scholarly journals DYNAMICS OF UNSTABLE SOLUTIONS FOR THE WAVE EQUATION WITH SOURCES

2020 ◽  
Vol 12 (4) ◽  
pp. 51-61
Author(s):  
O.N. Shablovskii ◽  
Keyword(s):  
Wave Equation ◽  
Inflection Point ◽  
Threshold Value ◽  
Strong Discontinuity ◽  
Homogeneous State ◽  
Finite Moment ◽  
Unstable Solutions ◽  
Self Similar ◽  
The Stability ◽  
Fourth Order Wave Equation

Two new accurate solutions of the wave equation with sources are obtained. The dynamics of unstable states described by these solutions is studied. Analytical forms are given for the partial derivatives of the required function with respect to the spatial coordinate and time on the plane of independent variables “the required function – time”. This structure of the solution allows us to consider nonstationary analogs of self-similar kinks describing the transition between two equilibrium states of the “medium – source” system. For the classical wave equation, a nonlinear rheonomic source is used, the behavior of which affects the properties of the relaxing kink. The conditions under which the speed of movement of the formed self-similar transfer wave is subsonic or supersonic are determined. An important role of the velocity of the inflection point of a nonselfsimilar kink has been analyzed; the threshold value of the velocity is calculated, which separates the subsonic and supersonic regimes. An unstable version of the presented solution gives a strong discontinuity of the required function with an unlimited increase in time. The stopping of the kink inflection point is an indicator of a strong rupture. An estimate of the value of the moment in time preceding the beginning of the return motion of the inflection point is indicated. A solution to a spatially nonlocal fourth-order wave equation with two additively entering sources is given. One source depends on the desired function in a linear homogeneous way; the second one depends on the modulus of the gradient of the desired function the same way. The solution is an analog of an overthrow wave in an interval with non-stationary boundaries. At each finite moment of time this solution is continuous, and for an infinite time there is a loss of smoothness of the solution, we have the so-called “slow explosion”. In the unstable solution, the isolines of the sought-for function on the concave section (the lower part of the kink) move towards the convex section, which is adjacent to the upper boundary of the kink. In the stable version, the kink degenerates into a homogeneous state. It has been analyzed that for a nonselfsimilar process, the inversion of the sign of the gradient source gives an inversion of the stability conditions for the kink and antikink. An unstable kink/ antikink corresponds to a gradient sink/source.

Analysis of Hiemenz flow of Reiner-Rivlin fluid over a stretching/shrinking sheet

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Golam Mortuja Sarkar ◽  
Suman Sarkar ◽  
Bikash Sahoo
Keyword(s):  
Nusselt Number ◽  
Stability Analysis ◽  
Friction Coefficient ◽  
Skin Friction Coefficient ◽  
Dual Solutions ◽  
Shrinking Sheet ◽  
Content Type ◽  
Hiemenz Flow ◽  
Self Similar ◽  
The Stability

Purpose This paper aims to theoretically and numerically investigate the steady two-dimensional (2D) Hiemenz flow with heat transfer of Reiner-Rivlin fluid over a linearly stretching/shrinking sheet. Design/methodology/approach The Navier–Stokes equations are transformed into self-similar equations using appropriate similarity transformations and then solved numerically by using shooting technique. A simple but effective mathematical analysis has been used to prove the existence of a solution for stretching case (λ> 0). Moreover, an attempt has been laid to carry the asymptotic solution behavior for large stretching. The obtained asymptotic solutions are compared with direct numerical solutions, and the comparison is quite remarkable. Findings It is observed that the self-similar equations exhibit dual solutions within the range [λc, −1] of shrinking parameter λ, where λc is the turning point from where the dual solutions bifurcate. Unique solution is found for all stretching case (λ > 0). It is noticed that the effects of cross-viscous parameter L and shrinking parameter λ on velocity and thermal fields show opposite character in the dual solution branches. Thus, a linear temporal stability analysis is performed to determine the basic feasible solution. The stability analysis is based on the sign of the smallest eigenvalue, where positive or negative sign leading to a stable or unstable solution. The stability analysis reveals that the first solution is stable that describes the main flow. Increase in cross-viscous parameter L resulting in a significant increment in skin friction coefficient, local Nusselt number and dual solutions domain. Originality/value This work’s originality is to examine the combined effects of cross-viscous parameter and stretching/shrinking parameter on skin friction coefficient, local Nusselt number, velocity and temperature profiles of Hiemenz flow over a stretching/shrinking sheet. Although many studies on viscous fluid and nanofluid have been investigated in this field, there are still limited discoveries on non-Newtonian fluids. The obtained results can be used as a benchmark for future studies of higher-grade non-Newtonian flows with several physical aspects. All the generated results are claimed to be novel and have not been published elsewhere.

