Vertical Wave Research Articles

Hydrocarbon condensation flow and heat transfer in wave helical pipes: Effect of structure parameters

In this study, two types of wave-structured pipes for heat exchangers that are easy to process are proposed, and the condensation pressure drop and heat transfer performances for hydrocarbon refrigerant upward flow in wave helical pipes are investigated. A numerical method based on the inhomogeneous two-fluid model is introduced and validated by experimental data in literature. The effect of wave parameters (wave height and wave length) on heat transfer, pressure drop and flow patterns are studied. At lower vapor quality conditions, it is found that as wave height increases, frictional pressure drop and heat transfer coefficient exhibit a trend of initially increasing, followed by decreasing, and then increasing again. However, under higher vapor quality conditions, frictional pressure drop and heat transfer coefficient continue to increase. Besides, both the frictional pressure drop and heat transfer coefficient increase with the decrease of wave length. The averaged enhancement on frictional pressure drop for vertical wave pipes and horizontal wave pipes are respectively 1.279–5.148 and 1.238–5.808 times, while the average augmentation in heat transfer coefficient is 1.243–3.006 and 1.316–3.579 times, respectively. The comprehensive thermal performance of wave pipes was assessed using the performance evaluation criterion. The range of averaged performance evaluation criteria (under different vapor qualities) in vertical wave pipes and horizontal wave pipes are respectively 1.150–1.737 and 1.230–2.026. The horizontal wave pipe when the wave height is 5 mm and wave length is 5.24 mm shows the best overall thermal performance, with an averaged performance evaluation criterion of 2.026. The two types of wave-structured pipes proposed in this paper can increase the pipe length of the spiral-wound heat exchanger at the same volume, while also improving the performance of the spiral-wound heat exchanger. The outcomes of the study can offer some assistance in creating simple but effective spiral wound heat exchangers.

Vibration Response of Soil under Low-Frequency Vibration Using the Discrete Element Method

The vibration response of soil is a key property in the field of agricultural soil tillage. Vibration components of tillage machinery are generally used to reduce tillage resistance and improve work efficiency, and the pressure variation under low-frequency vibration will affect the fragmentation and dispersion of farmland soil. However, the gradient of pressure variation, frequency domain response, and effective transmission range is unclear. A new method based on the DEM (discrete element method) is presented to study the vibration response and pressure transmission under low-frequency vibration. Bench test results have shown that peak pressure positively correlates with the vibration frequency and attenuates rapidly at a vibration distance of 100 to 250 mm. The resulting data were also selected to determine the simulation model’s parameters. Amplitude, vibration frequency, and soil depth were used as test factors in single-factor simulation tests, and their effects on the peak pressure, frequency domain response, and effective transmission distance were analyzed. The results showed a positive relationship between the peak pressure and the test factors. The peak pressure increased with a maximum gradient of 19.02 kPa/mm at a vibration distance of 50 mm. The amplitude, vibration frequency, and soil depth positively correlated with the dominant frequency amplitude. The main frequency was independent of amplitude and soil depth. At a vibration distance of 250 mm, the dominant frequency was approximately twice the vibration frequency at 7–11 Hz and approximately equal to the vibration frequency at 13–15 Hz. Multiple exponential functions were used to fit the peak pressure attenuation function, obtaining an effective transmission distance range of 347.15 to 550.37 mm for the 5 kPa cut-off pressure. For a soil depth of 300 mm, the vertical shear wave diffusion angle was greater than the horizontal shear wave diffusion angle. This study clarifies the vibration response of soil under low-frequency vibration, which helps to design vibration-type, soil-engaging components of tillage machinery and match vibration parameters for energy-saving and resistance reduction purposes in soil tillage.

Bragg Scattering of Surface Gravity Waves by a Submerged Composite Wavy Porous Plate

Abstract Surface gravity wave interaction of composite wavy porous plate is studied by developing a numerical model using the boundary element method in the context of two-dimensional linear potential theory. Bragg scattering phenomenon is studied by considering the linearized pressure drop condition known as Darcy’s law passing through the porous structure. Numerical results are obtained through the boundary element method for the special limiting case of the existing previous literature to authenticate the accuracy of the numerical solution. The influence of wave and structural design parameters such as the number of ripple wavelengths of the wavy plate, relative plate length, structural porosities, and relative submergence depth on hydrodynamics properties such as reflection, transmission, horizontal wave load, and vertical wave coefficients are discussed. The study results of composite wavy porous plate indicate improved hydrodynamic performance as compared to the horizontal porous plate and wavy porous plate. This study is significant for practical applications in coastal engineering environments.

