水下航行体湍流数值模拟方法研究进展综述

In this paper,we present an overview of numerical simulation methods for the flow around typical underwater vehicles at high Reynolds numbers,which highlights the dominant flow structures in different regions of interest.This overview covers the forebody,midbody,stern,wake region,and appendages and summarizes flow phenomena,including laminar-to-turbulent transition,turbulent boundary layers,flow under the influence of curvatures,wake interactions,and all associated complex vortex structures.Furthermore,the current issues and challenges of capturing these flow structures are addressed.This overview provides a deep insight into the use of numerical simulation methods,including the Reynolds-averaged Navier–Stokes(RANS)method,large eddy simulation(LES)method,and the hybrid RANS/LES method,and evaluates their applicability in capturing detailed flow features.

Application Progress of Computational Fluid Dynamic Techniques for Complex Viscous Flows in Ship and Ocean Engineering

Complex flow around floating structures is a highly nonlinear problem,and it is a typical feature in ship and ocean engineering.Traditional experimental methods and potential flow theory have limitations in predicting complex viscous flows.With the improvement of high-performance computing and the development of numerical techniques,computational fluid dynamics(CFD)has become increasingly powerful in predicting the complex viscous flow around floating structures.This paper reviews the recent progress in CFD techniques for numerical solutions of typical complex viscous flows in ship and ocean engineering.Applications to free-surface flows,breaking bow waves of high-speed ship,ship hull-propeller-rudder interaction,vortexinduced vibration of risers,vortex-induced motions of deep-draft platforms,and floating offshore wind turbines are discussed.Typical techniques,including volume of fluid for sharp interface,dynamic overset grid,detached eddy simulation,and fluid-structure coupling,are reviewed along with their applications.Some novel techniques,such as high-efficiency Cartesian grid method and GPU acceleration technique,are discussed in the last part as the future perspective for further enhancement of accuracy and efficiency for CFD simulations of complex flow in ship and ocean engineering.

Review:Recent Development of High⁃Order⁃Spectral Method Combined with Computational Fluid Dynamics Method for Wave⁃Structure Interactions

The present paper reviews the recent developments of a high⁃order⁃spectral method(HOS)and the combination with computational fluid dynamics(CFD)method for wave⁃structure interactions.As the numerical simulations of wave⁃structure interaction require efficiency and accuracy,as well as the ability in calculating in open sea states,the HOS method has its strength in both generating extreme waves in open seas and fast convergence in simulations,while computational fluid dynamics(CFD)method has its advantages in simulating violent wave⁃structure interactions.This paper provides the new thoughts for fast and accurate simulations,as well as the future work on innovations in fine fluid field of numerical simulations.

Vortex identification methods in marine hydrodynamics

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/RortexΩR method are utilized for vortex identification for propeller open water test,ship drag test,ship propeller-rudder interaction,VIV of a marine riser and VIM of a Spar platform.The limitation of Q andλ2-criterion is discussed.The Liutex/RortexΩR method is promising for convenient and accurate vortex identification and visualization.However,care should be taken when choosing the small parameter b0 forΩR.We proposed recommended values of b0 for marine hydrodynamic problems.

Numerical Simulations of Liquid-Solid Flows in A Vertical Pipe by MPS-DEM Coupling Method

In the process of deep-sea mining,the liquid-solid flows in the vertical transportation pipeline are very complex.In the present work,an in-house solver MPSDEM-SJTU based on the improved MPS and DEM is developed for the simulation of hydraulic conveying.Firstly,three examples including the multilayer cylinder collapse,the Poiseuille flow and two-phase dam-break are used to validate the precision of the DEM model,the pipe flow model and MPS-DEM coupling model,respectively.Then,the hydraulic conveying with coarse particles in a vertical pipe is simulated.The solid particle distribution is presented and investigated in detail.Finally,the coupling method is successfully applied for the simulation of the liquid-solid flows in a vertical pipe with rotating blades,which shows the stability of the solver under rotating boundary conditions.This fully Lagrangian model is expected to be a new approach for analyzing hydraulic conveying.

Overview of Moving Particle Semi-implicit Techniques for Hydrodynamic Problems in Ocean Engineering

With the significant development of computer hardware,many advanced numerical techniques have been proposed to investigate complex hydrodynamic problems.This article aims to provide a detailed review of moving particle semi-implicit(MPS)techniques and their application in ocean and coastal engineering.The achievements of the MPS method in stability and accuracy,boundary conditions,and acceleration techniques are discussed.The applications of the MPS method,which are classified into two main categories,namely,multiphase flows and fluid-structure interactions,are introduced.Finally,the prospects and conclusions are highlighted.The MPS method has the potential to solve practical problems.

