21-Aug-2015 - National Aeronautics and Space Administration (NASA)

From fluids to flames, research on the space station is helping advance technology

A study explored the finer points of fluid dynamics, something that is experienced across the planet, but cannot quite be studied as carefully on Earth. A phenomenon called Marangoni convection is one of the fundamental principles of liquid motion and is revealed much more clearly in microgravity.

Marangoni convection is the tendency for heat and mass to travel in areas of higher surface tension within a liquid. To learn how heat is transferred in space, researchers suspend a silicone oil bridge between two small solid discs, one of which is slowly heated to cause convection. Scientists observe the flow patterns to learn how heat is transferred in microgravity, an effect that gravity masks on Earth. Understanding the physics of this convection will improve research in high-quality crystal growth, such as crystals used for semiconductors and optics, and in various micro-fluid applications, such as DNA examination on the space station and on Earth.

Another fluid study on the orbiting laboratory could lead to a low-energy medical device with enormous public health benefits. Capillary flow, also known as wicking, is the ability of a liquid to flow without the assistance of gravity and other external forces. For example, a paper towel will draw, or wick, liquid into it without having to move closer to the source. In the absence of gravity, the effect of capillary forces is more dramatic. The station's Capillary Flow Experiment (CFE) is a basic physics investigation that refined our understanding of how capillary action helps fluids flow.

A technology of tiny elements studied on the station could have applications in everything from braking systems and robotics to earthquake-resistant bridges and buildings. Investigating the Structure of Paramagnetic Aggregates from Colloidal Emulsions (InSPACE) is a set of experiments that is gathering fundamental data about Magnetorheological (MR) fluids. They are a type of smart fluid that tends to self-assemble into shapes when exposed to magnetic fields.

MR fluids change viscosity in a magnetic field and can even be made to change their arrangement at the nanoscale level, or one billionth of a meter. Such tiny distances are typical for molecules and atoms. When exposed to magnetic fields, MR fluids can quickly transition into a nearly solid state. When the magnetic field is removed, the MR fluids return to a liquid state. This process produces useful properties that can be harnessed for a variety of mechanical devices, from robotic motions to strong braking and clutch mechanisms.

A unique test facility for droplet combustion research on the space station could provide technology for better mileage and a very real possibility of reduced pollution on Earth. The Flame Extinguishing Experiments study (FLEX and FLEX-2) is revealing new insights into how fuel burns. Recent results of the FLEX investigations revealed a never-before-seen, two-stage burning event. While a heptane droplet of fuel appeared to extinguish, it actually continued to burn without a visible flame. Improved prediction of flame behavior during combustion could inform methods to reduce pollution and get better fuel mileage in engine design.

Facts, background information, dossiers
  • NASA
  • gravity
  • liquid dynamics
  • fluid dynamics
  • Marangoni convection
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