Wave Configuration Research Articles

Study on fatigue damage optimization mechanism of deepwater lazy wave risers based on multiple waveform serial arrangement

Lazy wave risers can mitigate the kinematic coupling between floating structure and riser touchdown zone (TDZ), so as to improve its fatigue life. However, due to the introduction of buoyancy blocks, nonlinear dynamic response and fatigue damage prediction will be more complicated. In this paper, a concept of “multiple lazy wave riser”, namely, deepwater lazy wave riser configuration based on multiple waveform serial arrangement, is proposed. According to the improved slender rod theory and equivalent optimization of buoyancy sections, three riser configurations with different heave excitations and currents are structured. The dynamic response characteristics, excitation motion transfer paths and fatigue damage hotspots are well compared. Moreover, the influence law of riser fatigue damage and decoupling mechanism of riser TDZ movements are also explored. The results indicate that: by constructing lazy wave configuration, deepwater risers based on lazy wave configuration can attenuate the kinematic coupled response of floating structure in the first sag bend section, and reduce the normal motion response in the riser TDZ, so as to optimize its anti-fatigue performance; compared with lazy wave riser, multiple lazy wave riser has some competitiveness in the anti-fatigue performance for the riser TDZ. For flexible risers, this competitiveness will become even more prominent.

A comparison of two dynamic power cable configurations for a floating offshore wind turbine in shallow water

For the study of the double wave configuration for the dynamic power cable of a Floating Offshore Wind Turbine (FOWT) in shallow water, this paper presented a comparison of the hydrostatic and hydrodynamic performance between a lazy wave and a double wave configuration. The double wave shape’s parametric presentation was first developed based on an extension of a previous parametric lazy wave shape. An aero-hydro-servo-elastic integrated model fully coupling the FOWT and the dynamic power cable was then proposed in the SIMO/RIFLEX code for numerical simulation. Subsequently, the strain-cycle curve and the rain flow counting method were employed to estimate the copper conductor’s fatigue damage. The bending moment was proved to provide the major fatigue contribution. The results showed that the double wave offered superior performance than the lazy wave. The second arc of the double wave configuration was proved critical for suffering high curvature, tension, and fatigue damage. A lower position and less hogged wave arc were suggested for the determination of the double wave shape.

Morphology of oblique detonation waves in a stoichiometric hydrogen–air mixture

Abstract

Gasdynamic Flow Control by Ultrafast Local Heating in a Strongly Nonequilibrium Pulsed Plasma

—The paper presents a review of modern works on gasdynamic flow control using a highly nonequilibrium pulsed plasma. The main attention is paid to the effects based on ultrafast (on the nanosecond time scale for atmospheric pressure) local gas heating, since, at present, the main successes in controlling high-speed flows by means of gas discharges are associated with this thermal mechanism. Attention is paid to the physical mechanisms responsible for the interaction of the discharge with gas flows. The first part of the review outlines the most popular approaches for pulsed energy deposition in plasma aerodynamics: nanosecond surface barrier discharges, pulsed spark discharges, and femto- and nanosecond optical discharges. The mechanisms of ultrafast heating of air at high electric fields realized in these discharges, as well as during the decay of the discharge plasma, are analyzed separately. The second part of the review gives numerous examples of plasma-assisted control of gasdynamic flows. It considers control of the configuration of shock waves in front of a supersonic object, control of its trajectory, control of quasi-stationary separated flows and layers, control of a laminar–turbulent transition, and control of static and dynamic separation of the boundary layer at high angles of attack, as well as issues of the operation of plasma actuators in different weather conditions and the use of plasma for the de-icing of a flying object.

Gravitational waves in metric-affine gravity theory

We derive the exact gravitational wave solutions in a general class of quadratic metric-affine gauge gravity models. The Lagrangian includes all possible linear and quadratic invariants constructed from the torsion, nonmetricity and the curvature. The ansatz for the gravitational wave configuration and the properties of the wave solutions are patterned following the corresponding ansatz and the properties of the plane-fronted electromagnetic wave.

