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Experiment/Payload OverviewBrief Summary
Capillary Flow Experiment (CFE) is a suite of fluid physics experiments that investigate capillary flows and flows of fluids in containers with complex geometries. Results will improve current computer models that are used by designers of low gravity fluid systems and may improve fluid transfer systems on future spacecraft.
Principal Investigator
Payload Developer
National Center for Microgravity Research, Cleveland, OH, United States
Glenn Research Center, Cleveland, OH, United States
ZIN Technologies Incorporated, Cleveland, OH, United States
National Aeronautics and Space Administration (NASA)
Sponsoring Organization:Exploration Systems Mission Directorate (ESMD)
ISS Expedition Duration:April 2004 - April 2008
Expeditions Assigned
9, 12, 13, 14, 15, 16
Previous ISS MissionsSimilar experiments were performed on Mir as well as ISS Expeditions 9, 12, 13, 14 and 15.
Experiment/Payload Description
Research Summary
- Without gravity, it is more difficult to control the flow of fluids and this is a challenge for designing spacecraft systems such as liquid propellants/cryogens, thermal control systems, wastewater management and recycling.
- Capillary forces (the interaction of liquid with solid that can draw a fluid up a narrow tube) continue to act in the absence of gravity and can be exploited to control fluid orientation so that fluid systems on spacecraft perform predictably.
- CFE uses the low-gravity environment provided by the International Space Station to understand the special dynamics of capillary flow and will aid in the design of fluid transport systems on future spacecraft.
The Capillary Flow Experiment (CFEs) is a suite of fluid physics experiments whose purpose is to investigate capillary flows and phenomena in low gravity. The CFE data to be obtained will be crucial to future space exploration because they provide a foundation for physical models of fluids management in microgravity, including fuel tanks and cryogen storage systems, Thermal Control Systems (TCS) (e.g., water recycling), and materials processing in the liquid state. NASA's current plans for Exploration missions assume the use of larger liquid propellant masses than have ever flown before. Under low-gravity conditions, capillary forces can be exploited to control fluid orientation so that such large mission-critical systems perform predictably.
The handheld experiments common to the suite aim to provide results of critical interest to the capillary flow community that cannot be achieved in ground-based tests; for example, dynamic effects associated with a moving contact boundary condition, capillary-driven flow in interior corner networks, and critical wetting phenomena in complex geometries. Specific applications of the results center on particular fluids challenges concerning propellant tanks. The knowledge gained will help spacecraft fluid systems designers increase system reliability, decrease system mass, and reduce overall system complexity.
CFE encompasses three experiments, CFE-Contact Line (CFE-CL), CFE-Interior Corner Flow (CFE-ICF), and CFE Vane Gap (CFE-VG), with two unique experimental apparatuses per experiment. There are multiple tests per experiment. Each of the experiments employs conditions and test cell dimensions that cannot be achieved in ground-based experiments. All of the units use similar fluid injection hardware made of Lucite, have simple and similarly sized test chambers, and rely solely on video for highly quantitative data. Silicone oil is used as the fluid. Differences between units are primarily fluid properties, wetting conditions (determined by the coating inside the test chamber), and test cell cross section.
- CFE-CL investigates the properties of the contact line (the boundary between the liquid and the solid surface of the container). The contact line controls the interface shape, stability, and dynamics of capillary systems in low gravity.
- CFE-ICF studies capillary flow in interior corners. Structured inside tanks providing interior corners are used in the design of fuel tanks so that the fuel will always flow to the outlet of the tank in the absence of gravity. The equations governing the process are known but, to date, have not been solved analytically because of a lack of experimental data identifying the appropriate boundary conditions for the flow problem. Experimental results will guide the analysis by providing the necessary boundary conditions as a function of container cross section and fill fraction. The benchmarked theory can then be used to improve propellant management aboard spacecraft.
- CFE-VG studies capillary flow when there is a gap between interior corners, such as in the gap formed by an interior vane and tank wall of a large propellant storage tank or the near intersection of vanes in a tank with complex vane network.
