Obliqueness Angles Research Articles

Investigation of solution structures in a nonlinear electric transmission network incorporating dissipative elements through physical phenomena analysis

This paper presents an innovative approach to solving the voltage equation in a multi-coupled nonlinear transmission network with dissipative elements. By employing the G′G2 -expansion method and fractional derivatives, we explore the behavior of current and voltage, considering memory effects. Our investigation delves into the impact of fractional calculus on signal transmission, revealing insights into period, amplitude, and propagation direction. Additionally, we analyze the influence of obliqueness angles and various fractional-order derivatives on voltage waveforms Stability analysis demonstrates the significant role of dissipative elements and modulation parameters on signal stability and network resistance to interference. Furthermore, we examine the effects of free parameters on signal transmission characteristics. Our findings highlight the intricate interplay between fractional order, wave obliqueness, and physical parameters on voltage propagation, addressing gaps in previous research.

Dynamics of Oceanic Slab Tearing During Transform‐Fault Horizontally‐Oblique Subduction: Insights From 3D Numerical Modeling

AbstractOceanic‐plates vertical tearing is seismically identified in the present‐day Earth. This type of plate tearing is frequently reported in horizontally‐oblique subduction zones where transform‐faulted oceanic plates are subducting (or subducted). However, the mechanisms behind vertical slab tearing are still poorly understood, thus we utilize 3D time‐dependent Stokes' flow thermo‐mechanical numerical models to further study this problem. We find that (a) the age offset of transform fault and (b) the horizontal obliqueness of subduction fundamentally control the tearing behavior of two generic, materially homogeneous oceanic slabs separated by a low‐viscosity zone. The two slabs sequentially bend, which combined with the age‐thickness difference between slabs, causes the differential sinking of them. Based on the modeling results, well‐developed slabs vertical tearing would happen when the oblique angle of subduction is ≥30° or the age ratio of the secondly bent to firstly bent slab being ∼<0.6. Quantifying the horizontal distance‐vector between sinking slabs, we find that subduction at medium‐low horizontal‐obliqueness angles (≤40°) of young lithosphere (slabs‐average ∼15 Myr) tends to produce fault‐perpendicular tearing. Contrastingly, old‐age slabs (average ≥ 30 Myr) with medium‐large obliqueness angles (∼>20°) tend to produce fault‐parallel tearing, related to differential slab‐hinge retreat or rollback. Correlations between slabs' (a) computed tearing horizontal‐width and (b) scaling‐theory forms of their subduction‐velocity differences, are reasonable (0.76–0.97). Our numerically predicted scenarios are reasonably consistent with plate‐tear imaging results from at least four natural subduction zones. Our modeling also suggests that continual along‐trench variation in subduction dip angle may be related to a special case of oblique subduction.

Nanotube structures: material characterization and structural analysis of Ge–Se thin films

Nanotube structures, formed in thin films of chalcogenide glasses open avenues for new applications, since they offer directional options for many effects in these otherwise completely disordered systems. One way to grow nanotubes is through formation of nano-columnar structures by confining them. In this work nano-columnar growth of thermally evaporated GexSe100−x (x = 20, 30, 40) films is achieved through oblique films deposition. The columnar structural organization of the films and its dependence upon the deposition angle and films composition are established by imaging the cross-sectional areas of the films through scanning electron microscopy. Atomic force microscopy, energy dispersive X-ray spectroscopy and Raman Spectroscopy studies reveal respectively variation in the surface porosity, composition changes and structural reorganizations occurring in the films as a function of obliqueness angles and material’s composition. These results are discussed in respect to the structural organization of films deposited under normal flux incidence and deformations and other structural effects caused by films' deposition under variable angles. Based on the experimental results an empirical formula for the tangent rule is suggested which links the incident flux angle α, and the nanotube inclination angle β.

Non-localized boundary layer instabilities resulting from leading edge receptivity at moderate supersonic Mach numbers

This paper uses matched asymptotic expansions to study the non-localized (which we refer to as global) boundary layer instabilities generated by free-stream acoustic and vortical disturbances at moderate supersonic Mach numbers. The vortical disturbances produce an unsteady boundary layer flow that develops into oblique instability waves with a viscous triple-deck structure in the downstream region. The acoustic disturbances (which for reasons given herein are assumed to have obliqueness angles that are close to a certain critical angle) generate slow boundary layer disturbances which eventually develop into oblique stable disturbances with an inviscid triple-deck structure in a region that lies downstream of the viscous triple-deck region. The paper shows that both the vortically generated instabilities and the acoustically generated oblique disturbances ultimately develop into modified Rayleigh-type instabilities (which can either grow or decay) further downstream.

