scholarly journals Three-dimensional multispecies hybrid simulation of Titan's highly variable plasma environment

2007 ◽  
Vol 25 (1) ◽  
pp. 117-144 ◽  
Author(s):  
S. Simon ◽  
A. Boesswetter ◽  
T. Bagdonat ◽  
U. Motschmann ◽  
J. Schuele
Keyword(s):  
Plasma Flow ◽  
Flow Direction ◽  
Three Dimensional ◽  
Hybrid Simulation ◽  
Slight Modification ◽  
Magnetospheric Plasma ◽  
Particle Model ◽  
Tail Region ◽  
Simulation Code ◽  
Ion Species

Abstract. The interaction between Titan's ionosphere and the Saturnian magnetospheric plasma flow has been studied by means of a three-dimensional (3-D) hybrid simulation code. In the hybrid model, the electrons form a mass-less, charge-neutralizing fluid, whereas a completely kinetic approach is retained to describe ion dynamics. The model includes up to three ionospheric and two magnetospheric ion species. The interaction gives rise to a pronounced magnetic draping pattern and an ionospheric tail that is highly asymmetric with respect to the direction of the convective electric field. Due to the dependence of the ion gyroradii on the ion mass, ions of different masses become spatially dispersed in the tail region. Therefore, Titan's ionospheric tail may be considered a mass-spectrometer, allowing to distinguish between ion species of different masses. The kinetic nature of this effect is emphasized by comparing the simulation with the results obtained from a simple analytical test-particle model of the pick-up process. Besides, the results clearly illustrate the necessity of taking into account the multi-species nature of the magnetospheric plasma flow in the vicinity of Titan. On the one hand, heavy magnetospheric particles, such as atomic Nitrogen or Oxygen, experience only a slight modification of their flow pattern. On the other hand, light ionospheric ions, e.g. atomic Hydrogen, are clearly deflected around the obstacle, yielding a widening of the magnetic draping pattern perpendicular to the flow direction. The simulation results clearly indicate that the nature of this interaction process, especially the formation of sharply pronounced plasma boundaries in the vicinity of Titan, is extremely sensitive to both the temperature of the magnetospheric ions and the orientation of Titan's dayside ionosphere with respect to the corotating magnetospheric plasma flow.

scholarly journals Plasma environment of Titan: a 3-D hybrid simulation study

2006 ◽  
Vol 24 (3) ◽  
pp. 1113-1135 ◽  
Author(s):  
S. Simon ◽  
A. Bößwetter ◽  
T. Bagdonat ◽  
U. Motschmann ◽  
K.-H. Glassmeier
Keyword(s):  
Plasma Flow ◽  
Molecular Nitrogen ◽  
Hybrid Simulation ◽  
Spherical Geometry ◽  
Magnetospheric Plasma ◽  
Simulation Code ◽  
Plasma Environment ◽  
Ion Production ◽  
Solar Uv ◽  
Magnetohydrodynamic Models

Abstract. Titan possesses a dense atmosphere, consisting mainly of molecular nitrogen. Titan's orbit is located within the Saturnian magnetosphere most of the time, where the corotating plasma flow is super-Alfvénic, yet subsonic and submagnetosonic. Since Titan does not possess a significant intrinsic magnetic field, the incident plasma interacts directly with the atmosphere and ionosphere. Due to the characteristic length scales of the interaction region being comparable to the ion gyroradii in the vicinity of Titan, magnetohydrodynamic models can only offer a rough description of Titan's interaction with the corotating magnetospheric plasma flow. For this reason, Titan's plasma environment has been studied by using a 3-D hybrid simulation code, treating the electrons as a massless, charge-neutralizing fluid, whereas a completely kinetic approach is used to cover ion dynamics. The calculations are performed on a curvilinear simulation grid which is adapted to the spherical geometry of the obstacle. In the model, Titan's dayside ionosphere is mainly generated by solar UV radiation; hence, the local ion production rate depends on the solar zenith angle. Because the Titan interaction features the possibility of having the densest ionosphere located on a face not aligned with the ram flow of the magnetospheric plasma, a variety of different scenarios can be studied. The simulations show the formation of a strong magnetic draping pattern and an extended pick-up region, being highly asymmetric with respect to the direction of the convective electric field. In general, the mechanism giving rise to these structures exhibits similarities to the interaction of the ionospheres of Mars and Venus with the supersonic solar wind. The simulation results are in agreement with data from recent Cassini flybys.