Applications
Space Applications
The knowledge gained from this payload has the potential to be instrumental in the design of future fluid systems for spacecraft-impacting fluid bearing containers such as propellant and cryogenic fluids tanks, thermal control system coolant reservoirs, water storage and management systems, liquid state low-gravity materials processing equipment, and biofluids handling instruments for inflight human health systems. By performing this experiment, researchers will gain information that will lead to improvements in system reliability with reductions in system mass and complexity. These applications of CFE are in direct support of NASA's mission to develop safe, reliable, and affordable spacecraft to pursue the greater exploration of our solar system and universe.
Earth ApplicationsThe results of the flight experiments are also expected to provide insights into terrestrial interfacial phenomena and may lead to models predicting fluid flows in porous media (i.e. ground water transport), complex capillary structures (i.e. high performance wicks for heat pipes employed in electronics cooling), and Lab-On-Chip technologies (i.e., microscale biofluids processing).
Operations
Operational Requirements
During the CL experiments, crewmembers will allow the fluids to settle out for approximately 20 min. The crew will then impart disturbances by tapping, pushing, sliding, swirling, and shaking the CFE unit. The crew will start and stop the camcorder and change/label tapes as required to record all tests. Following each disturbance, the crew will allow the fluids to dampen before proceeding to the next disturbance.
For the VG sessions, crewmember will fills the test chamber with fluid and then record the background g-jitter during an undisturbed wait with the ISS camcorder. For VG-2, crewmembers will then increment the vane through one complete revolution capturing the advance and recession of the fluid along each side of the vane. The critical angles at which the fluid spontaneously rises to the top of each side the vane are also determined and recorded. This test is special in that the surface is dry and is not repeatable. During VG-1, crewmembers will increment the vane through two complete revolutions capturing the advance and recession of the fluid along each side of the vane. The critical angles at which the fluid spontaneously rises to the top of each side the vane are also determined and recorded. This test sees a wet surface in the test chamber and vane and may be repeated as many times as necessary.
For the ICF experiments, the crewmember injects a fluid from a self-contained reservoir into the test chamber and primes the tube between valve 2 and the test chamber vertex. The crewmember will then turn the knob and open/close valves 1 or 2 to dispense or retract fluid into test chamber. Fluid creeps from test chamber base to top vertex and is then recovered to a reservoir.
The crew will set up the Maintenance Work Area (MWA) work surface and camcorder, attach the CFE units onto the MWA, inject the fluids into the test chambers, and record the fluid's response to disturbances using the ISS camcorder.
Results/More Information
CFE is a suite of fluid physics experiments whose purpose is to investigate capillary flows and phenomena in low gravity and consists of three investigations: Interior Corner Flow (ICF), Vane Gap (VG) and Contact Line (CL). The results summarized here encompass the CFE experiments carried out onboard the International Space Station (ISS) beginning during Increment 9 (August 2004) and continuing through Increment 16 (December 2007). The results from these experiments will be used to develop more accurate fluid models to aide in the design of low gravity fluid systems and enhance the fluid transfer systems of future space vehicles (Weislogel 2008).
Interior Corner Flow (ICF)
CFE-ICF studies capillary flows in interior corners of two tapered containers. The ullage (empty part of the container) migration rates of four different flows (dry, wet, open loop and bubbly) in the units were observed and compared. Migration rates were found to be in surprising agreement with predictions for the dry tests, but were under-predicted for previously wetted surfaces.. In the case of ICF-2, the migration rate also increased for the bubbly flow test. For ICF-1, bubbly flows were created, but have not been analysed to date. This analysis is ongoing and will be completed in part with further experimental results to be collected during CFE-2 experiments currently onboard
ISS. In many cases the bubbles were separated during the bubble tests of ICF but small bubbles were unhindered (Weislogel 2008).
Vane Gap (VG)
The Capillary Flow Experiment-Vane Gap (CFE-VG) studies capillary flow when there is a gap between interior corners, such as in the gap formed by an interior vane and tank wall of a large propellant storage tank or the near intersection of vanes in a tank with a complex vane network.
In the case of the perfectly wetting fluid of VG-1, three wetting configurations were produced: wetting along the small gap between the vane and cylinder, wetting along the large gap and a large shift in fluid from one side of the container to the other (bulk shift). The most noteworthy condition was the bulk shift due to the considerable amount of liquid that was transferred. The average observed large and small gap critical wetting angles (vane angles at which fluid draws up the gap formed between the vane and cylinder wall and ?wets? the entire length of the vane) were in close agreement with analytical predictions. However, bulk shift was not predicted by analysis, which assumed perfect geometric symmetry of vane and cylinder. The occurrence of bulk shift indicates that small irregularities in geometry (such as tiny imperfections within the manufacturing tolerance of the experiment unit) can influence fluid behavior in a significant way (Chen 2008). Post flight measurements of test cell asymmetries were made to quantify such values and new predictions were made of the slightly asymmetric vessel. The agreement is informative as a method to assess tank symmetry for applications aboard spacecraft.
