Fluid-solid Interaction Model Research Articles

Contact status between seal ring and its support: crucial factor in hydrostatic mechanical face seal

PurposeThis paper aims to investigate the influence of the contact status between the seal ring and its support on the seal performance in hydrostatic mechanical face seal.Design/methodology/approachA thermal fluid-solid interaction (TFSI) model of hydrostatic mechanical face seal is further developed, in which the multi-body contacts between components are particularly given more attention. The numerical models of the flow field and complete seal assemblies are developed. A specific energy equation is obtained to simplify the calculation of film temperature. Based on the mechanism for the continuity condition of the physical quantities at the fluid–solid interface, the TFSI model uses an on-line iterative coupling method.FindingsThe contact status between seal ring and its support affects the seal performance significantly. The rotating ring and the stationary ring contribute differently because of the contact status difference.Originality/valueThe contact status between the seal ring and the ring seat is key to gain an insight into the performance of the hydrostatic mechanical face seal thus provides guidance for mechanical seal design.

Analysis of surface erosion of cohesionless soils using a three-dimensional coupled computational fluid dynamics – discrete element method (CFD–DEM) model

A fluid–solid interaction model has been implemented by coupling two numerical methods — computational fluid dynamics (CFD) and discrete element method (DEM) — that capture the mesoscale behaviors of the fluid–solid system. The model is first validated by comparing the results of simulations with two types of experiments: free settling of a single sphere in water and formation of angle of repose of particles under water, which show its capability in modeling the behaviors of both particle phase and fluid phase. The verified model is then used to study factors affecting the soil erodibility, where case studies are designed for soil particles deposited inside a pipe and subsequently subjected to water flow–induced surface erosion. Influencing factors for soil erodibility, including particle diameter and interparticle bond, are analyzed. For cohesionless soils without bond strength, the critical shear stress is found to be linearly related to particle size; while for soils with bond strength, simulation results show that interparticle bonding largely decelerates the erosion process and causes a much lower erosion rate. To further the understanding of soil surface erosion under turbulent flow, the “k–ε” turbulence model has been successfully implemented for the fluid phase. Comparison between the laminar model and the turbulence model shows turbulence significantly accelerates the erosion process.

Review of peridynamics for multi-physics coupling modeling

Generally, peridynamics is a theory focusing on the evolution of a physical system, which is based on the assumption that each material point interacts with the other material points within a certain domain through non-contact or nonlocal interactions. It provides a unified mathematical framework for analyzing problems involving the evolving discontinuities and nonlocality. After a brief introduction of the peridynamic solid models and the urgent requirements on multi-physics models and corresponding commercial software, which have the capability of dealing with the evolving discontinuities, we made a systematic review on peridynamic nonlocal diffusion and peridynamic multi-physics coupled modeling. It can be found that the existing multi-physics coupled modeling studies mostly concentrated on the problems in the electronic components, electronic packaging and geotechnical engineering fields, including the un-coupled, partial coupled and fully coupled models about thermo-mechanics, hygro-thermo-mechanics, thermo-oxidative, thermo-mechanics-oxidative, mechanics-electronics, thermo-electronics, thermo-mechanics-electronics, fluid-solid interaction model for porous medium. Finally, several potential problems in the theoretical model, numerical algorithm and engineering application of peridynamic diffusion modeling and multi-physics coupled modeling are suggested.

A 3D fluid-solid interaction model of the air puff test in the human cornea

We present a numerical model of a contactless test commonly used to assess the biomechanics of the human cornea. The test, consisting in a rapid air jet applied to the anterior surface of the cornea, is controversial. Although the numerous studies documented in the literature have not been able yet to clarify its relevance as a diagnostic tool, the test has the potential to be combined with inverse analysis procedures to characterize the parameters of numerical models of the cornea. With the final goal of employing the air puff test in advanced material identification algorithms, here we propose to model the cornea with standard finite elements and the fluids filling the anterior chamber of the eye with a meshfree discretization. The interaction between moving fluids and deforming cornea is accounted for by modifying the interface boundary conditions of both fluid and solid. The proposed model represents the first fully 3D example of an aqueous-cornea fluid-solid interaction analysis which uses a robust meshfree approach for the fluid. Although we restrict our scope to isotropic nonlinear materials, numerical results confirm the undeniable importance of including internal fluids in the simulation of the air puff test. Thus the proposed approach stands as a procedural paradigm for the identification of the mechanical parameters of the human cornea.

