Maximum Wave Amplitude Research Articles

A prediction model for the rockslide-generated wave amplitude under the condition of bedrock mass breakup

Landslides along coastlines and rivers can cause landslide-generated waves and pose a threat to the offshore banks, navigation vessels and coastal buildings. The maximum amplitude of the landslide-generated wave, which is strongly related to the size and geometry of the landslide and gradually decreases with the increase of the propagation distance, is one of the important indexes to evaluate the secondary hazard caused by landslides. The fragmentation of rockslide has an influence on the effect of rockslide on water body. This study proposes a relationship between the maximum rockslide-generated wave amplitude and the number of fragmentation blocks which is defined to present different degrees of landslide bedrock mass breakup. The computational fluid dynamics (CFD) numerical method is used to simulate the whole process of landslide and wave propagation. The orthogonal array experiment algorithm is used to design the numerical simulation schemes. The Gauss-Newton algorithm is adopted to analyze the results and elect the optimal model with the strongest correlation. A series of conducted physical model experiments prove the applicability and accuracy of the optimal model. This optimal numerical model can offer a reference for rockslide-generated wave analysis when considering bedrock mass breakup.

Study on the steering capability of a meander-line coil EMAT

Electromagnetic acoustic transducers (EMATs) are well-established as a means of ultrasonic wave generation and reception without the use of a mechanical coupling. When comprising a bias magnetic field and a meander-line coil (MLC), these waves propagate at an angle normal to the emission surface. With the appropriate frequency, the propagation pathway of these ultrasonic waves can be steered to a particular angle. This paper presents the methodology used to find the steering limit of an MLC EMAT and the results from simulations and experimental validations on aluminium. The results show that the maximum shear wave amplitude occurred at around 30°, the steering limit was approximately 50° and the simulations were validated by the experimental set-up to a satisfactory degree.

Experimental Study on Pressure Characteristics of Gravity Dam Surface under Impact of Landslide-Generated Impulse Waves

Landslide-generated impulse waves of a mountain-river reservoir will endanger the dam body’s stability and the dam structure’s safety and even pose a significant threat to the property safety of downstream residents. Timely prediction of dam surface pressure is essential for dam safety assessment. The pressure distribution characteristics and variation law of the gravity dam surface under the impact of landslide-generated impulse waves are studied through a three-dimensional physical model test. The results show that the landslide volume and angle are the key control factors of the first wave amplitude in front of the dam. The maximum and minimum pressures are near the water surface and at two-thirds of the water depth, respectively. The maximum pressure has a power function relationship with the maximum amplitude of the wave in front of the dam. Furthermore, the maximum amplitude of the first wave in front of the dam significantly influences the total pressure of the single-width wave on the dam surface. Based on the research results, the single-width wave total pressure prediction method is constructed under different first wave amplitudes in front of the dam, which can provide theoretical guidance and technical support for dam safety assessment and landslide-generated surge risk assessment.

Effects of PAR2 Gene Knockout on Visceral Sensitivity, Stress Behaviors, and Colonic Electrical Activities in Irritable Bowel Syndrome.

