von Karman Institute Lecture Series and Events

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The registration is free of charge for the people attending the 8^th European Symposium on Aerothermodynamics for Space Vehicle. For the person not attending the symposium, the price is 100 Euro and should be paid in advance. No payment accepted on site.

Abstracts

Jean –Marie Buchlin is the Head of the Environmental and Applied Fluid Dynamics department at von Karman Institute and full professor at the Universté Libre de Bruxelles (ULB). His research domains are mainly related to heat transfer, phase changes, film instabilities and infrared thermography. He has published about 200 technical notes, books contributions, scientific manuscripts in refereed journals and conference proceedings.

 

 

 

 

PANORAMA OF LIQUID SLOSHING DYNAMICS
Raouf A. Ibrahim
Wayne State University, Department of Mechanical Engineering, Detroit, MI 48202, USA
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Raouf A. Ibrahim is a Professor of Mechanical Engineering at Wayne State University. His research activities deal with nonlinear random vibration, liquid sloshing dynamics, friction-induced vibration, vibro-impact dynamics, and structural life assessment and reliability. He has published more than 120 papers in refereed journals, and three research monographs entitled Parametric Random Vibration (Wiley, 1985), Liquid Sloshing Dynamics: Theory and Applications (Cambridge University Press, 2005), and Vibro-Impact Dynamics: Modeling, Mapping and Applications (Springer-Verlag, Berlin, 2009.

Abstract:

Sloshing refers to the free liquid surface motion inside its container. The problem of liquid sloshing dynamics remains of great concern to aerospace, civil, and nuclear engineers, physicists, designers of road tankers and ship tankers, and mathematicians. Each discipline treats the problem from a different point of view. For example, civil engineers and seismologists have been studying liquid sloshing effects on large dams, oil tanks and elevated water towers under ground motion. Liquid tanks are also mounted on the roof of multistory buildings as a passive means to control building oscillations due to earthquakes. Since the early 1960’s, the problem of liquid sloshing dynamics has been of major concern to aerospace engineers studying the influence of liquid propellant sloshing on the flight performance of jet vehicles. In ocean engineering, the dynamic stability of liquefied natural gas tankers and ship cargo tankers, and liquid hydrodynamic impact loading are problems of current interest to the designers of such systems. Liquid sloshing impact forces acting on road tankers can have a significant influence on the vehicle's driving dynamics and stability.

The basic problem of liquid sloshing involves the estimation of hydrodynamic pressure distribution, forces, moments and natural frequencies of the free liquid surface. These parameters have direct effect on the dynamic stability and performance of moving containers. The hydrodynamic pressure of liquids in moving rigid containers is comprised of two distinct components. The first is directly proportional to the acceleration of the tank, while the second is known as "convective" pressure and represents the free surface liquid motion. As the liquid free surface motion becomes nonlinear the free surface is no longer planar. The main sources of nonlinearity in the fluid field equations are the free surface boundary conditions. For circular cylinders and rectangular containers, there is a critical fluid depth, which separates two regimes of liquid nonlinearity; namely hard and soft nonlinearities.

Of particular interest is the problem of liquid parametric sloshing, known also as Faraday waves, which has been a long standing subject of interest. The development of the theory of Faraday waves has witnessed a number of controversies regarding the analytical treatment of sloshing modal equations and modes competition. Some controversies reported in the literature among different researchers regarding the formulations of nonlinear sloshing modal interactions will be assessed. One of the significant contributions is that the energy is transferred from lower to higher harmonics and the nonlinear coupling generated static components in the temporal Fourier spectrum leading to a contribution of a non-oscillating permanent sinusoidal deformed surface state. An overview of the physics of Faraday wave competition together with pattern formation under single-, two- three- and multi-frequency parametric excitation will be presented. Significant effort was made in order to understand and predict the pattern selection using analytical and numerical tools. Under random parametric excitation and g-jitter, the behavior of Faraday waves is described in terms of stochastic stability modes and spectral density function.

When interacting with its elastic container, or its support structure, the free liquid surface can exhibit fascinating types of motion in the form of energy exchange between interacting modes. The coupling may take place between the liquid free surface dynamics and either with the tank bending oscillations or the breathing modes (or shell modes). Breathing vibrations of the tank are essentially radial, such that both flexure and stretching deformations of the wall occur while the longitudinal axis of the tank remains straight. The linear analysis deals mainly with the estimation of the coupled natural frequencies of liquid-structure systems. Under low gravity field, the surface tension is dominant and the liquid may be oriented randomly within the tank depending essentially upon the wetting characteristics of the tank wall. Physicists and aerospace engineers focused on studying the stability of static and dynamic free liquid surface, and contact line and contact angle. The problem includes forcing sloshing for slipping and anchored contact lines. Capillary systems including Marangoni flow and liquid bridges for static and dynamic cases were extensively studied in the literature.

