Local Structural Stability of a Multidimensional Centered Rarefaction Wave for the Three-Dimensional Steady Supersonic Euler Flow around a Sharp Corner

2010 ◽  
Vol 42 (4) ◽  
pp. 1639-1687 ◽  
Author(s):  
Wang Zhan ◽  
Yin Huicheng
Keyword(s):  
Rarefaction Wave ◽  
Structural Stability ◽  
Three Dimensional ◽  
Sharp Corner ◽  
Euler Flow

Accelerating ion diffusion with unique three-dimensionally interconnected nanopores for self-membrane high-performance pseudocapacitors

Nanoscale ◽  
2017 ◽  
Vol 9 (46) ◽  
pp. 18311-18317 ◽  
Author(s):  
Yuan Gao ◽  
Yuanjing Lin ◽  
Zehua Peng ◽  
Qingfeng Zhou ◽  
Zhiyong Fan
Keyword(s):  
Aspect Ratio ◽  
Surface Area ◽  
Structural Stability ◽  
High Aspect Ratio ◽  
High Performance ◽  
Three Dimensional ◽  
Rate Capability ◽  
Large Surface Area ◽  
Nanoporous Structure ◽  
Ion Diffusion

Three-dimensional interconnected nanoporous structure (3-D INPOS) possesses high aspect ratio, large surface area, as well as good structural stability. Profiting from its unique interconnected architecture, the 3-D INPOS pseudocapacitor achieves a largely enhanced capacitance and rate capability.

scholarly journals Strong and Reversible Adhesion of Interlocked 3D-Microarchitectures

Coatings ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 48 ◽  
Author(s):  
Minho Seong ◽  
Hyun-Ha Park ◽  
Insol Hwang ◽  
Hoon Eui Jeong
Keyword(s):  
Aspect Ratio ◽  
Structural Stability ◽  
High Aspect Ratio ◽  
Three Dimensional ◽  
Normal Direction ◽  
One Dimensional ◽  
Reversible Adhesion ◽  
Adhesion Behavior ◽  
Organic Nanomaterials ◽  
Good Agreement

Diverse physical interlocking devices have recently been developed based on one-dimensional (1D), high-aspect-ratio inorganic and organic nanomaterials. Although these 1D nanomaterial-based interlocking devices can provide reliable and repeatable shear adhesion, their adhesion in the normal direction is typically very weak. In addition, the high-aspect-ratio, slender structures are mechanically less durable. In this study, we demonstrate a highly flexible and robust interlocking system that exhibits strong and reversible adhesion based on physical interlocking between three-dimensional (3D) microscale architectures. The 3D microstructures have protruding tips on their cylindrical stems, which enable tight mechanical binding between the microstructures. Based on the unique 3D architectures, the interlocking adhesives exhibit remarkable adhesion strengths in both the normal and shear directions. In addition, their adhesion is highly reversible due to the robust mechanical and structural stability of the microstructures. An analytical model is proposed to explain the measured adhesion behavior, which is in good agreement with the experimental results.

scholarly journals Rarefaction-driven Rayleigh–Taylor instability. Part 1. Diffuse-interface linear stability measurements and theory

2016 ◽  
Vol 791 ◽  
pp. 34-60 ◽  
Author(s):  
R. V. Morgan ◽  
O. A. Likhachev ◽  
J. W. Jacobs
Keyword(s):  
Linear Stability ◽  
Rarefaction Wave ◽  
Diffusion Model ◽  
Growth Rates ◽  
Three Dimensional ◽  
Mie Scattering ◽  
Taylor Instability ◽  
Diffuse Interface ◽  
Rayleigh Taylor Instability ◽  
Dynamic Diffusion

