Wave Flow Research Articles

Testing of Concrete Structures with Non-Destructive Test Method (NDT) Using Ultrasonic Pulse Velocity (UPV) at the Building on the Ancol Beach

The UPV test procedure with the PUNDIT device is set based on the concept of the wave flow speed passing through a solid object bound to the elastic properties of a tangible medium. When used properly and correctly, this tool will provide a lot of information about the condition of the surface or the inside of the concrete. Classification for pulse velocity results according to the speed criteria of concrete quality presented in BS 1881: Section 203:1986 as follows: 4500 m/s = excellent concrete condition, 3400 – 4500 m/s = good concrete conditions, 3000-3500 m/s = medium concrete situation, < 3000 m/ s = concrete problem condition (doubtful concrete condition). The pulse velocity test results are measured by three methods: direct transmission, semi-direct transmission and indirect or surface transmission. The test results for the structure of the beams, cylinders, tie beams, and floor plates of the office building on the edge of the anchor showed that it is in medium concrete condition. The average value of the estimated quality of concrete results of the test UPV Pundit for Beams was 25,29MPa, Slabs was 25,17MPa, Tie Beam was 25,06MPa, and Pilecap was 25,46MPa. The result has met the minimum requirement for concrete solid pressure of 21MPa for the quality of unique structures concrete according to SNI-2847-2019.

Реч и речезнание – предмет и опит за описание на науката

Speech as a gift of nature acquired by homo sapiens (‘wise man’ in Latin) in the process of communicative interaction is an indisputable phenomenon of paramount importance, which in turn justifies the interest of scientists in this type of homo loquens’ (speaking man) activity as a behavioral manifestation of personality. Oral speech offers a vast amount of information for describing communication since it signals discrete sequences of ‘digital’ information on the one hand, while providing additional ‘analogue’ information about the speaking person, on the other. This means that everyday speech in its real use contains speech features related to various speakers who take part in the process of communication. Speech is the material substance which explicates the concrete representation of discourse as it happens in real time, and exists as discourse special dimension in relation to human mind. Human speech can be characterised as a complex set of elements of prosody, which could be divided into the following main groups related to the sound and its time, pitch, force and timbre. The acoustic and perceptual-auditory continuity of speech has become a cornerstone for describing the process of speech in time when solving many practical tasks, since the sounding oral message represents a continuous flow of air waves separated by pauses. The wave-like nature of speech makes it possible to recognise in the structure of the spoken message simultaneous components, just like in a musical cord one can recognise the simultaneous tones of which it is composed. Therefore, the task of developing a special separate research area, called speech science, becomes logical and necessary.

Long-wave instabilities of sloping stratified exchange flows

We investigate the linear instability of two-layer stratified shear flows in a sloping two-dimensional channel, subject to non-zero longitudinal gravitational forces. We reveal three previously unknown instabilities, distinct from the well-known Kelvin–Helmholtz instability and Holmboe wave instability, in that they have longer wavelengths (of the order of 10 to $10^3$ shear-layer depths) and often slower growth rates. Importantly, they can grow in background flows with gradient Richardson number $\gg 1$ , which offers a new mechanism to sustain turbulence and mixing in strongly stratified flows. These instabilities are shown to be generic and relatively insensitive to Reynolds number, Prandtl number, base flow profile and boundary conditions. The nonlinear evolution of these instabilities is investigated through a forced direct numerical simulation, in which the background momentum and density are sustained. The growth of long unstable waves in background flows initially stable to short wave causes a decrease in the local gradient Richardson number. This leads to local nonlinear processes that result in small-scale overturns resembling Kelvin–Helmholtz billows. Our results establish a new energy exchange pathway, where the mean kinetic energy of a strongly stratified flow is extracted by primary unstable long waves and secondary short waves, and subsequently dissipated into internal energy.

