Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “slosh”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

Longitudinal and transverse modes of slosh wave excitation in rotating dewar associated with gravity jitters

Characteristics of slosh waves based on the dynamical behavior of oscillations at the liquid-vapor interface have been investigated. Twelve case studies of slosh wave excitation due to various frequencies of gravity jitters under different rotating speeds of the propellant tank and different levels of background gravity environment have been simulated. The study shows that slosh waves excited inside the spacecraft propellant tank are characterized by the lowest frequency of the waves initiated, frequencies of the gravity jitters imposed on the propellant system, the levels of background gravity environment, and dewar rotating speeds. Conditions for suppression and amplification of the slosh waves are discussed.

Hung, R. J.↗
NASA NTRS1991

Analysis of small-amplitude low gravity sloshing in axisymmetric tanks

The theory of linearized, low-gravity sloshing in axisymmetric tanks is developed in an integral minimization form that permits numerical solutions to be computed easily and that can be modified readily when better knowledge about the important surface physics phenomena becomes available from space experimentation. The slosh force and equivalent mechanical model are also derived, including the correction of errors in previous analyses. Several numerical examples are presented for spherical and cylindrical tanks. The contact angle used in the examples is 5 deg and a 'free' contact line is assumed. The results show that the nondimensional slosh frequency and slosh mass for a spherical tank are smaller for low gravity conditions than for normal gravity conditions, whereas they are larger for cylindrical tank.

Dodge, Franklin T.↗
NASA NTRS1992

Fluid stress disturbance activated by gravity jitters induced slosh waves in microgravity

A full scale Gravity Probe-B (GP-B) Spacecraft propellant dewar tank subjected to various frequencies of gravity jitter have been investigated. Excitation of slosh waves induced by gravity jitter are simulated. Results show that fluid stress distribution exerted on the walls of the rotating dewar are closely related to the characteristics of slosh waves excited on the liquid-vapor interface in the rotating dewar tank. Slosh wave excitations shift the fluid mass distribution in the dewar tank which impose time dependent variations in GP-B Spacecraft moment of inertia, angular momentum, and torque produced by imbalance fluid stresses. This can provide a set of data leading toward the control of spacecraft imbalance caused by the uneven fluid stress distribution from slosh waves.

Hung, R. J.↗
NASA NTRS1993

Sloshing dynamics on rotating helium dewar tank

The generalized mathematical formulation of sloshing dynamics for partially filled liquid of cryogenic superfluid helium II in dewar containers driven by both the gravity gradient and jitter accelerations applicable to scientific spacecraft which is eligible to carry out spinning motion and/or slew motion for the purpose to perform scientific observation during the normal spacecraft operation are investigated. An example is given with Gravity Probe-B (GP-B) spacecraft which is responsible for the sloshing dynamics. The jitter accelerations include slew motion, spinning motion, atmospheric drag on the spacecraft, spacecraft attitude motions arising from machinery vibrations, thruster firing, pointing control of spacecraft, crew motion, etc. Explicit mathematical expressions to cover these forces acting on the spacecraft fluid systems are derived. The numerical computation of sloshing dynamics were based on the non-inertia frame spacecraft bound coordinate, and solve time dependent, three-dimensional formulations of partial differential equations subject to initial and boundary conditions. The explicit mathematical expressions of boundary conditions to cover capillary force effect on the liquid vapor interface in microgravity environments are also derived. The formulations of fluid moment and angular moment fluctuations in fluid profiles induced by the sloshing dynamics, together with fluid stress and moment fluctuations exerted on the spacecraft dewar containers were derived. Results were widely published in the open journals.

Hung, R. J.↗
NASA NTRS1995

Slosh wave and geyser excitations due to liquid hydrogen shut-off during draining in microgravity

The dynamical behavior of liquid hydrogen shut-off during draining, and shut-off at the moment of the incipience of a suction dip have been investigated. It shows that a large amplitude surge is observed for liquid in the container at the moment of liquid hydrogen shut-off in reduced gravity. It also shows that slosh waves accompanied by a strong geyser are developed for surge-related flow fields induced by liquid hydrogen shut-off at the incipience of a suction dip. In the slosh wave excitation, both a lower gravity environment and higher flow rate before the shut-off of liquid draining are resonsible for the initiation of greater amplitude slosh waves. Slosh wave excitation, due to shut-off during liquid hydrogen draining, shift the fluid mass distribution in the container which imposes time-dependent variation in the spacecraft moment of inertia. This provides important information necessary for on-orbit guidance and attitude control of spacecraft.