scholarly journals Some arguments for the wave equation in Quantum theory

2021 ◽  
Vol 5 (1) ◽  
pp. 314-336
Author(s):  
Tristram de Piro ◽  
Keyword(s):  
Electromagnetic Field ◽  
Wave Equation ◽  
Quantum Theory ◽  
Continuity Equation ◽  
Wave Equations ◽  
Maxwell's Equations ◽  
Atomic System ◽  
Balmer Series ◽  
Inertial Frames ◽  
The Stability

We clarify some arguments concerning Jefimenko’s equations, as a way of constructing solutions to Maxwell’s equations, for charge and current satisfying the continuity equation. We then isolate a condition on non-radiation in all inertial frames, which is intuitively reasonable for the stability of an atomic system, and prove that the condition is equivalent to the charge and current satisfying certain relations, including the wave equations. Finally, we prove that with these relations, the energy in the electromagnetic field is quantised and displays the properties of the Balmer series.

scholarly journals Boundary Stabilization of a Semilinear Wave Equation with Variable Coefficients under the Time-Varying and Nonlinear Feedback

2014 ◽  
Vol 2014 ◽  
pp. 1-6 ◽  
Author(s):  
Bei Gong ◽  
Xiaopeng Zhao
Keyword(s):  
Wave Equation ◽  
Riemannian Geometry ◽  
Nonlinear Term ◽  
Variable Coefficients ◽  
Time Varying ◽  
Nonlinear Feedback ◽  
Boundary Stabilization ◽  
Semilinear Wave Equation ◽  
The Stability ◽  
Stability Results

We study the boundary stabilization of a semilinear wave equation with variable coefficients under the time-varying and nonlinear feedback. By the Riemannian geometry methods, we obtain the stability results of the system under suitable assumptions of the bound of the time-varying term and the nonlinearity of the nonlinear term.

Stability of a CD4+ T cell viral infection model with diffusion

2018 ◽  
Vol 11 (05) ◽  
pp. 1850071 ◽  
Author(s):  
Zhiting Xu ◽  
Youqing Xu
Keyword(s):  
T Cell ◽  
Viral Infection ◽  
Lyapunov Functions ◽  
Threshold Value ◽  
Endemic Equilibrium ◽  
Infection Model ◽  
Asymptotically Stable ◽  
Globally Asymptotically Stable ◽  
The Stability ◽  
Viral Infection Model

This paper is devoted to the study of the stability of a CD[Formula: see text] T cell viral infection model with diffusion. First, we discuss the well-posedness of the model and the existence of endemic equilibrium. Second, by analyzing the roots of the characteristic equation, we establish the local stability of the virus-free equilibrium. Furthermore, by constructing suitable Lyapunov functions, we show that the virus-free equilibrium is globally asymptotically stable if the threshold value [Formula: see text]; the endemic equilibrium is globally asymptotically stable if [Formula: see text] and [Formula: see text]. Finally, we give an application and numerical simulations to illustrate the main results.

Gravitational analysis of neutral regular black hole in Rastall gravity

2020 ◽  
Vol 35 (27) ◽  
pp. 2050225 ◽  
Author(s):  
Riasat Ali ◽  
Muhammad Asgher ◽  
M. F. Malik
Keyword(s):  
Black Hole ◽  
Wave Equation ◽  
Quantum Gravity ◽  
Generalized Uncertainty Principle ◽  
Gravity Effect ◽  
Tunneling Radiation ◽  
Regular Black Hole ◽  
Quantum Gravity Effect ◽  
Stability And Instability ◽  
The Stability

