwards. Waves and currents are speciﬁed as positive
in the direction of the vector, as opposed to the nautical
convention of waves coming from a direction. Currents ﬂow
from upstream to downstream, with left and right assuming a
viewpoint looking downstream in the direction of the current.
B. Test method
All tests were run with a current direction of 0◦, i.e. ﬂow
in the +Xdirection. At least 10 minutes was allowed for the
current to fully stabilise following changes in velocity before
taking measurements of the steady state condition. The results
from the temporal stability test, Section III-A, demonstrates
that this is sufﬁcient.
For testing with only current, the wavemakers are powered
down and rest on their backstops. This results in the water
level in the tank dropping by approximately 80 mm. This
Control Desk 1
15mØ raisable floor
Fig. 2. Tank reference coordinates
conﬁguration was used for all tests, with a water depth in
the test section of 1.93 m. Water temperature during the tests
was approximately 15◦C.
1) Measurement of vertical proﬁles: Vertical proﬁles of
velocity were measured to determine both the variation in
velocity with depth and input velocity (U0−Z) and also the
spatial variation in velocity proﬁles across the tank (X−Z).
Tests were undertaken at a range of nominal target veloc-
ities, speciﬁed for the centre of the tank 1.5 m above the
ﬂoor. These were the tank’s design velocity speciﬁcation of
0.8 m/s, a typical low end test velocity of 0.2 m/s, and three
additional intermediate velocities of 0.42 m/s, 0.5 m/s, and
0.58 m/s. The preliminary calibration of velocity in the tank
against primary control motor rpm was used to set these
velocities. The variation in the vertical proﬁle with input
velocity was measured at the tank centre throughout the whole
The development of the vertical proﬁle, from the turning
vanes across the usable test area, was characterised by a
vertical slice along the ﬂow direction. A series of seven
velocity proﬁles were measured at 2.5 m horizontal spacing
along the direction of current, covering the full diameter of the
raisable ﬂoor. Velocity measurements were taken throughout
the whole depth of the water column at each location.
For these tests, a Valeport model 801 single-axis electro-
magnetic (EM) current meter with a ﬂat-type sensor head
for which the sensing volume is a cylinder of approximately
20 mm Ø ×10 mm high. . This was mounted to a height-
adjustable bracket ﬁxed to the gantry across the tank, with the
sensor cable helically wrapped around the supporting pole to
reduce the effects of vortex induced vibration. The raw ASCII
output from the Valeport control display unit was logged
directly to a laptop for further processing.
To measure each vertical proﬁle, the sensor was lowered to
the base of the tank (Z = 0.05 m), and data logged at 2 Hz for
60 seconds. It was raised by 0.05 m to the next measurement
position, and the process repeated. In total 38 measurements
were taken for each proﬁle (Z = 0.05 m to Z = 1.90 m). Repeat
measurements conﬁrmed the temporal stability over the time
taken to measure each proﬁle. Vertical position was measured
with a 0.5 mm graduated scale ﬁxed to the height adjustable
bracket. The gantry position was measured with a laser range
ﬁnder. A small degree of lateral vibration was observed during
some tests, with the sensor head moving by approximately
±10 mm at around 1-2 Hz, however it is not anticipated that
this will affect the averaged inline velocity.
2) Measurement of spatial variability in plan: To determine
the planar extents of the usable test area, plus any variation
in velocity therein, the velocity was measured on a number of
horizontal transects across the tank, both along and transverse
to the ﬂow direction. This was conducted at three nominal
velocities, 0.2 m/s, 0.5 m/s, and 0.8 m/s.
These tests used two separate 2-axis EM current meters,
Valeport model 802 ﬁtted with a 32 mm discus-type sensor
head, for which the sensing volume is a cylinder of approxi-
mately 32 mm Ø ×16 mm high . The two sensors were
ﬁxed 2 m apart onto a carriage mounted frame that could be
moved along the gantry to set the Y-position in the tank. The
X-position in the tank was adjusted using translation of the
gantry as before. The sensor height was ﬁxed at 1.5m above
the ﬂoor for all tests (i.e. 0.43 m below the water surface),
with the supporting frame mostly above the water level.
