scholarly journals Linear stability analysis of a time-divergent slamming flow

2022 ◽  
Vol 934 ◽  
Author(s):  
Devaraj van der Meer
Keyword(s):  
Stability Analysis ◽  
Gas Phase ◽  
Gas Flow ◽  
Vertical Wall ◽  
Classical Case ◽  
Stability Diagrams ◽  
Impact Problems ◽  
The Stability ◽  
The Moment ◽  
The Impact

When a liquid slams into a solid, the intermediate gas is squeezed out at a speed that diverges when approaching the moment of impact. Although there is mounting experimental evidence that instabilities form on the liquid interface during such an event, understanding of the nature of these instabilities is limited. This study therefore addresses the stability of a liquid–gas interface with surface tension, subject to a diverging flow in the gas phase, where the liquid and the gas phase are both represented as potential fluids. We perform a Kelvin–Helmholtz-type linear modal stability analysis of the surface to obtain an amplitude equation that is subsequently analysed in detail and applied to two cases of interest for impact problems, namely, the parallel impact of a wave onto a vertical wall, and the impact of a horizontal plate onto a liquid surface. In both cases we find that long wavelengths are stabilised considerably in comparison with what may be expected based upon classical knowledge of the stability of interfaces subject to a constant gas flow. In the former case, this leads to the prediction of a marginally stable wavelength that is completely absent in the classical analysis. For the latter we find much resemblance to the classical case, with the connotation that the instability is suppressed for smaller disk sizes. The study ends with a discussion of the influence of gas viscosity and gas compressibility on the respective stability diagrams.

Diurnal variability of frontal dynamics, instability, and turbulence in a submesoscale upwelling filament

2021 ◽  
Author(s):  
Jen-Ping Peng ◽  
Lars Umlauf ◽  
Julia Dräger-Dietel ◽  
Ryan P. North
Keyword(s):  
Solar Radiation ◽  
Early Morning ◽  
Shear Instability ◽  
Surface Boundary ◽  
Surface Boundary Layer ◽  
Diurnal Variability ◽  
Frontal Dynamics ◽  
The Stability ◽  
The Moment ◽  
The Impact

AbstractRecent high-resolution numerical simulations have shown that the diurnal variability in the atmospheric forcing strongly affects the dynamics, stability, and turbulence of submesoscale structures in the surface boundary layer (SBL). Field observations supporting the real-ocean relevance of these studies are, however, largely lacking at the moment. Here, the impact of large diurnal variations in the surface heat flux on a dense submesoscale upwelling filament in the Benguela upwelling system is investigated, based on a combination of densely-spaced turbulence microstructure observations and surface drifter data. Our data show that during nighttime and early-morning conditions, when solar radiation is still weak, frontal turbulence is generated by a mix of symmetric and shear instability. In this situation, turbulent diapycnal mixing is approximately balanced by frontal restratification associated with the cross-front secondary circulation. During daytime, when solar radiation is close to its peak value, the SBL quickly restratifies, the conditions for frontal instability are no longer fulfilled, and SBL turbulence collapses except for a thin wind-driven layer near the surface. The drifter data suggest that inertial oscillations periodically modulate the stability characteristics and energetics of the submesoscale fronts bounding the filament.

scholarly journals Theoretical stability analysis of mixed finite element model of shale-gas flow with geomechanical effect

2020 ◽  
Vol 75 ◽  
pp. 33
Author(s):  
Mohamed F. El-Amin ◽  
Jisheng Kou ◽  
Shuyu Sun
Keyword(s):  
Finite Element ◽  
Stability Analysis ◽  
Shale Gas ◽  
Gas Flow ◽  
Mixed Finite Element ◽  
Mixed Finite Element Method ◽  
Element Model ◽  
Mathematical Proofs ◽  
The Stability ◽  
Shale Gas Transport

In this work, we introduce a theoretical foundation of the stability analysis of the mixed finite element solution to the problem of shale-gas transport in fractured porous media with geomechanical effects. The differential system was solved numerically by the Mixed Finite Element Method (MFEM). The results include seven lemmas and a theorem with rigorous mathematical proofs. The stability analysis presents the boundedness condition of the MFE solution.

