Wave Flow Research Articles

Damage Curves Derived from Hurricane Ike in the West of Galveston Bay Based on Insurance Claims and Hydrodynamic Simulations

Hurricane Ike, which struck the United States in September 2008, was the ninth most expensive hurricane in terms of damages. It caused nearly USD 30 billion in damage after making landfall on the Bolivar Peninsula, Texas. We used the Delft3d-FM/SWAN hydrodynamic and spectral wave model to simulate the storm surge inundation around Galveston Bay during Hurricane Ike. Damage curves were established through the relationship between eight hydrodynamic parameters (water depth, flow velocity, unit discharge, flow momentum flux, significant wave height, wave energy flux, total water depth (flow depth plus wave height), and total (flow plus wave) force) simulated by the model and National Flood Insurance Program (NFIP) insurance damage data. The NFIP insurance database contains a large amount of building damage data, building stories, and elevation, as well as other information from the Ike event. We found that the damage curves are sensitive to the model grid resolution, building elevation, and the number of stories. We also found that the resulting damage functions are steeper than those developed for residential structures in many other locations.

Computational fluid dynamics modelling of the regular wave flow regime in air-water downwards annular flows

Although the global flow characteristics of annular gas-liquid flows have been studied experimentally for more than 50 years, the spatiotemporally-resolved details of these flows have remained relatively unexplored until recently, with data provided via advanced experimental methods based, e.g., on optical techniques. Similarly, the numerical modelling of annular flows is still an immature process. The present work aims to provide a computational fluid dynamics (CFD) model based on the volume of fluid (VOF) method for simulating annular gas-liquid flows, setting the stage for a deeper investigation of these flows at global and local scales. The work focuses on the most common downwards annular flow (DAF) flow pattern: the regular wave regime. 3-D and 2-D axisymmetric transient simulations have been performed using a commercial code (ANSYS Fluent 2021 R1). The code is validated through available experimental data regarding topological flow properties, mainly film thickness and wave statistics. The validation results suggest that 3-D simulations are needed to provide predictions that agree with the experimental data, highlighting strong 3-D features in the flow.

Experimental and theoretical analysis of pulsatile flow in elastic tubes: Wave propagation and attenuation

The objective of this study was to comprehensively examine the pulsatile flow behavior within an elastic tube using experimental and theoretical approaches. This work is an extension of our earlier report [Roknujjaman et al., Phys. Fluids, 34, 123612 (2022)]. In this paper, we adapted a quasi-one-dimensional model to elucidate the wave propagation and pulse attenuation phenomena in an elastic tube and compared with experimental findings. According to our investigation, the key findings were as follows: the experimental and predicted flow wave propagation trend agreed well. Additionally, because of the silicon tubes greater deformation than the urethane tubes, the pulsation was decreased farther in the silicon tubes than in the urethane ones. Furthermore, because of the reflected wave near the tube exit, the pulsations amplitude significantly increased, but it did not enlarge when the resistance was installed at the exit. Finally, we infer that the quasi-one-dimensional model is a better fit for experimental results compared to the two-dimensional model.

Aerodynamic performance test and flow visualization for reducing acoustic liner drag in grazing flow

We aim to reduce aerodynamic drag over an acoustic liner, which comprises of a perforated plate, a honeycomb core, and a rigid backplate, for aero-engine applications through both performance testing and flow visualization. Whereas the acoustic liner can attenuate engine noise, the structural characteristic of the liner surface causes the additional drag in grazing flow, resulting in deterioration of engine fuel efficiency. In this work, acoustic liner test pieces with various hole geometries are tested in the flow duct rig capable of generating sound wave and grazing air flow inside the duct. The static pressure drop measurement reveals that the perforation in the grazing flow direction wound increase the drag despite the same overall perforation for all test pieces. We further conduct the flow visualization using the test rig designed for water flow to be analogous to the air flow of the flow duct rig, and the analogy is based on Reynolds number defined with the friction velocity and the representative size of an acoustic liner. The result via particle image velocimetry represents the flow patterns causing the drag.