Hydrodynamic effects and water environment improvement of topographic reconstruction in shallow lakes

This paper focuses on a typical shallow lake, Lake Changdanghu, which is subject to frequent hydrodynamic disturbances and suspended sediment deposition, resulting in reduced water clarity and the degradation of the grass-type ecosystem. Using a combination of long-term systematic observations and numerical simulations, the impact of terrain modification on the hydrodynamic characteristics of Lake Changdanghu and its resulting environmental improvements are systematically analyzed. The results indicate that there is a significant correlation between the wind wave intensity, suspended solids concentration of the water, and water clarity. The artificial shoal project effectively reduces the local wind wave intensity, increases the water area of the weak waves, and alters the flow structure and transport path of the lake. The wave reduction effect of the artificial shoal significantly improves the transparency of the local water, especially under high wind wave conditions, with a 60% increase in the sheltered area, significantly improving the physical habitat environment. Additionally, the flow resistance and guidance roles of the artificial shoal concentrate the impact of the poor water quality of the inflow in a local area, reducing its adverse effects on the main body of the lake. Our research demonstrates that for shallow lakes, the water transparency can be improved, the physical habitat conditions for aquatic vegetation can be enhanced, and grass-type ecosystems can be gradually restored through artificial intervention and vegetation recovery projects by reducing the wave energy, flow resistance, and guidance through the construction of artificial shoals. This approach achieves long-term maintenance of eutrophication control and water quality improvement in shallow lakes.

Scale effect on wave planing performance of amphibious aircraft at constant speed

Scaled model testing is commonly recognized as a valuable approach for predicting aircraft performance in the aeronautical applications. However, challenges arise in the case of wave planing events for amphibious aircraft due to difficulties in satisfying the scaling laws of Reynolds number and Froude number simultaneously in a water tank. Therefore, it is important to evaluate the scale effect of regular wave planing process for amphibious aircraft. In this study, by fixing the Froude number, five geosim cases with different scale factors (1/1, 1/2, 1/4, 1/8 and 1/16) are carried out based on the Reynolds-Averaged Navier–Stokes equations (RANS) framework. The hydrodynamic and aerodynamic characteristics at different scales are respectively examined in detail through several physical results, including acceleration, pressure, shear force, velocity and free surface elevation. Comparative analyses among all scaled models reveal that the aerodynamic and hydrodynamic performance both monotonously change with the scale factor, yet the proportion of aerodynamic and hydrodynamic loads remains within a reasonably small range. Furthermore, the results indicate that the scale effect primarily stems from the lack of similarity in Reynolds number, thus resulting in the discrepancies of boundary layer, wave surface elevation and flow separation between the scale model and prototype.

Wake characteristics behind a tidal turbine with surface waves in turbulent flow analyzed with large-eddy simulation

To design tidal stream turbine arrays, turbine wakes need to be fully characterized to assess the adequate row spacing considering environmental factors such as onset turbulence, velocity shear, and surface waves. The role of waves on wake development varies depending on their characteristics, such as wavelength and amplitude, and needs to be carefully understood. Here large-eddy simulations are performed to analyze the instantaneous and time-averaged wake characteristics developed downstream of a tidal stream turbine for four wave-current conditions ranging from nearly deep to intermediate waves and compared to current-only results. The tip-vortex convection near the free surface is highly influenced by the waves. During the period of increased surface elevation, there is an upwards motion of the vortices which have merged into a single vortical structure during the wave trough period. Downwards vertical transport of tip vortices occurs after the pass of the wave crest, enabling vertical entrainment of momentum into the turbine wake region. Disk-averaged velocity deficit recovery increases for wave-current cases compared to the current-alone condition, with all intermediate wave cases showing a very similar wake recovery rate throughout the wake length. The nearly deep-water waves lead to a slightly slower recovery rate up to 12 turbine diameters (D) downstream while, after this distance, the recovery rate is the highest among the simulated wave conditions. The integration of the mean kinetic energy (MKE) budget in the region up to 12D shows there is a similar distribution in the balance between terms irrespective of the wave-current case. However, in the far-wake region covering from 12D to 20D, the nearly deep waves have a larger contribution for MKE replenishment from the transverse convection and turbulence transport terms, balanced with their vertical counterparts and the streamwise convection term. Analysis of the wake self-similarity shows that a Gaussian model description holds for the recovery rate and lateral profile of the wake of a tidal turbine operating in coupled wave-current conditions, with a similar rate of velocity recovery after 12D irrespective of the wave characteristics. Lateral wake spreading is smaller for the shortest wavelength, which relates to an increased contribution of transverse fluxes in the MKE budget. Published by the American Physical Society 2024