At each data point the raw ASCII output was recorded at
8 Hz over a 60 s period. The mean uand vhorizontal velocity
components, plus the horizontal velocity vector ~
U, were then
calculated. The measured data points were interpolated to a
regular 0.1 m grid in MATLAB using a triangulation-based
natural neighbour approach.
3) Measurement of long duration temporal variation: As
a ﬁrst measure of the temporal stability of the tank, the
current ramp-up from rest and the subsequent stable ﬂow was
measured for a period of 20 minutes. The measurement was
taken at the tank centre at 1.5 m above the ﬂoor, with a nominal
velocity of 0.48 m/s at 50 rpm.
This longer duration temporal variation test was undertaken
in a similar manner to the spatial plan tests, with a single
Valeport 802 discus-type sensor. At the start of the test the
primary drive motor was increased to 50 rpm in 5 steps over
approximately 1 minute, and then held at this speed throughout
III. RES ULTS
A. Temporal variability
Conditions in the tank need to be consistent over the
duration of the test and repeatable between tests, in order to
undertake useful model tests. The normalised velocity proﬁles
in Section III-B show that conditions in the tank are self-
similar and scaleable between different velocities.
As an example of the temporal stability of the tank, Fig. 3
shows a test where the motors were ramped up to 50 rpm and
held at that speed for 20 minutes. During this test, velocity
in the centre of the tank increases asymptotically, to within
10% of target after approximately 2 minutes, and reaches a
stable velocity after 5 or 6 minutes. The ﬂow remains stable
thereafter, with only minor ﬂuctuations.
B. Variation of Vertical Proﬁle with Velocity
Vertical proﬁles of velocity were measured at the centre of
the tank for ﬁve nominal input velocities, shown in Fig. 4. The
drive motors have a linear relationship between rpm and ﬂow,
which is conﬁrmed by these tests, the depth-averaged velocity
increases in a linear manner with nominal velocity, see Fig. 5.
The depth-averaged standard deviation increases as a power
law, with an exponent just below unity.
The shape of the vertical proﬁle of velocity in the tank
is almost independent of average velocity, as shown by the
similarity between the normalised velocity plots in Fig. 6a.
This is most closely described by a 1/15th power law, Fig. 6b,
although it is not dissimilar to other proﬁles used within the
0 2 4 6 8 10 12 14 16 18 20
Measured data points (8Hz)
10s moving average
60s moving average
0.48m/s nominal velocity
Fig. 3. Temporal stability test, showing velocity at the centre of the tank 1.5 m above ﬂoor, over the 20 minute test duration
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
25 rpm 46 rpm 54 rpm 61 rpm 82 rpm
Fig. 4. Vertical velocity proﬁles measured at tank centre for different input
drive motor rpm, with error bars showing ±1σdeviation, and water surface
at 1.93 m shown dashed grey
Primary Control Motor RPM
0 10 20 30 40 50 60 70 80 90
Depth Averaged Velocity [m/s]
Depth Averaged Standard Deviation
Fig. 5. Depth averaged velocity and standard deviation against primary control
motor rpm, showing linear relationship
C. Development of vertical proﬁle along ﬂow direction
The vertical proﬁles across the 15 m diameter ﬂoor were
used to construct a vertical slice through the tank, parallel to
the direction of ﬂow and passing through the centre, Fig. 7.
This shows an increase in ﬂow speed towards the centre of
the tank, a result of the converging nature of the ﬂow in this
region that is required to create uniform ﬂow in a circular tank,
as discussed above.
There is a signiﬁcant velocity deﬁcit in the lower part of
the water column at the extreme ‘upstream’ edge of the ﬂoor
(X = -7.5 m). Above this is a jet of higher velocity ﬂow,
approximately 0.6 m to 1.0 m above the ﬂoor. Both of these
features are clearly apparent in the vertical proﬁle Fig. 8a, and
are a result of the current rising at an angle from the turning
Close to the centre of the tank, in the middle of test area, is a
relatively uniform section of ﬂow. This covers approximately
X = -2.5 m to X = +5.0 m in the lower part of the water
column, and X = ±10 m in the upper half of the water column.