A comparative analysis of intraglottal geometry and velocity flow fields: Excised human, canine, and synthetic vocal fold models

Synthetic vocal fold models imitate the characteristics of human vocal folds and offer advantages over tissue models, such as accessibility and prolonged lifespan, all while producing comparable vibration frequencies to those in humans. Nonetheless, due to their simplified design, they may not fully capture the intricate behavior observed in tissue models like the canine larynx model. Canine larynges, like human’s, exhibit a vertical mucosal wave, which yields a phase delay between the inferior and superior edges of the vocal folds free margin. Consequently, a divergent glottis forms during closing, producing intraglottal flow separation vortices (FSVs) that increase voice loudness and intelligibility. To bridge the knowledge gap between silicone and tissue vocal fold models, we compared the intraglottal geometry and velocity flow fields during phonation of these three models. At low subglottal pressures, the synthetic model displayed small divergence angles and no flow separation, where both tissues models exhibited FSVs. At higher pressures, FSVs observed in tissue models were correlated with increased glottal flow waveform skewing and higher MFDR values. These findings highlight why the excised canine larynx model should be the preferred choice over synthetic vocal fold models for studying the aerodynamics and fluid-structure interaction during phonation.

Effects of roll motion on linear and nonlinear gap resonances in a moonpool excited by various incident-wave heights

The linear and nonlinear gap resonances in a free-rolling moonpool are investigated using a two-dimensional in-house code based on the constrained interpolation profile method. This study primarily focuses on the effects of roll motion on hydrodynamic characteristics, taking into account both the linear gap resonance and the nonlinear process-driven gap resonances. The analysis of the incident-wave height is conducted to illustrate the relationship between higher-order harmonics and nonlinear gap resonances. Numerical results demonstrate that the resonant frequency is insensitive to the roll motion. However, the roll response plays an important role in influencing the vertical wave loads on the barges and affecting the energy conversion pattern in the fluid field. According to the analysis of the incident-wave height parameter, the magnitudes of resonance at the linear and nonlinear resonant points are approximately in sub-linear and superlinear relationships with the incident-wave height, respectively. Moreover, the vortex shedding modes around the entrance of the free-rolling moonpool gradually transit from being dominated by the pairs of vortices to being dominated by the single vortex as the gap resonance changes from linear to quartic.

Loss of autumn Kara-East Siberian Sea ice intensifies winter Ural blocking and cold anomalies in high latitudes of Eurasia

Sea ice in the Kara-East Siberian Sea (KESS) declined to the lowest record in the autumn of 2020 and has been suggested to affect the Eurasian climate in the following winter. By analyzing reanalysis data from 1979 to 2021 and performing model experiments, this study demonstrates that the loss of autumn KESS sea ice acts to intensify the Eurasian cold spells in winter. Low autumn KESS sea ice attenuates the stratospheric polar vortex through driving upward planetary wave activities. The weakening of polar vortex persists to winter and induces anomalies in tropospheric zonal wind and meridional gradient of potential vorticity through downward wave propagation. These intraseasonal to cross-seasonal processes lead to enhancement and prolonged duration of Ural blocking that aggravates Eurasian cold spells. A positive feedback likely exists between the weak stratospheric polar vortex induced by autumn sea ice loss and the wintertime Ural blocking via vertical wave propagation. The results establish a link between autumn KESS sea ice and Eurasian winter climate, with implications for seasonal prediction of Eurasian cold events.

