When constructing a low-noise submarine, it is crucial to consider the non-cavitating noise from the propeller. Non-cavitating noise reduction is crucial for submarine stealth and survivability. Recently, several stud...
详细信息
When constructing a low-noise submarine, it is crucial to consider the non-cavitating noise from the propeller. Non-cavitating noise reduction is crucial for submarine stealth and survivability. Recently, several studies have been conducted on the use of flexible propellers as a means of reducing non-cavitating noise. However, there are no studies on the use of flexible propellers with adaptive charac-teristics to reduce noise in wake fields. Thus, this study investigated the noise reduction effect of adaptive characteristics on non-cavitating noise for the flexible propeller in the wake field. Numerical in-vestigations on the main propeller variables were conducted based on the proposed procedure using fluid-structure interaction and acoustic analysis models. The results were compared with those of rigid propellers to determine the possible reasons for noise reduction. Finally, the acoustic analysis results of the flexible propeller were compared with those of the rigid propeller to reveal the effectiveness of the adaptive characteristics.& COPY;2023 Society of Naval Architects of Korea. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://***/licenses/by-nc-nd/4.0/).
Despite promising experimental works, high fidelity numerical simulations of chordwise flexible blade are useful to better understanding. However, such simulation remains a challenging problem as it requires a fluid- ...
详细信息
Despite promising experimental works, high fidelity numerical simulations of chordwise flexible blade are useful to better understanding. However, such simulation remains a challenging problem as it requires a fluid- structureinteraction (FSI) solver capable of accurately predicting the stall dynamics, while computing the deformation of a solid with complex geometry. In this paper, the authors propose a LES-based FSI solver using 3D solid elements for the solid and unstructured grid for fluid and solid solvers. This approach aims at being universal and is based on a partitioned coupling scheme, allowing low density ratios of the structure to the fluid. It uses an original pseudo-solid method for the mesh movement solving, specifically developed for this work. Besides, this solver is suited for massively parallel computing and can perform Dynamic Mesh Adaptation to be able to take into account any solid movement. Both fluid and solid solvers are validated independently before validation of the FSI solver against a 2D laminar benchmark, including mesh convergence study. The entire methodology is then successfully applied to experimental 3D complex case with high Reynolds number, confirming the potential of the FSI solver for its intended use, without geometry restriction. This is finally illustrated with a simulation of an experiment involving a chordwise flexible blade with large deformation, which has never been reproduced with a 3D LES approach in literature so far.
While students may find spline interpolation quite digestible based on their familiarity with the continuity of a function and its derivatives, some of its inherent value may be missed when they only see it applied to...
详细信息
While students may find spline interpolation quite digestible based on their familiarity with the continuity of a function and its derivatives, some of its inherent value may be missed when they only see it applied to standard data interpolation exercises. In this paper, we offer alternatives in which students can qualitatively and quantitatively witness the resulting dynamical differences when objects are driven through a fluid using different spline interpolation methods. They say that seeing is believing;here we showcase the differences between linear and cubic spline interpolation using examples from fluid pumping and aquatic locomotion. Moreover, students can define their own interpolation functions and visualize the dynamics that unfold. To solve the fluid-structure interaction system, the open-source fluid dynamics software IB2d is used. In that spirit, all simulation codes, analysis scripts, and movies are provided for streamlined use.
In this manuscript a POD-Galerkin based Reduced Order Model for unsteady fluid-structure interaction problems is presented. The model is based on a partitioned algorithm, with semi-implicit treatment of the coupling c...
详细信息
In this manuscript a POD-Galerkin based Reduced Order Model for unsteady fluid-structure interaction problems is presented. The model is based on a partitioned algorithm, with semi-implicit treatment of the coupling conditions. A Chorin-Temam projection scheme is applied to the incompressible Navier-Stokes problem, and a Robin coupling condition is used for the coupling between the fluid and the solid. The coupled problem is based on an Arbitrary Lagrangian Eulerian formulation, and the Proper Orthogonal Decomposition procedure is used for the generation of the reduced basis. We extend existing works on a segregated Reduced Order Model for fluid-structure interaction to unsteady problems that couple an incompressible, Newtonian fluid with a linear elastic solid, in two spatial dimensions. We consider three test cases to assess the overall capabilities of the method: an unsteady, non-parametrized problem, a problem that presents a geometrical parametrization of the solid domain, and finally, a problem where a parametrization of the solid's shear modulus is taken into account.