scholarly journals Plasma environment of magnetized asteroids: a 3-D hybrid simulation study

2006 ◽  
Vol 24 (1) ◽  
pp. 407-414 ◽  
Author(s):  
S. Simon ◽  
T. Bagdonat ◽  
U. Motschmann ◽  
K.-H. Glassmeier
Keyword(s):  
Solar Wind ◽  
Three Dimensional ◽  
Hybrid Simulation ◽  
Interaction Region ◽  
Bow Shock ◽  
The Other ◽  
Simulation Code ◽  
Kinetic Effects ◽  
Intrinsic Magnetic Moment ◽  
The One

Abstract. The interaction of a magnetized asteroid with the solar wind is studied by using a three-dimensional hybrid simulation code (fluid electrons, kinetic ions). When the obstacle's intrinsic magnetic moment is sufficiently strong, the interaction region develops signs of magnetospheric structures. On the one hand, an area from which the solar wind is excluded forms downstream of the obstacle. On the other hand, the interaction region is surrounded by a boundary layer which indicates the presence of a bow shock. By analyzing the trajectories of individual ions, it is demonstrated that kinetic effects have global consequences for the structure of the interaction region.

scholarly journals Influence of non-stationary electromagnetic field conditions on ion pick-up at Titan: 3-D multispecies hybrid simulations

2008 ◽  
Vol 26 (3) ◽  
pp. 599-617 ◽  
Author(s):  
S. Simon ◽  
U. Motschmann ◽  
K.-H. Glassmeier
Keyword(s):  
Electromagnetic Field ◽  
Electromagnetic Fields ◽  
Three Dimensional ◽  
Magnetospheric Plasma ◽  
Field Conditions ◽  
Shielding Effect ◽  
Tail Region ◽  
Field Orientation ◽  
Time Period ◽  
Tail Structure

Abstract. Titan's interaction with the corotating Saturnian magnetospheric plasma is studied in terms of a three-dimensional electromagnetic hybrid model. This approach treats the electrons as a massless, charge-neutralizing fluid, whereas the ions are represented by macroparticles. The model considers two magnetospheric and three ionospheric ion species. In contrast to any foregoing simulation study, the magnetospheric upstream conditions are not assumed to be stationary, but time variations have been imposed on the electromagnetic fields. The model includes simple periodic distortions of the fields near Titan, the purpose being to illustrate the basic physical mechanisms of ion pick-up in a non-stationary electromagnetic environment. In order to allow a straightforward access to the influence of the electromagnetic field orientation on the pick-up, no variations have been imposed on the density of the impinging magnetospheric plasma. Under stationary upstream conditions, Titan's exospheric tail exhibits a strong asymmetry with respect to the direction of the convective electric field. The simulations show that this characteristic asymmetry cannot develop, if the ambient electromagnetic fields are highly distorted. However, the central tail region directly behind the satellite remains nearly unaffected by the distorted magnetospheric upstream conditions. The central tail where the slow ionospheric species are predominant is able to shield itself against any kind of distortion in the ambient magnetospheric field conditions. The shorter the time period of the distortions, the more efficient is this shielding effect. The dependency of the pick-up on the characteristic time scales of the distortions is discussed in detail for the investigated model cases. Besides, the reaction of Titan's exospheric tail structure on sudden, non-continuous changes of the magnetospheric plasma conditions is analyzed, providing an illustration of some effects that may occur when Titan crosses Saturn's magnetopause.

scholarly journals Physics of the Ion Composition Boundary: a comparative 3-D hybrid simulation study of Mars and Titan

2007 ◽  
Vol 25 (1) ◽  
pp. 99-115 ◽  
Author(s):  
S. Simon ◽  
A. Boesswetter ◽  
T. Bagdonat ◽  
U. Motschmann
Keyword(s):  
Solar Wind ◽  
Plasma Flow ◽  
Dynamic Pressure ◽  
Hybrid Simulation ◽  
Ion Composition ◽  
Simulation Code ◽  
Ambient Flow ◽  
Planetary Ionosphere ◽  
Mach Numbers ◽  
Characteristic Features