Numerical multi‐span segmented trapdoor test with viscoelastic boundary for soil arching within pile‐supported embankment under cyclic loading

AbstractDynamic wave reflections would interfere with the laboratory observation of the soil arching under cyclic loading when a traditional trapdoor model with rigid boundaries was used. This problem would be prominent when investigating the soil arching in pile‐supported embankments where the stationary support (pile) would be small, making the rigid boundary close to the domain of interest affected by dynamic loads. To avoid dynamic wave reflections and narrow the calculation domain, soil arching within a pile‐supported embankment under cyclic loading is numerically investigated in a multi‐span segmented trapdoor model with flexible boundaries by the particle flow code (PFC). In addition, a pavement structure is included and the springs supporting the trapdoor follow a bi‐linear constitutive model. The energy‐absorbing flexible boundary at the bottom weakens the dynamic wave reflections and is in favor of passing vertical dynamic waves to compact the fill and weaken the influence of cyclic loading on the soil arching effect during the loading stage. Lateral flexible boundaries would facilitate realistically reproducing the effect of cyclic loading on the soil arching because they could consider the weakening of the plugging effect that occurs during the lateral expansion. The development of soil arches of mid‐span and side‐span are different when the load applied at the mid‐span is laterally transferred to adjacent spans by the arching effect.

Determination of Formulae for the Hydrodynamic Performance of a Fixed Box-Type Free Surface Breakwater in the Intermediate Water

A two-dimensional viscous numerical wave tank coded mass source function in a computational fluid dynamics (CFD) software Flow-3D 11.2 is built and validated. The effect of the core influencing factors (draft, breakwater width, wave period, and wave height) on the hydrodynamic performance of a fixed box-type free surface breakwater (abbreviated to F-BW in the following texts) are highlighted in the intermediate waters. The results show that four influence factors, except wave period, impede wave transmission; the draft and breakwater width boost wave reflection, and the wave period and wave height are opposite; the draft impedes wave energy dissipation, and the wave height is opposite; the draft and wave height boost the horizontal extreme wave force; four influence factors, except the draft, boost the vertical extreme wave force. Finally, new formulas are provided to determine the transmission, reflection, and dissipation coefficients and extreme wave forces of the F-BW by applying multiple linear regression. The new formulas are verified by comparing with existing literature observation datasets. The results show that it is in good agreement with previous datasets.

Analysis of bending waves and parametric influence on band gaps in periodic track structure

Vibration of railway tracks generated due to rail-wheel interaction is a key research concern. A rail with equally spaced supports can be regarded as a periodic structure. Such a structure possesses unique property of band gap because of that they act as vibro-acoustic filters. Here, the propagation behavior of vertical and lateral bending waves is studied in a periodic ballastless track structure. Bloch-Floquet theorem is used to formulate the dispersion relations for the propagation of two types of waves which is validated by corresponding finite element model. The results show coexistence of both resonance and Bragg type band gaps they are owing to locally resonant units and spatial periodicity in the track. Furthermore, the study also explores the impact of track parameters, such as pad stiffness and sleeper spacing, on the properties of these band gaps.

Stratosphere‐Troposphere Coupling of Extreme Stratospheric Wave Activity in CMIP6 Models

AbstractExtreme stratospheric wave activity has been suggested to be connected to surface temperature anomalies, but some key processes are not well understood. Using observations, we show that the stratospheric events featuring weaker‐than‐normal wave activity are associated with increased North American (NA) cold extreme risks before and near the event onset, accompanied by less frequent atmospheric river (AR) events on the west coast of the United States. Strong stratospheric wave events, on the other hand, exhibit a tropospheric weather regime transition. They are preceded by NA warm anomalies and increased AR frequency over the west coast, followed by increased risks of NA cold extremes and north‐shifted ARs over the Atlantic. Moreover, these links between the stratosphere and troposphere are attributed to the vertical structure of wave coupling. Weak wave events show a wave structure of westward tilt with increasing altitudes, while strong wave events feature a shift from westward tilt to eastward tilt during their life cycle. This wave phase shift indicates vertical wave coupling and likely regional planetary wave reflection. Further examinations of CMIP6 models show that models with a degraded representation of stratospheric wave structure exhibit biases in the troposphere during strong wave events. Specifically, models with a stratospheric ridge weaker than the reanalysis exhibit a weaker tropospheric signal. Our findings suggest that the vertical coupling of extreme stratospheric wave activity should be evaluated in the model representation of stratosphere‐troposphere coupling.