An Ultrasound Matrix Transducer for High-Frame-Rate 3-D Intra-cardiac Echocardiography

Described here is the development of an ultrasound matrix transducer prototype for high-frame-rate 3-D intra-cardiac echocardiography. The matrix array consists of 16×18 lead zirconate titanate elements with a pitch of 160 µm×160 µm built on top of an application-specific integrated circuit that generates transmission signals and digitizes the received signals. To reduce the number of cables in the catheter to a feasible number, we implement subarray beamforming and digitization in receive and use a combination of time-division multiplexing and pulse amplitude modulation data transmission, achieving an 18-fold reduction. The proposed imaging scheme employs seven fan-shaped diverging transmit beams operating at a pulse repetition frequency of 7.7 kHz to obtain a high frame rate. The performance of the prototype is characterized, and its functionality is fully verified. The transducer exhibits a transmit efficiency of 28 Pa/V at 5 cm per element and a bandwidth of 60% in transmission. In receive, a dynamic range of 80 dB is measured with a minimum detectable pressure of 10 Pa per element. The element yield of the prototype is 98%, indicating the efficacy of the manufacturing process. The transducer is capable of imaging at a frame rate of up to 1000 volumes/s and is intended to cover a volume of 70°×70°×10 cm. These advanced imaging capabilities have the potential to support complex interventional procedures and enable full-volumetric flow, tissue, and electromechanical wave tracking in the heart.

Two-phase flow in a supersonic separator for carbon capture

This work investigates a possible approach of carbon capture and two-phase flow involved. The nonequilibrium condensation, high velocity flow and shock wave in decarbonization process are described by a mathematical model. The separator is optimized through the calculations. The results show that the nonequilibrium state makes CO2 in flue gas condense spontaneously, and the system does not transfer to the equilibrium state instantly when condensation nuclei appear, but gradually turn to the equilibrium state after nucleation rate reaches the maximum. The separator with a larger separation angle is the first to condense, and the liquefied CO2 content is higher, while separator with a smaller angle produces larger droplets. Reducing the contraction ratio makes the shock wave move to the exit, and obtain higher liquid content and larger droplets. In practice, increasing the separation section length equates to a longer droplet growth time, which facilitates carbon liquefaction and separation.

Numerička simulacija prometnog toka

The paper discusses the concept of traffic flow described by hyperbolic differential equations. In this paper the Lighthill-Whitham-Richards model (LWR model) is used to describe traffic flow. The said model uses two parameters to describe the traffic flow – density and average speed of vehicles. Numerical approximation of the LWR model is formulated through scalar conservation laws. The finite volume method is used for numerical results. The term of shock wave and propagation of rarefaction wave in traffic flow are described. This paper focuses on numerical simulation of traffic flow via fluid dynamics model for a single road with a traffic light. The results obtained in this paper are compared with previous studies.

Computational Analysis of Shrouded Ejector Effect on Starting Vortex and Combustion Efficiency in Pulse Detonation Combustor with Different Fuels

ABSTRACT This research paper deals with the starting vortex of detonation combustion wave flow field in pulse detonation combustor (PDC). In order to achieve the potential pressure gain from PDC the shrouded ejectors are placed at exit section of detonation tube. Therefore, influence of shrouded ejector position plays a great role on leading vortex and reduction of NOx formation. Furthermore, n-butane (C4H10) and hydrogen (H2) fuel are used for stoichiometric (= 1) fuel-air mixture condition to simulate the thermal and prompt NOx formation at pulse time of 0.022s to 0.030s. The LES turbulence model is used to simulate the unsteady flow field in CFD based fluent platform. The one step irreversible chemical kinetics model analyzed the details of exothermic chemical reaction mechanism inside the combustor. The non-dimensional value of /d = 1.5 geometry position of shrouded ejector is better for leading vortex. So far, pickup detonation wave speed of 2306 ms−1 is obtained at shortest pulse time of 0.028s and this magnitude is higher than C-J velocity. The minimum pollutant number of 0.0000341 is obtained from hydrogen-air detonation, this magnitude is lesser compared to n-butane (C4H10)-air combustion. Furthermore, the maximum combustion efficiency of 85% is obtained from hydrogen-air mixture in detonation combustion process, which is comparatively higher than deflagration combustion process.

