This paper provides a current overview of the in-flight operations and experimental results of the capillary flow experiment (CFE) performed aboard the International Space Station (ISS) beginning August 2004 to present, with at least 16 operations to date by five astronauts. CFE consists of six approximately 1–2 kg experiment units designed to probe certain capillary phenomena of fundamental and applied importance, such as capillary flow in complex containers, critical wetting in discontinuous structures, and large length scale contact line dynamics. Highly quantitative video images from the simply performed experiments provide direct confirmation of the usefulness of current analytical design tools as well as provide guidance to the development of new ones. A description of the experiments, crew procedures, performances and status of the data collection and reduction is provided for the project. The specific experimental objectives are briefly introduced by way of the crew procedures and a sample of the verified theoretical predictions of the fluid behavior is provided. The potential impact of the flight experiments on the design of spacecraft fluid systems is discussed in passing.
Research Containing: CFE
Preliminary Results from the Capillary Flow Experiment Aboard ISS: The Moving Contact Line Boundary Condition
The Capillary Flow Experiment (CFE) consists of six approximately 2kg test vessels constructed by NASA to probe certain capillary phenomena of fundamental and applied importance. The light weight, low-volume hardware can be shipped to orbit on short notice as cargo space permits and the experiment performed in stand-alone mode by a single crewmember on, for example, the Maintenance Work Area (workbench) of the International Space Station. Video images from the simply performed crew procedures provide highly quantitative data for the confirmation of current analytical design tools as well as directions for further theoretical development. This paper presents a narrative of preliminary results from the first Capillary Flow Experiment (CFE) conducted aboard ISS in August-September 2004. The tests are performed as per of NASA’s Saturday Morning Science Program on ISS and completed in good order by Astronaut Michael Fincke who collected approximately 100 data sets that compare large length scale capillary surface oscillations and damping for two otherwise identical cylindrical tanks differing only in respect to a critical yet uncertain boundary condition at the contact line. Linear, nonlinear, and destabilizing slosh, swirl, axial, and other disturbances are studied. The large data set is being reduced for comparisons to the blind predication of a group of numerical analysis assembled to gauge the accuracy of present methods to predict large length scale capillary dynamics critical to fluids management in spacecraft (i.e. fuels, cryogens, water). The success of the experiment reported herein serves as a testimony to astronaut ingenuity and the perhaps surprisingly flexible fluids laboratory of the ISS for safe and simple fluids experimentation.
This paper serves as a first presentation of quantitative data reduced from the Capillary Flow Contact Line Experiments recently completed aboard the International Space Station during Expeditions 9-16, 8/2004-11/2007. The simple fluid interface experiments probe the uncertain impact of the boundary condition at the contact line—the region where liquid, gas, and solid meet. This region controls perhaps the most significant static and dynamic characteristics of the large length scale capillary phenomena critical to most multiphase fluids management systems aboard spacecraft. Differences in fluid behavior of nearly identical static interfaces to nearly identical perturbations are attributed primarily to differences in fluid physics in the vicinity of the contact line. Free and pinned contact lines, large and small contact angles, and linear and nonlinear perturbations are tested for a variety of perturba- tion types (i.e. axial, slosh, and other modes) to right circular cylinders. The video and digi- tized datasets are to be made publicly available for model benchmarking. In parallel with the experimental effort, blind numerical predictions of the dynamic interface response to the experimentally applied input perturbations are offered as a demonstration of current capa- bilities to predict such phenomena. The agreement and lack of agreement between the experiments and numerics is our best guide to improve and/or verify current analytical methods to predict such phenomena critical to spacecraft fluid systems design.
urrent experiments aboard the International Space Station (ISS) illustrate an extent to which liquid behavior aboard spacecraft can be controlled by wetting and container geometry. The experiments are referred to as the 'Vane-Gap' experiments and are part of a more general set of simple handheld Capillary Flow Experiments1) (CFE) designed and developed at NASA's Glenn Research Center for conduct on ISS. The CFE-Vane Gap experiments highlight the sensitivity of a capillary fluid surface to container shape and how small changes to said shape may result in dramatic global shifts of the liquid within the container. Understanding such behaviors is central to the passive management of liquids aboard spacecraft and in certain cases permits us the ability to move (pump) large quantities (potentially tons) of liquid by a simple choice of container shape. In particular, the Vane-Gap experiments identify the critical geometric wetting conditions of a vane structure that does not quite meet the container wall-a construct arising in various fluid systems aboard spacecraft such as liquid fuel and cryogen storage tanks, thermal fluids management, and water processing equipment. In this paper experimental results are compared with preliminary theoretical and numerical analyses.
