Microgravity Science Glovebox / ISS Research Program
Capillary Channel Flow
(CCF)
Status
June 10, 2013, The CCF fluid physics experiment is scheduled to be installed in the Microgravity Science Glovebox (MSG) on June 15, 2013. This second session of CCF operations will use Experiment Unit #2 (EU # 2) with the MSG cameras instead of the Optical Diagnostic Unit.
June
13, 2012, The CCF experiment team is planning to
re-install the CCF experiment in the Microgravity Science Glovebox
after several MSG experiments are completed. CCF operations
are anticipated in mid-December 2012. The Principal Investigator
for Experiment Unit #1 (EU#1), Michael Dryer and his team have
developed a test matrix to fill in the gaps in the data points
for subcritical and supercritical steady flow for the groove geometry
and the parallel plate geometry, not obtained in the first run
of CCF in 2011. The Principal Investigator for Experiment
Unit #2 (EU#2), Mark Weislogel and his team have developed a test
matrix to test EU#2 to fill in data points for steady, subcritical
two-phase re-stabilization, and transient positive acceleration
flows in the wedge geometry. CCF will utilize an on-board
MSG camera as the primary science image camera.
April 30, 2012, The
Microgravity Science Glovebox team and the CCF experiment team are working the
ability to substitute an on-board MSG camera in place of the CCF high-speed camera.
January 16,
2012, The Microgravity Science Glovebox team worked with the
CCF experiment team to schedule additional CCF operations to expand the CCF test
points for both experiment units EU#1 and EU#2.
October 5, 2011, The
EU#2 critical flow and subcritical flow tests were completed. In addition,
a preliminary 2-phase flow regime map for the wedge-shaped capillary geometry
was generated from over 270 separate bubble generation test points.
September 19, 2011, Mike Fossum performed additional
procedures on CCF to re-align the MSG camera and remove a stray optical
surface cover. CCF completed commissioning and Experiment Unit
#2 operations commenced.
September 13, 2011, CCF was re-installed in the Microgravity
Science Glovebox (MSG) by Increment 29 commander Mike Fossum.
October 5, 2011, The EU#2 critical flow and subcritical
flow tests were completed. In addition, a preliminary 2-phase
flow regime map for the wedge-shaped capillary geometry was generated
from over 270 separate bubble generation test points.
September 19, 2011, Mike Fossum performed additional procedures
on CCF to re-align the MSG camera and remove a stray optical surface
cover. CCF completed commissioning and Experiment Unit #2
operations commenced.
September 13, 2011, CCF was re-installed
in the Microgravity Science Glovebox (MSG) by Increment 29 commander
Mike Fossum.
On March 17, 2011, CCF Experiment Unit #1 completed its
test operations with 900 test points. The CCF Experiment Unit
#1 Principal Investigator Michael Dryer and his team are starting
the data analysis.
As of February 9, 2011, CCF has collected 547 test points
for Experiment Unit #1 out of the planned 900 test point test matrix.
On January 4, 2011, CCF began remote controlled experiment
operations at ZARM in Bremen, Germany.
On January 2, 2011, CCF completed full commissioning (a
series of checkout tests) at MSFC.
On December 27, 2010, CCF was installed in the Microgravity
Science Glovebox (MSG) by Increment 26 commander, Scott Kelly.
On April 5, 2010, CCF was launched to the ISS on STS-131
(flight 19A).
The test matrix has been completed for the Experimental Unit #1 (EU#1),
i.e. the parallel plate/groove channel geometry, and the CCF hardware
was removed from the MSG on March 17. Plans are to re-install
CCF with the EU#2 (wedge geometry) in MSG in August 2011 to complete
the second half of CCF science.
CCF is a versatile experiment for studying a critical variety of inertial-capillary
dominated flows key to spacecraft systems that cannot be studied
on the ground. The results of CCF will help innovate existing and
inspire new applications in the portion of the aerospace community
that is challenged by the containment, storage, and handling of
large liquid inventories (fuels, cryogens, and water) aboard spacecraft.
The results will be immediately useful for the design, testing,
and instrumentation for verification and validation of liquid management
systems of current orbiting, design stage, and advanced spacecraft
envisioned for future lunar and Mars missions. The results will
also be used to improve life support system design, phase separation,
and enhance current system reliability.