On the hydrodynamic behaviour of second-order harmonic induced sloshing-mode resonance in moonpool

Fluid resonance in moonpool formed by two-identical rectangular hulls under the regular-wave action is investigated by employing the Computational Fluid Dynamics (CFD) package OpenFOAM®. In this study, the second-order harmonic induced sloshing-mode resonance occurs simultaneously with the first-order induced piston-mode resonance, generating a significant peak value on the free surface amplitudes in moonpool at the corresponding frequency. One period of piston-mode oscillation and two periods of sloshing-mode oscillation can be identified during one incident wave period. It is confirmed that the piston- and sloshing-mode resonances above are generated by the wave frequency and double frequency of incident waves, respectively. The non-monotonic variations of normalized resonant amplitudes in moonpool with incident wave amplitudes can be observed, which is the combined influence of free surface nonlinearity and energy dissipation on wave responses in moonpool. Finally, the second-order harmonic induced sloshing-mode resonance can also affect horizontal wave forces; while it has insignificant effect on vertical wave forces.

Comparing Loon Superpressure Balloon Observations of Gravity Waves in the Tropics With Global Storm‐Resolving Models

AbstractSuperpressure balloons, which drift approximately on isopycnal surfaces, get displaced by gravity waves and are thus capable of detecting gravity wave signatures. The project Loon provides superpressure balloon data in the upper troposphere and lower stratosphere from 2011 to 2021. We compare Loon data from the 6 years of best data coverage with output of global storm‐resolving models from the DYnamics of the Atmospheric general circulation Modeled On Non‐hydrostatic Domains winter initiative in the tropics. We study the variance of the vertical velocity and, for the models, the gravity wave momentum flux as function of distance to closest convection. The models show large differences in the variance of the vertical wind velocity, which is crucial for calculating vertical gravity wave momentum fluxes. We find large differences between the models with respect to simulated convection, lateral propagation, and the wave background away from sources. We then sample balloons as models by optimizing the match of vertical wind distributions using a temporal low pass filter. The average distance the balloons travel during the optimum low pass filtering time turns out to correspond approximately to four times the model grid spacing. The functional dependence of the vertical velocity variance on distance to closest convection is similar between the models and the observations sampled as models. The robustness of this result across all models suggests that storm‐resolving models provide a useful resource for machine learning some characteristics of convectively generated gravity waves.

Surface gravity wave interaction with a floating dock in the presence of a submerged composite wavy porous plate

A numerical model based on the multi-domain boundary element method is adopted to study surface gravity wave interaction with a finite floating dock in the presence of a submerged composite wavy porous plate in the two-dimensional Cartesian coordinate system. Physical parameters of interest such as reflection coefficient, transmission coefficient, dissipation coefficient, horizontal and vertical wave force coefficients of the wavy plate, vertical force and moment coefficients about the centre of the dock are calculated. The influence of structural parameters such as the number of ripple wavelengths, relative ripple amplitude, structural porosity and relative submergence depth of wavy plate, relative space between the plate and dock are computed and studied. An insight into the comparison of various types of plates such as flat plate, wavy plate and composite wavy plate is also presented. The study reveals that the mitigation of wave force on the dock is significant due to a wavy porous plate. Besides, the study exhibits that placing the wavy porous plate at a finite distance from the floating dock has a significant role in dissipating incident wave energy compared to that placing the submerged plate below the dock. Bragg reflection occurs due to the presence of the submerged wavy plate, which diminishes with an increase in structural porosity and depth of submergence of the wavy plate.

Estimating hurricane-induced vertical surge and wave loads on elevated coastal buildings based on CFD simulations and ensemble learning

This study focuses on developing Machine Learning models based on CFD simulations to estimate hurricane induced vertical wave and surge forces on elevated coastal buildings caused by regular waves. In particular, this study aims at addressing the existing gap in designing elevated coastal buildings, which stems from lack of a generalizable equation for estimating vertical hurricane wave and surge forces for a variety of building geometries and wave conditions. To this end, based on a validated Computational Fluid Dynamics (CFD) model, six key variables that affect the wave forces on buildings are considered, which include building dimensions (length and width of rectangular plan buildings) and wave characteristics. In addition, the effect of building length in relation to wave length on the resulting vertical forces is explicitly considered, while the effect of building width is considered implicitly. Subsequently, a Latin Hypercube Sampling (LHS) strategy is implemented for generating 256 random samples, each representing a unique building geometry with a rectangular plan and wave condition scenario. A pipeline is then developed for generating CFD models corresponding to each sample, which are then deployed on a high-performance computing (HPC) cluster, creating a dataset of vertical surge and wave forces. Based on the key design variables, an ensemble of Machine Learning (ML) models is developed to predict vertical wave forces. For the purpose of design and risk assessment, different force levels may be of interest. Therefore, different models were trained to predict multiple levels of forces on elevated buildings, including maximum, average, 25th, 75th, and 99th percentiles of peak forces. The developed model for each of these force levels is then investigated to identify the main building geometry and wave conditions features that affect the resulting forces, which can inform the decisions of the designers in the early-stage phases. For further assistance in the early-stage design, based on a subset of identified important features, a simple expression for each force level is provided to narrow down the design space to top performing early design candidates, while the main estimators can be used for the final design of elevated buildings. Results show that based on CFD simulations, highly accurate and generalizable predictive models with error rates of about 4% on the test set can be developed.