A robust numerical strategy for finding surface waves in flows of non-Newtonian liquids

Gravity-driven flows of liquid films are frequent in nature and industry, such as in landslides, lava flow, cooling of nuclear reactors, and coating processes. In many of these cases, the liquid is non-Newtonian and has particular characteristics. In this paper, we analyze numerically the temporal stability of films of non-Newtonian liquids falling by gravity, on the onset of instability. The liquid flows over an incline, where surface waves appear under certain conditions, and we do not fix a priori its rheological behavior. For that, we made used of the Carreau–Yasuda model without assigning specific values to its constants, and we compute general stability solutions. The numerical strategy is based on expansions of Chebyshev polynomials for discretizing the Orr–Sommerfeld equation and boundary conditions, and a Galerkin method for solving the generalized eigenvalue problem. In addition, an Inverse Iteration method was implemented to increase accuracy and improve computational time. The result is a robust and light numerical tool capable of finding the critical conditions for different types of fluids, which we use to analyze some key fluids. We show that the outputs of the general code match previous solutions obtained for specific computations. Besides increasing our knowledge on surface-wave instabilities in non-Newtonian liquids, our findings provide a new tool for obtaining comprehensive solutions on the onset of instability.

Multi-phase simulation for understanding morphodynamics of gravel beaches

This paper presents the use of an Eulerian–Eulerian multi-phase model to examine sediment transport over a gravel beach under regular waves. A previously published full-scale experiment is reproduced numerically; the simulated wave deformation, flow velocity, pore pressure, and morphological evolution are consistent with measurements. The multi-phase model can produce berm formation for smaller waves and beach erosion for larger waves as observation in previous field studies. The sensitivity analysis suggests that the nonlinear component of drag has significant effect on the berm formation through infiltration and exfiltration. The two simulated forces applied on the sediment (drag and buoyancy) are examined. The drag is the main force directly for sediment transport; therefore the sediment transport rate has high correlation with depth-averaged flow velocity. The buoyancy that is caused by plunging flow impacting beach face can push the sediment landward in the bore front, where the flow acceleration has its peak. The flow acceleration is considered in some previous sediment transport models empirically for simulating morphological evolution of gravel beach under waves. The buoyancy links the flow acceleration and sediment transport rate in the bore front.

A method to reduce the fluid mass transfer loss of rotating jet: A kind of microstructure design and research for wave rotor refrigerator

Wave rotor refrigerator (WRR) is a device that uses compressed flow and pressure wave to produce low-temperature gas. When the high-pressure nozzle gradually approached the wave tube, two vortices are generated in the high-pressure gas incidence stage which caused jet mass transfer loss, which is an important factor that causes the loss of cooling efficiency of the wave rotors. By studying the utility of microstructures in fluid mass transfer field, a method for improving the cooling efficiency of WRR from the mesoscopic aspect has been proposed. The addition of microstructures has the effect of hindering the development of vortices in the tubes. The optimal size parameters of the microstructure were found, and feasible processing conditions were synthesized through numerical simulation. And then, a wave rotor with the microstructure was created, and a comparative test was performed. The results reveal that the rotor with microstructure efficiently undercut the vortices in the tubes and increased the expansion depth of the high-pressure gas, consequently boosting the WRR's cooling performance. With varying pressure ratios and rotational speeds, the approach has a gain impact. When the pressure ratio reaches 2.6 and the relative rotating speed reaches 2900 rpm, the isentropic expansion efficiency of this type of WRR can be boosted by up to 19.04 %, and the temperature drop is increased by a maximum of 3℃, which is significant for reducing jet loss and promoting efficiency for the wave equipment.

The directional flow generated by peristalsis in perivascular networks-Theoretical and numerical reduced-order descriptions.