For the partial wetting fluid of VG-2, wetting occurred along both the small and large gaps, similar to VG-1. However, unlike VG-1, the difference between the average observed and average predicted critical wetting angles was substantial, and could be due to asymmetry inherent in the experiment unit and contact angle hysteresis (the difference between the receding (uphill) angle and advancing (downhill) angle made by the fluid on a tilted plane right before the fluid drop begins to roll). Bulk shift of the fluid was not predicted and did not occur, or was not observed in previous studies (Chen 2008).
Contact Line (CL)
CFE-CL investigates the properties of the contact line (the boundary between the liquid and the solid surface of the container), which controls the interface shape, stability, and dynamics of capillary systems in low gravity. From the over 400 events evaluated thus far, damping rate, frequency and qualitative waveform were found to be plainly influenced by contact line and contact angle conditions. The pinning condition produced higher frequencies and lower damping rates than the smooth condition. Larger contact angles also produced the same trend in higher frequencies and lower damping rates. Fluid depth was found to have little effect on the fluid response to disturbances except in cases where shallow tests were performed intentionally (Weislogel 2008).
Observed results were also compared to model predictions. Agreement between numerical predictions and observed results varied widely. The most accurately modeled instance was the perfectly wetting case of CL-2 for both the pinning and smooth conditions and for both axial and lateral disturbance events. The least accurately modeled instances were the high contact angle push-type disturbance events with free-slip conditions, since contact line translation is not included in the constant contact angle slip model. In general, modeled and observed results were in best agreement for pinned conditions, as a result of the more predictable and confined contact line movement (Weislogel 2008).
A database comprising videos and datasheets containing experiment parameters, data and preliminary results of all CL events is being compiled by the investigators to facilitate further investigation and model refinement (Weislogel 2008).
Related Web Sites
Publications
- Weislogel M M,Jenson R ,Klatte J ,Dreyer M ,Interim Results from the Capillary Flow Experiment Aboard ISS; the Moving Contact Line Boundary Condition 45th AIAA Aerospace Sciences Meeting and Exhibit 2007
- Klatte J ,Haake D ,Weislogol M M,Dreyer M ,A fast numerical procedure for steady capillary flow in open channels Acta Mech 2008 201 269-276
- Jenson R ,Weislogel M ,Tavan N ,Bunnell C ,Capillary Flow Experiments Aboard ISS 47th AIAA Aerospace Sciences Meeting including The New Horizons Forum and Aerospace Exposition 2009
- Weislogel M M,Preliminary Results from the Capillary Flow Experiment Aboard ISS: The Moving Contact Line Boundary Condition Proceedings of the 43rd AIAA Aerospace Sciences Meeting and Exhibit 2005
- Weislogel M M,Jenson R M,Klatte J ,Dreyer M E,The Capillary Flow Experiments aboard ISS: Moving Contact Line Experiments and Numerical Analysis 46th AIAA Aerospace Sciences Meeting and Exhibit 2008
- Chen Y ,Jenson R M,Weislogel M M,Collicott S H,Capillary Wetting Analysis of the CFE-Vane Gap Geometry 46th AIAA Aerospace Sciences Meeting and Exhibit 2008
- Weislogel M M,Jenson R ,Chen Y ,Collicott S H,Klatte J ,Dreyer M ,The capillary flow experiment aboard the International Space Station: Status Acta Astronautica 2009 65 861-869
Ground Based Results Publications
ISS Patent Publications
Related Publications
- Chen Y ,Weislogel M M,Bolleddula D A,Capillary Flow in Cylindrical Containers with Rounded Interior Corners 45th AIAA Aerospace Sciences Meeting and Exhibit Reno, NV, January 8 - 11, 2007
- Weislogel M M,Jenson R ,Bolleddula D A,Capillary Driven Flows in Weakly 3-Dimensional Polygonal Containers 45th AIAA Aerospace Sciences Meetng and Exhibit Reno, NV January 8 - 11, 2007