Life–Threatening Hyperkalemia Presenting with Cardiac Arrest during Combined Therapy with Angiotensin – Converting Enzyme Inhibitor and Spironolactone: a Case Report

A 56-year-old man with history of previous coronary artery bypass graft (CABG) surgery and prior history of mild renal impairment was brought to the emergency department at mid night in gasping state. On presentation his pulse and blood pressure (BP) were non recordable. Cardiopulmonary resuscitation (CPR) was started immediately and he was intubated in the emergency room. Within few minutes his pulse became perceptible but BP still remained non recordable. His bed side 12 leads electrocardiogram (ECG) revealed sine wave configuration,suggestive of severe hyperkalemia with heart rate 30-35 beats per minute (bpm).Urgently he was transferred to cardiac catheterization laboratory for temporary pacemaker insertion (TPI). After putting TPI he regained consciousness and BP raised to normal. His blood gas analysis showed severe hyperkalemia (Serum potassium level-9.4 mmol/L). In coronary care unit (CCU) he was commenced on standard treatment of hyperkalemia and his electrolyte imbalance normalized within 24 hours. His cardiac rhythm reverted back to sinus within 24 hours of admission and he was extubated next day and discharged from the hospital after 5 days in a relatively stable state.
 J Dhaka Medical College, Vol. 28, No.2, October, 2019, Page 212-215

Integrated Analysis of Multisensor Datasets and Oil Drift Simulations—A Free‐Floating Oil Experiment in the Open Ocean

AbstractA free‐floating oil spill experiment (two oil types) in the open ocean is described, and the results from slick characterization through integrated analysis of drift simulations with remote sensing and in situ data are discussed. We compare oil drift simulations (OpenOil), applying various configurations of wind, wave, and current information, with the observed slick positions and shape. We describe trajectories and dynamics of the spills, slick extent, and their evolution, and the differences in detection capabilities in optical instruments versus multifrequency PolSAR acquired by Deutsches Zentrum für Luft‐und Raumfahrt F‐SAR. When using the best available forcing from in situ data and forecast models, good agreement with the observed position and extent was found. A fair agreement is obtained using only numerical forecast data as input. This case study reveals that the accuracy when using modeled current is relatively higher after one full local inertial period, as the effect of incorrectly modeled amplitude of the inertial current is then vanishing. This should be a general result applicable to any oceanic drift forecast based on the modeled current. A novelty is the comparison of viscous‐similar soybean and mineral oil. Our findings indicate that biological oil emulsions potentially could replace mineral oil emulsions in contingency and rehearsal campaigns, but this finding is only supported from an oil drift prediction perspective. Differences in mineral oil detection capabilities are found between synthetic aperture radar and optical imagery of thinner sheen regions. F‐SAR appears to be more sensitive to thinner oil and detect a larger extent, and differences between the thinner and thicker parts are observed.

Standing wave impacts on vertical hydraulic structures with overhangs for varying wave fields and configurations

This study focuses on standing wave impacts on vertical hydraulic structures with relatively short overhangs. It addresses the demand for extended knowledge and loading prediction expressions for these structures. Based on laboratory experimental data from 146 tests, this paper works on two complementary objectives. Firstly, this study extends the knowledge on this type of wave impacts addressing the following aspects: changes in hydraulic loading conditions (regular/irregular waves and varying freeboards) and changes in the structure geometry (lateral constriction and loading reducing ventilation gaps). All laboratory tests consider relatively short overhangs, with ratios of wave length to overhang length between 10 and 40, and ratios of overhang height to overhang length of 3 and 6. The regular wave tests showed that the tests with the longer overhang were related to longer impact durations and larger loading variability compared to the tests with the shorter overhang. Also, tests with reduced freeboards produced larger impact loads. In addition, repeated tests presented equal impulse values (I, Beta, td, Lambda). Furthermore, the pressure peaks measured at one location were found to not represent the pressure peaks averaged over the structure width, while the pressure-impulses measured at one location were found to properly represent the pressure-impulses averaged over the width. The constriction tests showed that a lateral constriction amplifies pressure peaks and pressure-impulses at the constriction edge. The ventilation gap tests showed that ventilation gaps are effective in reducing force peaks and force-impulses. The irregular wave tests highlighted that the dynamic interactions of the incident waves with the structural configurations are even more dynamic and variable in tests with irregular wave conditions. Secondly, this study presents loading prediction expressions for preliminary loading estimations built up by the previously developed pressure-impulse theory that is empirically calibrated using the presently acquired experimental data. To that end, the relation between the effective bounce-back factor (1<Beta<2) with the Gamma Parameter is described. These loading prediction expressions may be used for preliminary load estimations and in combination with structural response models.