 

NONLINEAR MODELING AND CONTROL OF SPACE VEHICLES WITH PROPELLANT SLOSH DYNAMICS
Mahmut Reyhanoglu
Department of Physical Sciences Embry-Riddle Aeronautical University Daytona Beach, FL 32114, USA

Mahmut Reyhanoglu received the Ph.D. degree in Aerospace Engineering from the University of Michigan, Ann Arbor, Michigan, in 1992. He is currently a Professor of Engineering Physics at Embry-Riddle Aeronautical University, Daytona Beach, Florida, USA. He has authored/co-authored four book chapters and over 100 archival journal and proceedings papers in the areas of nonlinear dynamics, controls, and robotics. Dr. Reyhanoglu is a senior member of AIAA and IEEE.

Abstract:

Propellant slosh has been a problem studied in spacecraft design since the early days of large, liquid–fuel rockets. In launch vehicles or spacecraft, sloshing can be induced by propellant tank motions resulting from guidance and control system commands or from changes in vehicle acceleration. When the fuel tanks are only partially filled, large quantities of fuel move inside the tanks under translational and rotational accelerations and generate the slosh dynamics. To mitigate the destabilizing effects of sloshing, a variety of passive techniques have been employed, including the use of baffles, bladders, and partitions, which are meant to increase energy dissipation and limit the movement of liquid fuel. However, these passive techniques do not completely succeed in cancelling the sloshing effects. Moreover, these suppression methods add mass and structural complexity to the vehicle. Therefore, it is desirable to control the sloshing using active methods.

We formulate the dynamics of a spacecraft with a liquid propellant tank including the prominent fuel slosh modes characterized by using multi-mass-spring and multi-pendulum models. It is assumed that the spacecraft acceleration due to the main engine thrust is large enough so that surface tension forces do not significantly affect the propellant motion during main engine burns. The control objective, as is typical in a thrust vector control design for a liquid upper stage spacecraft during orbital maneuvers, is to control the translational velocity vector and the attitude of the spacecraft, while attenuating the sloshing modes characterizing the internal dynamics. Lyapunov-based nonlinear feedback control laws are designed to achieve the control objective. The theoretical results are applied to the AVUM upper stage--the fourth stage of the European launcher Vega. Simulation examples are included to illustrate the effectiveness of the control laws.

 

INTRODUCTION CFD FOR SLOSHING PHENOMENA AND APPLICATION OF SUPPRESSION DEVICES
Konstantinos Myrillas
von Karman Institute for Fluid Dynamics, Chaussée de Waterloo 72, 1640 Rhode-St-Genèse, Belgium

Konstantinos Myrillas is a senior research engineer at the von Karman Institute for Fluid Dynamics in Belgium. He received a PhD in Applied Physics from the “Universitè Libre de Bruxelles” in 2011. His research activities mainly focus on CFD modelling of liquid/gas interface systems.

Abstract: 

Sloshing phenomena can have very serious effects on the stability and control of space vehicles, therefore their study began early in the design phases of rockets and spacecrafts. For these studies theoretical, experimental and numerical models can be employed. Due to the recent progress in Computational Fluid Dynamics (CFD), new ways to simulate the sloshing phenomena are available today. Numerical simulations can utilize the processing power of modern computers with parallel capabilities in order to provide accurate predictions of the most complex problems for sloshing in space vehicles. Moreover, the application of different devices for the reduction or suppression of sloshing can be studied using such numerical tools, providing a cost and time effective tool in the design process.  

Many CFD codes with similar capabilities are available today. The open source CFD code OpenFoam is discussed in the lecture as an example of an increasingly popular code, readily available to everyone and highly customizable. Complex geometries nowadays are not difficult to simulate, thanks to advanced meshing tools, which are mostly automated and can provide a high quality mesh for the computations in rather short time.  

From the different numerical approaches available, focus is set on the Volume of Fluid (VOF) method for multiphase flows with a free surface. The method uses the volume fraction of the phases to track the liquid inside the computational domain and compute the dynamics of the free surface. It exhibits high robustness that allows for complex motions including folding of the interface, gas entrainment and splashing. 