Unsteady impulsive oblique stagnation-point flow impinging axisymmetrically on a vertical circular cylinder with mixed convection heat transfer

For the rst time, the problem of impulsive oblique stagnation-point flow on a vertical cylinder along with mixed convection heat transfer due to buoyancy forces has been solved in this study. The uid at rest with uniform temperature, T1, around the cylinder starts flowing towards it at strength rate of k, and the cylinder temperature rises to Tw at t = 0, simultaneously. The governing equations induced by the impinging flow on the constant-temperature vertical cylinder at any obliqueness angle, , have been reducedto ODEs by using similarity transformations, and then they have been solved numerically. Considering a sample case of incompressible flow with Re = 1 and Pr = 0:7, the results of Nusselt number and similarity functions of velocity and temperature distributions have been obtained for di erent values of time and angle, . At the initial instants of time, the Nusselt number, regardless of 's magnitude, has large values; for example Nu = 5:1 at = 0:01. As time passes, the value of the Nusselt number reduces intensely within ashort period of time (until  0:4), and then it changes with a moderate reduction rate, such that in the steady-state situation, its value reaches 0.67, 0.61, and 0.51 for obliqueness angles = 10, 30, 60.

Influence of orientation on the evolution of small perturbations in compressible shear layers with inflection points.

We investigate the influence of orientation on the evolution of small perturbations in compressible shear layers with inflection points. By using linear analysis, we demonstrate that perturbations along the shear plane are most affected by compressibility. The influence of compressibility gradually diminishes with increasing obliqueness of the perturbations with respect to the shear plane. It is demonstrated that the effective gradient Mach number is an appropriate compressibility parameter. We establish that spanwise perturbations, orthogonal to the shear plane, are impervious to compressibility effects. Direct numerical simulations of compressible mixing layers subject to the perturbations at various obliqueness angles verify the analytical findings.

Small perturbation evolution in compressible Poiseuille flow: pressure–velocity interactions and obliqueness effects

Small perturbation evolution in compressible Poiseuille flow is contrasted against the incompressible case using direct simulations and non-modal linear analysis. The onset of compressibility effects leads to a profound change in the behaviour of pressure and its interaction with the velocity field. Linear analysis shows that the most significant compressibility outcome is the harmonic coupling between pressure and wall-normal velocity perturbations. Oscillations in normal perturbations can lead to periods of negative production causing suppression of perturbation growth. The extent of the influence of compressibility can be characterized in terms of an effective gradient Mach number ($M_{g}^{e}$). Analysis shows that $M_{g}^{e}$ diminishes as the angle of the perturbation increases with respect to the shear plane. Direct numerical simulations show that streamwise perturbations, which would lead to Tollmien–Schlichting instability in the incompressible case, are completely suppressed in the compressible case and experience the highest $M_{g}^{e}$. At the other extreme, computations reveal that spanwise perturbations, which experience negligible $M_{g}^{e}$, are entirely unaltered from the incompressible case. Perturbation behaviour at intermediate obliqueness angles is established. Moreover, the underlying pressure–velocity interactions are explicated.

Sensitivity analysis of a streamwise corner flow

The stability of the flow formed by the intersection of two perpendicular flat plates is revisited through a study of the sensitivity to base-flow variations. After a brief presentation of the asymptotic regime, sensitivity functions underlying corner mode (concentrated close to the intersection) and Tollmien–Schlichting modes, with different obliqueness angles, are computed. Taking this into consideration, associated mechanisms as well as active regions are identified, which further confirm the sensitivity area of the corner mode along the intersection of two flat plates. Furthermore, the concept of ΔU-pseudospectra indicates that under a small base-flow modification, a certain range of frequencies underlying the corner mode could become unstable. Then, an optimization technique tracking the worst-case scenario, i.e., the deviation leading to a maximum temporal amplification rate, shows that a small variation in the reference field in the area of uncertainty leads to a significant decrease in the critical Reynolds number as observed in experiments. A hypothesis based on the onset of an inflectional mechanism is thus proposed to explain the experimental results.