Abstract. The plasma environments of Mars and Titan have been studied by means of a 3-D hybrid simulation code, treating the electrons as a massless, charge-neutralizing fluid, whereas ion dynamics are covered by a kinetic approach. As neither Mars nor Titan possesses a significant intrinsic magnetic field, the upstream plasma flow interacts directly with the planetary ionosphere. The characteristic features of the interaction region are determined as a function of the alfvénic, sonic and magnetosonic Mach number of the impinging plasma. For the Martian interaction with the solar wind as well as for the case of Titan being located outside Saturn's magnetosphere in times of high solar wind dynamic pressure, all three Mach numbers are larger than 1. In such a scenario, the interaction gives rise to a so-called Ion Composition Boundary, separating the ionospheric plasma from the ambient flow and being highly asymmetric with respect to the direction of the convective electric field. The formation of these features is explained by analyzing the Lorentz forces acting on ionospheric and ambient plasma particles. Titan's plasma environment is highly variable and allows various different combinations of the three Mach numbers. Therefore, the Ion Composition Boundary may vanish under certain circumstances. The relevant physical mechanism is illustrated as a function of the Mach numbers in the upstream plasma flow.

A Nonlinear Rail Vehicle Dynamics Computer Program SAMS/Rail: Part 1—Theory and Formulations

2009 ◽  
Author(s):  
Khaled E. Zaazaa ◽  
Brian Whitten ◽  
Brian Marquis ◽  
Erik Curtis ◽  
Magdy El-Sibaie ◽  
...  
Keyword(s):  
High Speed ◽  
Dynamic Performance ◽  
Three Dimensional ◽  
Contact Element ◽  
Contact Forces ◽  
Simulation Code ◽  
Vehicle Performance ◽  
Normal Contact ◽  
Advantages And Disadvantages ◽  
High Speed Trains

Accurate prediction of railroad vehicle performance requires detailed formulations of wheel-rail contact models. In the past, most dynamic simulation tools used an offline wheel-rail contact element based on look-up tables that are used by the main simulation solver. Nowadays, the use of an online nonlinear three-dimensional wheel-rail contact element is necessary in order to accurately predict the dynamic performance of high speed trains. Recently, the Federal Railroad Administration, Office of Research and Development has sponsored a project to develop a general multibody simulation code that uses an online nonlinear three-dimensional wheel-rail contact element to predict the contact forces between wheel and rail. In this paper, several nonlinear wheel-rail contact formulations are presented, each using the online three-dimensional approach. The methods presented are divided into two contact approaches. In the first Constraint Approach, the wheel is assumed to remain in contact with the rail. In this approach, the normal contact forces are determined by using the technique of Lagrange multipliers. In the second Elastic Approach, wheel/rail separation and penetration are allowed, and the normal contact forces are determined by using Hertz’s Theory. The advantages and disadvantages of each method are presented in this paper. In addition, this paper discusses future developments and improvements for the multibody system code. Some of these improvements are currently being implemented by the University of Illinois at Chicago (UIC). In the accompanying “Part 2” and “Part 3” to this paper, numerical examples are presented in order to demonstrate the results obtained from this research.

scholarly journals Study of the Effect of Centrifugal Force on Rotor Blade Icing Process

2017 ◽  
Vol 2017 ◽  
pp. 1-9 ◽  
Author(s):  
Zhengzhi Wang ◽  
Chunling Zhu
Keyword(s):  
Numerical Simulation ◽  
Centrifugal Force ◽  
Rotor Blade ◽  
Flow Direction ◽  
Three Dimensional ◽  
Simulation Method ◽  
Two Phase ◽  
Numerical Simulation Method ◽  
Calculation Results ◽  
Flow Field Characteristics

In view of the rotor icing problems, the influence of centrifugal force on rotor blade icing is investigated. A numerical simulation method of three-dimensional rotor blade icing is presented. Body-fitted grids around the rotor blade are generated using overlapping grid technology and rotor flow field characteristics are obtained by solving N-S equations. According to Eulerian two-phase flow, the droplet trajectories are calculated and droplet impingement characteristics are obtained. The mass and energy conservation equations of ice accretion model are established and a new calculation method of runback water mass based on shear stress and centrifugal force is proposed to simulate water flow and ice shape. The calculation results are compared with available experimental results in order to verify the correctness of the numerical simulation method. The influence of centrifugal force on rotor icing is calculated. The results show that the flow direction and distribution of liquid water on rotor surfaces change under the action of centrifugal force, which lead to the increasing of icing at the stagnation point and the decreasing of icing on both frozen limitations.