The excitation of the reservoir can be simulated with moving mesh methods, where the excitation can be described by simple expressions or complex 3D motions in time. The possibility of changing the body forces allows for simulating low gravity conditions easily.

All these tools allow for accurate prediction of the sloshing behavior inside the reservoir at different conditions. The effectiveness of sloshing suppression devices can also be tested numerically, reducing the design time and cost.

IMPACT OF LIQUID SLOSHING ON SPACECRAFT BEHAVIOR
Philipp Behruzi
Airbus Defence & Space, Bremen, Germany

Philipp Behruzi is Expert and Team Leader Fluid Mechanics in the department Thermal Engineering at EADS Astrium in Bremen, Germany. He received his PhD at Aachen University (RWTH), Germany, in 2000. He also received his Diploma in Aerospace Engineering at the University of Aachen. After his PhD, Philipp Behruzi signed up at EADS Astrium. Philipp Behruzi is Expert in Fluid Mechanics, since 2010 he is Team Leader and since 2013 he is Designated Senior Expert.

Abstract:

Sloshing of liquids in spacecraft propellant tanks, including satellites, transfer vehicles and upper stages, is a major point of continuous study. Driven by the increasing needs to carry out developments in a cost effective manner, Airbus DS assures a continuous improvement of the modelling capability with respect to sloshing. For the space industry the Ariane 6 and the MPCV projects are at this time ongoing. The presentation therefore focuses on sloshing aspects which are relevant for these projects.

Upper stages such as the Ariane launchers or the MPCV spacecraft will encounter ballistic flight phases leading to strong sloshing motions. An effective layout of the mission phases however requires considering the complex interactions including the sloshing motion, the rigid body dynamics, external disturbances, the propulsion system and the flight controller. This concerns the optimization e.g. of the controller, the propellant budget or the maneuver sequences.

Considering cold gas RCS, the thrust level may even change over time as the tank pressure changes during flight or in case liquid is vented overboard. A strong emphasis is also put on phase change which is of relevance for cryogenic liquids. At Airbus DS these aspects of in-orbit behavior are simulated with our in-house software tool "FiPS". The tool was frequently used for the layout of the Ariane upper stages and will now be utilized e.g. for Ariane 6 and MPCV. Details are given concerning the software.

The verification of the tool is an ongoing task. As a first step isothermal sloshing tests will be carried out at the DLR Institute in Bremen under 1g conditions. The facility's 2.6 ton Hexapod is used to carry out sloshing tests for benchmarking FiPS on ground. The test will be carried out beginning of 2015. Details will be given. In a second step a 0g experiment on the ISS is under consideration which will be also discussed.

The accuracy of the analyses carried out with FiPS depend on the accuracy of the CFD solver. Slosh modeling, especially with CFD, is therefore continuously assessed by comparisons with benchmark experiments and by making use of new numerical models. Airbus DS participates to dedicated projects such as the COMPERE project (steered by CNES and DLR) since the last two decades in order to improve slosh modeling in high-g and low-g environments. Selected test cases will be described.

In the frame of COMPERE and the ESA MAP project benchmark experiments were also conducted under 0g on the Maser 12 sounding rocket. The benchmark results of this sounding rocket flight will be discussed.

 

LIQUID SLOSHING CHARACTERIZATION BY MEAN OF NON-INTRUSIVE
Alessia Simonini and Maria Rosaria Vetrano
von Karman Institute for Fluid Dynamics, Chaussée de Waterloo 72, 1640 Rhode-St-Genèse, Belgium

Maria Rosaria Vetrano is Assistant professor at the von Karman Institute for Fluid Dynamics in Belgium. She received a PhD in Applied Physics from the “Universitè Libre de Bruxelles” in 2006. Her research activities focus on the development of non-intrusive measurement techniques in two-phase flows, Mie scattering theories, inverse modelling and phase change processes. She has published about 70 scientific manuscripts in refereed journals and conference proceedings.

