The aim of this work is to study the solution of the smoothed particle hydrodynamics (SPH) discrete formulation of the hydrostatic problem with a free surface. This problem, in which no time dependency is considered, takes the form of a system of linear equations. In particular, the problem in one dimension is addressed. The focus is set on the convergence when both the particle spacing and the smoothing

The accuracy of large eddy simulation (LES) is highly dependent on the performance of sub-grid scale (SGS) model. In the present paper, a dynamic cubic nonlinear sub-grid scale model (DCNM) proposed by Huang et al. is implemented for the simulation of unsteady cavitating flow around a 3-D Clark-Y hydrofoil in OpenFOAM. Its performance in predicting the evolution of cloud cavitation is discussed in

Wave propagation on uniformly sloped beaches is a canonical coastal engineering topic that has been studied extensively in the past few decades. However, most of these studies treat beaches as solid boundaries even though they are often made of porous materials, such as sediment and vegetation. Permeable beaches struck by tsunami-like waves have not been adequately investigated. It is expected that

Vegetation is of great significance in river ecosystems in terms of hydrodynamics, water environment and ecology. The question of how to predict the bulk velocity in channel flow through submerged vegetation is currently a hot topic in hydraulics research. The present study addresses this question. The various formulae used for bulk velocity estimation in previous work were reviewed and compared. The

For violent sloshing, the flow field becomes complicated and 3-D effect is non-negligible. In addition to the excitation direction, the wave can also propagate perpendicular to the excitation direction. Due to the superposition of waves from different directions, the impact pressure imposed on the wall of the tank may increase. In this paper, our in-house solver MPSGPU-SJTU based on moving particle

The Liutex core line method, first combined with the snapshot proper orthogonal decomposition (POD), is utilized in a supersonic micro-vortex generator (MVG) wake flow at Ma = 2.5 and Reθ = 5 760 to reveal the physical significance of each POD mode of the flow field. Compared with other scalar-based vortex identification methods, the Liutex core line identification is verified to be the most appropriate

Based on the computational fluid dynamics (CFD) and the experiment technology, this paper presents a new type of the twin-screw pump for the water-supply and studies its hydraulic performance with the hydraulic performance test. The internal flow characteristics and the hydraulic performance of the twin-screw pump are numerically simulated. The CFD results show that at different heads, the screw pressure

The non-physiologic turbulent flows in centrifugal rotary blood pumps (RBPs) may result in complications such as the hemolysis and the platelet activation. Recent researches suggest that the turbulent viscous dissipation in the smallest eddies is the main factor of the blood trauma caused by the turbulent flow. The turbulent viscous shear stress (TVSS) was taken as the realistic physical force acting

Helmholtz velocity decomposition and Cauchy-Stokes tensor decomposition have been widely accepted as the foundation of fluid kinematics for a long time. However, there are some problems with these decompositions which cannot be ignored. Firstly, Cauchy-Stokes decomposition itself is not Galilean invariant which means under different coordinates, the stretching (compression) and deformation are quite

In this article, a coupling of the direct numerical simulation (DNS) and the population balance modeling (PBM) is implemented to study the effect of turbulence on nanoparticle dynamics in homogenous isotropic turbulence (HIT). The DNS is implemented based on a pseudo-spectral method and the PBM is implemented using the Taylor-series expansion method of moments. The result verifies that coagulation

Behaviors of a prolate ellipsoid inside circular tube Poiseuille flow are studied experimentally. In the study, Reynolds number Re ∈ (100,700) and the confinement ratio D/A ∈ (1.2,2.8) are considered, where D is the diameter of the tube and A is the length of the major axis of the ellipsoid. Two typical stable motion modes are identified, namely, the horizontal, and inclined modes. Then another inclined

As a fundamental fluid-structure interaction (FSI) phenomenon, vortex-induced vibrations (VIVs) of circular cylinders have been the center of the FSI research in the past several decades. Apart from its scientific significance in rich physics, VIVs are paid great attentions by offshore engineers, as they are encountered in many ocean engineering applications. Recently, with the development of research

The turbulent flow in the draft tube of a Francis turbine is very complicated while working under off-design conditions. Although the off-design conditions were widely studied, the vortex core line in the draft tube of a Francis turbine with splitter blades is not well understood, especially the vortex rope property. This letter presents a prediction of the behavior of the vortex rope in the draft

In the published article [1] there is an error in the listing of the last author. “Dahlhaug G. Ole” should be “Ole Gunnar Dahlhaug” as listed in this erratum.