MPS Method for Interaction Between Solitary Waves and Submerged Horizontal Plate

The interaction between structure and wave is a typical phenomenon in naval architecture and ocean engineering.In this paper,numerical simulation is carried out to study the interaction between a two-dimensional submerged,fixed,horizontal rigid plate and solitary wave with our in-house meshless particle CFD solver MLParticle-SJTU.First,the in-house CFD solver is verified by experimental results conducted at the State Key Laboratory of Coastal and Offshore Engineering,Dalian University of Technology.During the verification,the plate is submerged under water and the solitary wave with a given amplitude is generated by a piston-type wave maker.Free surface elevation of the wave and the pressure impacting on the plate is recorded and compared with experimental data respectively.The predicted pressure and surface elevation agree well with the experimental results.Then in order to further investigate factors affecting wave-structure interaction,wave height,submerged depth and plate length are analyzed.

Numerical investigation of the coupled aero-hydrodynamic performances of a semi-submersible floating offshore wind turbine with inclined columns

Numerical investigations of floating platforms with different outer column inclined angles under two operating conditions of regular wave and irregular wave are presented in this paper.A coupled aero-hydrodynamic computational fluid dynamics in-house solver FOWT-UALM-SJTU is applied for the calculation.First,the validation for wave and wind generation are conducted to determine mesh distribution strategy.Based on these,the hydrodynamic motion response,aerodynamic performance and wake flow are analyzed to explore the impact of inclined angle.Conduct spectral analysis on the motion response under wave action,discuss the aerodynamic attack angle and inflow wind velocity along the blade spanwise direction in detail,reveal different trends in wake development and recovery.The results show that for the regular wave condition with the increase of inclined angles,the equilibrium position of surge motion is constantly rising,while pitch is decreasing.The maximum root mean square(rms)value occurs at angle=30°,compared with the original OC4 FOWT,the rms in power and thrust increase 0.35%,0.71%.And there are two low regions of attack angle and high regions of axial inflow velocity,corresponding to aerodynamic loads.The spectral analysis indicates that the natural frequency of pitch motion will increase with inclined angle.Besides,from the middle to far region of wake flow,the velocity recovery of FOWT with inclined angle will become faster,which is beneficial for downstream turbines to enhance more wind energy.

Numerical study of air cavity characteristics of bow wave breaking of KCS ship under different speeds

Ship bow wave breaking contains complex flow mechanism,which is very important for ship performance.In this study,a practical numerical simulation scheme for bow wave breaking is proposed and the scheme is applied to the simulation of bow wave breaking of KCS ship model with Fr=0.26,0.30,0.35,0.40,analyzing the impact of speed on the bow wave breaking.The results indicate that an increase in speed leads to a significant rise in viscous pressure resistance and more pronounced bow wave breaking.Moreover,it is found that the traditional wave height function in OpenFOAM is not suitable for detailed studies of bow wave breaking.This study extracts different free surfaces through top and bottom views to further analyze the free surface overturning,droplet splashing,and cavity entrainment in bow wave breaking.Additionally,the spatial and temporal distribution of cavities at Fr=0.40 is analyzed,revealing that cavity distribution is closely related to vortex structures and exhibits a periodic pulsation characteristic of approximately 12 s.

Numerical simulation of liquid sloshing in a spherical tank by MPS method

This paper investigates the sloshing phenomena in a spherical liquid tank using the moving particle semi-implicit(MPS)method,a crucial study in fluid dynamics.Distinct from previous research focused on rectangular or LNG tanks,this work explores the unique motion patterns inherent to spherical geometries.The accuracy of our in-house MPS solver MLParticle-SJTU is validated against experimental data and finite volume method(FVM).And the MPS method reveals a closer alignment with experimental outcomes,which suggests that MPS method is particularly effective for modeling complex,non-linear fluid behaviors.Then the fluid’s response to excitation at its natural frequency is simulated,showcasing vigorous sloshing and rotational motion.Detailed analyses of the fluid motion are conducted by drawing streamline diagrams,velocity vector diagrams,and vorticity maps.The fluid’s motion response is explored using both time-domain and frequency-domain curves of the fluid centroid,as well as the sloshing force.