Novel coupled model for power loss prediction in a record-breaking electric aircraft motor

PurposeThe purpose of this paper is to devise an analytical approach to calculate conductor winding losses, considering multiple contributing aspects simultaneously. These include the geometric configuration of coil windings, frequency of the electric current and the dependency on the coil temperature, derived studying a coupled fluid–solid model considering the cooling system characteristics. The obtained results allow identifying power loss trends according to such system variables as coolant inlet temperature or overall flow rate of the motor.Design/methodology/approachAn easy-to-use coupled analytical approach is applied, which is suitable for rapid estimations of the impact of parameter variation on the resulting conductor winding power losses that facilitates decision-making in the design process of electric aircraft engines.FindingsIn the considered cooling parameters, the overall conductor winding power losses vary approximately between 6 kW and 7.2 kW. More than 95 per cent of this loss is because of direct current losses. These losses cause the variation in maximal coil temperature ranging between 115°C and 170°C.Practical implicationsThe SP260D motor is set and was currently tested in Extra 330. It recently broke two world records.Social implicationsOne of the current trends in aircraft engineering is electric aircraft. Advantages of electric aircraft include improved manoeuvrability because of greater torque from electric motors, increased safety because of decreased chance of mechanical failure, less risk of explosion or fire in the event of a collision and less noise. There will be environmental and cost benefits associated with the elimination of dependency on fossil fuels and resultant emissions.Originality/valueThe use of a novel fluid–solid interaction model for predicting conductor winding power loss of the SP260D electric aircraft motor has not been done earlier. A novel alternative derivation of the widely applied Dowell’s formula (Dowell, 1966) is presented for the estimation of proximity losses in square winding conductors.

Parametric Studies of Flat Plate Trajectories Using VIC and Penalization

Flying debris is generated in several situations: when a roof is exposed to a storm, when ice accretes on rotating wind turbines, or during inflight aircraft deicing. Four dimensionless parameters play a role in the motion of flying debris. The goal of the present paper is to investigate the relative importance of four dimensionless parameters: the Reynolds number, the Froude number, the Tachikawa number, and the mass moment of inertia parameters. Flying debris trajectories are computed with a fluid-solid interaction model formulated for an incompressible 2D laminar flow. The rigid moving solid effects are modelled in the Navier-Stokes equations using penalization. A VIC scheme is used to solve the flow equations. The aerodynamic forces and moments are used to compute the acceleration and the velocity of the solid. A database of 64 trajectories is built using a two-level full factorial design for the four factors. The dispersion of the plate position at a given horizontal position decreases with the Froude number. Moreover, the Tachikawa number has a significant effect on the median plate position.

Erosion mechanism of local scour around cushioned caisson on reinforced ground

ABSTRACTThe scour behavior of cushioned caisson constructed on reinforced ground, which is used to support superstructure constructed in deep water in seismic zones, was investigated by experimental and numerical methods. Flume tests under nine different flow velocities between 18 and 48 cm/s were performed based on hydraulic similarity design. Complementary numerical simulations were also conducted for the flow velocities ranging from 16 to 46 cm/s. Five typical working modes of the foundation under erosion, namely, ideal working, well working, edge failure, shear failure, and total failure, are analyzed together with their potential impacts on seismic-designed foundation. The critical shear stress, local flow structures, and streamlines were used as the key factors to analyze the change of bed materials and the scour characteristics. Fluid–solid interaction model was built by computational fluid dynamics with sediment transport model, and k–ε turbulent model has been implemented to describe the turbulence in the fluid phase typical of scour process. The mechanisms of two possible failure models for the foundation layer elements were identified, based on which recommendations were provided for scour protection to ensure the integrity and performance of seismic-designed foundations. The integrated computational model and model experiments also demonstrate a framework to understand the local scour mechanism for the cushioned caisson on reinforced ground.