Processing Receiver Function Data in Mentawai Region, Sumatra

The Mentawai Islands are located in the western part of Sumatra, in the Indo-Australian and Eurasian plate subduction zone. Because of these tectonic settings, the Mentawai Region has a high level of seismicity, making it particularly appealing for subsurface structure study. We used the receiver function method in this study to see response receiver function on plate subduction zone and compare the two deconvolution. This method uses the conversion of P-to-S waves, which have a larger amplitude in the radial component than vertical waves. The deconvolution technique is used to extract the two components of the receiver function signal. Water level deconvolution and iterative deconvolution were employed in this study. In practice, any deconvolution method cannot produce a suitable receiver function due to various methodologies that cannot be used in all conditions. Therefore, an evaluation is needed of each deconvolution method used to obtain the best results. This study utilizes two teleseismic stations located in the north and south of Mentawai, which were obtained through the IRIS website, and applied the Butterworth filter to obtain organized and noise-free data. The first results show that the water level is stronger than the iterative, which is more sensitive to the Gaussian filter width parameter. However, they produced almost identical results at both stations, precisely the arrival time of Ps, which was in 3-4 seconds and was followed by a low velocity.

Comparative analysis of the long-term extreme VWBM calculated according to IACS Rec. No 34 rev 1 and rev 2

After facing some criticism regarding assumptions contained in IACS Rec. No. 34 Rev 1 (2001), efforts have been put in by IACS members resulting in a new revision of this document, which provides a procedure for computation of the long-term extreme wave loads on ocean-going ships. The main changes include a new scatter diagram, modification of the wave spectral model and energy spreading function, as well as probability level of design load. Preliminary, the reduction of extreme loads from 10% to 30%, depending on the vessel and response type, is estimated. As this reduction could have serious implications for ship structural design, the present research aims to further investigate consequences on the most important load component, i.e., vertical wave bending moment (VWBM) at midship. Transfer functions of VWBM are calculated using closed-form expressions, which are convenient for comparative studies where many computations are required. Ships of different types and sizes are subjected to the long-term VWBM analysis comparing extreme values based on the procedures proposed in Rev 1 and Rev 2. Although this study is not intended to provide extreme VWBM in absolute terms, the comparison with IACS UR 11 is nevertheless presented as a reference. It is found that Rev 2 long-term VWBMs never exceed corresponding IACS Rule values, which can’t be stated for Rev 1. Results also indicate that differences in scatter diagrams between Rev 1 and Rev 2 could explain a large decrease in the extreme VWBM.

Numerical investigation of a Wave-Powered Vertical Profiler

The wave-power vertical profiler harvests surface wave energy through a buoy, and the converts the wave energy into a kinetic energy of a vehicle (underwater vehicle with sensors for profiling) via a mooring cable. The vehicle is aided by a unidirectional motion mechanism to submerge and surface in water. In this paper, a numerical simulation method is proposed to analyze the motion characteristics of the wave-power vertical profiler and reconstruct the entire moving process.Firstly, numerical work is conducted using Ansys Fluent software to investigate the response of the buoy to Stokes waves of different heights. Secondly, the relationship between the underwater vehicle's motion velocity and fluid resistance are studied. Finally, the numerical simulation results are combined using Matlab software to reconstruct the motion process and draw corresponding curves. Compared with the results from the water tank tests, our method can effectively reconstruct the vehicle's motion, with an accuracy rate of 96.5% in simulating the velocity values during the surfacing phase and a good match with the experimental results under natural sea conditions. We found that wave height is the determining factor for the vehicle's sinking time; the weight of the counterweight affects the vehicle's maximum sinking speed; the vehicle's net buoyancy and drag coefficient determine its surfacing speed, while the weight of the buoy can be ignored. Based on these conclusions, we recommend a counterweight weight of 100 N when the wave height is less than 0.6 m and an increase in weight when it exceeds 0.6 m. The recommended net buoyancy value for the vehicle is between 10 and 40 N, and the recommended buoy weight is 65 kg. We hope that these findings will be helpful for the design of wave energy buoys.