scholarly journals Impedance Aggregation Method of Multiple Wind Turbines and Accuracy Analysis

Energies ◽  
2019 ◽  
Vol 12 (11) ◽  
pp. 2035 ◽  
Author(s):  
Liang Chen ◽  
Heng Nian ◽  
Yunyang Xu
Keyword(s):  
Stability Analysis ◽  
Reference Frame ◽  
Wind Turbines ◽  
Power Distribution ◽  
Wind Farm ◽  
System Level ◽  
Small Signal ◽  
Impedance Model ◽  
The Stability ◽  
The Impact

The sequence domain impedance modeling of wind turbines (WTs) has been widely used in the stability analysis between WTs and weak grids with high line impedance. An aggregated impedance model of the wind farm is required in the system-level analysis. However, directly aggregating WT small-signal impedance models will lead to an inaccurate aggregated impedance model due to the mismatch of reference frame definitions among different WT subsystems, which may lead to inaccuracy in the stability analysis. In this paper, we analyze the impacts of the reference frame mismatch between a local small-signal impedance model and a global one on the accuracy of aggregated impedance and the accuracy of impedance-based stability analysis. The results revealed that the impact is related to the power distribution of the studied network. It was found that that the influence of mismatch on stability analysis became subtle when subsystems were balanced loaded. Considering that balanced loading is a common configuration of the practical application, direct impedance aggregation by local small-signal models can be applied due to its acceptable accuracy.

Uncertainty Model of Concrete Elastic Modulus Effect to Critical Reinforced Concrete Buckling Load

2014 ◽  
Vol 931-932 ◽  
pp. 525-528
Author(s):  
Sanguan Vongchavalitkul
Keyword(s):  
Elastic Modulus ◽  
Stability Analysis ◽  
Statistical Data ◽  
Stability Index ◽  
Buckling Load ◽  
Design Code ◽  
Critical Buckling Load ◽  
Uncertainty Model ◽  
The Stability ◽  
The Impact

There are differences in each countrys design code for concrete elastic modulus that cause uncertainty in stability analysis of critical buckling load column. This paper investigates the impact of uncertainty on concrete elastic modulus for designing of critical buckling load of building column. The statistical data on materials and applied load being collected in Thailand are used together with an investigation on the uncertainty of the concrete elastic modulus in the design code from 8 countries. Finally the Monte Carlo simulation is used to find out the stability index in term of reliability index. The results show that the uncertainty of the concrete elastic modulus plays an important role in stability analysis and should be considered in the design.

Stability Analysis about the Impact of Soft Rock to the Underground Cavern Group

2013 ◽  
Vol 706-708 ◽  
pp. 560-564
Author(s):  
Yi Huan Zhu ◽  
Guo Jian Shao ◽  
Zhi Gao Dong
Keyword(s):  
Finite Element ◽  
Rock Mass ◽  
Stability Analysis ◽  
Soft Rock ◽  
Element Model ◽  
Underground Excavation ◽  
Power Station ◽  
Excavation Process ◽  
The Stability ◽  
The Impact

Soft rock is frequently encountered in underground excavation process. It is difficult to excavate and support in soft rock mass which has low strength, large deformation and needs much time to be out of shape but little time to be self-stabilized. Based on a large underground power station, finite element model analysis was carried out to simulate the excavation process and the results of displacement, stress and plasticity area were compared between supported and unsupported conditions to evaluate the stability of the rock mass.