Irritable bowel syndrome (IBS) could seriously affect the patient's health quality by its recurrence. There is a great medical and social need to explore the mechanisms and new treatment strategies of IBS. To explore the influence of protease-activated receptor 2 (PAR2) gene knockout on IBS visceral sensitivity, stress behaviors, and colonic electrical activities. The PAR2 gene knockout and IBS model rats were generated and divided into PAR2+/+ wild control (WC) group, PAR2+/+ wild IBS model (WM) group, PAR2-/- knockout control (KC) group and PAR2-/- knockout IBS model (KM) group. The stress behaviors scores, minimum rectal fluid injection capacity threshold value of abdominal withdrawal reflex (AWR) = 3, and the colonic electrical activities indexes were recorded and the experimental results were analyzed statistically. (1) PAR2 gene deletion and IBS models were successfully generated. (2) The scores of aggressive and exploratory behaviors in WM and KM groups were higher than WC and KC groups (p < 0.05). The grooming behavior scores in WC and KC groups were higher than the WM and KM groups (p < 0.05). WM group had the highest aggressive and exploratory behavior scores; WC group had the highest grooming behavior scores. (3) The minimum rectal fluid injection capacity threshold value of AWR = 3 in WM and KM groups were lower than WC and KC groups (p < 0.05); WM group had the lowest value. (4) The maximum amplitude and wave frequency of colonic fast and slow waves in WM and WC groups were greater than in the KM and KC groups, respectively (p < 0.05). The amplitude index and number of colonic contraction waves in WM and KM groups were greater than the WC and KC groups (p < 0.05). Colonic electrical activity indexes were highest in the WM group. The PAR2 gene deletion could have a beneficial effect on visceral sensitivity, stress behaviors and colonic electrical activities in rats with IBS.

AXIAL ACOUSTIC VELOCITY INTERACTION WITH HOLLOW CONE LIQUID SHEET IN A SWIRLING FLOW FIELD

This experimental investigation concerns the effect of imposed axial acoustic velocity fluctuations on the primary atomization of a hollow cone liquid sheet in the presence of a strong air swirl. The atomization dynamics are elucidated by positioning the spray at an acoustic velocity node, antinode, and a mixed point in the standing wave field generated due to the imposed axial acoustic excitation. High-speed shadowgraph images acquired in-sync with dynamic pressure measurements are processed to clarify the unstable behavior observed in the spray dynamics; this was achieved by extracting key parameters such as breakup length, spatial growth rates, phase differences, and by employing Proper Orthogonal Decomposition (POD). A novel method to obtain the breakup length of a hollow cone spray from the position of maximum wave amplitude is presented. The breakup length is the smallest for the mixed point. The phase difference between the left and right half-angle fluctuations shows that the flapping motion of the spray is predominantly observed at the mixed point for different air-to-liquid ratios. Another novel approach is adopted to identify the physical mechanisms corresponding to each POD spatial mode by comparing POD spatial modes obtained from experiments to those generated artificially.

Focusing of a compression waves in a toroidal bubble cluster

The dynamics of waves in a cylindrical channel containing a toroidal bubble cluster is studied. It is shown that the existence of a cluster cause of focusing of waves in the channel. The dependence of the maximum amplitude of the compression wave formed in the domain on the parameters of the domain, as well as on the amplitude of the initial pulse, is analyzed.

Numerical simulations of water waves generated by subaerial granular and solid-block landslides: Validation, comparison, and predictive equations

We compare waves generated by subaerial solid-block and granular landslides and propose equations for predicting their maximum initial wave amplitudes. The recent Anak Krakatau subaerial landslide tsunami in December 2018, which resulted in more than 450 deaths, demonstrated the knowledge gap on this subject and motivated this study. Here, we make numerical models using the numerical package FLOW3D-Hydro for solid-block and granular landslides and validate them using physical experiments. Results indicate that the maximum initial wave amplitudes generated by solid-block landslides are 107% larger than those generated by granular landslides in our experiments. The relationship between maximum initial wave amplitude and slope angle is inverse for solid-block slides whereas, it is direct for granular slides. However, a critical angle of 60° is achieved for granular slides, and for slope angles more than this critical value, the maximum wave amplitudes start to decrease. Regarding wave period, our results show that it remains nearly unchanged for both types of landslides as water depth and slide volume vary. The period generated by solid-block slides increases as the slope angle decreases; however, it remains unchanged for granular slides. The predictive equations are applied to real landslide tsunamis and resulted in satisfactory performances.