Origin of giant photocontraction in obliquely deposited amorphousGexSe1−xthin films and the intermediate phase

Obliquely deposited amorphous Ge x Se 100-x thin films at several compositions in the 15%<x<33.3% range and at several obliqueness angles in the 0<α<80° range at each x were evaporated on Si and glass substrates. Here α designates the angle between film normal and direction of vapor transport. Raman scattering, IR reflectance, and optical absorption measurements were undertaken to characterize the vibrational density of states and optical band gaps. Edge views of films in scanning electron microscopy (SEM) confirm the columnar structure of obliquely (α=80°) deposited films. Films, mounted in a cold stage flushed with N 2 gas, were irradiated to UV radiation from a Hg-Xe arc lamp, and photocontraction (PC) of oblique films were examined. Compositional trend of PC exhibit a bell-shaped curve with a rather large effect (0.25 μm) centered in the 20% 25%, the stressed rigid phase, and at x 25 Se 75 ) that demix from a Ge-rich (∼Ge 40 Se 60 ) phase that fills the intercolumnar space. Loss of PC in such films is traced to the growth of the Ge-rich phase, which is intrinsically stressed and photoinactive. In contrast, Se-rich films are homogeneous, and loss of PC as x decreases below 20% is traced to the accumulation of network stress in the Se-rich nanofilaments. The microscopic origin of the giant PC effect in amorphous semiconducting thin films can be traced, in general, to three conditions being met: (i) growth of a columnar structure leading to porous films, (ii) formation of columns that are rigid but intrinsically stress free, and (iii) an appropriate flux of pair-producing radiation leading to photomelting of columns. These findings lead us to predict that PC will, in general, be maximized in obliquely deposited films of semiconducting networks glasses residing in their IP when irradiated with supra-band-gap radiation.

Onset of electroconvection of homeotropically aligned nematic liquid crystals

We present experimental measurements near the onset of electroconvection (EC) of homeotropically aligned nematic liquid crystals Phase 5A and MBBA. A voltage of amplitude square root 2V0 and frequency f was applied. With increasing V0, EC occurred after the bend Freedericksz transition. We found supercritical bifurcations to EC that were either stationary bifurcations or Hopf bifurcations to traveling convection rolls, depending on the sample conductances. Results for the onset voltages Vc, the critical wave numbers kc, the obliqueness angles thetac, and the traveling-wave (Hopf) frequencies at onset omegac over a range of sample conductances and driving frequencies are presented and compared, to the extent possible, with theoretical predictions. For the most part good agreement was found. However, the experiment revealed some unusual results for the orientations of the convection rolls relative to the direction selected by the Freedericksz domain.

Numerical investigations of small-amplitude disturbances in a boundary layer with impinging shock wave at Ma=4.8

The stability behavior of a laminar boundary layer with shock boundary layer interaction and small amplitude disturbances is investigated by linear stability theory and direct numerical simulation. By a complex interaction of several physical properties, the impinging shock wave locally influences stability behavior of the boundary layer, dependent on its shock strength, applied disturbance frequency, and disturbance propagation angle with respect to the flow direction (obliqueness angle). Due to the displacement of the boundary layer near shock impingement and the according Reynolds number effect in this area, the boundary layer is locally destabilized. The displacement of the boundary layer also produces an increase of the thickness of local regions of relative supersonic speed, which promotes second mode instability. For the results obtained by direct numerical simulation nonparallel effects could be identified and quantified. Taking these nonparallel effects into account, linear stability theory is able to represent the stability behavior of wall distant disturbance amplitude maxima having small obliqueness angles for the cases investigated here. For larger obliqueness angles and disturbance amplitudes at or close to the wall the agreement between linear stability theory and direct numerical simulation declines considerably.

Navier-Stokes Simulation of Harmonic Point Disturbances in an Airfoil Boundary Layer

Laminar-turbulenttransitionmechanismsinducedbyaharmonicpointsourcedisturbanceinae at-plateboundary layerwithadversepressuregradientareinvestigated by fourth-orderaccuratespatialdirectnumericalsimulation based on the complete three-dimensional Navier ‐Stokes equations for incompressible e ow. The disturbance is introduced into thetwo-dimensionalbasee owbytime-periodicsimultaneousblowing andsuction within acircular spot at the wall to quietly mimic the momentum input by an active loudspeaker below a hole in the surface in respective experiments. Thus a wave train consisting of pure Tollmien ‐Schlichting waves of a singlefrequency and a large number of obliqueness angles is stimulated, and its downstream evolution in both physical and spectral space is investigated. A breakdown scenario dominated entirely by oblique modes is observed that shows a spanwise peak/valley amplitude splitting with the valley plane at the centerline of the wave train. Dominant vorticity structures develop off centerline, and a clear-cut -shaped structure is formed in e nal stages related to the wall shear being a footprint of a e rst pair of K -vortices in the e ow.