With higher demand of affordable electricity and rapid development of wind turbine technology, scale of wind turbines has been upsizing. As a consequence, blades grow longer and slender. Large geometrically nonlinear ...
详细信息
With higher demand of affordable electricity and rapid development of wind turbine technology, scale of wind turbines has been upsizing. As a consequence, blades grow longer and slender. Large geometrically nonlinear deformation and vibration of the blades lead to more challenges in the structural design. In the aerodynamic analysis, traditional blade element momentum theory cannot predict the complicated behavior of these modern blades while fully resolved Navier-Stokes equation methods cost much time modeling and refinement. To overcome these challenges, this paper proposes a new numerical method to analyze turbine aeroelastic performance and fluid-structure interaction based on flexible multibody dynamics and large eddy simulation with anisotropic actuator line method. By comparing the results with various existing numerical methods, we show that the newly proposed method can effectively predict the performance of the wind turbine, such as deformation and power output. We find that blade flexibility poses noticeable impact on the performance of large scale turbines in normal working conditions. The location of nascent vortex is postponed by blade deflection. The max difference between rigid and flexible blades in downstream velocity distributions reaches 10% and occurs at a radial distance around 0.55D. The new method also takes the fluid- structure coupling effect and momentum interaction into consideration and eliminates the non-physical oscillations caused by uncoupled methods. Also, blades deflection and vibration are found to accelerate momentum exchange, which facilitates the wake recovery process. Furthermore,compared to the rigid-blade model, the turbulent kinetic energy obtained by the newly developed flexible-blade model is higher in the lowfrequency region, in which large-scale vortices develop and the turbulent mixing effect is strong. This paper is expected to provide a framework for researchers and technology developers to design or estimate the per
In this study, a moderately flexible rotor is investigated experimentally in a water channel. The rotor consists of a single blade with a simplified rectangular geometry and is tested with various pitch angles at diff...
详细信息
In this study, a moderately flexible rotor is investigated experimentally in a water channel. The rotor consists of a single blade with a simplified rectangular geometry and is tested with various pitch angles at different rotational speeds. The flapwise bending deformation and induced torsion of the blade are measured using image processing tools, and flow fields are extracted with Particle Image Velocimetry. The blade deformation behaviour depends strongly on the pitch angle, it includes extreme downstream and upstream bending for high negative and positive pitch, respectively. In addition, large-amplitude, low-frequency bending fluctuations are observed in a certain range of rotational speeds for negative pitch. The wake vorticity fields show large-scale recirculation zones being formed and intermittently shed behind the rotor, resembling the dynamics of the Vortex Ring State known from helicopter aerodynamics. A comparison with the flow generated by a rigid rotor of the same geometry is also carried out. (C) 2021 Elsevier Ltd. All rights reserved.
In this work, an explicit velocity correction-based Immersed Boundary-Hybrid Lattice Boltzmann Flux Solver (IBHLBFS) is developed for fluid-structure interaction (FSI) problems with large solid deformation in twodimen...
