Lassonde School of Engineering
http://hdl.handle.net/10315/30507
Mon, 18 Jan 2021 22:36:23 GMT2021-01-18T22:36:23ZThree-Dimensional High-Fidelity Dynamic Modeling of Tether Transportation System with Multiple Climbers
http://hdl.handle.net/10315/37653
Three-Dimensional High-Fidelity Dynamic Modeling of Tether Transportation System with Multiple Climbers
Zhu, Zheng H.; Li, Gangqiang; Shi, Gefei
This paper studies the dynamics of a tether transportation system by the nodal position finite element method in the framework of an arbitrary Lagrangian–Eulerian description. Material coordinate is introduced as a state variable that is decoupled with the position coordinate. The movement of climbers is represented by moving nodes associated with the material coordinates. It is integrated into the finite element method by a variable-length tether together with a process of dividing and merging elements. The dynamic behavior of the tether transportation system with multiple climbers is studied. The results show that the elastic-flexible tether model is able to capture the high-frequency oscillation of the tether transportation system. The oscillation could have an adverse effect on the safe operation of the tether transportation system, especially in causing fatigue failure of the tether, and must be considered.
Mon, 04 Mar 2019 00:00:00 GMThttp://hdl.handle.net/10315/376532019-03-04T00:00:00ZFlight Dynamics and Control Strategy of Electric Solar Wind Sails
http://hdl.handle.net/10315/37651
Flight Dynamics and Control Strategy of Electric Solar Wind Sails
Zhu, Zheng H.; Li, Gangqiang; Du, Chonggang
This paper studies the flight dynamics and control strategy for electric solar wind sails based on the nodal position finite element method, where the coupling effects between tether dynamics and the electrical field are considered. A modified throttling control strategy is proposed to control the attitude of electric sails by modulating individual tether voltage synchronously with the spinning motion of the sails. The effects of four critical physical parameters (tether numbers, tether length, sail spin rate, and mass of remote units) are investigated. The results show that the effect of the relative velocity of the solar wind has a significant effect on the spin rate of the sail in attitude maneuvering, which in turn affects the attitude dynamics and orbit motion of the sail. Numerical results show that the proposed control strategy work successfully stabilizes the spin rate of sail when the new type sail is adopted.
Wed, 27 Nov 2019 00:00:00 GMThttp://hdl.handle.net/10315/376512019-11-27T00:00:00ZThe bifurcation of periodic orbits and equilibrium points in the linked restricted three-body problem with parameter ω
http://hdl.handle.net/10315/37648
The bifurcation of periodic orbits and equilibrium points in the linked restricted three-body problem with parameter ω
Shan, Jinjun; Liang, Yuying; Xu, Ming; Lin, Mingpei
This paper is devoted to the bifurcation of periodic orbits and libration points in the linked restricted three-body problem (LR3BP). Inherited from the classic circular restricted three-body problem (CR3BP), it retains most of the dynamical structure of CR3BP, while its dynamical flow is dominated by angular velocity ω and Jacobi energy C. Thus, for the first time, the influence of the angular velocity in the three-body problem is discussed in this paper based on ω-motivated and C-motivated bifurcation. The existence and collision of equilibrium points in the LR3BP are investigated analytically. The dynamic bifurcation of the LR3BP under angular velocity variation is obtained based on three typical kinds of periodic orbits, i.e., planar and vertical Lyapunov orbits and Halo orbits. More bifurcation points are supplemented to Doedel's results in the CR3BP for a global sketch of bifurcation families. For the first time, a new bifurcation phenomenon is discovered that as ω approaches to 1.4, two period-doubling bifurcation points along the Halo family merge together. It suggests that the number and the topological type of bifurcation points themselves can be altered when the system parameter varies in LR3BP. Thus, it is named as “bifurcation of bifurcation” or “secondary bifurcation” in this paper. At selected values of ω, the phase space structures of equilibrium points L2 and L3 are revealed by Lie series method numerically, presenting the center manifolds on the Poincaré section and detecting three patterns of evolution for center manifolds in LR3BP.
Holding the key to the origin of the universe, small bodies, e.g., asteroids are attracting more and more interest from academic and industrial fields. Current simulation on asteroid is implemented based on the regular spinning rate of an asteroid body. However, recently, the observation results on some asteroids show that their spinning velocity varies due to the solar radiation pressure, such as 2000 PH5, whose spinning velocity increases by (2.0 ± 0.2) × 10−4°/day2. The effect of the variable spinning velocity has not been fully understood. To cope with the orbital dynamics near a celestial object with varying angular velocity, a linked restricted three-body problem (LR3BP) is proposed in this paper given that the primary and the secondary are connected by a massless link. The bifurcations motivated by both angular velocity and Jacobi energy are detected to present the influence of the angular velocity. The expected results will provide new insights into orbital dynamics near asteroids, serving for future asteroid exploration mission. The LR3BP and the discovered bifurcation phenomena are important theoretical supplementation to the classic three-body problem theory.
Tue, 08 Oct 2019 00:00:00 GMThttp://hdl.handle.net/10315/376482019-10-08T00:00:00ZElectro‐Thermal Subsurface Gas Generation and
Transport: Model Validation and Implications
http://hdl.handle.net/10315/37647
Electro‐Thermal Subsurface Gas Generation and
Transport: Model Validation and Implications
Molnar, Ian; Mumford, Kevin; Krol, Magdalena
Gas generation and flow in soil is relevant to applications such as the fate of leaking geologically sequestered carbon dioxide, natural releases of methane from peat and marine sediments, and numerous electro‐thermal remediation technologies for contaminated sites, such as electrical resistance heating. While traditional multiphase flow models generally perform poorly in describing unstable gas flow phenomena in soil, Macroscopic Invasion Percolation (MIP) models can reproduce key features of its behavior. When coupled with continuum heat and mass transport models, MIP has the potential to simulate complex subsurface scenarios. However, coupled MIP‐continuum models have not yet been validated against experimental data and lack key mechanisms required for electro‐thermal scenarios. Therefore, the purpose of this study was to (a) incorporate mechanisms required for steam generation and flow into an existing MIP‐continuum model (ET‐MIP), (b) validate ET‐MIP against an experimental lab‐scale electrical resistance heating study, and (c) investigate the sensitivity of water boiling and gas (steam) transport to key parameters. Water boiling plateaus (i.e., latent heat), heat recirculation within steam clusters, and steam collapse (i.e., condensation) mechanisms were added to ET‐MIP. ET‐MIP closely matched observed transient gas saturation distributions, measurements of electrical current, and temperature distributions. Heat recirculation and cluster collapse were identified as the key mechanisms required to describe gas flow dynamics using a MIP algorithm. Sensitivity analysis revealed that gas generation rates and transport distances, particularly through regions of cold water, are sensitive to the presence of dissolved gases.
Fri, 07 Jun 2019 00:00:00 GMThttp://hdl.handle.net/10315/376472019-06-07T00:00:00Z