• Title/Summary/Keyword: Fluid/solid Interaction

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Numerical Stability of Serial Staggered Methods in Fluid-Structure Interaction Analysis of Solid Rocket Motors (고체추진기관의 유동-구조 상호작용 해석에서 Serial Staggered 기법의 수치 안정성)

  • Cho, Hyun-Joo;Lee, Jee-Ho;Lee, Chang-Soo;Kim, Chong-Am;Kim, Shin-Hoe;Lee, Jeong-Sub
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.29 no.2
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    • pp.179-185
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    • 2016
  • In this paper numerical stability of CSS and ISS schemes in axisymmetric fluid-structure-burning simulation for solid rocket motors are studied. The implemented CSS and ISS algorithms for two-dimensional axisymmetric FSI problems are used to analyze ACM and BCM solid rocket motors. Numerical results from CSS and ISS schemes are compared to investigate the efficacy of ISS scheme over CSS scheme in stabilizing the numerical solution. The ACM and BCM simulation results show that ISS scheme gives stable and converged numerical solutions with appropriately small system time step size, while CSS scheme fails to converge after generating rapidly amplified oscillatory solutions. It is concluded that ISS scheme can be useful in improving the numerical stability of FSI analysis for ACM and BCM solid rocket motor simulations, which is not successfully obtained with CSS scheme.

Direct forcing/fictitious domain-Level set method for two-phase flow-structure interaction (이상 유동에서의 유체-구조 연성해석을 위한 Direct Forcing/Ficititious Domain-Level Set Method)

  • Jeon, Chung-Ho;Yoon, Hyun-Sik;Jung, Jae-Hwan
    • Journal of Ocean Engineering and Technology
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    • v.25 no.4
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    • pp.36-41
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    • 2011
  • In the present paper, a direct forcing/fictitious domain (DF/FD) level set method is proposed to simulate the FSI (fluid-solid interaction) in two-phase flow. The main idea is to combine the direct-forcing/fictitious domain (DF/FD) method with the level set method in the Cartesian coordinates. The DF/FD method is a non-Lagrange-multiplier version of a distributed Lagrange multiplier/fictitious domain (DLM/FD) method. This method does not sacrifice the accuracy and robustness by employing a discrete ${\delta}$ (Dirac delta) function to transfer quantities between the Eulerian nodes and Lagrangian points explicitly as the immersed boundary method. The advantages of this approach are the simple concept, easy implementation, and utilization of the original governing equation without modification. Simulations of various water-entry problems have been conducted to validate the capability and accuracy of the present method in solving the FSI in two-phase flow. Consequently, the present results are found to be in good agreement with those of previous studies.

NUMERICAL STUDY ON THE UNSTEADY FLOW PHYSICS OF INSTECTS' FLAPPING FLIGHT USING FLUID-STRUCTURE INTERACTION (FSI를 활용한 2차원 곤충날개 주위 유동장 해석)

  • Lee, K.B.;Kim, J.H.;Kim, C.
    • 한국전산유체공학회:학술대회논문집
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    • 2009.11a
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    • pp.151-158
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    • 2009
  • To implement the insects' flapping flight for developing flapping MAVs(micro air vehicles), the unsteady flow characteristics of the insects' forward flight is investigated. In this paper, two-dimensional FSI(Fluid-Structure Interaction) simulations are conducted to examine realistic flow features of insects' flapping flight and to examine the flexibility effects of the insect's wing. The unsteady incompressible Navier-Stokes equations with an artificial compressibility method are implemented as the fluid module while the dynamic finite element equations using a direct integration method are employed as the solid module. In order to exchange physical information to each module, the common refinement method is employed as the data transfer method. Also, a simple and efficient dynamic grid deformation technique based on Delaunay graph mapping is used to deform computational grids. Compared to the earlier researches of two-dimensional rigid wing simulations, key physical phenomena and flow patterns such as vortex pairing and vortex staying can still be observed. For example, lift is mainly generated during downstroke motion by high effective angle of attack caused by translation and lagging motion. A large amount of thrust is generated abruptly at the end of upstroke motion. However, the quantitative aspect of flow field is somewhat different. A flexible wing generates more thrust but less lift than a rigid wing. This is because the net force acting on wing surface is split into two directions due to structural flexibility. As a consequence, thrust and propulsive efficiency was enhanced considerably compared to a rigid wing. From these numerical simulations, it is seen that the wing flexibility yields a significant impact on aerodynamic characteristics.