Abstract:

The development of commercial and scientific space activities depends on the possibility for the spacecraft to operate in terms of space mission requirements. The management of conventional and cryogenic propellants on spacecraft is one of the key technologies, which influence the normal operating conditions. The main component of this technology is the tank which allows the storage of the propellant, its pressure and thermal control, the propellant acquisition and its transfer. The development of a system which satisfies space mission requirements, needs a deep understanding of the behavior of the propellant subjected to extreme environmental conditions, such as variation of gravity level, exposure to low gravity, external imposed unsteady acceleration, as well as radiation and conductive heat transfer. Understanding the propellant behavior means being able to predict its position and topology inside the tank, for given external unsteady and gravitational accelerations. The prediction and control of the fluid motion is difficult due to the different parameters playing a role in the dynamic system such as the geometry of the container, the type of external excitation (shape, frequency content and amplitude) and finally the level of the liquid. In this context, the creation of a reliable and consistent experimental database is crucial for assessing the accuracy and the range of validity of existing numerical models.

The main goal of this work is to present an overview of the experimental measurement techniques which can be used to characterize the liquid sloshing phenomenon. The talk will be focused on such techniques, which generates a minimal disturbance to the flow, i.e. the ones generally called “non-intrusive”. More in particular it will be shown how Particle Image Velocimetry (PIV) and Hyper Resolution PIV can be used to both track the liquid/gas interface during sloshing and give accurate measurement of the velocity field into the fluid. A new technique, capable to evaluate the 3D shape of liquid sloshing (linear conditions) will be also presented. The final part of the talk will be addressed to the possibility of using such nonintrusive measurement conditions in presence of sloshing of cryogenic fluids.

8th European Symposium on Aerothermodynamics for Space Vehicles

Since 1991, a regular forum at European level for technology discussion and interaction on aerothermodynamics and fluid mechanics has been established by ESA through the European Symposium on Aerothermodynamics for Space Vehicles. The Symposium encompasses the whole spectrum of moving bodies at high speed, from take-off to landing, but also orbital ascent / descent, aeroheating and thermodynamics of propulsion, presenting them through four major lines:

(i) spacecrafts and exploration missions including aerothermodynamics; aero-breaking; stability; aero-decelerators and stabilisers; ablation and dust-erosion modelling; ground testing facilities improvements, qualifications and measurement techniques; non-intrusive measurement techniques development and sensors miniaturization; flight measurement techniques and extrapolation from ground to flight, etc

(ii) expendable launchers including propulsion and combustor analysis related to liquid and solid engines; multi-phase flow phenomena; free-surface flow-models; cooling, atomization, ignition; chemistry models; acoustics and instabilities; plume interaction; payload impingement; buffeting and flight testing; etc

(iii) innovative access to space & suborbital flights including vehicle & system studies and re-usability; computational fluid dynamics CFD and multi-disciplinary analysis (including aero-elastic, materials, flight mechanics); safety & risk analysis, regulations and rules; propulsion aerodynamics, air-breathing and hybrid engines cycle & analysis (LRE, SRM, ABE, TBCC, RBCC, DMR, ATR); pre-cooling; etc

(iv) fundamentals in physical modelling including radiative gas dynamics; gas-surface interactions; spectroscopic-measurement techniques; theoretical and computational spectroscopy; thermo-chemical-nonequilibrium flows; aerothermodynamics-electromagnetism coupling (MHD, etc); polarisable and magnetisable gases; quantum-chemistry applications in aerothermodynamics; thermodynamics statistical, irreversible & thermodynamic properties;  multi-temperature gases and plasmas & transport properties (with/without electromagnetic field); relaxation processes, chemical kinetics, thermal relaxation, state-to-state kinetics; etc

This time, organized in collaboration with the von Karman Institute for Fluid Dynamics and the Institute for Plasma and Nuclear Fusion, the 8th Symposium event will take place in March 2015 in the city of Lisbon, at the door of Europe and will provide with two major highlights in the field:

Inauguration ceremony of the European Shock Tube for High Enthalpy Research, ESTHER & Presentation of the post-flight results and hardware of the Intermediate eXperimental Vehicle, IXV

This 8th edition is organized around 6 axes:

• An opening day dedicated to plenary sessions and round tables on commercial access to space
• 3 days dedicated to presentations, including key note lectures on current space programs (European and abroad)
• Special sessions on radiation, ablation, hypersonic combustion and trans-atmospheric flight
• Dedicated workshops:

1. 1st Spacecraft Demise Workshop
2. Annual workshop on the European Space Propulsion System Simulation
3. Workshop on prediction tools for ablation

• 1 day dedicated to a VKI-LS short course (more information under  http://www.vki.ac.be)
• A space reserved to exhibitors

More information on: http://www.congrexprojects.com/15A01