Rapid acquisition method for structural strength evaluation stresses of the ship digital twin model

The existing ship hull structure stress monitoring can only give the stress state of typical measuring points, but the monitoring point may not be the most dangerous location of the ship hull structure. To solve this problem, this paper carried out the research of ship strength digital twin. Concretely, to meet the real-time requirements for obtaining the structural stress state, this paper proposed a rapid acquisition method for structural strength evaluation stresses of the ship digital twin model, which realizes the rapid acquisition for structural yield strength evaluation stresses at the monitoring point and the non-monitoring point. To illustrate the specific application and application effect of the proposed method, the amidships three compartments section of a 21,000TEU ultra-large container ship was selected as the research object. And the case that this research object may suffer from the vertical wave bending moment and the horizontal wave bending moment simultaneously was considered. Related studies show that the proposed method can accurately recognize the load actually suffered by the ship monitoring structure. And the specific meaning of the ship monitoring structure referred to here is the ship hull structure that requires structural stress state monitoring. At the same time, related studies also show that the maximum error of the calculation results obtained by the proposed method does not exceed 0.0005% in obtaining the structural yield strength evaluation stress at the monitoring point, while the maximum calculation error does not exceed 0.032% in obtaining the structural yield strength evaluation stress at the non-monitoring point.

A study on the interaction between circular or elliptical cross-section submerged floating tunnels and elevation internal solitary waves

Recently, submerged floating tunnels (SFTs) have been widely studied around the world, as it is viewed as one of the alternatives to sea bridges and underwater tunnels for wide and deep sea-crossings. Being submerged in the water, SFTs face the potential safety risk from the internal waves, which contain huge amounts of energy and span across a substantial portion of the water column. To better understand the nonlinear interaction between elevation internal solitary waves (ISWs) and SFTs with different cross-sections in stratified fluids, a numerical model based on the Navier-Stokes equations and density transport equation has been developed. The accuracy of this numerical model is then confirmed through comparisons with both theoretical and experimental results. By applying this model, a comparative study focusing on the three wave forces acting on fixed circular and elliptical SFTs, including horizontal wave force, vertical wave force variation and moment, has been conducted with the consideration of different submergences, incident wave amplitudes and density ratios. Subsequently, a typical tether-constrained SFT system under the wave forces of elevation ISW is studied. The results show motion responses of sway, heave and roll are relatively small compared to the size for both circular and elliptical SFTs, which implies that the elevation ISW-SFT interaction can be effectively limited by the mooring lines. Nevertheless, the motion responses under mooring line constraint are close to the allowable deflection limit for floating bridges. Therefore, the potential for fatigue failure should still be carefully considered, particularly when the SFT encounters internal soliton trains.

Nonlocal theory of propagation and reflection of plane waves in higher order thermo diffusive semiconducting medium

The present article is related to propagation and reflection of elastic wave through a nonlocal generalized thermo-diffusive semiconducting elastic solid. The non-local theory is employed to study the wave behavior. Three phase lag model with higher order fractional order derivative is incorporated to discuss heat propagation through the medium, in addition with two phase lags diffusion equation. The Helmholz vector rule is applied to decompose the system into longitudinal and transverse components. The frequency dispersion relation indicates the presence of four coupled longitudinal and one un-coupled shear vertical wave. The speed of the waves is plotted against angular frequency for local and nonlocal medium. The cutoff frequency of the waves is also depicted graphically. The longitudinal P-wave is taken to be an incident wave at the free surface of the solid to compute the reflection coefficients. The influences of fractional order and nonlocal parameters on amplitude ratios are also studied. The effect of these parameters is found to be significant. The results are proved in the context of energy conservation. The results obtained from the current investigation are very useful for scientists working on problems of geophysics and various fields of mechanics.