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The Interaction Between Stress Waves in Elastic Solids for an Ultrasonic Viscometer and Adjacent Viscous Fluids (초음파 점도계용 고체 매질의 탄성파와 인접 점성유체 간의 상호작용)

  • 김진오
    • The Journal of the Acoustical Society of Korea
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    • v.18 no.5
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    • pp.28-34
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    • 1999
  • The effects of the viscosity of an adjacent viscous fluid on the characteristics of the elastic waves have been studied theoretically and experimentally. Expressions for the wave speed and attenuation of the elastic waves of transverse motion, such as the torsional wave propagating in a circular cylinder and the Love wave in a layered half-space solid, have been obtained as functions of the viscosity and mass density of the fluid by exact and asymptotic analyses. The theoretical results have been compared with experimental observations, and it has been demonstrated that a device described herein can be used as a sensor for measuring the viscosity of a fluid with a known mass density.

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Design of LQR controller for active suspension system of Partially Filled Tank Cars

  • Feizi, Mohammad Mahdi;Rezvani, Mohammad Ali
    • Structural Engineering and Mechanics
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    • v.49 no.3
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    • pp.329-353
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    • 2014
  • Increasing usage of tank cars and their intrinsic instability due to sloshing of contents have caused growing maintenance costs as well as more frequent hazards and defects like derailment and fatigue of bogies and axels. Therefore, varieties of passive solutions have been represented to improve dynamical parameters. In this task, assuming 22 degrees of freedom, dynamic analysis of partially filled tank car traveling on a curved track is investigated. In order to consider stochastic geometry of track; irregularities have been derived randomly by Mont Carlo method. More over the fluid tank model with 1 degree of freedom is also presented by equivalent mechanical approach in terms of pendulum. An active suspension system for described car is designed by using linear quadratic optimal control theory to decrease destructive effects of fluid sloshing. Eventually, the performance of the active suspension system has been compared with that of the passive one and a study is carried out on how active suspension may affect the dynamical parameters such as displacements and Nadal's derailment index.

Effect of Process Gas and Burner Gas Temperature on Reaction and Thermal Deformation Characteristics in a Steam Reformer (증기 개질기의 반응 및 열변형 특성에 미치는 공정가스와 버너가스 온도의 영향)

  • Han, Jun Hee;Kim, Ji Yoon;Lee, Jung Hee;Lee, Seong Hyuk
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.17 no.9
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    • pp.126-132
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    • 2016
  • This study numerically investigates the characteristics of chemical reactions and thermal deformation in a steam reformer. These phenomena are significantly affected by the high-temperature burner gas and the process gas conditions. Because the high temperature of the burner gas ranges from 800 to 1000 K, the reformer tubes undergo substantial thermal deformation, eventually resulting in structural failure. Thus, it is necessary to understand the characteristics of the reaction and thermal deformation under the operating conditions to evaluate the reformer tubes for sustainable, stable operation. Extensive numerical simulations were carried out using commercial CFD code (ANSYS FLUENT/MECHANICA Ver. 13.0) while considering three-dimensional turbulent flows and combined heat transfer including conduction, convection, and radiation. Structural analysis considering conjugated heat transfer between solid tubes and fluid flows was conducted using the Fluid-Solid Interaction (FSI) method. The results show that when the injection temperature of the process gas and burner gas decreased, the hydrogen production rate decreased significantly, and thermal deformation decreased by at least 15 to 20%.