A semi-analytical method to evaluate the dynamic response of functionally graded plates subjected to underwater shock

Functionally graded (FG) plates are of current interest and are widely used in a variety of applications including deep sea exploration and naval/marine and coastal engineering, despite the fact that there has, to date, been little research undertaken on the subject. In order to remedy the situation, an analytical method to investigate the elastic dynamic responses of FG plates to underwater shock is proposed here, their material properties varying by the same exponential law along the thickness direction. Taylor׳s one dimensional fluid solid interaction (FSI) model is extended to fit a three dimensional model suitable for FG plates. The extended FSI model and Laplace transform are integrated into the state space method, with the transient solution in the time domain being obtained by using the numerical inversion of the Laplace transform. The solutions of the total forces acting throughout the front and back faces in the time domain are derived for the first time. The present method is validated by comparing it with the results of other methods and experiments found in the relevant literature. The influence of the boundary conditions at the backside of the plate and FG parameters on front and back side pressures, cavitations, displacements, stresses and total forces acting throughout the faces are then investigated, with the time progression of the cavitation areas of air-backed plates and water-backed plates being investigated in detail. The method proposed in this paper may prove useful for the future three-dimensional assessment of the response of FG structures when FSI effects are taken into consideration. It is hoped that the results will lead to a full understanding of the mechanism of the interaction between fluid and an FG plate, and that they can be used as benchmark solutions in further research.

Simulation and modeling of friction for honed and wave-cut cylinder bores of marine engines

A fluid solid interaction model (FSI) developed for two different structural cylinder patterns in order to simulate the frictional performance of piston ring–cylinder liner systems for marine engines. Computational fluid dynamics (CFD) analysis is used to solve the Navier Stokes equations. A fully flooded inlet and outlet conditions are assumed taking into account the piston ring elasticity. Honing and wave-cut cylinder geometries were compared while the pressure distribution along the ring thickness and the lubricant film is determined for each crank angle. The present results demonstrate that the honed cylinder geometry improves the friction results increasing the oil film thickness. Further, the artificially textured piston rings with the honed cylinder liner were investigated. As a result, we propose the operational function between the textured rings with the modified cylinder liners in marine engines.

Thermal fluid-solid interaction model and experimental validation for hydrostatic mechanical face seals

Hydrostatic mechanical face seals for reactor coolant pumps are very important for the safety and reliability of pressurized-water reactor power plants. More accurate models on the operating mechanism of the seals are needed to help improve their performance. The thermal fluid-solid interaction (TFSI) mechanism of the hydrostatic seal is investigated in this study. Numerical models of the flow field and seal assembly are developed. Based on the mechanism for the continuity condition of the physical quantities at the fluid-solid interface, an on-line numerical TFSI model for the hydrostatic mechanical seal is proposed using an iterative coupling method. Dynamic mesh technology is adopted to adapt to the changing boundary shape. Experiments were performed on a test rig using a full-size test seal to obtain the leakage rate as a function of the differential pressure. The effectiveness and accuracy of the TFSI model were verified by comparing the simulation results and experimental data. Using the TFSI model, the behavior of the seal is presented, including mechanical and thermal deformation, and the temperature field. The influences of the rotating speed and differential pressure of the sealing device on the temperature field, which occur widely in the actual use of the seal, are studied. This research proposes an on-line and assembly-based TFSI model for hydrostatic mechanical face seals, and the model is validated by full-sized experiments.

