Remi Jean Noumana Issokolo

Theoretical analysis of local instability in flexible pipe-conveying non-uniform transient flow considering fluid–structure interaction

Hyacinthe Simo Kaptue, Dieudonné Zanga, Remi Jean Noumana Issokolo

Physics of Fluids

In this paper, we present an analytical study of the stability of a flexible pipe-conveying non-uniform viscous flow in order to characterize the fatigue situation which induces damage. Based on the fluid–structure interaction mechanisms in the pipe-conveying fluid, we provide physical mechanisms responsible for the emergence of helical-type vortices in transient pipe flows. Additionally, we establish the Lange–Newell criterion for the appearance of flow patterns in the pipe. To achieve these goals, the nonlinear generic models are first transformed into a two-dimensional coupled complex Ginzburg–Landau equation. Thereafter, this equation is explored to perform linear stability analysis, and some modulational instability properties are derived and found to be modified by the change in the Reynolds number, which is set as the control parameter. A bifurcation analysis is performed analytically and numerically and based on these, we find that the system undergoes Hopf or Bautin bifurcations. As a result, a phase portrait-like helical-type vortices of the velocity, pressure, and pipe displacement are obtained. Moreover, frequency analysis is implemented to show the influence of parameters on the power spectral density curve. The results obtained in this work find applications in aeronautics for sizing reactors, in the water processing industry, in the oil industry, in hydraulics for sizing flexible pipes, and in heat exchangers in the nuclear industry.

• #vibration and dynamic analysis
• #fluid dynamics and turbulent flows
• #rheology and fluid dynamics studies
• #reynolds number

Dynamic analysis in (3 + 1) dimensions of the fluid-structure interaction of an anchored floating pontoon in oceanic waves

HYACINTHE SIMO KAPTUE, Remi Jean Noumana Issokolo, Loïc Ngou Zeufo, Yves C. Mbono Samba, Timoléon Crépin Kofané

Physics of Fluids

The development of giant waves represents a fundamental information field in oceanic research, such as energy harvesting. In this work, we consider the effects of fluid-structure interaction (FSI) in studying and analyzing the dynamics of a floating pontoon immersed in Newtonian fluid flow. In this respect, a nonlinear coupled model, based on the Navier–Stockes and Navier–Lamé equations, is applied to solve the fluid-structure interaction problem. To this end, a set of coupled dynamical equations is established, and using the multi-scales method, a coupled complex Ginzburg–Landau equation is derived. First, it is demonstrated that Young's modulus (E) as well as the Poisson's ratio (νs) have considerable effects on the giant waves occurrence. In this regard, we have obtained a critical value of νs above which giant waves can occur, meanwhile, the results obtained also indicate that the increase in E decreases the probability of giant wave formation. Moreover, the dynamic study to explore the dynamical responses from the interaction between the fluid and the structure exhibits different phase portraits that depend on the temporal frequencies of the incident wave from the flowing fluid (ω) and the frequency of the fluid wave reflected by the structure (ω′). These results aim to find applications in the marine industry, where they can be applied to problems related to the stability of ships and offshore structures, sea-keeping problems, and resistance to wave actions. They could also be used to develop floating offshore wind turbines and dimensional buoys for energy harvesting from the ocean surface.

• #ocean waves and remote sensing
• #wave and wind energy systems
• #ship hydrodynamics and maneuverability
• #physics

Localized discrete and asymmetric dark-bright soliton-like modes as nonlinear dynamics in microtubules

Remi Jean Noumana Issokolo, S. E. Mkam Tchouobiap, F. Naha Nzoupe

Heliyon

-model of MTs. It has been shown that during the hydrolysis of guanosine 5'- triphosphate into guanosine 5'-diphosphate, the energy released is transferred along the MTs through kink-like solitons. Substantially, we propose to theoretically investigate the dynamic of MTs by intrinsically taking into account the effect of oriented molecules of polarized cytoplasmic water and enzymes surrounding the MT. In this regards, we introduce a cubic nonlinear term in the electric potential characterizing the polyelectrolyte features of MTs and show that in addition to the kink and anti-kink dynamics, asymmetrical bright and dark solitons, and discrete modes can also propagate along the MTs. These results are supported by numerical analysis. The investigation shows us that the nonlinear dynamics of MTs is strongly impacted by the intrinsic electric field, the polyelectrolyte and the viscous effects. Moreover, new solitonic dynamics and discrete solitary modes might aid in the discovery of novel microtubulin system phenomena.