Study on Wave Overtopping Discharge Affected by Guiding Wall Angle of Wave Dragon Device Using FLOW-3D Software

The Wave Energy Converters (WECs) have become the main attraction in producing electricity by converting the wave's energy to electricity. The focus of the WECs is the overtopping of the wave. The higher of overtopping water collected in the basin, the higher the power produced. Producing the higher overtopping also requires higher wave flow rate entry. In the Wave Dragon system, the rate of wave flow entering the reservoir is influenced by the guiding wall (reflector) angles and wave height. Hence, most overtopping concepts have tried to increase the water addition into the pool studying their geometrical parameter, mainly on the guiding wall of Wave Dragon. The unknown effect of the guiding wall angles on the overtopping and effect of the wave characteristic remained. Thus, this study aims to investigate the appropriate guiding wall angle on the influence of different wave heights affecting the performance of the Wave Dragon unit. Then, using FLOW 3D software to apply different guiding wall angles and wave characteristics to the device parameters for investigation. The numerical result highlights that the higher overtopping discharge is obtained during the upper limit of wave height and guiding wall angle. Besides, percentage different between the simulations model and experimental observation, was found at 15%. The result of this study will be beneficial to the industry related to wave potential energy, especially Wave Dragon, and it will also help them improve their device performance.

A Weakly Nonlinear System for Waves and Sheared Currents over Variable Bathymetry

The wave–current–seabed interaction problem is studied by using a coupled-mode system developed for modeling wave scattering by non-homogeneous, sheared currents in variable bathymetry regions. The model is based on a modal series expansion of wave velocity based on vertical eigenfunctions, dependent on local depth and flow parameters, including propagating and evanescent modes. The latter representation is able to accurately satisfy the wave flow continuity condition and the no-entrance boundary condition on the sloping parts of the seabed. A new derivation of a simplified nonlinear system is introduced using decomposition to a mean flow and a perturbative wave field. To force the system to consider incoming waves at the inlet, boundary knowledge of periodic, travelling nonlinear water waves over a flat bottom is required. For this purpose, specific solutions are derived using the semi-analytical method based on the stream function formulation, for cases of water waves propagating above linearly and exponentially sheared currents. Results obtained by the application of the CMS concerning the propagation of waves and currents—in particular, examples characterized by depth inhomogeneities—are presented and discussed, illustrating the applicability and performance of the method.

Airfoil flow field for proton exchange membrane fuel cells enhancing mass transfer with low pressure drop

Optimal configuration of bipolar plate (BP) embedding flow field is of great significance in improving the power density and durability of proton exchange membrane fuel cells (PEMFCs). Inspired by the airfoil in aircraft dividing the airflow into two streams causing pressure difference, a novel airfoil flow field (AFF) is designed to enhance the mass transfer capacity in channel and across the rib between two adjacent channels, which hardly increases the pressure drop in channel, unlike many baffle designs. The performance improvement achieved by implementing AFF in PEMFC is compared with common parallel flow field (PFF) and the wave flow field (WFF) by experimental test with respect to polarization curve and electrochemical loss and numerical simulation via a three-dimensional (3D) PEMFC model. The experimental results indicate that the novel AFF exhibits best fuel cell performance at various operation conditions (e.g. relative humidity, air stoichiometric ratio) mainly benefitted from the enhanced oxygen transfer, which contributes to the improvement of maximum power density by 8.85 % and 14.37 % compared to PFF and WFF, respectively. The modeling results indicate that the pressure drop increase in AFF is negligible compared with PFF, and is even slightly lower than WFF, indicating high practicability. Moreover, the utilization of AFF also helps the uniformity of oxygen concentration, current density and temperature in PEMFC.