Numerical Simulation of Impact Effect of Internal Gas Pressure on Chamber Housing in Low-Voltage Circuit Breaker

In this paper, the fluid-solid interaction model of the impact process of internal pressure in arc chamber on housing structure of low-voltage circuit breaker is established, including the computational fluid dynamic (CFD) module that can assess 3-D pressure distribution of internal gas flow in the arcing chamber and finite element module (FEM) to calculate the impact of high-pressure gas flow on the housing. Based on the CFD module, the internal pressure distribution under different breaking currents and venting conditions is simulated, in which the simulation results agree well with the experimental results. Then, based on the 3-D pressure distribution, through the 3-D FEM of housing impact, the dynamic stress and deformation of chamber housing are simulated and analyzed. By this method, the stress concentration region of arc chamber housing can be predicted, which can provide reference for structure optimization design of arc chamber. For the region where stress is concentrated, structural strength needs to be enhanced, which can effectively avoid rupture problems due to local excessive stress on the housing.

Numerical method to measure velocity integration, stroke volume and cardiac output while rest: using 2D fluid-solid interaction model

Article history: Received September 20, 2013 Received in Revised form October, 14, 2013 Accepted 9 February 2014 Available online 12 February 2014 Development of knowledge of cardiovascular diseases and treatments strongly depends on understanding of hemodynamic measurements. Hemodynamic parameters, therefore, have been investigated using simulation-based methods. A two-dimensional model was applied for seven healthy subjects with echo-Doppler at rest. Echocardiography imaging was also utilized to gain the geometry of the aortic valve. Fluid-Structure Interaction (FSI) model was carried out, coupling an Arbitrary Lagrangian-Eulerian mesh. Pressure loads were used as boundary conditions on the valve’s ventricular and aortic sides. Pressure loads used were the calculated brachial pressures plus differences between brachial, central and left ventricular pressures. The FSI model predicted the velocity integration, stroke volume and cardiac output over a range of heart rates while rest. Numerical results generally had a difference of 5.4 to 15.87% with Doppler results. Linear correlations between numerical and clinical approaches have been applied. This makes possible predictions achieved from the FSI model to be gained which are highly accurate (e.g. correlation factor r = 0.995, 0.990 and 0.990 for velocity integration, stroke volume and cardiac output, respectively). The obtained numerical results showed that numerical methods can be combined with clinical measurements to provide good estimates of patient specific hemodynamics for different subjects. © 2014 Growing Science Ltd. All rights reserved.

Numerical prediction on volumetric efficiency of progressive cavity pump with fluid–solid interaction model

Abstract Surface-driven progressive cavity pump (PCP) has been widely used as an effective artificial lift equipment in various oilfield productions. During the operation of PCPs, the problem of internal slip, which defines the pump performance in terms of volumetric efficiency and lifting capacity, always occurs. However, due to the complex geometrical structure and coupling interactions between the stator and the oil lifted, it is difficult to solve the volumetric efficiency analytically. In this study, we established a new finite element model of PCP, which consists of the stator, the rotor, the lifted fluid and the fluid–solid interaction. The controlling equations of solid deformation and fluid dynamics are solved using different solvers for solid domain and fluid domain respectively, and their results are exchanged through the fluid–solid interface. Partitioned solution algorithm is employed to tackle the problem of this two-way fluid–solid interaction. From our numerical simulation results, we found two leakage mechanisms: longitudinal slippage and transversal slippage. We took GLB500 PCP as a benchmark to validate our model and simulation method. Our computed volumetric efficiency of PCP with specified design parameters is consistent with experimental result of laboratory test. Furthermore, the model with fluid–structure interaction was used to compare the hydraulic characteristic curves of conventional and even-thickness PCPs and study the influence of different material and structure parameters on internal slip of PCP. The interference and stator thickness are found to be the two main factors influencing the volumetric efficiency, which can be used to optimize the design of PCP for specified purpose.