How to identify tsunami prevention zones: a case study of Putuoshan Island in China

Tsunamis can cause massive damage and loss of life in coastal areas. This study uses Putuoshan Island as a case study to discuss ways to identify tsunami prevention zones based on the analysis of physical factors such as inundation, maximum wave amplitude, and tsunami flow. In the Ryukyu Trench Mw 9.0 tsunami scenario, the tsunami prevention zones of Putuoshan Island consist of land areas and marine areas. Our analysis identified two inundation areas in the western and southern Putuoshan Island as tsunami prevention zones. With the exception of the western marine area, the coastal waters of Putuoshan Island are also identified as tsunami prevention zones. The tsunami flow impact is greater in the waters of north and south Putuoshan Island. The results of this study could be used by emergency departments to take protective measures and thus to prevent the disastrous effects of tsunamis.

The Effects of Liver Cirrhosis on Electrical Autorhythmicity of Isolated Duodenum in Rats

Background: Cirrhosis reduced small bowel motility and transit time, with unknown mechanisms. Moreover, intestinal motility depends on the electrical activity and the autorhythmicity of interstitial cells of Cajal (ICC). If cirrhosis directly affects the intrinsic mechanism of intestinal motility, the isolated bowel of cirrhotic cases will also exhibit an electrical abnormality compared with normal cases. Objectives: This study aimed to identify the effects of liver cirrhosis on the electrical autorhythmicity of isolated duodenum in rats. Materials and Methods: Six weeks after bile duct ligation (BDL) surgery, animals were anesthetized, and blood samples were obtained from the heart for the evaluation of plasma cirrhosis indices, including weight, plasma albumin, serum glutamic oxaloacetic transaminase (SGOT), serum glutamic pyruvic transaminase (SGPT), bilirubin, and direct bilirubin. Then, the duodenum of rats was isolated and compared with the control group for the rate of electrical slow waves and the maximum amplitude of slow waves. Results: Significant differences were observed between the control and BDL group in terms of weight, plasma albumin, SGOT, SGPT, bilirubin, and direct bilirubin. Moreover, there was a significant decrease in the maximum amplitude of slow waves in the BDL group compared with the control. Conclusion: It seems that different factors directly harm the ICC network such as inflammation caused by microbiome amplification as a result of cirrhosis, which in turn reduces small bowel motility.

Effects of Slide Shape on Impulse Waves Generated by a Subaerial Solid Slide

We review several historical landslide tsunami events and perform a set of numerical experiments to investigate the particular effects of slide shape on impulsive waves generated by a subaerial solid slide. The computational model is based on OpenFOAM, which solves 2D RANS formulations with a volume of fluid method used to capture the air–water interface. We consider triangular prism shaped solid slides in our numerical experiments and introduce a slide shape parameter σ to describe the front face steepness of the slide. Observations from the experiments reveal that slide shape can have significant impacts on the characteristics of impulsive waves, such as maximum wave amplitude and its location, impact energy conversion rate, and the amplitude ratio between the first wave crest and the second crest in the leading wave group. In particular, the maximum wave amplitude is inversely proportional to σ; the impact energy conversion ratio decays exponentially with σ; and the wave period is almost independent of σ.

Quantitative evaluation in classification and amplitude of near-field landslide generated wave induced by granular debris

Landslides falling into water bodies can generate impulsive waves. The process of wave generation induced by far subaerial granular landslide has been investigated through series physical experiments. The slide Froude number has been quantified considered the parameters of slide mass and water such as grain size, water depth and impact angle. The effect of impact angle, grain size and water depth on the variation of generated wave amplitude is 0.11%, 1.52% and 2.89% respectively when every 1% change in the value of the parameter. On the three governing parameters the water depth is the most sensitive to the wave amplitude, secondly the grain size and final for the impact angle. The intruding pattern of granular debris, the landslide generated wave types and maximum wave amplitude have been systematically discussed. The degree of impact interaction between the slides and water under different conditions is characterized by the value of the slide Froude number, and the empirical relationships linking the slide Froude number with the produced wave amplitude and wave classifications have been conducted based on experimental data, which is useful to illustrate the triggering mechanisms and dynamic process of impact landslide waves on high debris avalanches.

