FLUIDICS: FLUId DynamICs in Space (CNES National Contribution)
  1. 2016 • ISS Increments 49-50
  2. 2017 • ISS Increments 51-52
  3. 2017 • ISS Increments 53-54
  4. 2018 • ISS Increments 55-56
  5. 2018 • ISS Increments 57-58
  6. 2019 • ISS 61S (Soyuz MS-15) SpaceFlight Participant mission
  7. 2019 • ISS Increments 59-60
  8. 2019 • ISS Increments 61-62
  9. 2020 • ISS Increment 63
  10. 2020 • ISS Increment 64
Physical Sciences:
  • Fluid physics
J. Mignot (1), A. Llodra-Perez (2), L. Oro Marot (2)
Centre d´Aide au Développement des activités en Micro-pesanteur et des Opérations Spatiales
How liquids behave on Earth is hard to predict and even harder in space without gravity. Getting the last drop out of a packet of orange juice can be a frustrating experience - imagine the challenge for engineers designing satellites to use every drop of fuel in weightlessness or designing rockets with fuel tanks that must deliver fuel to the engines under extreme loads. Satellites and launch vehicles use liquid fuel.

The FLUIDICS experiment - a fluid mechanics experiment - is looking at a phenomenon called ‘sloshing’ - how liquids move inside closed spaces under the conditions on board the ISS. This is the first part of the experiment.
To do this, the FLUIDICS device will simulate the motions undergone by a satellite going into space using a centrifuge that will shake a transparent sphere filled with a coloured liquid to facilitate observations. The goal is to optimise the manoeuvres of satellites and extend their operating life.

The second part of the experiment is used to analyse, at the most fundamental level, the energy transfers that occur on the surface of liquid in motion. These phenomena called "wave turbulence" are little known by the scientific community today. On Earth, gravity and surface tension influence how a force dissipates in waves or ripples. By conducting Fluidics in space, scientists can observe how surface forces behave without gravity – removing one factor from the equation simplifies understanding the phenomenon. A better understanding would help to develop better climate models and predict the state of the seas more accurately for the benefit, for example, of the production of electrical energy from the waves (wave on the surface of the sea).

"Wave turbulence" is the name given to irregular movements of the surface of a liquid, as the waves of the ocean. Despite the existence for over 40 years of numerous theoretical approaches, the phenomena of wave turbulence is a not well research field of interest. FLUIDICS will allow researchers at the ENS Paris and CNRS to deepen the understanding of this area of research which is seeking new revelations globally.

The purpose of this experiment is to validate the foreseen behaviour of fluids under microgravity.

The first part of the experiment addresses technological issues relative to the slosh of fluids during satellites manoeuvers.

The second one will help to report the observation of capillary wave turbulence on the surface of a fluid layer in a low-gravity environment.

The objectives of this experiment are:
- To correct mathematical models of fluid sloshing provided by CFD tools;
- To derive predictive models for future sloshing  under different operational conditions;
- To observe the fluid covering all the internal surface of the spherical container that is submitted to random forcing. 

Such a large-scale observation without gravity waves has never been reached during ground experiments. When the forcing is periodic, two-dimensional spherical patterns are observed on the fluid surface such as sub-harmonic stripes or hexagons with wavelength satisfying the capillary wave dispersion relation. The duration of the experiment of some minutes allows observing wavelength never observed neither on ground nor during parabolic flights.

Dedicated tanks will be used to address these different points: two similar tanks filled at 50 or 75% for sloshing and a specific one using internal instrumentation of the tank dedicated to the wave turbulence observation.


The applications of this investigation are numerous: improving climate models forecasting the sea state, the understanding of rogue waves (very high, sudden waves), but also the development of new renewable energy using ocean waves. Also, it is aimed at designing better satellite fuel-systems to increase their life and make them less expensive.
The experiment consists of three small transparent spheres with a centrifuge to move the liquids inside. One sphere used for the wave turbulence experiment will hold distilled coloured-water, the other two spheres used for the sloshing experiments use a special liquid developed with low viscosity and little surface tension.

The experiment will be uploaded during the first half of the Proxima mission, installed on Columbus Deck and deployed following a predefined scenario.

An overview of the hardware and PODF familiarisation is required with a training session on a ground device is intended.
No Pre-flight BDC is required

One prime session is required demanding 3 hours crew time for experiment assembly, preparation, execution and closing-out activities.
One additional session can be performed if crew time available (3 hours crew time).

The experiment hardware assembly is done in three steps:
- installation of the guiding/actuation device, which is also providing the power interface to ISS
- a payload assembly carrying both instruments and the tanks (there are 3 different tanks to be installed/de-installed to the payload assembly, once at a time for executing the experiment)
- a containment box covering the rotating arm and providing the electrical interface for operation.