On the Stability of the Impact Damper

1966 ◽  
Vol 33 (3) ◽  
pp. 586-592 ◽  
Author(s):  
S. F. Masri ◽  
T. K. Caughey
Keyword(s):  
Exact Solution ◽  
Stability Analysis ◽  
Asymptotically Stable ◽  
Impact Damper ◽  
The Stability ◽  
The Impact

The exact solution for the symmetric two-impacts-per-cycle motion of the impact damper is derived analytically, and its asymptotically stable regions are determined. The stability analysis defines the zones where the modulus of all the eigenvalues of a certain matrix relating conditions after each of two consecutive impacts is less than unity.

scholarly journals Numerical Simulation of Gas-Particle Two-Phase Flow in a Nozzle with DG Method

2019 ◽  
Vol 2019 ◽  
pp. 1-12 ◽  
Author(s):  
Duan Maochang ◽  
Yu Xijun ◽  
Chen Dawei ◽  
Qing Fang ◽  
Zou Shijun
Keyword(s):  
Flow Field ◽  
Gas Phase ◽  
Mass Fraction ◽  
Gas Flow ◽  
Two Phase Flow ◽  
Phase Flow ◽  
Governing Equations ◽  
Two Phase ◽  
Dg Method ◽  
The Impact

In this paper, the discontinuous Galerkin (DG) method is applied to solve the governing equations of the dispersed two-phase flow with the two-fluid Euler/Euler approach. The resulting governing equations are simple in form and the solution process is very natural. The characteristics of the gas-particle two-phase flow in an engine nozzle are mainly analyzed, and the impacts of the particle mass fraction and particle size on the flow field and engine performance are evaluated. Because of the addition of particles, the gas flow field undergoes significant modifications. Increase in the mass fraction leads to a significant thrust loss in the gas phase, and the impact of the particles on the gas phase could be substantial. Therefore, a quantitative study of thrust loss in the nozzle due to the particle impact is made. It is found that the gas thrust in the two-phase flow is reduced, but the total thrust of the two-phase flow increases to a certain extent.

Research on Periodic Motion Stability of Multi-DOF Rotor-Bearing System with Crack Fault

2011 ◽  
Vol 148-149 ◽  
pp. 3-6 ◽  
Author(s):  
Chao Feng Li ◽  
Qin Liang Li ◽  
Jie Liu ◽  
Bang Chun Wen
Keyword(s):  
Stability Analysis ◽  
Vibration Control ◽  
Shooting Method ◽  
Crack Depth ◽  
Continuous System ◽  
Oil Film ◽  
Rotor Bearing ◽  
The Stability ◽  
The Impact ◽  
Bearing System

Multi-DOF model of double-disc rotor-bearing system taking crack and oil film support into account is established, and the continuation shooting method combined with Newmark is also applied to stability analysis of continuous system. This paper mainly studied the variation law of five parameters domain in crack depth and location, then a number of conclusions are found: first, it’s feasible to study the stability of nonlinear rotor-bearing system with crack faults using FEM; secondly, the crack depth and location has a certain impact on instability speed, but the impact is not great and owns its certain law. As the crack depth and location is getting close to the middle position of rotor, due to its impact on the oil film support, the instability speed of system increases. This method and results in this paper provides a theoretical reference for stability analysis and vibration control in more complex relevant rotor-bearing system with crack fault.

scholarly journals A fractional-order love dynamical model with time delay for synergic couple : Stability analysis and Hopf bifurcation

2021 ◽  
Author(s):  
SANTOSHI PANIGRAHI ◽  
Sunita Chand ◽  
S Balamuralitharan
Keyword(s):  
Stability Analysis ◽  
Hopf Bifurcation ◽  
Time Delay ◽  
Fractional Order ◽  
Reproduction Number ◽  
Equilibrium Points ◽  
Order Model ◽  
Fractional Order Model ◽  
The Stability ◽  
The Impact

We investigate the fractional order love dynamic model with time delay for synergic couples in this manuscript. The quantitative analysis of the model has been done where the asymptotic stability of the equilibrium points of the model have been analyzed. Under the impact of time delay, the Hopf bifurcation analysis of the model has been done. The stability analysis of the model has been studied with the reproduction number less than or greater than 1. By using Laplace transformation, the analysis of the model has been done. The analysis shows that the fractional order model with a time delay can sufficiently improve the components and invigorate the outcomes for either stable or unstable criteria. In this model, all unstable cases are converted to stable cases under neighbourhood points. For all parameters, the reproduction ranges have been described. Finally, to illustrate our derived results numerical simulations have been carried out by using MATLAB. Under the theoretical outcomes from parameter estimation, the love dynamical system is verified.

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