An Analytical Method for Evaluating the Dynamic Response of Plates Subjected to Underwater Shock Employing Mindlin Plate Theory and Laplace Transforms

It is often in the interest of a designer to know the transient state of stress in a plate subjected to an underwater explosion. In this paper, an analytical method based on Taylor’s fluid-solid interaction (FSI) model, Mindlin plate theory, Laplace transform, and its inversion is proposed to examine the elastic dynamic response of a plate subjected to an underwater explosion. This analytical method includes shear deformation, the moments and membrane stress in the plate, and the FSI effect and considers a full profile of possibilities. The results of the response-time histories and the response distribution on the plate in terms of displacements and stresses from the analytical method are compared with finite element analysis (FEA) to validate this method, and the comparison indicates good agreement. Comparison of the acceleration at the center of an air-backed plate between the analytical method and the experiment from relevant literature, shows good agreements, and the analytical method and its FSI model are validated. The influence of the FSI is investigated in detail. All extreme values of the response-time histories decrease as the thickness increases for the non-FSI case. The results can be used as benchmark solutions in further research.

Fluid-solid interaction model for hydraulic reciprocating O-ring seals

Elastohydrodynamic lubrication characteristics of hydraulic reciprocating seals have significant effects on sealing and tribology performances of hydraulic actuators, especially in high parameter hydraulic systems. Only elastic deformations of hydraulic reciprocating seals were discussed, and hydrodynamic effects were neglected in many studies. The physical process of the fluid-solid interaction effect did not be clearly presented in the existing fluid-solid interaction models for hydraulic reciprocating O-ring seals, and few of these models had been simultaneously validated through experiments. By exploring the physical process of the fluid-solid interaction effect of the hydraulic reciprocating O-ring seal, a numerical fluid-solid interaction model consisting of fluid lubrication, contact mechanics, asperity contact and elastic deformation analyses is constructed with an iterative procedure. With the SRV friction and wear tester, the experiments are performed to investigate the elastohydrodynamic lubrication characteristics of the O-ring seal. The regularity of the friction coefficient varying with the speed of reciprocating motion is obtained in the mixed lubrication condition. The experimental result is used to validate the fluid-solid interaction model. Based on the model, The elastohydrodynamic lubrication characteristics of the hydraulic reciprocating O-ring seal are presented respectively in the dry friction, mixed lubrication and full film lubrication conditions, including of the contact pressure, film thickness, friction coefficient, liquid film pressure and viscous shear stress in the sealing zone. The proposed numerical fluid-solid interaction model can be effectively used to analyze the operation characteristics of the hydraulic reciprocating O-ring seal, and can also be widely used to study other hydraulic reciprocating seals.

Computational simulations of hemodynamic changes within thoracic, coronary, and cerebral arteries following early wall remodeling in response to distal aortic coarctation

Mounting evidence suggests that the pulsatile character of blood pressure and flow within large arteries plays a particularly important role as a mechano-biological stimulus for wall growth and remodeling. Nevertheless, understanding better the highly coupled interactions between evolving wall geometry, structure, and properties and the hemodynamics will require significantly more experimental data. Computational fluid-solid-growth models promise to aid in the design and interpretation of such experiments and to identify candidate mechanobiological mechanisms for the observed arterial adaptations. Motivated by recent aortic coarctation models in animals, we used a computational fluid-solid interaction model to study possible local and systemic effects on the hemodynamics within the thoracic aorta and coronary, carotid, and cerebral arteries due to a distal aortic coarctation and subsequent spatial variations in wall adaptation. In particular, we studied an initial stage of acute cardiac compensation (i.e., maintenance of cardiac output) followed by early arterial wall remodeling (i.e., spatially varying wall thickening and stiffening). Results suggested, for example, that while coarctation increased both the mean and pulse pressure in the proximal vessels, the locations nearest to the coarctation experienced the greatest changes in pulse pressure. In addition, after introducing a spatially varying wall adaptation, pressure, left ventricular work, and wave speed all increased. Finally, vessel wall strain similarly experienced spatial variations consistent with the degree of vascular wall adaptation.