- installation of fluidics in Columbus module (including cable routing) and laptop installation
- execution of a minimum of profile to verify setup, includes 5 min for tank installation
- crew needs to copy the video generated and visualise it for validation and continuation of activities
- 1st experiment run to be executed after successful completion of Setup Verification
- 2nd experiment run, 5 min to include tank installation
- 3rd experiment run, 5 min to include tank installation
- experiment close-out

Sloshing profiles

A typical test profile will involve 4 phases, with a typical bang-bang acceleration profile.
- a constant angular acceleration. This part allows first to reach the target rate, but is also the initial excitation for the fluid that induces the sloshing behaviour.
- a constant rate phase, during which the main observation takes place: here the fluid sloshing cycles damp, with a specific G level (depending on the angular rate)
- a breaking phase, to reach steady state and 0 G level.
- a post manoeuvre phase, during which the fluid tranquilisation and reorientation in 0G can be observed.

Following profiles should be tested:
Profile; Bond; Acceleration [m/s²]; Rate (0.5m lever) [rad/s]
A; 0.5; 0.0064; 0.11
B; 1; 0.012; 0.15
C; 3; 0.039; 0.28
D; 10; 0.13; 0.51
E; 20; 0.26; 0.72
F; 30; 0.40; 0.89

Each profile is divided as shown in Figure 3.

The acceleration and breaking phases are used to excite the fluid sloshing, acting as “step” input to the fluid. Acceleration and breaking profiles are both designed to be representative of a specific Bond regime, according to considered satellite manoeuvers. Figure 3 gives an example of simulated liquid sloshing: using DIVA code, the position of the fluid centre of mass is displayed, and shows the potential sloshing waves that can be recorded by the cameras.

The selected test profiles involve a maximal angular rate close to 2 rad/s, and initial acceleration phase close to 0.3 rad/s², in turns resulting in a centrifugal acceleration of 0.5 m/s².

With a dedicated motor assembly, virtually any torque level can be selected in the operating range, and a more precise realization of the profile is possible.
Furthermore, the motor can be selected to fit the disturbing torque values (friction, etc…) and thus it is guaranteed that all kinematics can be generated.

Wave turbulence profile
During this part of the experiment the tank used is a specific one using a gauging measurement to be connected to the acquisition device. The excitation profile is an oscillation of some degrees in the frequency range of 3 to 5 Hz.
For Wave turbulence a random or sinus displacement with frequencies up to 5 Hz is required - see Figure 5.

This specific need will induce a different actuation of the device and probably an adjustment of the length of the arm in order to ensure a ratio of acceleration tangential / normal of approximately 10.Thats leads to an amplitude of A= 0.1 rad.
The motor will be chosen to ensure the require tangential acceleration and respect the value of A by reducing the length of the arm.

The fluid movement will be recorded using 2 cameras from two different points of view of the tank during each profile execution. The acquisition electronic will also capture and record forces due to the slosh. The two videos, as well as a set of recorded data from the embedded sensors will be downloaded after the session.
The SAMS data will be also used for the knowledge of the micro-vibration environment. The SAMS measurement unit available in Columbus is convenient for FLUIDICS use. No specific location is required. The measurement will be done during the whole duration of the experiment, so it is needed a minimum of 1 SAMS sensor data recording located in Columbus. 

Post-flight BDC:
No post-flight BDC required.
click on items to display

Figure 1: Experiment hardware.

Figure 2: Experiment hardware.

Figure 3: Each profile is divided as shown here.

Figure 4: Example of simulated liquid sloshing.

Figure 5: Wave turbulence profile.

Figure 6: Have you ever tried walking while carrying a full cup of water? Your steps invariably cause the water to slosh about, making spills hard to avoid. Now imagine a satellite turning - the fuel inside will slosh, affecting the satellite’s stability. France’s CNES space agency Fluidics experiment will run during ESA astronaut Thomas Pesquet’s Proxima mission on the International Space Station to probe how fluids behave in weightlessness. Co-funded by Airbus DS, the experiment will help to improve the performance of satellite propellant systems, extending their working lives by using every last drop in their tanks. A second part of Fluidics will look at surface turbulence in liquids. On Earth, gravity and surface tension influence how energy dissipates in waves or ripples. In space, scientists can observe how surface forces behave without gravity - removing one factor simplifies our understanding. The experiment consists of three small transparent spheres in a centrifuge. One sphere holds water for the wave-turbulence research; the other two carry a special liquid with low viscosity and little surface tension for sloshing. credit: CNES/E.Grimault, 2016

Figure 7: Developed by French space agency CNES and co-funded by Airbus Defense and Space, the Fluidics or Fluid Dynamics in Space experiment is probing how fluids behave in weightlessness. The experiment will help improve the performance of satellite propellant systems, extending their working lives by using every last drop in their tanks. A second part of the Fluidics experiment will look at capillary wave turbulence in liquids. On Earth, gravity and surface tension influence how energy dissipates in waves or ripples. In space, scientists can observe how surface forces behave without gravity. By looking at capillary wave turbulence without gravity interfering, researchers can single out non-linear interactions. This could help us improve climate models forecasting the sea states and better understand wave formation on Earth, like rogue waves for example. The experiment is made up of five small, transparent spheres housed in a black centrifuge seen here. Three spheres hold water for the wave-turbulence research; the other two carry a special liquid with low viscosity and little surface tension for sloshing. Credit: ESA/NASA

Fluidics: infographic. credit: ESA/K.Oldenburg
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