Normalised Velocity [U/U]
0.7 0.8 0.9 1 1.1
Normalised Depth [z/h]
0.7 0.8 0.9 1 1.1
Fig. 6. Normalised vertical velocity proﬁles measured at tank centre, showing
a) different input drive motor rpm, and b) these proﬁles overlain with various
At the ‘downsteam’ edge of the ﬂoor (X = 7.5 m) the velocity
throughout the water column reduces, as a result of the ﬂow
diverging into the tuning vanes around that half of the tank.
D. Spatial variability of velocity across the plan area
The spatial variation in ﬂow across the central section of the
tank is shown in Figs. 9 and 10 for three nominal velocities.
This shows the velocity magnitude to be broadly symmetrical
about the current ﬂow direction. It is also relatively consistent
(around ±10% or ±0.05 m/s) across a test area approximately
8 to 10 m wide and 6 m long, which is offset about 1 m
downstream of the tank centre.
The measurements show a slight asymmetry in the velocity
magnitude, with marginally faster ﬂows (<5%) on the right
hand side of the ﬂow. There is also marginally slower ﬂow
(≈5%) along the centreline of the current near the middle
of the tank. The velocity vector plots in Fig. 11 show that
an acceptable horizontally uniform ﬂow can successfully be
created in the circular tank, with only a slight directional bias
around the outside of the raisable ﬂoor.
Physical model testing is a well-established practice in
the development of new technologies. Experiments in a tank
facility offer more control over test parameters than conducting
open water testing, however this requires the facility to be well
calibrated. Dedicated test facilities are also able to produce the
desired conditions on demand, rather than being dependent on
the vagaries of the weather.
A. Velocity Calibration and Stability
Measured velocity at a reference point in the tank needs
to be calibrated against the control input, the primary drive
motor rpm. Together with a transfer function based on the
velocity variations measured throughout the tank, this allows
a prescribed velocity to be produced at any particular location
in 3D space above the test area ﬂoor.
The depth averaged velocity in the tank has been shown to
vary linearly with drive motor rpm. This allows for accurate
control of the reference velocity in the tank. Initial test results
demonstrate that the tank can also produce a stable current
over time. There are minor ﬂuctuations around this stable
current that may be due to large scale turbulent structures,
and further work is required to investigate this.
B. Velocity Shear Proﬁle and Comparison with Theory
The 1/7th power law is frequently used to describe the
vertical distribution of velocities ﬂuid ﬂow. This was originally
developed to model boundary layer effects in turbulent pipe
ﬂow, however it is often applied to tidal ﬂow in coastal regions.
Other power law proﬁles, such as 1/10th, are also commonly
used. Guidance by the UK Health and Safety Executive 
suggests the following discontinuous function for the velocity
proﬁle for coastal seas around the UK with a uniform velocity
in the upper half of the water column.
Uis the mean volumetric ﬂow velocity, hthe water
depth, and zthe position in the water column.
In reality, ﬂow in highly energetic tidal ﬂows is far more
complex than a simple vertical shear proﬁle, with signiﬁcant
effects from large scale turbulent eddies and bathymetry
effects. Measurements undertaken at the European Marine
Energy Centre (EMEC) tidal test site at the Fall of Warness
as part of the ReDAPT project show complex shear proﬁles,
with the velocity at the surface signiﬁcantly less than at points
lower in the water column for some states of the tide , .
Fig. 7. Vertical section across the tank in line with ﬂow, for nominal 0.8 m/s input velocity. Flow direction left to right.
0 0.4 0.8
0 0.4 0.8
0 0.4 0.8
0 0.4 0.8
0 0.4 0.8
0 0.4 0.8
0 0.4 0.8
Fig. 8. Vertical velocity proﬁles across the tank in line with ﬂow, at X coordinates noted. Nominal 0.8 m/s input velocity, with depth averaged velocity given
for each proﬁle location. Error bars show ±1σ.
Fig. 9. Variation in velocity across test area for horizontal plane 1.5 m above ﬂoor. Three different nominal input velocities: a) 0.2 m/s b) 0.5 m/s c) 0.8 m/s,
with ﬂow direction from left to right. Measurement points indicated by + marker, 15 m diameter raisable ﬂoor shown as a grey circle
Fig. 10. Variation in velocity, relative to nominal input, across test area for horizontal plane 1.5 m above ﬂoor. Three different nominal input velocities:
a) 0.2 m/s b) 0.5 m/s c) 0.8 m/s, with ﬂow direction from left to right. Nominal test area shown by black dashed rectangle, 15 m diameter raisable ﬂoor
shown as a grey circle.