Theory and experiments are reported that explore the behaviour of the Rayleigh–Taylor instability initiated with a diffuse interface. Experiments are performed in which an interface between two gases of differing density is made unstable by acceleration generated by a rarefaction wave. Well-controlled, diffuse, two-dimensional and three-dimensional, single-mode perturbations are generated by oscillating the gases either side to side, or vertically for the three-dimensional perturbations. The puncturing of a diaphragm separating a vacuum tank beneath the test section generates a rarefaction wave that travels upwards and accelerates the interface downwards. This rarefaction wave generates a large, but non-constant, acceleration of the order of $1000g_{0}$, where $g_{0}$ is the acceleration due to gravity. Initial interface thicknesses are measured using a Rayleigh scattering diagnostic and the instability is visualized using planar laser-induced Mie scattering. Growth rates agree well with theoretical values, and with the inviscid, dynamic diffusion model of Duff et al. (Phys. Fluids, vol. 5, 1962, pp. 417–425) when diffusion thickness is accounted for, and the acceleration is weighted using inviscid Rayleigh–Taylor theory. The linear stability formulation of Chandrasekhar (Proc. Camb. Phil. Soc., vol. 51, 1955, pp. 162–178) is solved numerically with an error function diffusion profile using the Riccati method. This technique exhibits good agreement with the dynamic diffusion model of Duff et al. for small wavenumbers, but produces larger growth rates for large-wavenumber perturbations. Asymptotic analysis shows a $1/k^{2}$ decay in growth rates as $k\rightarrow \infty$ for large-wavenumber perturbations.

Study on the structural stability evaluation of umbilical winch for ROV LARS

2018 ◽  
Vol 35 (1) ◽  
pp. 202-210
Author(s):  
Namsub Woo ◽  
Sangmok Han ◽  
Youngju Kim ◽  
Sunchul Huh ◽  
Hyunji Kim
Keyword(s):  
Structural Analysis ◽  
Dynamic Simulation ◽  
Structural Stability ◽  
Three Dimensional ◽  
High Technology ◽  
Design Methods ◽  
Stability Evaluation ◽  
Content Type ◽  
Dimensional Models ◽  
Three Dimensional Models

Purpose The purpose of this study is structural stability evaluation of umbilical winch. In accordance with the recent trend for developing natural resources, high-technology equipment on exploration ships is becoming more technologically advanced. One such piece of high-technology equipment is the umbilical winch. In this study, the umbilical winch is divided into two parts (drum and winch), where each is respectively designed with three dimensional models using CATIA, and dynamic simulation and structural analysis are performed using ANSYS. Design/methodology/approach In this paper, the winch is divided into two parts for finite element analysis, the drum and whole winch model, and the parts are designed as three-dimensional models except for some small parts, such as bolt holes. Dynamic simulation and structural analysis are then performed using ANSYS. The analysis results ensure the reliability of the design methods and will be used in the domestic localization of remote operated vehicle (ROV) launch and recovery systems (LARS). Findings The strain is identified from the results, but it is very small. Some stress is concentrated at the lower corner of the drum, but the maximum stress value is lower than the allowable stress; therefore, the structure has no impact on the strain and stress. Thus, it is determined that the designed structure is safe. The results ensure the reliability of the design methods and will be used in the domestic localization of ROV LARS. Originality/value Previous studies focus on the static and mechanic problems of the winch by considering winch and drum breakage in the umbilical winch system. However, ships have a nonlinear motion characteristic with six degrees of freedom according to the constant influence of the external environment. In addition, from a design perspective, the dynamic characteristics (e.g. the ship’s motions) are more important than the static characteristics. Thus, the authors focus on winch stability securement with variable loads, such as ships moving, wave disturbance and other such important environment conditions.

scholarly journals Rarefaction-driven Rayleigh–Taylor instability. Part 2. Experiments and simulations in the nonlinear regime

2018 ◽  
Vol 838 ◽  
pp. 320-355 ◽  
Author(s):  
R. V. Morgan ◽  
W. H. Cabot ◽  
J. A. Greenough ◽  
J. W. Jacobs
Keyword(s):  
Rarefaction Wave ◽  
Three Dimensional ◽  
Single Mode ◽  
Taylor Instability ◽  
Nonlinear Regime ◽  
Diffuse Interface ◽  
Late Time ◽  
Two Dimensional ◽  
Rayleigh Taylor Instability ◽  
Atwood Number