Temperature Field Numerical Simulation on the Exhaust Silencer with Adiabatic Envelope

Exhaust noise is the major noise source of the internal combustion engines, and the exhaust silencer is the device to reduce the exhaust noise. Exhaust gas of the internal combustion engine is high-temperature, therefore in the study of internal combustion engine exhaust silencer, the surface temperature’s influence on the surrounding adjacent facilities should be controlled to a certain range and the status of the temperature field depends on the material and structure of the adiabatic envelope. The model of exhaust silencers discussed in this article is fluid-solid interaction model and this paper uses the CFD software for numerical simulation of the model. Using appropriate boundary conditions, calculation models and silencer model with heat transfer surface, this paper uses N-S equation and standard turbulent model to simulate the flow field and wall temperature field inside the silencer, and does post-processing analysis of the results.

Optimization design for mechanical seals in reactor coolant pumps based on a fluid–solid strong-interaction model

The study on the mechanism and performance of the mechanical seals in reactor coolant pumps (RCPs) is very important for the safe operations of pressurized water reactor power plants. By exploring the operating mechanism of the first seal of the hydrostatic mechanical seal in RCPs, an analytical fluid–solid strong-interaction model of the seal is proposed in this article. The model holds that the mechanical deformations of the seal assembly are dominated by the deflections of the seal rings, and this idea is demonstrated by the numerical simulation result of a fluid–solid interaction (FSI) model. Using the analytical FSI model, the regularity that the leakage rate of the first seal varies with the differential pressure in a RCP is obtained, and compared with the operational data, which is used to verify the model. Based on the understanding of the reliability of the seal, a dimensionless parameter Λ that acts as an attribute to the reliability is proposed in this article. Using the analytical FSI model and Λ as the optimization algorithm and optimization object, respectively, the optimum designs about the seal faceplateconfigurations are performed. Also, the specific optimization conclusions are given simultaneously.

Acoustic streaming induced elimination of nonspecifically bound proteins from a surface acoustic wave biosensor: Mechanism prediction using fluid-structure interaction models

Biosensors typically operate in liquid media for detection of biomarkers and suffer from fouling resulting from nonspecific binding of protein molecules to the device surface. In the current work, using a coupled field finite element fluid-structure interaction simulation, we have identified that fluid motion induced by high intensity sound waves, such as those propagating in these sensors, can lead to the efficient removal of the nonspecifically bound proteins thereby eliminating sensor fouling. We present a computational analysis of the acoustic-streaming phenomenon induced biofouling elimination by surface acoustic-waves (SAWs) propagating on a lithium niobate piezoelectric crystal. The transient solutions generated from the developed coupled field fluid solid interaction model are utilized to predict trends in acoustic-streaming induced forces for varying design parameters such as voltage intensity, device frequency, fluid viscosity, and density. We utilize these model predictions to compute the various interaction forces involved and thereby identify the possible mechanisms for removal of nonspecifically-bound proteins. For the range of sensor operating conditions simulated, our study indicates that the SAW motion acts as a body force to overcome the adhesive forces of the fouling proteins to the device surface whereas the acoustic-streaming induced hydrodynamic forces prevent their reattachment. The streaming velocity fields computed using the finite element models in conjunction with the proposed particle removal mechanism were used to identify the optimum conditions that lead to improved removal efficiency. We show that it is possible to tune operational parameters such as device frequency and input voltage to achieve effective elimination of biofouling proteins in typical biosensing media. Our simulation results agree well with previously reported experimental observations. The findings of this work have significant implications in designing reusable, selective, and highly sensitive biosensors.

Regularity of boundary traces for a fluid-solid interaction model

We consider a mathematical model for the interactions of an elastic body fully immersedin a viscous, incompressible fluid.The corresponding composite PDE system comprises a linearized Navier-Stokes systemand a dynamic system of elasticity; the coupling takes place on the interface between the two regions occupied by the fluid and the solid, respectively.We specifically study the regularity of boundary traces (on the interface)for the fluid velocity field.The obtained trace regularity theory for the fluid component of the system-ofinterest in its own right-establishes, in addition, solvability of the associated optimal (quadratic) control problems on a finite time interval, along with well-posedness of the corresponding operator Differential Riccati equations.These results complement the recent advances in the PDE analysis and control of theStokes-Lamé system.