Since hydrostatic pressure is absent in microgravity, technologies
for liquid management in space use capillary forces to position and
transport liquids. On earth, the effect of capillary forces is limited
to a few millimeters. In space, these forces still affect free surfaces
that extend over meters. For the application of open channels in propellant
tanks of spacecraft, design knowledge of the limitations of open capillary
channel flow is a requirement. These limitations are based on the
restriction that the liquid fuel must be free of bubbles prior to
entering the thrusters.
Video clip of a capillary channel flow experiment onboard the TEXUS-37
sounding rocket with a parallel plates geometry.
Currently, spacecraft fuel tanks rely on an additional
reservoir to prevent the ingestion of gas into the engines during
firing. Research is required to update current models, which do not
adequately predict the maximum flow rate achievable through the capillary
vanes.
CCF will test the theoretical predictions for the free surface shapes
and the critical flow velocities for open capillary channel (vane)
flows in microgravity. CCF is designed to validate the assumptions
used to develop the governing equations. The experiments will provide
the verifications for the flow rate limits and corresponding critical
flow velocities.
Of the myriad of geometries envisioned for the capillary control of
fluids in low-g environments, CCF will examine flows in parallel plate
channels, grooves, and interior corner capillary conduits. These geometries
represent a class of practical capillary geometries that are implemented
in designs of the fuels and tank community of the aerospace industry.
Current spacecraft fluid processing equipment is replete with such
constructs. Validation of theoretical models developed for such geometries
is expected to lend confidence to the application of theory to other
geometries pertinent to advanced microgravity fluid systems development.
The highlights of the CCF experiments may be described as follows:
Provide performance limits for capillary dominated
systems such as passive fluids management (i.e. capillary collection,
pumping, and containment) and processes such as passive phase separation
and transport. This is a current and pressing requirement for a
wide range of spacecraft fluid systems.
CCF will use multiple test cell geometries and
variable parameter ranges to investigate the ability of capillary
systems to passively change multiphase flow regimes. It will also
be used to study capillary dominated multiphase flow that may be
exploited to assist other active or passive systems.
CCF will provide critical data for the uniquely
low-g inertial-capillary flow regime important to liquid fuels and
cryogen storage and management.
Methods
Forced liquid flows through open capillary channels
with free liquid surfaces will be investigated in the Microgravity
Science Glovebox (MSG) onboard ISS. In open capillary channels, if
a certain critical flow rate is exceeded, the flow becomes unsteady,
the surfaces collapse, and gas ingestion occurs at the outlet. From
a fluid mechanical point of view, a characteristic critical velocity
must exist at which the steady subcritical flow turns into an unsteady
supercritical flow, which involves the collapse of the free surfaces.
To find this velocity and the location of collapse of the free surface,
the surface profile must be measured with great accuracy. Furthermore,
the local flow velocity must be known at dedicated points of the channel.
In order to achieve a high degree of flexibility, the experiment was
designed as a modular system consisting of the Fluid Management System
(FMS), the Board Computer (BC), and two Experiment Units (EU), which
include the Test Units (TU). For the investigation of the selected
channel geometries (parallel plates channel, groove channel, and a
wedge-shaped channel) and different channel dimensions, the TUs are
exchangeable. This also enables the use of the setup for other projects
with similar technology driven research objectives. Furthermore, TU2
includes a gas bubble generator to test two-phase flow stability.
The FMS is equipped with the required components to establish the
flow (pumps, plungers, valves), while the EU contains the TU, a phase
separation chamber, (PSC), a compensation tube (CT), cameras for the
video observation as well as the required illumination. The experiment
control, the sampling of the housekeeping data, and the communication
with both the MSG interfaces and the ground station (PI site) is performed
by the BC.
The experiments are scheduled to take place on the ISS in 2010 and
will be monitored from the ground station in Bremen, Germany.
Liquid flow through an open
capillary channel consisting of two parallel plates.
The experimental setup insde
the Microgravity Science Glovebox (MSG) onboard the ISS.
A capillary
channel flow experiment onboard the TEXUS-37 sounding rocket with
a parallel plates geometry.