In order to study the effects of the confining pressure on the erosion characteristics of the self-resonating cavitating jet under wellbore and deep-water conditions, experiments are conducted on aluminum specimens impinged by the organ pipe cavitation nozzle and the conical nozzle with the confining pressure in the range 0 MPa–10.0 MPa. Meanwhile, through the numerical simulation of the collapsing

In this paper, an artificial neural network (ANN) trained through a deep reinforcement learning (DRL) agent is used to perform flow control. The target is to look for the wake stabilization mechanism in an active way. The flow past a 2-D cylinder with a Reynolds number 240 is addressed with and without a control strategy. The control strategy is based on using two small rotating cylinders which are

To solve the problem of inaccurate boundary identification and to eliminate the spurious pressure oscillation in the previously developed immersed smoothed point interpolation method (IS-PIM), a new sharp-interface IS-PIM combining mass conservation algorithm, called Sharp-ISPIM-Mass, is proposed in this work. Based on the so called sharp-interface method, the technique of quadratic local velocity

In-depth analyses of existing direct numerical simulations (DNS) data led to a logical and important classification of generic turbulent boundary layers (TBLs), namely Type-A, -B and -C TBL, based on the distribution patterns of the time-averaged wall-shear stress. Among these types, Type-A TBL and its related law formulations were investigated in terms of the analytical velocity profiles independent

In recent years, artificial neural networks (ANNs) and deep learning have become increasingly popular across a wide range of scientific and technical fields, including fluid mechanics. While it will take time to fully grasp the potentialities as well as the limitations of these methods, evidence is starting to accumulate that point to their potential in helping solve problems for which no theoretically

Nowadays the rapidly developing artificial intelligence has become a key solution for problems of diverse disciplines, especially those involving big data. Successes in these areas also attract researchers from the community of fluid mechanics, especially in the field of active flow control (AFC). This article surveys recent successful applications of machine learning in AFC, highlights general ideas

The analytical method was adopted to investigate the earthquake-induced hydrodynamic pressure on a circular cylinder surrounded by two-layer fluid. Based on the radiation theory, the analytical expressions of hydrodynamic pressure, hydrodynamic force on a rigid circular cylinder were obtained. Then, the dispersion relation for radiation problem in a two-layer fluid, and the added mass and damping coefficients

In this paper, several commonly used vortex identification methods for marine hydrodynamics are revisited. In order to extract and analyse the vortical structures in marine hydrodynamics, the Q, λ2 - criterion and modified normalized Liutex/Rortex Ω͂R method are utilized for vortex identification for propeller open water test, ship drag test, ship propeller-rudder interaction, VIV of a marine riser

In combination with a channel bed, suspended vegetationin an open channel can alter flow structure and generate vertically asymmetric flow. This study investigated the mean flow and turbulence structure of an open channel with suspended vegetation through theoretical analysis and laboratory experiments. Three patterns of bionic leaves with different roughness were adopted to imitate suspended vegetation

Most hydrodynamic problems in ship and ocean engineering are complex and highly coupled. Under the trend of intelligent and digital design for ships and ocean engineering structures, comprehensive performance evaluation and optimization are of vital importance during design. In this process, various coupling effects need to be accurately predicted. With the significant progress of computational fluid

The third-generation vortex identification method of Liutex (previously called Rortex) was introduced by the team led by Prof. Chaoqun Liu from University of Texas at Arlington to mathematically extract the rigid rotation part from the fluid motion, and thus to define and visualize vortices. Unlike the vorticity-based first generation and the scalar-valued second generation, Q, λ2, Δ and λci methods

An unstructured mesh Reynolds-averaged Navier-Stokes (RANS) solver has been developed for numerical simulation of violent sloshing flows inside a tank with complicated inner structures. The numerical solver employs the unstructured multi-dimensional tangent hyperbolic interface capturing method (UMTHINC) for free-surface capturing combined with various turbulence models. The sloshing motion is numerically

The wave parameters (the wave height and period) are important environmental factors in the ocean engineering design. General numerical wave models, such as SWAN and WAVEWATCH, are widely employed to simulate the wave conditions. However, significant differences were observed between the measurement and the simulation for both the wave height and period, which asks for wave model improvements. The

In the present work, a 3-D aerator device with backward lateral deflectors, called BLD-3-D aerator device, is developed, and the lateral cavity and fin performance of the BLD-3-D aerator device are experimentally investigated. The findings show that, the relative lateral cavity length with backward lateral deflectors is shorter than that with current lateral deflectors under the same approach flow

