Fluids Education (Fluids Education) - 07.15.14
ISS Science for Everyone
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Designed by undergraduate engineering students, the Fluids Education experiment tests complex mathematical codes used in computer models of fluid physics. The models are used to study capillary behavior, such as creating droplets or wicking liquid along tight spaces despite the influence of gravity. The results test the reliability of these computer codes for designing miniaturized medical devices and fuel cells, and even studying the function of human lungs, in space and on Earth.
Science Results for Everyone
OpNom Fluids Education
Purdue University, West Lafayette, IN, United States
North Carolina A&T State University, Greensboro, NC, United States
Sponsoring Space Agency
National Aeronautics and Space Administration (NASA)
NASA Education (EDU)
ISS Expedition Duration
September 2014 - March 2015
Previous ISS Missions
On-orbit operations are modeled after those of the successful CFE Vane-Gap experiments.
- The research is needed because capillary flows (flows where surface tension and wetting of a liquid on a solid govern the physics) are increasingly common in space flight and Earth-bound applications. ISS oxygen generator, heat-transfer loops, biological experiments, human physiology, and similar applications can be advanced more rapidly and safely if computer models are properly tested. On Earth, miniature medical devices or sensors, automotive fuel cells, and even pulmonary health involve this type of fluid behavior. Testing the ability of computer codes for predicting both static stability and the motion of liquid when it moves from one stable state to another will either prove the codes or provide discoveries that will highlight precisely the failures of the code which require additional development efforts.
- Computer modeling prior to flight predicted the liquid behavior that is to be tested and also drove the design of a number of test vessels in Fluids Education. On orbit, numerous test cases are formed within the single hardware unit of Fluids Education. Liquid droplets, plugs, and sleeves are created by injection of a pre-determined volume of liquid into one of several carefully designed test vessels. The stability of the droplet, plug, or sleeve of liquid is verified. The volume is then carefully increased or decreased according to a research plan and either the stability of the new state is assessed or the transition of liquid from the old state to the new state is recorded and then the stability of the new state is assessed. The astronaut controls liquid volume and any perturbations to the system. The video record of all steps of the experiment execution is the data to be downloaded and analyzed.
- The impacts of Fluids Education are numerous. With computer models for this type of fluid physics confirmed, engineers can apply these codes to improving designs of spaceflight and Earth-bound systems involving certain capillary fluid physics phenomena, such as droplets in gas flows and the changes of droplet to plugs or other geometries. Management of condensed water in fuel cell gas passages is one such application. Spaceflight electrolysis, boiling, and condensation are three components of life support systems for which the design and safety can be improved with better computer models. Educational impact of the research is two-fold: the undergraduate students performing the necessary science, hardware and operations design, astronaut training, data processing, and similar benefit immediately and in the years ahead. The second educational impact is extensive middle school STEM impact generated through focused STEM lessons, demos, curriculum, and design exercises created by the undergraduate student teams in the Fluids Education program. These lessons bring ISS science to classrooms by aligning examples of table-top capillary phenomena with those in ISS viewed by students.
The prediction of existence and stability of equilibrium capillary states has been greatly advance by the Surface Evolver computer code. Prediction of the dynamics of capillary-dominated flows, especially with moving contact lines, remains a research topic in spite of decades of computational fluid dynamics modeling and massive supercomputers. Yet predictions of existence and stability in new applications require testing to verify the proper application and performance of the computer modeling tool. Fluids Education is a unique experiment to test the capability to predict existence and stability and also to produce quantitative data to drive improvements in the modeling of dynamics of the transitions between linearly-stable states.
Unique to Fluids Education, in addition to being the first on-orbit experiment in this fluid physics topic, are the undergraduate student designed and built nature of the experiment and the integrated middle school STEM impact and curriculum development. The science, hardware design, much of the fabrication, the operations, astronaut training, and data analysis are performed by undergraduate teams from the School of Aeronautics and Astronautics at Purdue University and the Mechanical Engineering Department at North Carolina Agricultural and Technological State University.
The simplest geometry for such studies is a circular tube of air in which, depending on contact angle, liquid volume, and experiment history, the liquid can form stable wall-bound droplets, plugs, and annular sleeves. Slight modifications of the simple geometry make the experiment more suitable for International Space Station (ISS) experimentation while preserving the fluid physics and states of interest. Modeling of the modified geometry is performed by the students and is part of the original science content of the Fluids Education program. The time scale of transitions between static states is estimated from the computational predictions, but the actual motion must be modeled by a computation fluid dynamics (CFD) code, which is very difficult to do well when there are moving and joining or splitting contact lines such as in the motion expected in Fluids Education. The observations from Fluids Education will drive modeling capabilities in CFD. Thus the data from Fluids Education serves for multiple tasks in the field of capillary fluid physics.
Uneven container walls, bubbles and other variables can affect how well fluids move throughout equipment like oxygen generators and fuel lines. Commercial satellite propulsion systems are sometimes hampered by gas bubbles once they reach orbit, for instance. Improving computer models of fluid behavior leads to safer and better designs for diverse systems, such as fuel lines and common life-support systems, on the International Space Station and future spacecraft.
Improved computer models will help researchers studying capillary action in a wide range of systems, from the human body to a refrigerator. Such research could benefit development of small medical devices known as labs-on-a-chip, which use capillary action to draw blood or other fluids across their surfaces for analysis; clarify risks to workers who breathe misty air; and even improve small refrigeration devices, which use capillary flow to exchange heat with the refrigerant. The experiment is also unique for its involvement of students, who designed and built it and developed a related curriculum for middle school students.
Maintenance work area, one astronaut, HD camcorder and mount, video down-link, work light. Live video can be low-resolution with HD downlink afterwards as ISS operations permit is acceptable. Stowage for Fluids Education hardware between operations. Anticipated initial experiment program is 12 operations of up to 6 hours each. As astronauts become proficient with set-up, time required could drop.
The crewmember gathers HD camcorder, mount, and a work light, plus one sheet white paper and some tape at the Maintenance Work Area. Crewmember unstows Fluids Education, mounts and aligns Fluids Education and HD camcorder on work surface. Paper is taped into position. Work light is mounted to illuminate paper. Then fluid dynamics operations begin: setting valve positions and rotating reservoir knob to inject and withdraw liquid according to the schedule for the day. Sometimes waiting 10 to 20 minutes, sometimes wait just one minute, then further actuations of the reservoir knob. The operational process permits investigations of (predicted) stable and unstable configurations of the liquid in the various test vessels and the transitions between these states. An anomaly recovery task list is provided for crewmember use if necessary. At the end of the day’s operations, the crewmember powers off HD camcorder and light, then unmounts and stows hardware until the next planned research time.
The Fluids Education