This paper provides a summary of the experimental, analytical, and numerical results of the Capillary Flow Experiment (CFE) performed onboard the International Space Station (ISS) from Increment 9 (beginning August, 2004) through Increment 16 (ending December, 2007), with 19 operations by 7 astronauts; M. Fincke, W. McGarthur, J. Williams, S. Williams, M. Lopez-Alegria, C. Anderson, and P. Whitson. CFE consists of 6 approximately 1 to 2kg experiment units designed to probe certain capillary phenomena of fundamental and applied importance, such as capillary flow in complex containers, critical wetting in discontinuous structures, and large length scale contact line dynamics. Highly quantitative video images from the simply performed flight experiments provide immediate confirmation of the usefulness of current analytical design tools as well as provide guidance to the development of new ones. A brief review of the experiments and procedures is provided before reporting the status of the data collection, reduction, and comparisons with both analytic and numerical predictions. The products of the work include design tools for modeling capillary interface dynamics relevant to spacecraft engineering systems. The CFE experimental program was initiated in February 2003 as part of a fast-paced unscheduled payloads/experiments program. All six of the units were performed on standby or at times as part of NASA Saturday Science and all units have been returned to Earth for post flight analysis. The experiments were conducted in stand-alone mode by a single crewmember on the Maintenance Work Area of the ISS.
Interim Results from the Capillary Flow Experiment Aboard ISS: The Moving Contact Line Boundary Condition
This paper highlight the in-flight operations of the Capillary Flow Experiment Contact Line experiments (2 each) performed aboard the International Space Station (ISS) during the period between Increment 9 ad 13 (8/2004-9/2006). The CFE-CL vessels are simple fluid interface experiments that probe the uncertain impact of the boundary condition at the contact line – the region where liquid, gas, and solid meet. This region controls perhaps the most significant static and dynamic characteristics of the large length scale capillary phenomena critical to most multiphase fluid management systems aboard spacecraft. Difference in fluid behavior of nearly identical statics interfaces to nearly identical disturbances are attributed to differences in fluid physics in the vicinity of the contact line. The CFE-CL experiments are conducted on five occasions by ISS Astronauts M. Fincke, W. McArthur, and J. Williams. The number of tests performed including additional science experiments is made possible by various centrifuge techniques employed by the astronauts permitting the re-use of the once-wetted container. Several of these ‘extra science’ experiments are briefly described herein. Intermittent real-time video and audio downlink, continuous communication with the ground crews at NASA JSC, MSGFC and GRC, and the clear and entreating commentary of the crew made the conduct of the tests on ISS an enjoyable, laboratory-like experience for the science on the ground. The flight tapes from the onboard cameras have been results to Earth (name flight) and are expected to be digitized, reduced and made publically available in the near future. A concurrent blind numerical analysis is underway to predict the experiments result using a generally accepted CFD-tool with specific contact line boundary conditions.
This paper is concerned with forced flow through partially open capillary channels under microgravity conditions. The investigated channel consists of two parallel plates and is bounded by free liquid surfaces along the open sides. The curvature of the channel’s gas-liquid interface, which is exposed to the ambient pressure, adjusts to the pressure difference across the interface in accordance with the Young-Laplace equation. Flow within the channel becomes unstable when the free surface collapses and gas ingestion into the flow path occurs—a process that is also referred to as the “choking” phenomenon. During stable flow, the behavior of the free surface is influenced by flow conditions, geometric properties of the channel, and the pre-defined system pressure. In this work, a previously published stability theory is verified for a wide range of model parameters. A detailed study is provided for stable flow in capillary channels, including static and dynamic solutions. The results of the Capillary Channel Flow (CCF) experiment are evaluated and are found to agree well with numerical predictions. A clear limit is determined between stable and unstable flows. It is shown that the model can predict the shape of the free surface under various flow conditions. A numerical tool is employed to exploit the mathematical model, and the general behavior of free surfaces in said capillary channels is studied. Studies are conducted in both viscous and convective flow regimes and in the transition area between the two. The validity of the model is confirmed for a wide range of geometrical configurations and parameters.