Evolution of shock waves in dusty nonideal gas flow with magnetic field

Abstract This paper deals with the study of propagation of shock waves in 2-D steady supersonic magnetogasdynamics flow of nonideal dusty gas using wavefront analysis method. We derived the transport equation, which determines the condition for the shock formation. Our aim is to analyze the effect of interaction of dust particles with magnetic field in nonideal gas on the evolution of shock formation and to examine how the flow patterns of the disturbance vary with respect to the variations in the physical parameters of the medium. It is found that the presence of magnetic field plays an essential role in the wave propagation phenomena. The nature of the solution with respect to the Mach number is analyzed, and it is examined how the shock formation distance changes with an increase or decrease in the value of Mach number. Also, the combined effect of nonidealness, magnetic field, and dust particles on the shock formation distance is elucidated and examined how the formation of shocks is affected by the increase in the value of corresponding physical parameters.

Analysis of propagation of normal shocks in Van der Waals gas: Buongiorno model

This paper presents an analytical investigation into the propagation of a normal shock wave in Van der Waals gas flow, employing the Buongiorno model. It explores the dynamics of this flow type under a shock wave, considering modified Rankine–Hugoniot (RH) jump conditions within the Buongiorno model framework. By solving the RH conditions, this study provides a solution for gas flows with varying nanoparticle concentrations, facilitating an examination of parameter variations under discontinuity. The abstract further emphasizes the graphical representation of velocity coefficient and pressure in adiabatic gas flow during a shock wave, considering compressive and exponential waves. The analysis accounts for nanoparticle concentration and non-ideal parameters.

How do various forces affect pressure waves in bubbly flows?

This study investigated the weakly nonlinear propagation of pressure waves in compressible, flowing water with spherical microbubbles, considering various forces. Previous theoretical studies on nonlinear pressure waves in bubbly flows did not consider the forces acting on the bubbles, although the validity of ignoring these forces has not been demonstrated. We focused on every possible force such as drag, gravity, buoyancy, and Bjerknes (acoustic radiation) forces acting on bubbles and studied their effects on pressure waves in a one-dimensional setting. Using a singular perturbation method, the Korteweg–de Vries–Burgers equation describing wave propagation was derived. The following results were obtained: (i) Bjerknes force on the bubbles enhanced the nonlinearity, dissipation, and dispersion of the waves; (ii) Drag, gravity, and buoyancy forces acting on the bubbles increased wave dissipation; (iii) Thermal conduction had the most substantial dissipation effect, followed by acoustic radiation, drag, buoyancy, and gravity. We confirmed that the dissipation due to forces on gas bubbles was quantitatively minor.

Experimental investigation of flow patterns and rheological characteristics of compressed air foam in horizontal tube

The use of compressed air foam (CAF) for fire suppression has undergone rapid development in recent years. It has been successfully applied in fire incidents in the petroleum and chemical industries. The increasing need to fighting fires at high elevations necessitates an understanding of the rheological characteristics, pressure gradient changes, flow characteristics, and regularities of CAF within long firehoses. Therefore, this paper focuses on an investigation of the flow characteristics of CAF at foaming agent concentrations ranging from 0.1% to 1.2% and gas–liquid ratios ranging from 5 to 25. Specifically, it explores foam characteristics, pressure loss, and the relationship between flow rate and foaming agent concentration. The findings reveal that CAF exhibits four flow patterns: wave flow, elastic flow, ring flow, and dispersion flow. For most CAF firefighting applications, a foaming agent concentration of 0.3%–0.5% and a gas–liquid ratio of approximately 10 are suitable. However, for fire isolation purposes, a foaming agent concentration of 0.7%–1.0% and a gas–liquid ratio of over 15 should be employed. By utilizing a power-law rheological model and an experimental regression method, a prediction model is obtained for the flow characteristics and pressure loss of CAF in pipelines. The predictions of the model exhibit an error of less than 10% when compared with experimental results, validating the model. The results of this study provide a theoretical basis and technical support for understanding liquid supply resistance loss, which is crucial for maximizing firefighting effectiveness.