Hung, R. J.↗
NASA NTRS1995

Baffle Effect on Sloshing-Modulated Torques Responsed to Orbital Accelerations in Microgravity

The behavior of sloshing-dynamics-modulated fluid systems driven by orbital accelerations including gravity gradient and jitter accelerations has been studied. Partly liquid-filled rotating Dewars applicable to a full-scale Gravity Probe-B Spacecraft container with and without baffle are considered. Results show that a slosh wave excited along the liquid-vapor interface induced by jitter-acceleration-dominated orbital accelerations provides a torsional moment with an up-and-down movement of bubble oscillations in the rotating Dewar. The fluctuations of fluid forces and fluid moment (torque) exerted on the Dewar wall of the container caused by slosh-wave excitation driven by orbital accelerations are also investigated. Since the viscous force across a liquid-solid interface and the surface-tension force across a liquid-vapor or liquid-solid interface can greatly contribute to the damping effect of slosh-wave excitation, a rotating Dewar with a baffle provides more areas of liquid-solid, and liquid-vapor, and solid-vapor interfaces than does a rotating Dewar without a baffle. Results show that the damping effect provided by the baffle reduces the amplitudes of force and moment feedback from the fluids to the container-in particular, the components of fluctuations transverse to the direction of the baffle boards.

Pan, H. L.↗
NASA NTRS1994

Peculiar Behavior of He II Disturbances due to Sloshing Dynamics Driven by Jitter Accelerations Associated with Slew Motion in Microgravity

The mathematical formulation of Dewar container sloshing dynamics when partially filled with superfluid liquid He 11 driven by the gravity jitter acceleration associated with slew motion in a microgravity environment is studied. Numerical computation of the sloshing dynamics is based on the non-inertia container bound co-ordinate, and solving time-dependent, three-dimensional formulations of partial differential equations subject to initial and boundary conditions. This study discloses the capillary effect of the sloshing dynamics governing the liquid-vapour interface fluctuations driven by the gravity jitter acceleration associated with slew motion, which affects the stability of the fluid system in a microgravity environment. The peculiar behaviour of superfluid helium when reacting to the sloshing dynamics driven by the gravity jitter acceleration associated with slew motion in a microgravity environment is also investigated.

Hung, R. J.↗
NASA NTRS1995

Effect of Baffle on Gravity-Gradient-Excited Slosh Waves and Spacecraft Moment and Angular-Momentum Fluctuations in Microgravity

The dynamical behavior of fluids affected by the asymmetric gravity gradient acceleration has been investigated. In particular, the effects of surface tension on partially filled rotating fluids applicable to a full-scale Gravity Probe-B Spacecraft dewar tank with and without baffles are studied. Results of slosh wave excitation along the liquid-vapor interface induced by gravity gradient acceleration indicate that the gravity gradient acceleration is equivalent to the combined effect of a twisting force and a torsional moment acting on the spacecraft. The results are clearly seen from one-up one-down and one-down one-up oscillations in the cross-section profiles of two bubbles in the vertical (r, z)-plane of the rotating dewar, and from the eccentric contour of the bubble rotating around the axis of the dewar in a horizontal (r, theta)-plane. As the viscous force, between liquid and solid interface, greatly contributes to the damping of slosh wave excitation, a rotating dewar with baffles provides more areas of liquid-solid interface than that of a rotating dewar without baffles. Results show that the damping effect provided by the baffles reduces the amplitude of slosh wave excitation and lowers the degree of asymmetry in liquid-vapor distribution. Fluctuations of angular momentum and fluid moment caused by the slosh wave excited by gravity gradient acceleration with and without baffle boards are also investigated. It is also shown that the damping effect provided by the baffles greatly reduces the amplitudes of angular momentum and fluid moment fluctuations.