Numerical analysis of coupled sloshing and motion of a cylindrical FPSO in regular waves

In this paper,the coupled sloshing and motion characteristics of a cylindrical floating production storage offloading(CFPSO)are numerically investigated by means of computational fluid dynamics(CFD)tool.The simulations are performed using an in-house CFD solver naoe-FOAM-SJTU which is developed based on OpenFOAM.The active wave generating-absorbing boundary condition(GABC)is utilized for wave generation and absorption.The stabilized k-omega SST turbulence model are used to avoid excessive eddy viscosity near the free surface.CFPSO with and without partially filled liquid tanks in regular waves with different wave periods are simulated and vertical planar motions such as surge,heave and pitch response amplitude operators(RAOs)are compared.Forces due to liquid sloshing and wave loads are extracted and analyzed.The free surface motions inside liquid tanks in one wave period presented to explain the motion characteristics.

Numerical analysis of the correlation between fluid dynamic modes and hydrodynamic noise in flows around a three-dimensional circular cylinder

The flow around a circular cylinder for Re=1000 is characterized by flow separation and Karman vortex street.The typical flow features can be captured to study the correlation between fluid fields and sound fields.In this paper,the three-dimensional circular cylinder is taken as the research object,and the probes of surface fluctuating pressure and far field sound pressure are arranged every 10°.The directional diagram and the coherence of fluctuating pressure and sound pressure are analyzed.The relationship between the flow mode and hydrodynamic noise is studied by using dynamic mode decomposition(DMD).The characteristics of the dipole and quadrupole sound source term of a long span cylinder are studied.The results show that at the angles between 30°–120°and 190°–350°,the fluctuating pressure contributes more to the generation of dipole sounds.The quadrupole sound source shows three-dimensional effects,which is more obvious in a cylinder with large spanwise length.

Spectral and statistical analysis of bow wave breaking characteristics of KCS ship

Bow wave breaking is a common phenomenon during ship navigation,especially at a high speed,involving complex physical mechanism such as interface mixing,air entrainment,and jet splashing.This study uses the delayed detached eddy simulation(DDES)turbulence model on the OpenFOAM platform to simulate flow around a KRISO Container Ship(KCS)model for a Froude number of 0.35,examining trim angles of 0°,0.5°,1°.This paper analyzes the statistical and power spectral density(PSD)characteristics of bow wave heights.The analysis shows root mean square(rms)and mean difference between top and bottom views indicate wave breaking.As the trim angle increases,peaks of rms in the bottom view become much higher than that in the top view,reaching 38%at 1°.PSD analysis reveals that resistance and wave height periods differ by no more than 5%,with small-scale structures like jetting and splashing causing non-dominant periodic and high-frequency wave height variations.

Flow characteristics and bubble statistics during the fragmentation process of the ingested main cavity in plunging breaking waves

Plunging breaking waves play an important role in the exchange of heat,momentum,and mass between the atmosphere and ocean.In this paper,a series of direct numerical simulations is conducted to investigate the fragmentation process of the ingested main cavity in plunging breaking waves.The two-phase Navier-Stokes equations are solved using the finite-volume method based on adaptive refinement meshes.The free surface is captured using a geometrical volume of fluid method.Both 2-D,3-D simulations are conducted.Instantaneous flow fields at different stages of wave breaking are presented and quantitative analysis for bubbles is performed.The 2-D instantaneous vorticity field and local velocity field are visualized to discuss the general flow characteristics during the fragmentation process.Then a 2-D parametric study is conducted to investigate the differences in the flow characteristics during the fragmentation process under different wave parameters including initial wave steepness(ε),Bond number(Bo),and Reynolds number(Re).3-D vortex structures are shown to further investigate the mechanisms behind the differences in the flow characteristics.The bubble size distributions under two different initial wave steepness are also discussed with their relationship to the fragmentation process of the ingested main cavity.This research offers a significant understanding of the distinct procedures and fundamental dynamics involved in wave breaking,enhancing our comprehension of this intricate event.

An overview of flow field computational methods for hydrodynamic noise prediction

Recently,the hydrodynamic noise is becoming a research hotspot because it not only affects the concealment and comfort of ships,but also affects the living condition of underwater mammals.Accurate prediction of hydrodynamic noise requires that the detailed flow field has been simulated temporally and spatially with high fidelity method.In this paper,we introduce the current issues and challenges for the prediction of hydrodynamic noise,and provide an overview to several detailed flow field simulation methods which aim to resolve these issues.The overview could point the future directions for hydrodynamic noise prediction.