In order to manipulate large-scale coherent structures in the wall-bounded turbulence and reduce the skin-friction, an active-control experimental investigation was performed through synchronous and asynchronous vibrations of double piezoelectric vibrators embedded spanwisely on a smooth flat plate surface. A TSI-IFA300 hot-wire anemometer and TSI-1621A-T1.5 hot-wire probe were used to measure the

Nonlinear steady-state waves are obtained by the amplitude-based Homotopy Analysis Method (AHAM) when resonances among surface gravity waves are considered in water of finite depth. AHAM, newly proposed in this paper within the context of Homotopy Analysis Method (HAM) and well validated in various ways, is able to deal with nonlinear wave interactions. In waves with small propagation angles, it is

The added resistance of a ship in waves can be related to ship-generated unsteady waves. In the present study, the unsteady wave-pattern analysis is applied to calculate the added resistance in waves for two modified Wigley models using a Cartesian-grid method. In the present numerical method, a first-order fractional-step method is applied to the velocity-pressure coupling in the fluid domain, and

In the present work, a slot-type flip bucket with separated flows, called SFS-type flip bucket, is developed, and flow regime and energy dissipation are experimentally investigated. Comparing with the circular-shaped or slot-type flip bucket buckets, the present SFS-type flip bucket has better flow regime and larger energy dissipation since the three branches of the flows are separated through the

We present a numerical simulation of the so-called condensation shock on a NACA0015 hydrofoil with a finite mass transfer model for the first time. Most recently, condensation shock was indentified in the experimental measurement as a mechanism for partial cavity shedding in the flow past a hydrofoil. Compressible solvers, which were adopted in the previous simulations to study such phenomenon numerically

In this paper, the transient turbulent cavitating flow around a marine propeller behind a ship was investigated experimentally with emphasis on how vortex generator (VG) influences propeller cavitation and hull pressure fluctuations. The experiments were carried out in China Large Cavitation Channel with the closed test section covering 10.5 m in length and cross-section of 2.2 m2 ϗ 2.0 m2. The experiment

One of the critical issues in numerical simulation of fluid-structure interaction problems is inaccuracy of the solutions, especially for flows past a stationary thin elastic structure where large deformations occur. High resolution is required to capture the flow characteristics near the fluid-structure interface to enhance accuracy of the solutions within proximity of the thin deformable body. Hence

In this study, the effect of the free surface on the supercavitating flow that surrounds a low aspect ratio wedge-shaped hydrofoil is studied based on computational fluid dynamics (CFD), with Cartesian cut-cell mesh method. The volume of fraction (VOF) method and the k - ε turbulence model with the Schnerr Sauer cavitation model are used for simulating the supercavitation in turbulent flow. Both quasi-3-D

The hydrodynamics and flow structures of a base wing slotted with tip sails in proximity to the ground were studied experimentally in order to investigate the flow control efficiency of wing tip sails in ground effect. The experiment was conducted in a towing tank at a Reynolds number 1.5×105. The lift and drag forces were measured by a transducer, the velocity fields of the wing tip vortices were

Cavitating bubbly flows can form in separated flows and shear layers leading to local regions high vapor void fraction, and these flows often exhibit periodic shedding of vaporous clouds. Historically, the presence of a liquid re-entrant flow, driven by the kinematics of liquid flow stagnation, has been identified as an important mechanism leading to cavity shedding. However, high local vapor void

In the present paper, the turbulent cavitating flow generated by a Clark-Y hydrofoil is investigated by large eddy simulation (LES) combined with Zwart-Gerber-Belamri (ZGB) cavitation model. In order to shed light on the influence of cavitation on turbulent energy distribution among scales, energy spectrum obtained from the three-dimensional velocity field is firstly applied to turbulent cavitating

To study the serious valve top gap cavitation of Datengxia high head single-lift ship lock, the 1:1 scale slice experiment is carried out, to truly reveal the gap flow characteristics, as well as the valve top gap cavitation characteristics and the anti-cavitation mechanism of natural aeration. Three kinds of cavitation, namely, the throat cavitation, the mainstream inner cavitation, and the valve

This paper presents an analytical model to solve the linear wave diffraction problem by arrays of bottom-mounted cylinders with arbitrary smooth cross-section. Based on the assumption of ideal fluid and potential theory, the unknown coefficients of total velocity potential can be solved by system of linear equations, which are obtained from the boundary conditions. The accuracy of the present method

The hydrodynamics in a straight open channel with a multiple-embayment groyne field was investigated using the detached-eddy simulation (DES). A series of short groynes were included on a 1:3 side slope of the channel. This work focuses on the turbulent coherent structures around groynes on an uneven bottom. Flows around groyne fields are characterized by massive separation and highly unsteady vortices