Hung, R. J.↗
NASA NTRS1995

Mathematical Model of Bubble Sloshing Dynamics for Cryogenic Liquid Helium in Orbital Spacecraft Dewar Container

A generalized mathematical model is investigated of sloshing dynamics for dewar containers, partially filled with a liquid of cryogenic superfluid helium 2, driven by both gravity gradient and jitter accelerations applicable to two types of scientific spacecrafts, which are eligible to carry out spinning motion and/or slew motion to perform scientific observations during normal spacecraft operation. Two examples are given for the Gravity Probe-B (GP-B) with spinning motion, and the Advanced X-Ray Astrophysics Facility-Spectroscopy (AXAF-S) with slew motion, which are responsible for the sloshing dynamics. Explicit mathematical expressions for the modelling of sloshing dynamics to cover these forces acting on the spacecraft fluid systems are derived. The numerical computation of sloshing dynamics will be based on the noninertial frame spacecraft bound coordinate, and we will solve the time-dependent three-dimensional formulations of partial differential equations subject to initial and boundary conditions. Explicit mathematical expressions of boundary conditions lo cover capillary force effects on the liquid-vapor interface in microgravity environments are also derived. Results of the simulations of the mathematical model are illustrated.

Hung, R. J.↗
NASA NTRS2011

Sloshing in Liquid Hydrogen and LOX Propellant Tanks After Main Engine Cut-off

NASA Marshall Space Flight Center is designing and developing the Main Propulsion System (MPS) for Ares launch vehicles. The objective of this study is to calculate the sloshing forces and moments in the LH2 and LO2 propellant tanks using a CFD/VOF analysis under realistic flight conditions. Propellant sloshing in the liquid hydrogen (LH2) and the liquid oxygen (LO2) propellant tanks after Main Engine Cut Off (MECO) was modeled using the Volume of Fluid (VOF) module of the computational fluid dynamics code, CFD-ACE+. The present simulation shows that there are substantial sloshing side forces acting on the LH2 tank during the deceleration of the vehicle after MECO. The LH2 tank features a side wall drain pipe. The side loads result from the residual propellant mass motion in the LH2 tank which is initiated by the stop of flow into the drain pipe at MECO. The simulations show that radial force on the LH2 tank wall is less than 50 lbf and the radial moment calculated based up the center of gravity of the vehicle is predicted to be as high as 300 lbf-ft. The LO2 tank features a bottom dome drain system and is equipped with sloshing baffles. The remaining LO2 in the tank slowly forms a liquid column along the centerline of tank under the zero gravity environments. The radial force on the LO2 tank wall is predicted less than 100 lbf. The radial moment calculated based on the center of gravity of the vehicle is predicted as high as 4500 lbf-ft just before MECO and dropped down to near zero after propellant draining stopped completely.

Kim, Sura↗
NASA NTRS2004

Parameter Estimation of Spacecraft Fuel Slosh Model

Fuel slosh in the upper stages of a spinning spacecraft during launch has been a long standing concern for the success of a space mission. Energy loss through the movement of the liquid fuel in the fuel tank affects the gyroscopic stability of the spacecraft and leads to nutation (wobble) which can cause devastating control issues. The rate at which nutation develops (defined by Nutation Time Constant (NTC can be tedious to calculate and largely inaccurate if done during the early stages of spacecraft design. Pure analytical means of predicting the influence of onboard liquids have generally failed. A strong need exists to identify and model the conditions of resonance between nutation motion and liquid modes and to understand the general characteristics of the liquid motion that causes the problem in spinning spacecraft. A 3-D computerized model of the fuel slosh that accounts for any resonant modes found in the experimental testing will allow for increased accuracy in the overall modeling process. Development of a more accurate model of the fuel slosh currently lies in a more generalized 3-D computerized model incorporating masses, springs and dampers. Parameters describing the model include the inertia tensor of the fuel, spring constants, and damper coefficients. Refinement and understanding the effects of these parameters allow for a more accurate simulation of fuel slosh. The current research will focus on developing models of different complexity and estimating the model parameters that will ultimately provide a more realistic prediction of Nutation Time Constant obtained through simulation.