• #nonlinear photonic systems
• #advanced fiber laser technologies
• #nonlinear waves and solitons
• #dynamics (music)

Wavy approach for fluid–structure interaction with high Froude number and undamped structure

HYACINTHE SIMO KAPTUE, Remi Jean Noumana Issokolo, Loïc Ngou Zeufo, Yves C. Mbono Samba, Timoléon Crépin Kofané

Physics of Fluids

This paper addresses the fluid–structure interaction problem, with an interest on the interaction of a gravity wave with a flexible floating structure, anchored to a seabed of constant depth. To achieve this goal, we make use of the model equations, namely, the Navier–Stokes equations and the Navier–Lamé equation, as well as the associated the boundary conditions. Applying the multi-scale expansion method, these set of equations are reduced to a pair of nonlinearly coupled complex cubic Ginzburg–Landau equations (CCGLE). By applying the proposed modified expansion method, the group velocity dispersion and second-order dispersion relation are deduced. In the same vein, modulation instability (MI) is investigated as a mechanism of formation of pulse trains in fluid–structure system using a CCGLE. For the analytical analysis, we made use of the inverse scattering method to find analytical solutions to the coupled nonlinear equations. Through that method, the obtained solutions depict rogue-shaped waves. Our results suggest that uncontrolled MI within the interaction between a flexible body and gravity waves in viscous flow may be considered as the principal source of many structural ruptures, which are the first cause of critical damage due to the great energy and unpredictability of rogue waves. The present work aims to provide tools to model a wide range of physical problems regarding the interaction of surface gravity waves and an offshore-anchored structure, and it aims to be essential to our understanding of the nonlinear characteristics of offshore structures in real-sea states.

• #fluid dynamics and vibration analysis
• #fluid dynamics simulations and interactions
• #nonlinear waves and solitons
• #froude number

Discrete and Asymmetric Solitons-Like Modes as Nonlinear Dynamics in Microtubules

Remi Jean Noumana Issokolo, S. E. Mkam Tchouobiap, F. Naha Nzoupe

SSRN Electronic Journal

• #nonlinear photonic systems
• #nonlinear dynamics and pattern formation
• #microtubule and mitosis dynamics
• #nonlinear system

Discrete and solitons-like modes as nonlinear dynamics in microtubules based on an improved longitudinal u -model

S. E. Mkam Tchouobiap, Remi Jean Noumana Issokolo, F. Naha Nzoupe

In the present work, we focus on the longitudinal model of microtubules (MTs) proposed by Satar i c ̵́ et al. [Phy. Rev. E 48, 89 (1993)], that consider cell MTs to have ferroelectric properties, i.e., a displacive ferro-distortive system of dimers and usually referred to as u -model of MTs. It has been shown that during the hydrolysis of GTP into GDP, the energy released is transferred along the MTs trough kink-like solitons. Substantially, we propose to theoretically investigate the dynamic of MTs by intrinsically taking into account the effect of the oriented molecules of polarized cytoplasmic water and enzymes surrounding the MT. In this regards, we introduce a cubic nonlinear term in the electric potential characterizing the polyelectrolyte features of MTs and show that in addition to the kink and antikink solitons, asymmetrical bright and dark solitons, and discrete modes can also propagate along the MTs. Theses results are supported by numerical analysis. The investigation shows us that the nonlinear dynamics of MTs is strongly impacted by the intrinsic electric field, the polyelectrolyte and the viscosity effects. Moreover, new solitons and discrete solitary modes may help to find new phenomena occurring in the microtubulin systems.

• #microtubule and mitosis dynamics
• #nonlinear dynamics and pattern formation
• #magnetic and electromagnetic effects
• #nonlinear system

Modulational instability in thin liquid film flowing down an inclined uniformly heated plate

Remi Jean Noumana Issokolo, S. E. Mkam Tchouobiap, F. Naha Nzoupe, Alain M. Dikandé

AIP Advances

The modulational instability properties regarding the evolution of interfacial disturbances of the flow of a thin liquid film down an inclined uniformly heated plate subject to thermal Marangoni (thermocapillary) effects are investigated under the framework of linear stability analysis. The investigation has been performed both analytically and numerically using a complex cubic Ginzburg–Landau equation without the driving term to provide comprehensive pictures of the influence of nonlinearity, dissipation, and dispersion on interfacial disturbance generation and evolution. It is shown that when the interplay between linear and nonlinear effects is relatively important, the disturbances evolve as a superposition of groups of traveling periodic waves with different amplitudes, and the interfacial disturbances evolve as smooth modulations. Furthermore, the dynamic modes of these disturbances become aperiodic. Conversely, when the evolution of instabilities is influenced by strong nonlinearity, the flow saturates, and different situations lead to different possible modulated wavy structures, caused by the interplay between nonlinear and linear dispersive and dissipative effects. Moreover, the appearance and the spatial and temporal evolution of the modulated disturbance profiles are influenced by both the amplitude of the disturbances and the linear dissipative term. Here, based on our investigation, two cases are highlighted. In the first case, which corresponds to very small amplitude of the disturbances, the dynamic modes of the disturbances evolve from periodic traveling waves to spatial and temporal modulated periodic solitary wave patterns. In the second case, by increasing the amplitude of the disturbances, the appearance of modulational modes is rapid, and therefore, we can observe the development of modulationally marginal-like stable patterns or spatial and temporal modulated patterns with nonuniform profiles.

• #fluid dynamics and thin films
• #nonlinear dynamics and pattern formation
• #solidification and crystal growth phenomena
• #modulational instability