详细信息
In this work, an explicit velocity correction-based Immersed Boundary-Hybrid Lattice Boltzmann Flux Solver (IBHLBFS) is developed for fluid-structure interaction (FSI) problems with large solid deformation in twodimensional. The fluid domain is solved by the Lattice Boltzmann Flux Solver (LBFS) while the solid domain is solved by the Smoothed Point Interpolation Method (S-PIM). For coupling the two methods, the Explicit Velocity Correction (EVC) is developed and applied to both the fluid and the solid by implementing the Immersed Boundary Method (IBM). The fluid domain in IB-HLBFS can be discretized with non-uniform mesh so that the efficiency is improved meanwhile the accuracy is ensured compared with the original Lattice Boltzmann Method (LBM). Moreover, the explicit velocity correction simplifies the matrix inversion in the Implicit Velocity Correction (IVC) hence the efficiency is further improved. To show the advantages and the reliability of the present IB-HLBFS, the numerical simulations of flow past the elastic beam, flow past a circular cylinder with a flexible beam behind, and swimming of a self-propelled fishlike body are given to show the application of IBHLBFS in FSI with complex fluid dynamics and large solid deformation. The results indicate that the present method is advantageous in terms of efficiency and accuracy, and has a wide prospect in engineering applications as well.
The fluid-structure interaction in collapsible thin-walled vessels is an important topic of research to better understand the physical mechanisms behind many physiological processes and diseases. In this work, we esta...
详细信息
The fluid-structure interaction in collapsible thin-walled vessels is an important topic of research to better understand the physical mechanisms behind many physiological processes and diseases. In this work, we established an experimental setup to study the collapsible tube deformation and fluid-structure interaction within a thin-walled collapsible vessel. The effects of transmural pressure and flow rate were characterized experimentally using high-frequency pressure transducers and optical measurements. Various transmural pressures were also simulated through finite element analysis. Results suggest that the deformation of thin-wall vessel follows the pattern described by Shapiro’s tube law. The collapsed pattern and cross-sectional area changes with different transmural pressure and flow pressure gradients. Below a certain negative transmural pressure threshold, we observed self-induced oscillations whose frequency and magnitude are functions of flow rates. The critical non-dimensional parameter thresholds for self-induced oscillation and the related fluid flow behaviors were examined using Particle Image Velocimetry.
In this work,we propose a formulation based on the Polygonal Discontinuous Galerkin(PolyDG)method for contact mechanics that arises in fluid-structure interaction *** particular,we introduce a consistent penalization ...
详细信息
In this work,we propose a formulation based on the Polygonal Discontinuous Galerkin(PolyDG)method for contact mechanics that arises in fluid-structure interaction *** particular,we introduce a consistent penalization approach to treat the frictionless contact between immersed structures that undergo large *** key feature of the method is that the contact condition can be naturally embedded in the PolyDG formulation,allowing to easily support polygonal/polyhedral *** proposed approach introduced a fixed background mesh for the fluid problem overlapped by the structure grid that is able to move independently of the fluid *** assess the validity of the proposed approach,we report the results of several numerical experiments obtained in the case of contact between flexible structures immersed in a fluid.
A numerical model based on the Nodal Position Finite Element Method (NPFEM) is proposed in this work for fluid-structure interaction (FSI) analysis of moored bodies subject to multiphase free surface flows. The semiim...
详细信息
A numerical model based on the Nodal Position Finite Element Method (NPFEM) is proposed in this work for fluid-structure interaction (FSI) analysis of moored bodies subject to multiphase free surface flows. The semiimplicit CBS (Characteristic-Based Split) method is utilized here for discretization of the flow fundamental equations in the context of the Finite Element Method, where linear tetrahedral elements are adopted. Turbulence is analyzed using Large Eddy Simulation (LES) with the dynamic sub-grid scale model and the Level Set method is utilized for simulation of multiphase free surface flows. The structural system is modeled using a threedimensional rigid body approach for the floating object, while the mooring is discretized using a geometrically nonlinear cable formulation based on the NPFEM. A partitioned coupling scheme is adopted for fluid-structure interaction analysis taking into account the fluid-structure and cable-structure couplings, where the flow equations are kinematically described employing an Arbitrary Lagrangean-Eulerian (ALE) formulation with a numerical scheme for mesh motion. The algorithms constituting the numerical model are verified first considering classical applications on fluid dynamics and FSI, in addition to applications involving the dynamic analysis of cables. Finally, problems involving floating bodies with and without mooring are simulated to demonstrate the applicability and accuracy of the proposed numerical model.
暂无评论