Gangadharan, Sathya↗
NASA NTRS2016

Validation of High-Resolution CFD Method for Slosh Damping Extraction of Baffled Tanks

The predicted slosh damping values from Loci-Stream-VOF agree with experimental data very well for all fill levels in the vicinity of the baffle. Grid refinement study is conducted and shows that the current predictions are grid independent. The increase of slosh damping due to the baffle is shown to arise from: a) surface breakup; b) cascade of energy from the low order slosh mode to higher modes; and c) recirculation inside liquid phase around baffle. The damping is a function of slosh amplitude, consistent with previous observation. Miles equation under predicts damping in the upper dome section.

Yang, H. Q.↗
NASA NTRSDate not supplied

Characterization of Slosh Damping for Ortho-Grid and Iso-Grid Internal Tank Structures

Grid stiffened tank structures such as Ortho-Grid and Iso-Grid are widely used in cryogenic tanks for providing stiffening to the tank while reducing mass, compared to tank walls of constant cross-section. If the structure is internal to the tank, it will positively affect the fluid dynamic behavior of the liquid propellant, in regard to fluid slosh damping. As NASA and commercial companies endeavor to explore the solar system, vehicles will by necessity become more mass efficient, and design margin will be reduced where possible. Therefore, if the damping characteristics of the Ortho-Grid and Iso-Grid structure is understood, their positive damping effect can be taken into account in the systems design process. Historically, damping by internal structures has been characterized by rules of thumb and for Ortho-Grid, empirical design tools intended for slosh baffles of much larger cross-section have been used. There is little or no information available to characterize the slosh behavior of Iso-Grid internal structure. Therefore, to take advantage of these structures for their positive damping effects, there is much need for obtaining additional data and tools to characterize them. Recently, the NASA Marshall Space Flight Center conducted both sub-scale testing and computational fluid dynamics (CFD) simulations of slosh damping for Ortho-Grid and Iso-Grid tanks for cylindrical tanks containing water. Enhanced grid meshing techniques were applied to the geometrically detailed and complex Ortho-Grid and Iso-Grid structures. The Loci-STREAM CFD program with the Volume of Fluid Method module for tracking and locating the water-air fluid interface was used to conduct the simulations. The CFD simulations were validated with the test data and new empirical models for predicting damping and frequency of Ortho-Grid and Iso-Grid structures were generated.

Douglas G. Westra↗
NASA NTRS2018

Validation of Slosh Modeling Approach Using STAR-CCM+

Without an adequate understanding of propellant slosh, the spacecraft attitude control system may be inadequate to control the spacecraft or there may be an unexpected loss of science observation time due to higher slosh settling times. Computational fluid dynamics (CFD) is used to model propellant slosh. STAR-CCM+ is a commercially available CFD code. This paper presents a comparison between STAR-CCM+ liquid slosh modeling results and experimental, empirically, and analytically derived results. The geometries examined are a bare right cylinder tank and a right cylinder

Benson, David↗
NASA NTRSDate not supplied

Analytical Investigation of Propellant Slosh Stability Boundary on a Space Vehicle

The effect of propellant sloshing upon the stability of a liquid-propelled space vehicle has been studied extensively. For a typical space vehicle with thrust vector control and asingle slosh tank, the Bauer slosh danger zone is located between the vehicle center of mass and the center of percussion while ignoring effects like aerodynamics and axial acceleration. If the slosh mass is located between these two locations, baffles may be required toprovide additional damping for stability. Although this criteria is widely used in the launch vehicle flight controls community, its application is limited to the aforementioned configuration and assumptions. In this work, the methodology behind the classic single-tank criteria is extended to other tank configurations and includes previously ignored effects. First, the variation of the classic danger zone for a tandem tank configuration where the tanks are located along the vehicle centerline or symmetrically offset from the centerline is investigated. Second, a vehicle with a single centerline tank and pair of outboard reaction jets, rather than thrust vectoring, for attitude control is studied. Finally, the impacts of aerodynamics and vehicle axial acceleration on the classic single-tank criteria are analyzed.