On some configurations of oppositely charged trapped vortices in the plane

Our aim in the present work is to identify all the possible standing wave configurations involving few vortices of different charges in an atomic Bose-Einstein condensate (BEC). In this effort, we deploy the use of a computational algebra approach in order to identify stationary multi-vortex states with up to 6 vortices. The use of invariants and symmetries enables deducing a set of equations in elementary symmetric polynomials, which can then be fully solved via computational algebra packages. We retrieve a number of previously identified configurations, including collinear ones and polygonal (e.g. quadrupolar and hexagonal) ones. However, importantly, we also retrieve a configuration with 4 positive charges and 2 negative ones, which is unprecedented, to the best of our knowledge, in BEC studies. We corroborate these predictions via numerical computations in the fully two-dimensional PDE system of the Gross-Pitaevskii type which characterizes the BEC at the mean-field level.

Influence of gas-dynamic characteristics of a wide-range engine on energy-information exchange during flights at high supersonic speed

Using a conical nozzle as an example, the gas-dynamic and thrust characteristics of high-altitude nozzles are studied in a wide range of atmospheric pressures. A geometric model of the nozzle block and the computational domain is developed in a two-dimensional axisymmetric formulation. A calculation was carried out with setting the parameters of the standard atmosphere in the altitude range from 0 to 80 km. In one of the parts of this work, the most common shock-wave structures (triple configurations of shock waves) that arise during flights at supersonic and high supersonic speeds are considered, during jet outflows from propulsion systems. We also studied the influence of the extreme values of the discontinuities of the flow field parameters on the transmitted electromagnetic signals.

Some pioneering research in laboratory simulation of scaled astrophysical phenomena by Russian physicists

The review about the problems of astrophysical phenomena pioneering researching by Russian recognized physicists – S.Anisimov, I.V.Minin, O.V.Minin, V.F.Minin and A.Velikovich - is carried out. For the first time, a mode of hypercumulative collapse of a conical cavity was proposed for the formation of an ultra-high-speed plasma jet. The description of “cumulative plasma jets” is presented. The main parameters of the cumulative plasma jet and the results of laboratory studies on the creation of a hyper cumulative plasma jet are described. It was shown that the proposed mechanism allows one to obtain record characteristics of such a jet, which have not been surpassed so far. Test data description of the numerical simulation of the inter action between plungers and a conic cavity on the explosive initiation of the D-D reaction with the aid of aluminum plungers is discussed. The mechanisms of the plunger surface acceleration are described. The generation of the Mach configuration of shock waves in the target was also used for the explosive production of wurtzite with a record yield of the mass of the synthesized material and to focusing of the shock waves in water using plane diffractive optics.