Tadpole swimming, including a solitary tadpole swimming and schooling side-by-side in an in-phase mode, is investigated numerically in the present paper. The three-dimensional Navier-Stokes equations for the unsteady incompressible viscous flow are solved. A dynamic mesh fitting the tadpole’s deforming body surface is adopted. The results showed that for a solitary tadpole swimming, two vortex rings

The wave transformation over slope topography is widely studied, but most of studies are for common coastal slopes. This paper presents an experimental study of 2-D regular and irregular wave transformations on a simplified coral reef with a steep slope of 1:5 and a horizontal reef flat, focusing on the characteristics of the waves that break on the reef flat. The analyzed results show that the estimates

The hydraulic characteristics in an open channel with vegetation are very important in controlling the environment pollution and restoring the river ecology. This paper studies the influence of the bed form and the vegetation patch density on the spatial velocity pattern. Rigid fiberglass circular cylinders are used to simulate the vegetation and a 3-D acoustic Doppler velocimeter (ADV) is used to

A novel air bubble lubrication method using the winged air induction pipe (WAIP) device is used to reduce the frictional drag of the hull of the ship and hence increase the efficiency of the propulsion system. This bubble lubrication technique utilizes the negative pressure region above the upper surface of the hydrofoil as the ship moves forward to drive air to the skin of the hull. In the present

This paper applies numerical methods to investigate the non-spherical bubble collapse near a rigid boundary. A three-dimensional model, with the mass conservation equation reformulated for considering the compressibility effect, is built to deal with the coupling between the pressure and the flow velocity in the momentum and energy equations and to simulate the temporal evolution of the single bubble

Wash waves produced by ships disintegrate river banks and coastal lines. This phenomenon of bank erosion is mainly due to the height of the waves. Various factors govern the formation of these waves and their amplitudes: the geometry of the water channel, the shape and the speed of the boat, etc.. These factors play an important role on the wave generation, in addition on the resistance of the ship

This paper studies the 3-D turbulent channel flows over rough walls with stochastic roughness height distributions by using the large eddy simulation and the immersed boundary method. The obtained mean and fluctuating velocity profiles for the smooth and rough channel flows agree well with the available numerical and experimental results. The stochastic surface roughness is found to have a more significant

Cavitating flows are dominated by large gradients of physical properties and quantities containing complicated interfacial structures and lots of multi-scale eddies that need to be accurately characterized using a high-resolution mesh. The present work, within OpenFOAM, proposes an effective modeling framework using the large eddy simulation (LES) approach along with the volume of fluid (VOF) method

The flow structure and geomorphology of rivers are significantly affected by vegetation patterns. In the present study, the effect of vegetation in the form of discontinuous and vertically double layered patches particularly on the resulting flow turbulence was examined computationally in an open channel. A k-ɛ model was implemented in this research work which was developed using 3-D numerical code

The importance of properly treating boundary conditions (BCs) in numerical simulation of hemodynamics in intracranial aneurysm (IA) has been increasingly recognized. In this study, we constructed three types of computational model for each IA to investigate how the outcome of numerical simulation is affected by the treatment of BCs. The first type of model (i.e., Type-A model) was obtained by applying

This paper studies the unsteady three-dimensional cavitating turbulent flow in a jet pump. Specifically, thefocus is on the unstable limited operation stage, and both the computational and experimental methods are used. In the experiments, the distribution of the wall pressure, as well as the evolution of cavitation over time, are obtained for a jet pump. Computation is carried out using the large

In this paper, a novel numerical wave-current flume is implemented based on the Smoothed Particle Hydrodynamics (SPH) method. The proposed flume is more stable and computationally efficient than conventional ones because it cancels wave paddles or sponge layers while using a non-reflective open boundary condition to simultaneously generate and absorb waves and currents. Numerical tests of nonlinear

A reliable numerical tool for the prediction of the parametric roll is important in the development of the second generation intact stability criteria. The main difficulty of the prediction of the parametric roll comes from the significant coupling of the roll with other motions, especially the heave and pitch motions. In this paper, the numerical method for determining the parametric roll is studied

In view of the supercavitation effect, a novel device named the rotational supercavitating evaporator (RSCE) has been designed for the desalination. In order to improve the blade shape of the rotational cavitator in the RSCE for the performance optimization, the blade shapes of different sizes are designed by utilizing the improved calculation method for the blade shape and the validated empirical