Directional fluid flow in perivascular spaces surrounding cerebral arteries is hypothesized to play a key role in brain solute transport and clearance. While various drivers for a pulsatile flow, such as cardiac or respiratory pulsations, are well quantified, the question remains as to which mechanisms could induce a directional flow within physiological regimes. To address this question, we develop theoretical and numerical reduced-order models to quantify the directional (net) flow induceable by peristaltic pumping in periarterial networks. Each periarterial element is modeled as a slender annular space bounded internally by a circular tube supporting a periodic traveling (peristaltic) wave. Under reasonable assumptions of a small Reynolds number flow, small radii, and small-amplitude peristaltic waves, we use lubrication theory and regular perturbation methods to derive theoretical expressions for the directional net flow and pressure distribution in the perivascular network. The reduced model is used to derive closed-form analytical expressions for the net flow for simple network configurations of interest, including single elements, two elements in tandem, and a three element bifurcation, with results compared with numerical predictions. In particular, we provide a computable theoretical estimate of the net flow induced by peristaltic motion in perivascular networks as a function of physiological parameters, notably, wave length, frequency, amplitude, and perivascular dimensions. Quantifying the maximal net flow for specific physiological regimes, we find that vasomotion may induce net pial periarterial flow velocities on the order of a few to tens of m/s and that sleep-related changes in vasomotion pulsatility may drive a threefold flow increase.

Pore Pressure Diffusion Waves Transmission in Oil Reservoir

Recent studies on seismic wave excitation have revealed that mesoscopic wave-induced fluid flow (WIFF) is a process that attenuates the compressional (P) waves in reservoir rocks at seismic frequency bands. Fluid flow and Biot's slow diffusion (pressure) waves are produced when the P-waves create fluid-pressure gradients at mesoscopic-scale heterogeneities. Pore pressure continuity can be sustained by converting seismic energy into diffusion waves that diffuse away from the interfaces or boundaries. Biot’s diffusion waves fail to comply with a square-law approach because of their slow propagation velocity and higher attenuation. It is currently uncertain how to characterize reservoir fluids in mature oil reservoirs during seismic wave-based enhanced oil recovery (EOR). A simplified 1D two-layer reservoir model was investigated in this study. The findings demonstrate that diffusion wave propagation in oil reservoirs is frequency-dependent and affected by rock permeability and fluid viscosity. At a formation layer interface, it was discovered that diffusion waves obeyed the accumulation-depletion relationship rather than the reflection-refraction approach. Therefore, pore pressure diffusion waves can characterize reservoir fluid during seismic EOR and monitor the CO2 front in depleted reservoirs during storage for CCUS projects. It can also detect shale gas transport in low permeability layers and identify the propagation of fractures during gas/oil recovery.

Decomposition of Vertical Velocity and Its Zonal Wavenumber Kinetic Energy Spectra in the Hydrostatic Atmosphere

Abstract The spectrum of kinetic energy of vertical motions (VKE) is less well understood compared to the kinetic energy spectrum of horizontal motions (HKE). One challenge that has limited progress in describing the VKE spectrum is a lack of a unified approach to the decomposition of vertical velocities associated with the Rossby motions and inertia–gravity (IG) wave flows. This paper presents such a unified approach using a linear Rossby–IG vertical velocity normal-mode decomposition appropriate for a spherical, hydrostatic atmosphere. New theoretical developments show that for every zonal wavenumber k, the limit VKE is proportional to the total mechanical energy and to the square of the frequency of the normal mode. The theory predicts a VKE ∝ k−5 and a VKE ∝ k1/3 power law for the Rossby and IG waves, assuming a k−3 and a k−5/3 power law for the Rossby and IG HKE spectra, respectively. The Kelvin and mixed Rossby–gravity wave VKE spectra are predicted to follow k−1 and k−5 power laws, respectively. The VKE spectra for ERA5 data from August 2018 show that the Rossby VKE spectra approximately follow the predicted a k−5 power law. The expected k1/3 power law for the gravity wave VKE spectrum is found only in the SH midlatitude stratosphere for k ≈ 10–60. The inertial range IG VKE spectra in the tropical and midlatitude troposphere reflect a mixture of ageostrophic and convection-coupled dynamics and have slopes between −1 and −1/3, likely associated with too steep IG HKE spectra. The forcing by quasigeostrophic ageostrophic motions is seen as an IG VKE peak at synoptic scales in the SH upper troposphere, which gradually moves to planetary scales in the stratosphere. Significance Statement The spectrum of kinetic energy of vertical motions (VKE) is less well understood compared to the kinetic energy spectrum of horizontal motions. One challenge is a lack of a unified approach to the decomposition of vertical velocities associated with the Rossby motions and inertia–gravity (IG) wave flows. This paper presents such a unified approach using a linear Rossby–IG vertical velocity normal-mode decomposition appropriate for a spherical, hydrostatic atmosphere. It is shown that for every zonal wavenumber, the limit VKE is proportional to the total mechanical energy and to the square of the frequency of the normal mode. The theory is successfully applied to the ERA5 data. It leads the way for a more accurate computation of momentum fluxes.