Vortex tuning of a submarine by Liutex force field model

Vortical structures of a submarine with appendages are fully turbulent and complex.Thus,flow control and vortex manipulation are of great importance for the hydrodynamic performance and acoustic characteristics.Take the generic submarine model DARPA Suboff as the test case,a vortex tuning method based on the Liutex force field is proposed to manipulate the vorticity field.Viscous flow past the submarine model in straight-line motion at a Reynolds number of 1.2×107 is achieved by solving the Reynolds averaged Navier-Stokes(RANS)equations.Multi-block structured mesh topology is used to discretize the computational domain,and the shear stress transport(SST)k-ωturbulence model is implemented to close the equations.The control of vortex is achieved by introducing additional source terms based on Liutex vortex definition and identification system to the RANS equations.The resistance acting on the submarine,flow field as well as the vortical structures are compared and analyzed.Results show that Liutex force model can effectively reduce the resistance by 9.31%and change the vortical structures apparently.

Wall-modeled large eddy simulation for the flows around an axisymmetric body of revolution

The flow around an axisymmetric body of revolution(DARPA SUBOFF bare model)at Re=1.2×10^(7)is numerically investigated using the wall-modeled large eddy simulation(WMLES).To evaluate the capabilities of WMLES in such wall-bounded turbulent flows,the effects of the wall stress model and sampling distance are systematically studied.The numerical results of the non-equilibrium wall stress model with an appropriate sampling distance are in good agreement with the experiments in terms of pressure coefficient,skin-friction coefficient,and drag coefficient.On this basis,the thickening of the turbulent boundary layer and the expansion of the wake can be clearly observed through flow visualization,especially using the Liutex vortex identification method.

Assessment of subgrid-scale models in wall-modeled large-eddy simulations of turbulent channel flows

Considering the demanding of grid requirements for high-Reynolds-number wall-bounded flow,the wall-modeled large-eddy simulation(WMLES)is an attractive method to deal with near wall turbulence.However,the effect of subgrid-scale(SGS)models for wall-bounded turbulent flow in combination with wall stress models is still unclear.In this paper,turbulent channel flow at Reτ=1000 are numerically simulated by WMLES in conjunction with four different SGS models,i.e.,the wall-adapting local eddy-viscosity model,the dynamic Smagorinsky model,the dynamic SGS kinetic energy model and the dynamic Lagrangian model.The mean velocity profiles are compared with the law of the wall,and the velocity fluctuations are compared with direct numerical simulation data.The energy spectrum of velocity and wall pressure fluctuations are presented and the role of SGS models on predicting turbulent channel flow with WMLES is discussed.

Numerical simulations of faraday waves in cylindrical and hexagonal tanks based on MPS method

When a partially loaded liquid container vibrates along the vertical direction,the liquid inside will oscillate regularly,which is called Faraday wave.In some cases,the wave form of the Faraday wave is stable and smooth,and sometimes there is violent wave breaking and liquid splashing.In this paper,the Faraday waves inside the cylindrical tank and the hexagonal tanks are simulated by the in-house solver MLParticle-SJTU base on the moving particle semi-implicit(MPS)method.The surface tension model is used to better model the free surfaces with large deformations.Phenomena such as wave breaking and liquid splashing are well captured and simulated.The results show that the waveforms are significantly different at different excitation frequencies.And the tank shape also has an obvious effect on the waveform.

Numerical investigations of focused wave interact with a moving cylinder

This paper presents a numerical study on focused wave and current interactions with a cylinder.The cylinder is moving in the opposite direction to the wave propagation.An effective computational decomposition method is adopted to reduce the calculation resources.A potential solver high-order spectral(HOS)method is applied to generate focused wave field,while our in-house computational fluid dynamics(CFD)solver naoe-FOAM-SJTU with overset grid takes the charge of achieving the viscous effect around the moving cylinder.The viscous domain moving with the cylinder thus the size and mesh grids in computational domain is greatly reduced.The pressure on cylinder surface and wave fields around cylinder are compared with experimental data,shows a well agreement.Meanwhile,the scattering wave field and vortex shedding are discussed.With the existence of moving cylinder,the classical scattering wave types are still observed.