Experiments and large eddy simulation (LES) were performed to study the development of the Rayleigh–Taylor instability into the saturated, nonlinear regime, produced between two gases accelerated by a rarefaction wave. Single-mode two-dimensional, and single-mode three-dimensional initial perturbations were introduced on the diffuse interface between the two gases prior to acceleration. The rarefaction wave imparts a non-constant acceleration, and a time decreasing Atwood number, $A=(\unicode[STIX]{x1D70C}_{2}-\unicode[STIX]{x1D70C}_{1})/(\unicode[STIX]{x1D70C}_{2}+\unicode[STIX]{x1D70C}_{1})$, where $\unicode[STIX]{x1D70C}_{2}$ and $\unicode[STIX]{x1D70C}_{1}$ are the densities of the heavy and light gas, respectively. Experiments and simulations are presented for initial Atwood numbers of $A=0.49$, $A=0.63$, $A=0.82$ and $A=0.94$. Nominally two-dimensional (2-D) experiments (initiated with nearly 2-D perturbations) and 2-D simulations are observed to approach an intermediate-time velocity plateau that is in disagreement with the late-time velocity obtained from the incompressible model of Goncharov (Phys. Rev. Lett., vol. 88, 2002, 134502). Reacceleration from an intermediate velocity is observed for 2-D bubbles in large wavenumber, $k=2\unicode[STIX]{x03C0}/\unicode[STIX]{x1D706}=0.247~\text{mm}^{-1}$, experiments and simulations, where $\unicode[STIX]{x1D706}$ is the wavelength of the initial perturbation. At moderate Atwood numbers, the bubble and spike velocities approach larger values than those predicted by Goncharov’s model. These late-time velocity trends are predicted well by numerical simulations using the LLNL Miranda code, and by the 2009 model of Mikaelian (Phys. Fluids., vol. 21, 2009, 024103) that extends Layzer type models to variable acceleration and density. Large Atwood number experiments show a delayed roll up, and exhibit a free-fall like behaviour. Finally, experiments initiated with three-dimensional perturbations tend to agree better with models and a simulation using the LLNL Ares code initiated with an axisymmetric rather than Cartesian symmetry.

scholarly journals Experiments and Simulations on the Turbulent, Rarefaction Wave Driven Rayleigh–Taylor Instability

2020 ◽  
Vol 142 (12) ◽  
Author(s):  
R. V. Morgan ◽  
J. W. Jacobs
Keyword(s):  
Rarefaction Wave ◽  
Lawrence Livermore National Laboratory ◽  
National Laboratory ◽  
Mixing Layer ◽  
Three Dimensional ◽  
Quantitative Agreement ◽  
Diffuse Interface ◽  
Diffusion Layer Thickness ◽  
Average Value ◽  
Rayleigh Taylor Instability

Abstract Experiments were performed to observe the growth of the turbulent, Rayleigh–Taylor unstable mixing layer generated between air and SF6, with an Atwood number of A=(ρ2−ρ1)/(ρ2+ρ1)=0.64, where ρ1 and ρ2 are the densities of air and SF6, respectively. A nonconstant acceleration with an average value of 2300g0, where g0 is the acceleration due to gravity, was generated by interaction of the interface between the two gases with a rarefaction wave. Three-dimensional, multimode perturbations were generated on the diffuse interface, with a diffusion layer thickness of δ=3.6 mm, using a membraneless vertical oscillation technique, and 20 experiments were performed to establish a statistical ensemble. The average perturbation from this ensemble was extracted and used as input for a numerical simulation using the Lawrence Livermore National Laboratory (LLNL) Miranda code. Good qualitative agreement between the experiment and simulation was observed, while quantitative agreement was best at early to intermediate times. Several methods were used to extract the turbulent growth constant α from experiments and simulations while accounting for time varying acceleration. Experimental, average bubble and spike asymptotic self-similar growth rate values range from α=0.022 to α=0.032 depending on the method used, and accounting for variable acceleration. Values found from the simulations range from α=0.024 to α=0.041. Values of α measured in the experiments are lower than what are typically measured in the literature but are more in line with those found in recent simulations.

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