Numerical investigation of optical distortions by turbulent wake and shock wave in the transonic flow

Large eddy simulation with the explicit fifth-order weighted compact nonlinear schemes is performed to investigate the aero-optical distortion caused by a transonic flow over a cylinder at Reynolds numbers of Re = 1 × 105, Re = 2 × 105, and Re = 4 × 105. Proper orthogonal decomposition identifies two dominant modes: the antisymmetric “shifting” mode and the symmetric “breathing” mode, both peaking at the non-dimensionalized Strouhal number StD = 0.18. Optical distortion refers to the phenomenon where a beam passes through a non-uniform and fluctuating flow field, resulting in defocus, jitter, and significant energy reduction. Optical calculations for 12 cases demonstrate that local shock waves and turbulent wakes notably exacerbate optical distortion. In terms of temporal results, the peak frequency of the beam aligns with StD = 0.18 when passing through the cylinder shockwave and falls within StD = 0.16–0.42 as it crosses the shear layer. Significant fluctuations are observed in the turbulent wake and local shock wave, with frequency peaks ranging from StD = 0.12–0.72. Additionally, streamwise flow structures are found to primarily impact optical distortion. Comparative analysis across the three Reynolds numbers indicates that optical distortion is insensitive to Reynolds number variations within the same order of magnitude. The employed grid sufficiently resolves key flow structures impacting beam transmission.

Tollmien–Schlichting wave manipulation by a multi-input multi-output phononic subsurface

Recently, there has been a reinvigorated effort to identify passive control mechanisms to reduce drag on vehicles moving through a fluid medium. In 2015, Hussein et al. engineered a phononic crystal subsurface (PSub) to interact with Tollmien–Schlichting waves of a channel flow through an interaction surface, which caused a localized reduction in the kinetic energy of the flow. Since then, arrayed PSubs, Helmholtz resonators, and other embedded structures have been studied for their ability to produce similar effects. In this talk, an implementation of a multi-input multi-output (MIMO) PSub is presented and its ability to delay the onset of turbulence is shown to depend on simultaneously satisfying single-input single-output (SISO) PSub phase requirements at both interaction surfaces of the MIMO PSub. The MIMO architecture provides a method to place an arbitrary phasing between the T-S wave induced forcing and the displacement response of the interaction surface and can be optimized for the flow conditions of the environment.

Role of wave scattering in instability-induced Langmuir circulation

We consider a classical problem about dynamic instability that leads to the Langmuir circulation. The problem statement assumes that there is initially a wind-driven shear flow and a plane surface wave propagating in the direction of the flow. The unstable mode is a superposition of (i) shear flow and (ii) surface waves, both modulated in the horizontal spanwise direction and (iii) circulation that is made up with vortices forming near-surface rolls whose axes are coaligned along the shear flow streamlines and whose transverse size corresponds to the modulation period. Usually, the Langmuir circulation is understood as the vortical part of the mode slowly varying in time, which is the combination of the first and the last flows. The novelty of our approach is that we, first, take into account the scattering of the initial surface wave on the slow current. Second, we find the interference of the scattered and the initial waves generating a Stokes drift modulated in the same direction. Third, we establish the subsequent effect of the circulation by the vortex force created by the nonlinear interaction of the initial shear flow and the modulated part of the Stokes drift. Leibovich and Craik previously showed that the third part of the mechanism could maintain the Langmuir circulation. We calculate the growth rate that is approximately twice smaller than that obtained by Craik. The vertical structure of the circulation in the mode consists of two vortices, which corresponds to the next mode in Craik's model.

Laboratory data linking the reconfiguration of and drag on individual plants to the velocity structure and wave dissipation over a meadow of salt marsh plants under waves with and without current

Abstract. Salt marshes provide valuable ecosystem services, which are influenced by their interaction with currents and waves. On the one hand, currents and waves exert hydrodynamic forces on salt marsh plants, which shapes the distribution of species within the marsh. On the other hand, the resistance produced by the plants can shape the flow structure, turbulence intensity, and wave dissipation over the canopy. Because marsh plants are flexible structures, their reconfiguration modifies the drag felt by the plants and the flow. While several previous studies have considered the flexibility of the stem, few studies have considered the leaf component, which has been shown to contribute the majority of plant resistance. This paper reports a unique dataset that includes laboratory measurements of both the force on an individual plant and the flow structure and wave energy dissipation over a meadow of plants. In the individual plant experiment, the motion of the plant and plant drag, free-surface displacement, and velocity profile were measured. The individual plant experiments considered both a live marsh plant (Spartina alterniflora) and a mimic consisting of 10 leaves attached to a central stem. For the meadow experiment, velocity profiles were measured both upstream and within the meadow, and free-surface displacement was measured along the model marsh plant meadow with high spatial and temporal resolution. These experiments used five water depths (covering both submerged and emergent conditions), three wave periods (from long wave to short waves), seven wave heights (from linear to nonlinear waves), and six current conditions (including pure current, pure wave, and combined current and wave). In summary, there are 102 individual plant tests and 58 meadow tests. The drag, free-surface displacement, and velocity are reported in the SMCW.mat and SMCW.nc files including the raw data, the phase averages, and the statistical values. A link to the plant motion videos is also provided. This dataset provides high-quality measurements that can be used to develop and validate models of plant motion, hydrodynamic drag on individual plants, vegetation-generated turbulence, the evolution of flow structure through a meadow, and the transformation and dissipation of waves over natural salt marshes. The dataset is available from Figshare with detailed instructions for reuse (https://doi.org/10.6084/m9.figshare.24117144; Zhang and Nepf, 2023a).

