Fuel Slosh Research in Microgravity
2014 marks the eleventh year of Fuel Slosh studies that have been carried out at Embry-Riddle Aeronautical University. Initially funded by NASA Graduate Student Research Program (GSRP) along with Southwest Research Institute, the research was started by Keith Schlee, a graduate student, under the guidance of Dr. Sathya Gangadharan, professor at Embry-Riddle. The research involved extensive theoretical and computational analysis. A fuel slosh test rig was set up at the structures lab for the students and researchers to conduct various experiments and validate their results.
This research has evolved from the study of fuel slosh to the effect of diaphragms and baffles on slosh behavior and to the use of smart materials in actively damping the slosh. Tests on effectiveness of damping have also been carried out at NASA’s Spinning Slosh Test Rig (SSTR) located at the Southwest Research Institute (SwRI) in San Antonio, Texas. Research works are frequently published at but not limited to American Institute of Aeronautics and Astronautics (AIAA), American Society of Mechanical Engineers (ASME), NASA Technical Reports Server (NTRS) and so on.
A gist of some of the research works in Fuel Slosh carried out at Embry-Riddle is described below from the previous to the current on-going research:
(Note: Only selective research works are mentioned below, for complete list of fuel slosh research works contact Dr. Sathya Gangadharan)
Modeling and Parameter Estimation of Spacecraft Fuel Slosh Mode
The research is directed toward modeling fuel slosh on spinning spacecraft using simple pendulum analogs. The pendulum analog will model a spherical tank with no PMD’s. An electric motor will induce the motion of the pendulum to simulate free surface slosh. Parameters describing the simple pendulum models will characterize the modal frequency of the free surface sloshing motion. The one degree of freedom model will help to understand fuel sloshing and serve as a stepping stone for future more complex simulations to predict the NTC accurately with less time and effort.
A CFD Approach to Modeling Spacecraft Fuel Slosh
By using a Computational Fluid Dynamics (CFD) solver such as Fluent, a model for this fuel slosh can be created. The accuracy of the model must be tested by comparing its results to an experimental test case. Such a model will allow for the variation of many different parameters such as fluid viscosity and gravitational field, yielding a deeper understanding of spacecraft slosh dynamics.
Modeling of Free-Surface Fuel Slosh in Microgravity for Off-Axis Spacecraft Propellant Tanks
MATLAB SimMechanics fuel slosh model can be used to estimate slosh parameters and predict dynamic effects on dependent systems. Comparative flight data was acquired by spinning a mock spacecraft with partially filled propellant tanks in a microgravity environment. Empirical and simulated NTC’s are compared to validate a SimMechanics fuel slosh model.
A Computational and Experimental Analysis of Spacecraft Propellant Tanks Implemented with Flexible Diaphragms
The main objective of this research is to validate computational modeling of fuel slosh scenarios so that it may become the primary means of testing fuel slosh scenarios during initial spacecraft design. By expanding on past research objectives, this research aims at complementing the pre-existing data with new data from added computational and experimental simulations. Additionally, this research aims at conducting an extensive study of the computational fuel slosh models used in this investigation. The current research investigation presents detailed results of the fluid behavior within the tank and initiates an even more extensive investigation of fluid behavior for future fuel slosh research studies at ERAU.
An Investigation of Baffles and Asperities on Slosh Behavior in Propellant Tanks of Spacecraft and Launch Vehicles
The focus of this research is to investigate the fuel slosh behavior in propellant tanks. Different types of baffles and hemispherical asperities are introduced inside the tank to characterize the slosh behavior of the fluid. The modeling and the analysis of slosh is done using the CFD solver ANSYS CFX for tanks with and without baffles and for tanks with hemispherical asperities. Physical models are fabricated for experimental testing using the fuel slosh test facility at Embry Riddle Aeronautical University. Using the single axis linear actuator and fuel tank set up in the test facility, experimental results are obtained with and without baffles. The experiment and CFD modeling results are compared.
Slosh Damping with Floating Electro-active Micro-baffles
Embedding floating micro-baffles with an electro-active material such that the baffle can be manipulated when exposed to a magnetic field preserves the benefits of both floating and static baffle designs. Activated micro-baffles form a rigid layer at the free surface and provide a restriction of the fluid motion. Proposed micro-baffle design and magnetic activation source method along with proof-of-concept experiments comparing the scope of this research to previous PMD methods are presented. A computational fluid dynamics approach is outlined. Preliminary proof-of-concept testing indicates floating electro-active micro-baffles reduce the damping time of sloshing by up to 88% as compared to the same slosh condition with the absence of any PMDs.
Development of a Magnetostrictive Propellant Management Device (MSPMD) for Hybrid Active Slosh Damping in Spacecraft Application
To study the use of a hybrid Magnetostrictive membrane as a Magnetostrictive Propellant Management Device (MSPMD) to actively control the free surface effect and reduce fuel slosh.. The viability of merging existing diaphragm membrane aka Propellant management device (PMD) with a magnetostrictive inlay embedded with the Terfenol-D matrix / MR-Fluid allows us to actively control the membrane during in-flight conditions. Apart from the development, analysis on the control of the hybrid active membrane and the use of the same to dampen fuel slosh is also performed in order to establish the proof of concept. During the development process of the hybrid active membrane, the geometric dependency of the meta-smart structure is analyzed to optimize the membrane shape, size and material.
Dr. Sathya Gangadharan is a Professor of Mechanical Engineering at Embry-Riddle, Daytona Beach campus.