Study on the propagation characteristics of pressure wave generated by mechanical shock in leaking pipelines

This paper focuses on the characteristics of pressure wave generated by an active mechanical shock in leaking pipelines. A piston type pressure wave generator was designed and applied to the pipeline experimental system and a three-dimensional (3D) numerical simulation model was developed based on the k-ε turbulence model and dynamic mesh. The experimental results showed that the maximum amplitude of pressure wave was about 104.71 kPa, and the leakage intensified the attenuation of pressure wave in space and time through quantitative analysis. Based on the 3D simulations, the processes of the pressure wave generation and propagation were revealed. The amplitude of pressure wave increased linearly with the increase of the maximum velocity of mechanical shock, and the effects of leakage on the waveforms of pressure wave were observed under the dimensionless analysis. In addition, a shorter duration of mechanical shock can increase the amplitude of the pressure wave generated. The results presented in this paper will contribute to the development and application of the transient leak detection method for pipeline systems.

Wave breaking limit in arbitrary mass ratio warm plasmas

AbstractThe maximum sustainable amplitude, so‐called wave breaking limit, of a nonlinear plasma wave in arbitrary mass ratio warm plasmas is obtained in the non‐relativistic regime. Using the method of Sagdeev potential, a general wave breaking formula is derived by taking into account the dynamics of both the species having finite temperature. It is found that the maximum amplitude of the plasma wave decreases monotonically with the increase in temperature of the negative species (temperature of the positive species) and increases (decreases) with increase in mass ratio provided , where .

Study on Traveling Wave Wall Control Method for Suppressing Wake of Flow around a Circular Cylinder at Moderate Reynolds Number

In the present paper, the computational fluid dynamics (CFD) numerical simulation was utilized to investigate the effectiveness of the transverse traveling wave wall (TWW) method with the expectation of inhibiting the vortex shedding from a fixed circular cylinder. We mainly focused on the variations of four kinds of wave propagation directions, five different maximum wave amplitudes and ten different wave velocities for suppressing vortices shedding and aerodynamic forces. The aerodynamic coefficients and vortex structures under different propagation directions, wave amplitudes, wave numbers and wave velocities were investigated in detail. The results demonstrate that the alternate wake behind the cylinder can be effectively eliminated resorting to the “Downstream” propagating TWW. The mean drag coefficient is positively associated with wave velocity. Drag and lift coefficients remain relatively stable at different wave amplitudes. When the velocity ratio (wave velocity divided by incoming velocity) is 1.5, the lift coefficient fluctuation decreases to the minimum. In contrast, the optimal combination of control parameters under the present Reynolds number is concluded with “Downstream” propagating direction, maximum wave amplitude ratio of 0.02, and velocity ratio of 1.5.

Prediction of Postradical Prostatectomy Urinary Incontinence Through the Combination of the Urethral Pressure Profile With Electromyography of the Urethral Sphincter.

PurposeWe tested the hypothesis that the urethral pressure profile, in combination with electromyography of the urethral sphincter, may be useful as a predictor of urinary incontinence after radical prostatectomy (RP). The aim of this study was to assess whether the combination of these tests resulted in an improved tool for the prediction of post-RP urinary incontinence.MethodsPatients with indications for RP were included. The urethral pressure profile, including prostatic and sphincter components for maximum urethral closure pressure (MUCP) and functional urethral length, was recorded in combination with needle electromyography of the urethral sphincter. The mean and maximum amplitude of waves were measured twice: 1 month before RP and 6 months after the procedure. The 1-hour pad test was conducted in parallel with other tests. Patients completed the International Consultation on Incontinence Questionnaire - Short Form (ICIQ-SF). The relationship of the results of the tests with post-RP urinary incontinence was studied. Age, urodynamic parameters, pathologic stage, and surgical technique were recorded for analysis as potential confounding factors.ResultsNineteen patients were included within the 1-year study period. Their mean age was 63 years. According to the 1-hour pad test and ICIQ-SF, 42.1% of the sample had urinary incontinence after RP. Prostate MUCP with the mean and during-stress amplitude of waves predicted post-RP urinary incontinence with a sensitivity of 87.5% (P=0.002) in our model. Age, urodynamic parameters, pathological stage, and surgical technique were not related to incontinence after surgery.ConclusionsThe combination of the urethral pressure profile (prostatic MUCP) and electromyography of the urethral sphincter might be a useful prognostic predictor of post-RP urinary incontinence.