Thermal-Hydraulic Analysis Methodology of Nuclear Power Plant Steam Generator (원전 증기발생기 열유동 해석법)

  • Choi Seok-Ki;Kim Seong-O;Choi Hoon-Ki
    • Journal of computational fluids engineering
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    • v.7 no.2
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    • pp.43-52
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    • 2002
  • This paper presents the numerical methodology of ATHOS3 code for thermal hydraulic analysis of steam generators in nuclear power plant. Topics include porous media approach, governing equations, physical models and correlations for solid-to-fluid interaction and heat transfer, and numerical solution scheme. The ATHOS3 code is applied to the thermal hydraulic analysis of steam generator in the Korea Kori Unit-1 nuclear power plant and the computed results are presented

New insights about ice friction obtained from crushing-friction tests on smooth and high-roughness surfaces

  • Gagnon, Robert E.
    • International Journal of Naval Architecture and Ocean Engineering
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    • v.10 no.3
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    • pp.361-366
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    • 2018
  • Ice crushing occurs in many situations that involve a sliding frictional component such as sports involving ice-contact, ice interaction with ship hulls, and ice-on-ice sliding/crushing within glaciers and between interacting sea ice floes. Ice crushing-friction tests were conducted in the lab at $-10^{\circ}C$ using a set of acrylic ice-crushing platens that included a flat smooth surface and a variety of high-roughness surfaces with regular arrays of small prominences. The experiments were part of Phase II tests of the Blade Runners technology for reducing ice-induced vibration. Ice was crushed against the platens where the ice movement had both a vertical and a horizontal component. High-speed imaging through the platens was used to observe the ice contact zone as it evolved during the tests. Vertical crushing rates were in the range 10-30 mm/s and the horizontal sliding rates were in the range 4.14-30 mm/s. Three types of freshwater ice were used. Friction coefficients were extraordinarily low and were proportional to the ratio of the tangential sliding rate and the normal crushing rate. For the rough surfaces all of the friction coefficient variation was determined by the fluid dynamics of a slurry that flowed through channels that developed between leeward-facing facets of the prominences and the moving ice. The slurry originated from a highly-lubricating self-generating squeeze film of ice particles and melt located between the encroaching intact ice and the surfaces.

A Numerical Study on the Improvement of Performance for the 2 Vane Pump Impeller (2 Vane 펌프 임펠러의 성능 개선에 관한 수치해석적 연구)

  • KIM, SUNG;MA, SANG-BUM;CHOI, YOUNG-SEOK;KIM, JIN-HYUK
    • Journal of Hydrogen and New Energy
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    • v.31 no.3
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    • pp.293-301
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    • 2020
  • This paper describes a numerical study on the improvement of performance of the 2 vane pump impellers. The design of these impellers was optimized using a commercial computation fluid dynamics code and design of experiments. Geometric design variables were defined by the impeller blade angle distribution. The objective functions were defined as the total head, total efficiency and solid material size of the impellers. The importance of the geometric design variables was analyzed using 2k factorial designs. The interaction between the total head, total efficiency and solid material size, according to the impeller blade angle distribution, is discussed by analyzing the 2k factorial design results.

Numerical Simulation of Erosion Rate on Pipe Elbow Using Coupled Behavior of Fluid and Particle (유체-입자 연성 운동에 의한 굽힘형 배관의 침식률 수치해석)

  • Jang, Ho-Sang;Lee, Hawon;Hwang, Se-Yun;Lee, Jang-Hyun
    • Journal of Ocean Engineering and Technology
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    • v.31 no.1
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    • pp.14-21
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    • 2017
  • The erosion of solid particles in a pipe elbow was numerically investigated. A numerical procedure to estimate the sand erosion rate, as well as the particle motion, in the pipe elbow flow was introduced. This procedure was performed based on the combined empirical erosion model and computational fluid dynamics (CFD) analysis to consider the interaction between the particle motion and the eroded surface. The underlying turbulent flow on an Eulerian frame is described by the Reynolds averaged Navier-Stokes (RANS) equations with a $k-{\epsilon}$ turbulent model. The one-way coupled Eulerian-Lagrangian motion of the air flow and sand particles is employed to simulate the particle trajectories and particle-wall interactions on the pipe surfaces. The predicted CFD erosion magnitudes are compared with experimental data from pipe elbows. The erosion rate results do not reveal a good accordance between the simulation and experimental results. It seems that the CFD shows a slightly over-predicted erosion ratio.