This paper is devoted to the tunneling radiation and quantum gravity effect on tunneling radiation of neutral regular black hole in Rastall gravity. We analyzed the tunneling radiation and Hawking temperature of neutral regular black hole by applying the Hamilton-Jacobi ansatz phenomenon. Lagrangian wave equation have been investigated by generalized uncertainty principle (GUP), using the WKB-approximation and calculated the tunneling rate as well as temperature. Furthermore, we analyzed the temperature of this neutral regular black hole in the presence of gravity. The stability and instability of neutral regular black hole are also analyzed.

scholarly journals Chemostat Model of Competition between Plasmid-Bearing and Plasmid-Free Organism with the Impulsive State Feedback Control

2018 ◽  
Vol 2018 ◽  
pp. 1-10
Author(s):  
Fengmei Tao ◽  
Zhong Zhao ◽  
Lansun Chen
Keyword(s):  
Feedback Control ◽  
State Feedback ◽  
Impulsive Control ◽  
Continuous System ◽  
Threshold Value ◽  
State Feedback Control ◽  
Qualitative Properties ◽  
Chemostat Model ◽  
Impulsive State Feedback Control ◽  
The Stability

In this paper, we propose a chemostat model of competition between plasmid-bearing and plasmid-free organism with the impulsive state feedback control. The sufficient condition for existence of the positive period-1 solution is obtained by means of successor function and the qualitative properties of the corresponding continuous system. We show that the impulsive control system is more effective than the corresponding continuous system if we choose a suitable threshold value of the state feedback control in the process of manufacturing the desired products through genetically modified techniques. Furthermore, a new method of proving the stability of the order-1 periodic solution is given based on the theory of the limit cycle of the continuous dynamical system. Finally, mathematical results are justified by some numerical simulations.

scholarly journals Splash wave and crown breakup after disc impact on a liquid surface

2013 ◽  
Vol 724 ◽  
pp. 553-580 ◽  
Author(s):  
Ivo R. Peters ◽  
Devaraj van der Meer ◽  
J. M. Gordillo
Keyword(s):  
Numerical Simulations ◽  
Weber Number ◽  
Threshold Value ◽  
Bond Number ◽  
Radius Of Curvature ◽  
Time Varying ◽  
Self Similar Solution ◽  
Air Cushion ◽  
Self Similar ◽  
The Impact

AbstractIn this paper we analyse the impact of a circular disc on a free surface using experiments, potential flow numerical simulations and theory. We focus our attention both on the study of the generation and possible breakup of the splash wave created after the impact and on the calculation of the force on the disc. We have experimentally found that drops are only ejected from the rim located at the top part of the splash – giving rise to what is known as the crown splash – if the impact Weber number exceeds a threshold value ${\mathit{We}}_{crit} \simeq 140$. We explain this threshold by defining a local Bond number $B{o}_{\mathit{tip}} $ based on the rim deceleration and its radius of curvature, with which we show using both numerical simulations and experiments that a crown splash only occurs when $B{o}_{\mathit{tip}} \gtrsim 1$, revealing that the rim disrupts due to a Rayleigh–Taylor instability. Neglecting the effect of air, we show that the flow in the region close to the disc edge possesses a Weber-number-dependent self-similar structure for every Weber number. From this we demonstrate that ${\mathit{Bo}}_{\mathit{tip}} \propto \mathit{We}$, explaining both why the transition to crown splash can be characterized in terms of the impact Weber number and why this transition occurs for $W{e}_{crit} \simeq 140$. Next, including the effect of air, we have developed a theory which predicts the time-varying thickness of the very thin air cushion that is entrapped between the impacting solid and the liquid. Our analysis reveals that gas critically affects the velocity of propagation of the splash wave as well as the time-varying force on the disc, ${F}_{D} $. The existence of the air layer also limits the range of times in which the self-similar solution is valid and, accordingly, the maximum deceleration experienced by the liquid rim, that sets the length scale of the splash drops ejected when $We\gt {\mathit{We}}_{crit} $.

scholarly journals On the Stability of Evolution Galerkin Schemes Applied to a Two‐Dimensional Wave Equation System

2006 ◽  
Vol 44 (4) ◽  
pp. 1556-1583 ◽  
Author(s):  
M. Lukáčová‐Medviďová ◽  
G. Warnecke ◽  
Y. Zahaykah
Keyword(s):  
Wave Equation ◽  
Equation System ◽  
Two Dimensional ◽  
The Stability ◽  
Dimensional Wave
Sign in / Sign up

Export Citation Format

Share Document