-8 -4 0 4 8
Tank Y coordinate [m]
Tank X coordinate [m]
-8 -4 0 4 8
-8 -4 0 4 8
Fig. 11. Velocity vectors across test area for three different nominal input velocities: a) 0.2 m/s b) 0.5 m/s c) 0.8 m/s. Vector length is proportional to velocity
at measurement point relative to input velocity. Flow direction from left to right. Nominal test area shown by grey dashed rectangle, 15 m diameter raisable
ﬂoor shown as a grey circle.
The ﬂow proﬁle at FloWave was found to be close to a
1/15th power law, which is reasonably similar to observed
and theoretical proﬁles. By increasing the roughness on the
test ﬂoor, and/or using different spatial locations in the tank,
it should be possible to model a range of different ﬂow proﬁles.
This offers the ability to model differential loading at varying
water depths, something that is of concern for developers of
The development of the shear proﬁle across the tank, shown
in Fig. 7, follows the trend of previous work on inlet design
for combined wave and current test facilities . This work
was undertaken in a ﬂume channel, with a range of inlet vane
angles, so is not directly comparable to FloWave. However
the jet of water above mid depth with a region of slower
ﬂow below was clearly present in those tests as well as the
accompanying CFD model.
C. Spatial Variability and Usable Test Area
The usable test area in the tank is at least 50 m2, which is
large enough for testing small arrays of devices. Whilst there
is some variation in velocity over this area, it is only around
10% in plan and in depth. Knowing this baseline variation
allows a reference velocity to be calculated at any point in
the tank, or device in an array. Theoretical forces can then
be predicted with a computer model and compared to those
measured, for example. In addition, velocity measurements are
typically made at a point close to the model during testing.
D. Flow Field in a Circular Tank
The tests undertaken show that across the test area, the ﬂow
is acceptably straight and horizontally uniform. This allows
consistent testing over a large area of the tank, for example, to
investigate impacts between small arrays of devices. However
the conﬁguration of a circular tank, with circumferential wave-
makers and impeller drive units below the ﬂoor, by necessity
leads to non-uniformities in the current ﬂow ﬁeld around
the turning vanes. The extent of non-uniform ﬂow is limited
through careful design of the turning vanes and drive motor
Full characterisation of the variation in ﬂow ﬁeld allows
for a greater variety of ﬂow conditions to be modelled in the
tank, making use of the velocity gradients that exist in speciﬁc
locations away from the central test area. A circular tank also
has the signiﬁcant advantage of being able to create complex
multi-directional and multi-modal sea states, as discussed in
The FloWave facility offers the ability to test a wide variety
of realistic sea conditions prior to deployment of prototype
devices at sea, provided that the generation of these conditions
in the tank is well understood. Results of the initial character-
isation programme show that steady currents can be generated
in the tank, with a large uniform test volume in the centre of
•The vertical ﬂow proﬁle in the tank is not particularly
dependent on the input velocity, and can be approximated
by a 1/15th power law. This is a more uniform ﬂow than
the 1/7th and 1/10th proﬁles commonly used to represent
•The ﬂow over the test area is uniform within 10% or
0.05 m/s over an area greater than 50 m2around the
centre of the tank. The shape and size of this test area
is close to that predicted by the CFD modelling and
experimental tests carried out during the design phase.
•The velocity is broadly symmetrical on both sides of the
tank about the ﬂow direction, although it varies along the
direction of ﬂow from ‘upstream’ to ‘downstream’. The
variation in velocity across the tank is consistent between
the different input velocities tested.
•Steady ﬂows can be produced in the facility, following
a ramp up period of about 5 minutes. However further
work is required to better understand the turbulent nature
of the ﬂow.
The authors would like to thank the Energy Technology In-
stitute and RCUK Energy programme for funding this research
as part of the IDCORE programme (EP/J500847/1), and the
UK Engineering and Physical Science Research Council for
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