Slosh dynamics

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File:Schwappender Wein.jpg
Sloshing wine

In fluid dynamics, slosh refers to the movement of liquid inside another object (which is, typically, also undergoing motion). Strictly speaking, the liquid must have a free surface to constitute a slosh dynamics problem, where the dynamics of the liquid can interact with the container to alter the system dynamics significantly.[1] Important examples include propellant slosh in spacecraft tanks and rockets (especially upper stages), and cargo slosh in ships and trucks transporting liquids (for example oil and gasoline). However, it has become common to refer to liquid motion in a completely filled tank, i.e. without a free surface, as "fuel slosh".[not verified in body] Such motion is characterized by "inertial waves" and can be an important effect in spinning spacecraft dynamics. Extensive mathematical and empirical relationships have been derived to describe liquid slosh.[2][3] These types of analyses are typically undertaken using computational fluid dynamics and finite element methods to solve the fluid-structure interaction problem, especially if the solid container is flexible. Relevant fluid dynamics non-dimensional parameters include the Bond number, the Weber number, and the Reynolds number.

Slosh is an important effect for spacecraft,[4] ships, and some aircraft. Slosh was a factor in the recent Falcon 1 second test flight anomaly, and has been implicated in various other spacecraft anomalies, including a near-disaster[5] with the Near Earth Asteroid Rendezvous (NEAR Shoemaker) satellite.

Spacecraft effects

Liquid slosh in microgravity[6][7] is relevant to spacecraft, most commonly Earth-orbiting satellites, and must take account of liquid surface tension which can alter the shape (and thus the eigenvalues) of the liquid slug. Typically, a large part of the mass fraction of a satellite is liquid propellant at/near Beginning of Life (BOL), and slosh can adversely affect satellite performance in a number of ways. For example, propellant slosh can introduce uncertainty in spacecraft attitude (pointing) which is often called jitter. Similar phenomena can cause pogo oscillation and can result in structural failure of space vehicle.

Another example is problematic interaction with the spacecraft Attitude Control System (ACS), especially for spinning satellites[8] which can suffer resonance between slosh and nutation, or adverse changes to the rotational inertia. Because of these types of risk, in the 1960s the National Aeronautics and Space Administration (NASA) extensively studied[9] liquid slosh in spacecraft tanks, and in the 1990s NASA undertook the Middeck 0-Gravity Dynamics Experiment[10] on the space shuttle. The European Space Agency has advanced these investigations[11][12][13][14] with the launch of SLOSHSAT. Most spinning spacecraft since 1980 have been tested at the Applied Dynamics Laboratories drop tower using sub-scale models.[15] Extensive contributions have also been made[16] by the Southwest Research Institute, but research is widespread[17] in academia and industry.

Research is continuing into slosh effects on in-space propellant depots. In October 2009, the Air Force and United Launch Alliance (ULA) performed an experimental on-orbit demonstration on a modified Centaur upper stage on the DMSP-18 satellite launch in order to improve "understanding of propellant settling and slosh." "The light weight of DMSP-18 allowed 12,000 pounds (5,400 kg) of remaining LO2 and LH2 propellant, 28% of Centaur’s capacity," for the on-orbit tests. The post-spacecraft mission extension ran 2.4 hours before the planned deorbit burn was executed.[18] ULA has additional small-scale demonstrations of cryogenic fluid management are planned with project CRYOTE in 2012-2014[19] leading to a ULA large-scale cryo-sat propellant depot test under the NASA flagship technology demonstration program in 2015.[19]

Practical effects

Sloshing or shifting cargo, water ballast, or other liquid (e.g. from leaks or fire fighting) can cause disastrous capsizing in ships due to free surface effect; this can also affect trucks and aircraft.

The effect of slosh is used to limit the bounce of a roller hockey ball. Water slosh can significantly reduce the rebound height of a ball[20] but some amounts of liquid seem to lead to a resonance effect. Many of the balls for roller hockey commonly available contain water to reduce the bounce height.

See also

References

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  1. ↑ Moiseyev, N.N. & V.V. Rumyantsev. "Dynamic Stability of Bodies Containing Fluid." Springer-Verlag, 1968.
  2. ↑ Ibrahim, R.A. "Liquid Sloshing Dynamics: Theory and Applications." Cambridge University Press, 2005.
  3. ↑ "Liquid Sloshing Dynamics" (Google Books) @ http://books.google.com/books?id=ctvhvH74ZzEC&dq=liquid+slosh+ibrahim&printsec=frontcover&source=bn&hl=en&sa=X&oi=book_result&resnum=4&ct=result
  4. ↑ Reyhanoglu, M. "Maneuvering control problems for a spacecraft with unactuated fuel slosh dynamics." Control Applications, 2003. Proc 2003 IEEE Conference. Volume 1, 23-25 June 2003, pp695-699.
  5. ↑ Veldman, A.E.P. et al. "The Numerical Simulation of Liquid Sloshing On-Board Spacecraft." J. Comp. Phys. 224 (2007) 82-99.
  6. ↑ Monti, R. "Physics of Fluids in Microgravity." CRC, 2002.
  7. ↑ Antar, B.N. & V.S. Nuotio-Antar. "Fundamentals of Low Gravity Fluid Dynamics and Heat Transfer." CRC, 1994.
  8. ↑ Hubert, C. "Behavior of Spinning Space Vehicles with Onboard Liquids." NASA GSFC Symposium, 2003.
  9. ↑ Abramson, H.N. "The Dynamic Behavior of Liquids in Moving Containers." NASA SP-106, 1966.
  10. ↑ Crawley, E.F. & M.C. Van Schoor & E.B. Bokhour. "The Middeck 0-Gravity Dynamics Experiment: Summary Report." NASA-CR-4500, Mar 1993.
  11. ↑ Vreeburg, J.P.B. "Measured States of SLOSHSAT FLEVO." IAC-05-C1.2.09, Oct 2005.
  12. ↑ Prins, J.J.M. "SLOSHSAT FLEVO Project, Flight and Lessons Learned." IAC-05-B5.3./B5.5.05, Oct 2005.
  13. ↑ Luppes, R. & J.A. Helder & A.E.P. Veldman. "Liquid Sloshing in Microgravity." IAC-05-A2.2.07, Oct 2005.
  14. ↑ Vreeburg, J.P.B. "SLOSHSAT Spacecraft Calibration at Stationary Spin Rates." J. Spacecraft & Rockets, v45, n1, p65, Jan/Feb 2008.
  15. ↑ [1][dead link]
  16. ↑ "18-Fluid Dynamics in Space Vehicles Brochure". Swri.org. http://www.swri.org/3pubs/brochure/d04/fdynspac/fdynspac.htm. Retrieved 2012-03-09.
  17. ↑ "Slosh Central". Sloshcentral.bbbeard.org. http://sloshcentral.bbbeard.org/. Retrieved 2012-03-09.
  18. ↑ Successful Flight Demonstration Conducted by the Air Force and United Launch Alliance Will Enhance Space Transportation: DMSP-18, United Launch Alliance, October 2009, accessed 2011-01-10.
  19. ↑ 19.0 19.1 Propellant Depots Made Simple, Bernard Kutter, United Launch Alliance, FISO Colloquium, 2010-11-10, accessed 2011-01-10.
  20. ↑ Sport ball for roller hockey; U.S. Patent 5516098; May 14, 1996; Jeffrey Aiello.
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