Restrictions and New Possibilities of Technical and Conservation Diagnostics of Wood in Heritage Buildings

Identifying the mechanical properties of wood in existing buildings allows the search for an effective way to renovate wooden structures. Tests conducted on the historic structure's tissue preclude the use of destructive testing. Individual elements of the structure can be subjected to non-destructive testing (NDT) conducted in situ. The NDT testing methodology presented in the article is based on the use of ultrasonic and sclerometric technology. These methods can be used to determine the sites of biological corrosion and determine the effect of internal defects on the quality of wood. Ultrasonic testing usually uses devices that emit a longitudinal wave. The study additionally applied the author's method using devices analyzing the velocity of transverse wave flow for testing historic wood. The research was conducted on the roof truss of the heritage church of the Sacred Heart of Jesus in Jastrzębie Zdrój.

Research on time sequence prediction of supersonic cascade flow field based on compressed sensing artificial neural network

The aviation engine that achieves efficient energy conversion is the core power equipment for low-carbon navigation, and the thermal components represented by the combustion chamber greatly affect the stable state of the compressor cascade flow field. Accurate, comprehensive and promptly monitoring of the compressor cascade flow state is related to the safe operation of the engine. A flow field time sequence prediction framework named compressed convolutional gate recurrent unit (CC-GRU) was proposed in this study to predict future supersonic cascade flow parameters based on the flow field at previous moments. CC-GRU embedded convolution into gate recurrent unit (GRU) to deal with the complex spatial-temporal behavior of supersonic cascade flow field. Firstly, unsteady numerical simulations driven by linear changes in back pressure were carried out, and the dataset for model training and validation was obtained to verify the feasibility of time sequence prediction of the cascade flow field. The verification results indicate that the framework can comprehensively predict the flow field with high back pressure in the future according to the flow field with low back pressure in the past period, and further validated the effectiveness of the proposed time sequence prediction model in ground wind tunnel experiments. The CC-GRU model can accurately capture the fine shock wave structure and flow separation zone, with a relative error of less than 10% in predicting the pressure field, and is mainly concentrated within the shock wave structure. Therefore, this research provides new research perspective and technical support for comprehensive and promptly condition monitoring of supersonic cascade flow field.

An intentional random mathematical model for immigration: A case study of Spain

This paper presents a random discrete mathematical population model for immigration. This model incorporates not only rational factors, such as the economic gradient between destination and origin countries, geographical factors, and regulatory laws but also hidden intentional factors, such as the political interests of governments and the involvement of migrant smuggling by criminal organizations, which exploit immigration as a strategic tool. These non-rational factors are modeled as sudden, random arrival flow waves, represented by a Poisson distribution. The study’s time frame is short to ensure the reliability of economic forecasts for the coming years. Although the study focuses on Spain, the proposed approach is applicable to other geographic areas with appropriate data. The results obtained from this model can be applied to predict the national budget necessary for host countries to address this complex social phenomenon.