WaveNets: physics-informed neural networks for full-field recovery of rotational flow beneath large-amplitude periodic water waves

AbstractWe formulate physics-informed neural networks (PINNs) for full-field reconstruction of rotational flow beneath nonlinear periodic water waves using a small amount of measurement data, coined WaveNets. The WaveNets have two NNs to, respectively, predict the water surface, and velocity/pressure fields. The Euler equation and other prior knowledge of the wave problem are included in WaveNets loss function. We also propose a novel method to dynamically update the sampling points in residual evaluation as the free surface is gradually formed during model training. High-fidelity data sets are obtained using the numerical continuation method which is able to solve nonlinear waves close to the largest height. Model training and validation results in cases of both one-layer and two-layer rotational flows show that WaveNets can reconstruct wave surface and flow field with few data either on the surface or in the flow. Accuracy in vorticity estimate can be improved by adding a redundant physical constraint according to the prior information on the vorticity distribution.

Viscous dissipation effect on amplitude and oscillating frequency of heat transfer and electromagnetic waves of magnetic driven fluid flow along the horizontal circular cylinder

The significant importance of present research is to remove the extreme temperature along the magnetic driven horizontal circular cylinder. The induced electromagnetic field is applied around the surface of cylinder. The main novelty of current research is to control thermal and magnetic boundary layer in the presence of viscous dissipation and induced electromagnetic field. The dimensional mathematical form is developed with defined boundary conditions. The dimensional equations are transformed into dimensionless equations to generate physical factors. The primitive form is used to reduce dimensionless equations into convenient form for smooth algorithm. The finite difference method with Gaussian elimination technique is applied for numerical results in FORTRAN language tool. The velocity, temperature and electromagnetic field are sketched graphically with asymptotic sequence. The oscillatory shear stress, oscillating heat rate and periodical current density is plotted graphically and numerically. It is found that fluid velocity improves significantly as buoyancy force increases around each position. It is noticed that the increasing oscillations in heat transfer are sketched for maximum choice of Prandtl number. It is found that the maximum oscillations in current density are obtained for each Eckert parameter. It is noticed that the significant distribution in temperature profile is obtained in the presence of viscous dissipation and magnetic field.

Tube law parametrization using in vitro data for one-dimensional blood flow in arteries and veins: TUBE LAW PARAMETRIZATION IN ARTERIES AND VEINS.

The deformability of blood vessels in one-dimensional blood flow models is typically described through a pressure-area relation, known as the tube law. The most used tube laws take into account the elastic and viscous components of the tension of the vessel wall. Accurately parametrizing the tube laws is vital for replicating pressure and flow wave propagation phenomena. Here, we present a novel mathematical-property-preserving approach for the estimation of the parameters of the elastic and viscoelastic tube laws. Our goal was to estimate the parameters by using ovine and human in vitro data, while constraining them to meet prescribed mathematical properties. Results show that both elastic and viscoelastic tube laws accurately describe experimental pressure-area data concerning both quantitative and qualitative aspects. Additionally, the viscoelastic tube law can provide a qualitative explanation for the observed hysteresis cycles. The two models were evaluated using two approaches: (i) allowing all parameters to freely vary within their respective ranges and (ii) fixing some of the parameters. The former approach was found to be the most suitable for reproducing pressure-area curves.