Quantum many-body scars in a Landau level on a thin torus

We study a kinetically constrained pair hopping model that arises within a Landau level in the quantum Hall effect. At filling $\nu = 1/3$, the model exactly maps onto the so-called "PXP model", a constrained model for the Rydberg atom chain that is numerically known to exhibit ETH-violating states in the middle of the spectrum or quantum many-body scars. Indeed, particular charge density wave configurations exhibit the same revivals seen in the PXP model. We generalize the mapping to fillings factors $\nu = p/(2p+1)$, and show that the model is equivalent to non-integrable spin-chains within particular constrained Krylov Hilbert spaces. These lead to new examples of quantum many-body scars which manifest as revivals and slow thermalization of particular charge density wave states. Finally, we investigate the stability of the quantum scars under certain Hamiltonian perturbations motivated by the fractional quantum Hall physics.

Elliptic function solutions, modulation instability and optical solitons analysis of the paraxial wave dynamical model with Kerr media

The optical solitary waves explain non-dispersive and non-diffractive spatiotemporal localized waves envelopes promulgating in the media of optical Kerr. These propagations are generally described by the nonlinear Schro dinger equation. The modified extended mapping technique is utilized to assemble the solitons, solitary waves and rational solutions of time-dependent dimensionless paraxial wave equation. The obtained different sorts of wave solutions encompass key applications in physics and engineering. By giving appropriate values to parameter, special sorts of solitary waves configuration can be displayed graphically. The physical interpretation of the solution can be understood through the structure. The stability of this wave equation is investigated via using modulational instability analysis which authenticates that all soliton solutions are stable and exact. Several analytical results and working out have confirmed the strength and efficacy of the current technique.

EABR measurements during cochlear implantation in one-year-old, infant, child, adult, and elderly patients

Background Clinical application of electrically-evoked intracochlear auditory brainstem responses (eABRs) for evaluation of brainstem maturity or aging changes has not been well investigated. Aim/objective We compare the eV latencies of intraoperative eABR measurements in one-year-olds, infants, children, adults, and the elderly, with the goal of investigating the changes in the brainstem auditory pathway due to development and aging. Materials and methods We studied 58 ears of 51 patients who underwent cochlear implantation between 2013 and 2019 using MED-EL’s Concerto or Synchrony implants with Flex28 or Flex soft electrodes. EABRs were recorded during cochlear implantation. The stimuli were delivered by the MED-EL Maestro to the apical, middle, and basal turn electrodes at stimulus levels 1000, 800, and 600 cu, with a pulse width of 30 µs. Results In eABRs recorded from electrodes installed at both the mastoid and nape, there was no difference in latency between age groups within each stimulus level. Conclusion and significance ABR latency was not affected by development after age one and aging of the brainstem auditory pathway. Our study will be useful as a control in identifying abnormal eABR wave configurations in patients with cochlear malformations, cochlear nerve deficiencies, or auditory neuropathy, regardless of age.

Exact and explicit travelling-wave solutions to the family of new 3D fractional WBBM equations in mathematical physics

In this paper, the new 3D fractional Wazwaz-Benjamin-Bona-Mahony (WBBM) equations newly announced are investigated with the introduction of the spatial and sequential fractional-order derivatives expending in the sense of conformable derivative. Several solutions containing hyperbolic and trigonometric function solutions are created using the modified extended tanh-function (mETF) method. The productivity of the mETF process for building these solutions has been established. This method decreases the large volume of calculations. With the assist of computational software MALAB, the solutions' graphical exemplifications are illustrated in three-dimension (3D) and two-dimension (2D) plot. All plots represent the absolute wave configurations through the obtained solutions to the mentioned equation, preferring suitable parameters. Moreover, it may conclude that the attained solutions and their physical features might help comprehend the shallow water wave propagation in nonlinear dynamics.

Parameter-correlation study on shock–shock interaction using a machine learning method

To predict the maximum heating load induced by shock–shock interaction more reliably and accurately, the geometrical scale of the overall wave configuration of shock–shock interaction is very useful. However, it is hard to be solved with traditional shock theory due to its complexity. The results of numerical and experimental studies are case-by-case. Concise formulas correlating the geometrical scales of shock–shock interaction with the given flow parameters are desired but still unavailable. In the present work, a set of correlative formulas for the triple-points' coordinates of type IVa, IV, and III shock–shock interaction are derived by multilevel block building algorithm, a functional machine learning method. The key flow structure of shock–shock interaction, i.e., the supersonic impinging jet, can be determined with the help of shock theories and the formulas. In addition, the transition criteria respectively for the overall wave configuration transitions of type IVa ↔ type IV and type IV ↔ type III shock–shock interaction can be obtained by the machine learning based method.