Elastic wave propagation in nonlinear two-dimensional acoustic metamaterials

This study describes the wave propagation in a periodic lattice which is formed by a spring-mass two-dimensional structure with local Duffing nonlinear resonators. The wave propagation characteristics of the system are evaluated by using the perturbation method to determine the dispersion relationships and wave propagation characteristics in the nonlinear two-dimensional acoustic metamaterials. A quantitative study of wave amplitude is carried out to determine the maximum allowable wave amplitude for the whole structures under the assumption of small parameters. In particular, the harmonic balance method is introduced to investigate the frequency response and effective mass of the nonlinear systems. We find that the dispersion relations and group velocity of unit cell are related to wave amplitude. Furthermore, the dual-wave vector is observed in the nonlinear systems. Numerical simulations validate the dispersion analytical results. The results can be used to tune wave propagation in the nonlinear acoustic metamaterials and provide some ideas for the study of nonlinear metamaterials.

Analytical and numerical studies for wave generated by submarine landslide

In this research, we investigate how submarine landslides are able to produce extremely damaging tsunami waves and estimate the maximum height of the waves in question using a mathematical model. The model is based on the non-linear shallow water equations, which are solved numerically using the finite volume method on a staggered grid. We also derive a new analytical solution in order to obtain a description of surface waves generated by a submarine landslide. To validate the numerical model, several benchmark tests are conducted by comparing the results from the numerical scheme to those obtained from the analytical solution, experimental data, or other numerical results. After validation, the scheme is implemented on the real topography of Palu Bay to simulate the generation of tsunami waves by submarine landslides. The simulations provide excellent results. Accurate estimates of the maximum tsunami wave amplitude are produced by the numerical scheme, confirmed by data from records of the 2018 Palu tsunami.

Collapse of partially and fully submerged granular column generating impulse waves: An empirical law of maximum wave amplitude based on coupled multiphase fluid–particle modeling results

In this study, impulse waves generated by partially and fully submerged granular collapse are investigated using a modeling method coupling the volume of fluid and discrete element method. Of particular focus is the effects of geometrical and material parameters of granular samples on wave generation mechanisms, thereby determining the controlling factors of maximum wave amplitude, which were unclear or inconsistently reported in previous experimental studies. It is found that the relative submerged depth (i.e., the ratio of initial granular sample height to water depth) is the main geometrical parameter governing the maximum wave amplitude generated by partially and fully submerged granular collapse. The inter-particle friction of granular materials also influences the maximum wave amplitude via altering the material mobility and momentum transferred from particles to water during the collapse process. The density of the granular material, on the other hand, has a negligible effect on impulse wave generation. Based on numerical characterization, an empirical model of the maximum wave amplitude is proposed and validated against experimental data. Its practical application to estimate the maximum wave amplitude generated by partially submerged landslide events is also demonstrated, suggesting its potential for the hazard assessment of landslide-generated tsunamis.