- Concus P ,Finn R ,Weislogel M ,Capillary Surfaces in an Exotic Container: Results from Space Experiments Journal of Fluid Mechanics 1999 394 119-135
- Weislogel M M,Collicott S H,Gotti D J,Bunnell C T,Kurta C E,Golliher E L,The Capillary Flow Experiments: Handheld Fluids Experiments for International Space Station Proceedings of the 42nd AIAA Aerospace Sciences Meeting and Exhibit 2004
- Concus P ,Finn R ,Weislogel M ,Measurement of Critical Contact Angle in a Microgravity Experiment Experiments in Fluids 2000 28 197-205
- Chen Y ,Weislogel M M,Analysis of Capillary Flow in Rounded Corners Heat Transfer and Fluids Engineering Summer Conference, Charlotte, NC Jul 11 - 15, 2004
- Weislogel M M,Nardin C L,Passive Fluids Management in Low-g: Partially Wetting Systems Proceedings of the 42nd AIAA Aerospace Sciences Meeting and Exhibit 2004
Images
Video screen shot of the Capillary Flow Experiment-Contact Line (CFE-CL) apparatus on board ISS during Increment 9. + View Larger Image
Video screen shot of the CFE-Contact Line 2 Set-Up and Initial Condition on board ISS during Increment 9. + View Larger Image
Video screen shot of CFE-CL2 Bubble Test 1 on board ISS during Increment 9. + View Larger Image
NASA Image: ISS009E23445 - ISS Science Officer, Mike Fincke in the U.S. Lab aboard the International Space Station during Expedition 9 next to CFE-CL2. + View Larger Image
NASA Image: ISS009E20676 - ISS Science Officer, Mike Fincke in the U.S. Lab aboard the International Space Station during Expedition 9 narrating during CFE-CL2 operations. + View Larger Image
NASA Image: ISS009E23441 - ISS Science Officer, Mike Fincke in the U.S. Lab aboard the International Space Station during Expedition 9 narrating during CFE-CL2 operations. + View Larger Image
NASA Image ISS012E12911 - Astronaut William S. (Bill) McArthur Jr., Expedition 12 commander and NASA space station science officer, prepares the Capillary Flow Experiment (CFE) for video documentation. The CFE was positioned on the Maintenance Work Area in the Destiny laboratory of the International Space Station. + View Larger Image
NASA Image ISS013E08005 - Expedition 13 Science Officer and Flight Engineer Jeff Williams during Capillary Flow Experiment (CFE) operations in the U.S. Destiny Laboratory onboard the International Space Station. + View Larger Image
NASA Image: ISS013E73443 - Astronaut Jeffrey N. Williams, Expedition 13 NASA space station science officer and flight engineer, prior to performing one of multiple tests of the Capillary Flow Experiment (CFE) investigation in the Destiny laboratory of the International Space Station. CFE observes the flow of fluid, in particular capillary phenomena, in microgravity. + View Larger Image
NASA Image: ISS013E73479 - Astronaut Jeffrey N. Williams, Expedition 13 NASA space station science officer and flight engineer, performs one of multiple tests of the Capillary Flow Experiment (CFE) investigation in the Destiny laboratory of the International Space Station. CFE observes the flow of fluid, in particular capillary phenomena, in microgravity. + View Larger Image
NASA Image ISS015E05032 Astronaut Sunita L. Williams, Expedition 15 flight engineer, performs one of multiple tests of the Capillary Flow Experiment (CFE) investigation in the Destiny laboratory of the International Space Station. CFE observes the flow of fluid, in particular capillary phenomena, in microgravity. + View Larger Image
NASA Image ISS015E10587 View of Capillary Flow Experiment (CFE) in the U.S. Laboratory/Destiny. The purpose of this experiment is to investigate capillary flows and phenomena onboard the International Space Station (ISS). A video camera is set up to record the behavior of silicone oil in the Contact Line (CL) unit. Photo was taken during Expedition 15. + View Larger Image
If updates are needed to the summary please contact JSC-ISS-Program-Science-Group. For other general questions regarding space station research and technology, please feel free to call our help line at 281-244-6187 or e-mail at JSC-ISS-Payloads-Helpline.