Thermo-mechanical coupling particle simulation of three-dimensional large-scale non-isothermal problems

2017 ◽  
Vol 34 (5) ◽  
pp. 1551-1571 ◽  
Author(s):  
Ming Xia
Keyword(s):  
Large Scale ◽  
Three Dimensional ◽  
Simulation Method ◽  
Particle Simulation ◽  
Similarity Criteria ◽  
Particle Model ◽  
Length Scale ◽  
Content Type ◽  
Mechanical Coupling ◽  
Particle Simulation Method

Purpose The main purpose of this paper is to present a comprehensive upscale theory of the thermo-mechanical coupling particle simulation for three-dimensional (3D) large-scale non-isothermal problems, so that a small 3D length-scale particle model can exactly reproduce the same mechanical and thermal results with that of a large 3D length-scale one. Design/methodology/approach The objective is achieved by following the scaling methodology proposed by Feng and Owen (2014). Findings After four basic physical quantities and their similarity-ratios are chosen, the derived quantities and its similarity-ratios can be derived from its dimensions. As the proposed comprehensive 3D upscale theory contains five similarity criteria, it reveals the intrinsic relationship between the particle-simulation solution obtained from a small 3D length-scale (e.g. a laboratory length-scale) model and that obtained from a large 3D length-scale (e.g. a geological length-scale) one. The scale invariance of the 3D interaction law in the thermo-mechanical coupled particle model is examined. The proposed 3D upscale theory is tested through two typical examples. Finally, a practical application example of 3D transient heat flow in a solid with constant heat flux is given to illustrate the performance of the proposed 3D upscale theory in the thermo-mechanical coupling particle simulation of 3D large-scale non-isothermal problems. Both the benchmark tests and application example are provided to demonstrate the correctness and usefulness of the proposed 3D upscale theory for simulating 3D non-isothermal problems using the particle simulation method. Originality/value The paper provides some important theoretical guidance to modeling 3D large-scale non-isothermal problems at both the engineering length-scale (i.e. the meter-scale) and the geological length-scale (i.e. the kilometer-scale) using the particle simulation method directly.

Multiple Ship Motion Simulation Code Correlation with Model Test Results

2017 ◽  
Author(s):  
James A. Coller ◽  
Andrew Silver ◽  
Okey Nwogu ◽  
Benjamin S.H. Connell
Keyword(s):  
Real Time ◽  
Model Test ◽  
Three Dimensional ◽  
Angle Measurement ◽  
Ship Motion ◽  
Ship Motions ◽  
Simulation Code ◽  
Forecasting System ◽  
Scale Experiment ◽  
Response Amplitude Operators

The US Nav has developed a real-time multi-ship ship motion forecasting system which combines forecast wave conditions with ship motion simulations to produce a prediction of the relative motions between two ships operating in a skin-to-skin configuration. The system utilizes two different simulation methods for predicting ship motions: MotionSim and Reduced Order Model (ROM) based on AEGIR. MotionSim is a fast three-dimensional panel method that is used to estimate the Response Amplitude Operators (RAOs) necessary for multi-ship motion predictions. The ROM works to maximize the accuracy of high fidelity ship motion prediction methods while maintaining the computational speed required for real-time forecasting. A model scale experiment was performed in 2015 on two Navy ships conventionally moored together. The predicted relative ship motions from MotionSim and ROM were compared to the model data using three different metrics: RMS (root mean square) ratio, correlation coefficient, and average angle measurement (AAM).This paper provides an overview of the two methods for predicting the multi-ship motions, a description of the model test, challenges faced during testing, and a discussion on the methodology of the evaluation and the results of each code correlation.

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