Numerical Analysis of the Impact Parameters on the Dynamic Response of a Submerged Floating Tunnel under Coupling Waves and Flows

The Submerged Floating Tunnel (SFT) is a highly promising cross-sea transportation structure. Due to its body being suspended in water, waves and flows are the primary environmental loads it encounters. Existing numerical simulations have been based on potential flow theory, which fails to fully consider shear forces and the nonlinear characteristics of the flow field. To overcome this limitation, the Computational Fluid Dynamics (CFD) approach, relying on solving the Navier-Stokes equations, can be employed. In this study, we establish a CFD model for the SFT and analyze the impact mechanisms of wave-flow coupling on its dynamic response, considering parameters such as wave height, flow velocity, wave direction, and flow direction. With increasing wave height, the acceleration, mooring tension, and heave amplitude of the SFT significantly increase, and the nonlinear characteristics of its dynamic response become more pronounced. For example, when wave height, Hi, increases from 0.046 m to 0.138 m, the maximum value of dimensionless heave, δz/Hi, increases from 0.075 to 0.284, nearly quadrupling in magnitude. When waves and flows propagate in the same direction, the heave amplitude of the SFT increases compared to the case with waves acting alone, while sway and roll amplitudes decrease. Under conditions of higher flow velocity, the SFT displaces significantly along the direction of flow and water depth, deviating significantly from its original equilibrium position. At this point, the tunnel primarily experiences periodic forces due to vortex shedding, and the anchor chain on the downstream side remains slack. In scenarios where waves and flows propagate in opposite directions, both the maximum acceleration and mooring tension of the SFT increase significantly. For instance, the onshore tension of the cable, Fon, increases by 36%, while the offshore tension, Foff, increases by 89%.

A transient flow analysis method for high-rate mud pulse telemetry in rotary steerable system

With the development of ultra-deep offshore and onshore deep-water wells, there is a growing demand for high-speed data transmission. Mud pulse telemetry (MPT) is the most commercially mature wireless data transmission method. The time-domain parameter analysis of the down-hole mud pulse pressure signal is useful to study the optimization measures of the down-hole signal. Currently, the main approaches are experiment and computational fluid dynamics (CFD) numerical simulations, but both methods are time-consuming and costly, which is not conducive to multi-parameter studies. transient flow modelis widely used to analyze water hammers in pipelines, but its application to mud pulse telemetry (MPT) systems has been less studied. In this paper, based on the classical transient flow equation, the method of characteristics (MOC) is used to solve the governing equation, and the boundary conditions suitable for the MPT are proposed and verified with the experiment and CFD method. Based on the newly established transient flow mathematical model, the generation characteristics of the downhole pressure wave and the influence law of key parameters are studied. The results show that the essence of continuous wave is a three-wave coupling of pressure wave, density wave and flow wave. With the transmission of continuous wave, unsteady friction will be generated in the wave region of the wellbore, increasing the attenuation degree of the signal. The amplitude of continuous wave increases with the increase of density and displacement, independent of frequency and viscosity. However, as the frequency and viscosity increase, the continuous wave will decay faster. This paper provides the new transient flow method with fast computational time and a technical means for MPT studies under subsequent drilling conditions.

A Comparative Study of the Explicit Finite Difference Method and Physics-Informed Neural Networks for Solving the Burgers’ Equation

The Burgers’ equation is solved using the explicit finite difference method (EFDM) and physics-informed neural networks (PINN). We compare our numerical results, obtained using the EFDM and PINN for three test problems with various initial conditions and Dirichlet boundary conditions, with the analytical solutions, and, while both approaches yield very good agreement, the EFDM results are more closely aligned with the analytical solutions. Since there is good agreement between all of the numerical findings from the EFDM, PINN, and analytical solutions, both approaches are competitive and deserving of recommendation. The conclusions that are provided are significant for simulating a variety of nonlinear physical phenomena, such as those that occur in flood waves in rivers, chromatography, gas dynamics, and traffic flow. Additionally, the concepts of the solution techniques used in this study may be applied to the development of numerical models for this class of nonlinear partial differential equations by present and future model developers of a wide range of diverse nonlinear physical processes.