Tunable THz and Infrared Plasmonic Filters and Switches Based on Circular Graphene Resonator With 90$^\circ$ Bending of Output Port

Two types of novel graphene-based components, namely, filters and electro-optical switches in guided wave configuration are suggested and analysed. The filters differ from the known ones with collinear orientation of the input and output waveguides by geometry and symmetry. The components consist of a circular graphene disk and two nanoribbons oriented at 90° to each other in the plane of the graphene layer. The graphene elements are placed on a dielectric substrate. We show that change in symmetry leads to a drastic change in the properties of the components. The physical principle of the devices is based on the dipole, quadrupole and hexapole resonances in the graphene disk which define stop-band, pass-band and stop-band frequency characteristics, respectively. A combination of stop-band and pass-band filter properties by shifing the electronic Fermi level allows one to design a switch. Numerical simulations show that the suggested components have very small dimensions, good characteristics and provide a dynamic control of their central frequency via electrostatic gating.

Численное моделирование когерентных и турбулентных структур излучения методом нелинейных интегральных отображений

The propagation of stable coherent entities of an electromagnetic field in nonlinear media with parameters varying in space can be described in the framework of iterations of nonlinear integral transformations. It is shown that for a set of geometries relevant to typical problems of nonlinear optics, numerical modeling by reducing to dynamical systems with discrete time and continuous spatial variables to iterates of local nonlinear Feigenbaum and Ikeda mappings and nonlocal diffusion-dispersion linear integral transforms is equivalent to partial differential equations of the Ginzburg-Landau type in a fairly wide range of parameters. Such nonlocal mappings , which are the products of matrix operators in the numerical implementation, turn out to be stable numerical-difference schemes, provide fast convergence and an adequate approximation of solutions. The realism of this approach allows one to take into account the effect of noise on nonlinear dynamics by superimposing a spatial noise specified in the form of a multimode random process at each iteration and selecting the stable wave configurations. The nonlinear wave formations described by this method include optical phase singularities, spatial solitons, and turbulent states with fast decay of correlations. The particular interest is in the periodic configurations of the electromagnetic field obtained by this numerical method that arise as a result of phase synchronization, such as optical lattices and self-organized vortex clusters.

Numerical investigation of flow structures resulting from the interaction between an oblique detonation wave and an upper expansion corner

Abstract

Investigation of shock wave interactions involving stationary and moving wedges

The present study investigates the shock wave interactions involving stationary and moving wedges using a sharp interface immersed boundary method combined with a fifth-order weighted essentially non-oscillatory scheme. Inspired by Schardin’s problem, which involves moving shock interaction with a finite triangular wedge, we study the influence of incident shock Mach numbers and corner angles on the resulting flow physics under both stationary and moving conditions. The present study involves three incident shock Mach numbers (1.3, 1.9, and 2.5) and three corner angles (60°, 90°, and 120°), while its impact on the vorticity production is investigated using the vorticity transport equation, circulation, and rate of circulation production. Furthermore, the results yield that the generation of the vorticity due to the viscous effects is quite dominant compared to the baroclinic or compressibility effects. The moving cases presented involve shock driven wedge problems. The fluid and wedge structure dynamics are coupled using the Newtonian equation. These shock driven wedge cases show that wedge acceleration due to the shock results in a change in reflected wave configuration from single Mach reflection to double Mach reflection. The intermediary state between them, the transition Mach reflection, is also observed in the process. The effect of shock Mach numbers and corner angles on the triple point trajectory, as well as on the drag coefficient, is analyzed in this study.