Jing Pei↗
NASA NTRSDate not supplied

Slosh-Induced Ullage Collapse Validation by Computational Fluid Dynamics and Application to In-space Propellant Dynamics

Ullage collapse predictions made using Computational Fluid Dynamics (CFD) were validated then made for an in-space cryogenic propellant unsettling application. Ullage collapse is the decrease in propellant tank pressure due to cooling of the ullage gas, which can be significant for cryogenic propulsion systems. Vehicles may be developed that are robust to temperature and pressure changes caused by heat leaks, e.g., propellant tanks with high maximum operation pressures, technologies yielding active thermal conditioning, and systems with ample pressurant for conditioning. These methods are robust because additional mass, cost, and complexity are used to address cryogenic fluid management (CFM). As vehicles are optimized for increased payload capacity, tracking of events such as ullage collapse and self-pressurization in tanks will become increasingly important for propellant inventory calculations. Some ullage collapse events can be studied through ground experimentation, but propellant unsettling in and around in-space coast mission phases must be studied in the absence of an acceleration field. Computational Fluid Dynamics is a powerful tool to address this need, enabling prediction of complex physics prior to flight. Validation of the chosen CFD tool and modeling methodology was done using data from a previously conducted subscale slosh-induced ullage collapse ground test performed in part by the Japan Aerospace Exploration Agency (JAXA). A small tank was partially filled with liquid nitrogen and pressurized with gaseous nitrogen at various temperatures. The tank was oscillated laterally to induce high amplitude slosh dynamics resulting in wave breakup. Successful qualitative validation of slosh wave dynamics and quantitative validation of ullage collapse promoted confidence in extending ullage collapse predictions to a flight application. Mechanisms of ullage collapse caused by main engine cutoff while in-space were identified. Both slosh dynamics leading to engine shutdown and body dynamics following shutdown were shown to contribute to propellant unsettling and ullage collapse.

J M Brodnick↗
NASA NTRSDate not supplied

Evaluation of Long Term Microbial Regrowth in Slosh Water Tanks From the International Space Station

The NASA Launch Services Program (LSP) maintained the SPHERES-Slosh experiment aboard the International Space Station (ISS) between 2013 and 2019. The purpose of the Slosh experiment was to examine how liquids move inside fuel tanks in a microgravity environment. These tanks were similar to water storage tanks planned for use aboard future space systems, where large dormant periods between crew-use will provide similar conditions for biological growth or chemical leaching. The water within the SLOSH tanks remained undisturbed for over five years after testing concluded, providing a unique sample for stored water under microgravity conditions without prior protocols for microbial control such as sterilization or addition of biocides. The Slosh storage tanks were returned to Kennedy Space Center (KSC) aboard SpaceX CRS-18 mission in November 2019. Upon return of the tanks, the water within each tank was analyzed to determine how the water chemistry and biology changed during its tenure in microgravity. The data obtained and described within this publication provided a basis and reasoning for planning water storage and purification treatment methods aboard ISS, Gateway, and future space habitats. Results demonstrated that low microbial concentrations were present within the water, as expected since no biocide treatment was employed, yet no extensive biofilm formation was observed after 5 years even in the presence of microbial food sources such as the polycarbonate structure and food color additives. This experimentation demonstrates that future biofilm studies should be performed on this type of experimental setup with proper controls aboard ISS to examine microbial regrowth to improve microbial control within space water systems.

Luke B. Roberson↗
NASA NTRSDate not supplied

Modeling Low-G Slosh Using Negative Mass

The modeling of the behavior of fluids in low- or microgravity is a field with little validated data but of great interest to space agencies and companies in the face of humanity’s expanding presence beyond low Earth orbit. Efforts to refuel and repair satellites in geostationary orbit require an understanding of the behavior of sloshing fuel in microgravity. The stability of remote sensing equipment and satellites depends on robust fluid slosh dampening or very accurate modeling, and the Artemis program includes the refueling of large landing systems in its architecture. However, current methodologies are quite binary: either use a relatively low-accuracy equivalent mechanical model or use computational fluid dynamics which are not practical for onboard systems due to their relatively high computational cost. In this work, a novel method of tracking the bubble rather than tracking the fuel itself is presented. Computational fluid dynamics simulations are used to validate the model based on available experimental data, and the dynamics of a refueler spacecraft based on Gateway’s Logistics Module are simulated both for the sloshing case and without sloshing considered.

Matthew M. Wittal↗