Distribution of energy in propagation for ocean extreme wave generation in hydrodynamics laboratory

BACKGROUND AND OBJECTIVES: The hydrodynamic uncertainty of the ocean is the reason for testing marine structures as an initial consideration. This uncertainty has an impact on the natural structure of the topography as well as marine habitats. In the hydrodynamics laboratory, ships and offshore structures are tested using mathematical models as input to the wave marker. For large wavenumbers, Benjamin Bona Mahony's equation has a stable direction and position in the wave tank. During their propagation, the generated waves exhibit modulation instability and phase singularity phenomena. These two factors refer to Benjamin Bona Mahony as a promising candidate for generating extreme waves in the laboratory. The aim of this research is to investigate the distribution of energy in each modulation frequency change. The Hamiltonian formula that describes the phenomenon of phase singularity is used to observe energy. This data is critical in determining the parameters used to generate extreme waves.METHODS: The envelope of the Benjamin Bona Mahony wave group can be used to study the Benjamin Bona Mahony wave. The Benjamin Bona Mahony wave group is known to evolve according to the Nonlinear Schrodinger equation. The Hamiltonian governs the dynamics of the phase amplitude and proves the Nonlinear Schrodinger equation's singularity for finite time. The Hamiltonian is derived from the appropriate Lagrangian for Nonlinear Schrodinger and then transformed into the Hamiltonian with the displaced phase-amplitude variable.FINDINGS: Potential energy is related to wave amplitude and kinetic energy is related to wave steepness in the study of surface water waves. When , the maximum wave amplitude and steepness are obtained. When , extreme waves cannot be formed due to steepness. This is due to the possibility of breaking waves into smaller waves on the shore. In terms of position, the energy curve is symmetrical.CONCLUSION: According to Hamiltonian's description of the energy distribution, the smaller the modulation frequency, the greater the potential and kinetic energy involved in wave propagation, and vice versa. While the wave's amplitude and steepness will be greatest for a low modulation frequency, and vice versa. The modulation frequency considered as an extreme wave generator is , because the resulting amplitude is quite high and the energy in the envelope is also quite large.

Influence of perturbation amplitude and perturbation frequency on Fermi-Pasta-Ulam-Tsingou recurrence phenomenon

Fermi-Pasta-Ulam-Tsingou recurrence (FPUT) phenomenon refers to the property of a multimode nonlinear system returning to the initial states after complex stages of evolution. The FPUT recurrence phenomenon closely links with modulation instability (MI) by employing the perturbed continuous waves as the initial condition. When the perturbation frequency is located inside the MI spectra, then the perturbed CWs are unstable and the perturbations will grow up with evolution. This nonlinear MI evolution results in the FPUT phenomenon. In this work, we explore in detail the effects of perturbation amplitude and perturbation frequency on the FPUT recurrence phenomena numerically, which has never been studied systematically, to the best of our knowledge. Using the results of our studies, we find that the perturbation amplitude can significantly affect the FPUT phenomenon. Firstly, the number of FPUT cycles is very sensitive to the perturbation amplitude. Large (small) perturbation amplitude can result in much more (much less) FPUT cycles. Secondly, very irregular (regular) FPUT wave evolution together with the corresponding spectra evolution can be observed at relatively large (small) values of perturbation amplitude, where the unequal (equal) distances are observed between adjacent maximum wave amplitudes spatially in the background of optical fibers. In contrast, the effects of perturbation frequency on the FPUT cycles are relatively minor, and the maximum FPUT cycles are observed at perturbation frequencies around the optimal modulation frequency generating the peak MI gain. However, the perturbation frequency can drastically affect the number of high-order sidebands excited at the distances of periodic maximum wave amplitude formation. We find that larger perturbation frequency leads to much fewer high-order sidebands. According to our studies, for observing FPUT conveniently and observing more FPUT cycles, the perturbation amplitude of the input signal should be as large as possible and the perturbation frequency should be around the optimum modulation frequency. We should also emphasize that the large perturbation amplitude results in irregular FPUT patterns with unequal distances between adjacent maximum wave amplitude formations spatially in the background of optical fibers, and large perturbation frequency results in much less high-order sidebands. Our results will provide very helpful information for the FPUT observation in experiment, and should arouse the interest of the readers in nonlinear physics.