• Title/Summary/Keyword: 입자와법

Search Result 7, Processing Time 0.019 seconds

Numerical study of Flow around Impulsively Started Elliptic Cylinder using Vortex Particle Method (입자와법에 의한 급 출발하는 타원형 실린더 주위 유동해석)

  • Joo, Nam-Soo;Lee, Sang-Hwan
    • Proceedings of the KSME Conference
    • /
    • 2004.04a
    • /
    • pp.1601-1606
    • /
    • 2004
  • In this paper, the unsteady behavior of the viscous flow field past an impulsively started elliptic cylinder is studied numerically. In order to analyze flow field, we introduce vortex particle method. The vorticity transport equation is solved by fractional step algorithm which splits into convection term and diffusion term. The convection term is calculated with Biot-Savart law, the no-through boundary condition is employed on solid boundaries. The diffusion term is modified based on the scheme of particle strength exchange. The particle redistributed scheme for general geometry is adapted. The flows around an elliptic cylinder are investigated for various attack angles at Reynolds number 200. The comparison between numerical results of present study and experimental data shows good agreements.

  • PDF

Hybrid Diffusion Scheme of vortex Particle Method for Early Wake Past Semicircular Cylinder (반원형실린더 초기후류를 위한 입자와법의 하이브리드 확산기법)

  • Cho, Ji-Young;Lee, Sang-Hwan
    • Transactions of the Korean Society of Mechanical Engineers B
    • /
    • v.28 no.7
    • /
    • pp.771-779
    • /
    • 2004
  • Unsteady behavior of the early wake in the viscous flow field past an impulsively started semicircular cylinder is studied numerically. In this paper, we propose the hybrid diffusion scheme to simulate dynamic characteristics of wake such as a fishtail-like flapping and an alternate vortex-shedding more accurately. This diffusion scheme based on particle strength exchange is mixed with the stochastic nature of random walk method. Also, the viscous splitting algorithm which calculates convective and diffusion terms successively is applied in order to handle random walk method effectively. Consequently, the early behavior of wake due to the breakdown of symmetrical vortici balance is more practically simulated with the vortex particle method.

Numerical Study of Flow Around Impulsively Started Elliptic Cylinder Using Vortex Particle Method (입자와법에 의한 급 출발하는 타원형 실린더 주위 유동해석)

  • Lee, Sang-Hwan;Joo, Nam-Soo
    • Transactions of the Korean Society of Mechanical Engineers B
    • /
    • v.28 no.7
    • /
    • pp.809-817
    • /
    • 2004
  • In this paper, the unsteady behavior of the viscous flow field past an impulsively started elliptic cylinder is studied numerically. In order to analyze flow field, we introduce vortex particle method. The vorticity transport equation is solved by fractional step algorithm which splits into convection term and diffusion term. The convection term is calculated with Biot-Savart law, the no-through boundary condition is employed on solid boundaries. The diffusion term is modified based on the scheme of particle strength exchange. The particle redistributed scheme for general geometry is adapted. The flows around an elliptic cylinder are investigated for various attack angles at Reynolds number 200. The comparison between numerical results of present study and experimental data shows good agreements.

Flow Characteristics Around the Oscillating Sphere at High Strouhal Number Using Three-Dimensional Vortex Element Method (3차원 입자와법을 이용한 높은 스트롤수로 진동하는 구에 대한 유동장의 수치해석)

  • Lee, Sang-Hwan;Park, Yun-Sub;Cho, Young-Taek;Ahn, Cheol-O;Seo, In-Soo
    • Transactions of the Korean Society of Mechanical Engineers B
    • /
    • v.32 no.6
    • /
    • pp.421-428
    • /
    • 2008
  • In this paper, we investigated the flow of an incompressible viscous fluid past a sphere which is oscillated one-dimensionally over flow regimes including laminar flow at Reynolds number of 100, 200 and Strouhal number of up to 5000. In order to analyze flow and estimate critical Strouhal number, we introduce three-dimensional vortex element method. With this method, separation only appears in decreasing velocity region during the high Strouhal numbers. We find out that vorticity distribution around sphere is proportionl to the Strouhal number. And we can decide that low Strouhal number is below 100, high Strouhal number is above 500 from many results. Thus the critical Strouhal number(St) effected to the flow field is expected to be 100

Simulations of the Unsteady Viscous Flow Around an Impulsively Started Cylinder Using Improved Vortex Particle Method (개선된 입자와법을 이용한 급 출발하는 실린더 주위의 비정상 점성 유동 시뮬레이션)

  • Jin, Dong-Sik;Lee, Sang-Hwan;Lee, Ju-Hee
    • Transactions of the Korean Society of Mechanical Engineers B
    • /
    • v.24 no.5
    • /
    • pp.733-743
    • /
    • 2000
  • We solve the integral representation of the Navier-Stokes equations in a lagrangian view by tracking the particles, which have vortex strengths. We simulate the unsteady viscous flow around an impulsively started cylinder using the vortex particle method. Particles are advanced via the Biot-Savart law for a lagrangian evolution of particles. The particle strength is modified based on the scheme of particle strength exchange. The solid boundary satisfies the no-slip boundary condition by the vorticity generation algorithm. We newly modify the diffusion scheme and the boundary condition for simulating an unsteady flow efficiently. To save the computation time, we propose the mixed scheme of particle strength exchange and core expansion. We also use a lot of panels to ignore the curvature of the cylinder, and not to solve the evaluation of the surface density. Results are compared to those from other theoretical and experimental works.

Comparison of Two Viscous Models for Vortex Methods (와법에 사용되는 2가지 점성모델의 비교)

  • Jung, Jae-Hoon;Yoon, Jin-Sup;Jin, Dong-Sik;Ahn, Cheol-O;Lee, Sang-Hwan
    • Proceedings of the KSME Conference
    • /
    • 2001.06e
    • /
    • pp.518-523
    • /
    • 2001
  • Vortex methods were originally conceived as a tool to model the evolution of unsteady, incompressible, high Reynolds number flows of engineering interest. Recently various methods have been proposed for simulating the diffusion in vortex methods for two-dimensional incompressible flows. We test the diffusion schemes of vortex methods. In this paper we directly compare the particle strength exchange scheme with the vorticity redistribution scheme in tenus of their accuracy and computational efficiency. Comparisons between both viscous models described are presented for short-time runs of impulsively started flows past a circular cylinder for Reynolds number of 60. The particle strength exchange scheme has been shown more accurate and efficient than the vorticity redistribution scheme.

  • PDF

Simulations of the early wake behavior induced by an impulsively started a semicircualr cylinder (급 출발하는 반원형 실린더에 의한 초기 후류거동의 시뮬레이션)

  • Cho Jiyoung;Lee Sanghwan;Jin Dongsik
    • Proceedings of the KSME Conference
    • /
    • 2002.08a
    • /
    • pp.349-352
    • /
    • 2002
  • The time-development of the wake vortices of the unsteady viscous flow past a semicircular cylinder is simulated using the vortex particle methods for direct numerical simulations(DNS). The early wake behaviour of the flow behind an impulsively started a semicircualr cylinder is evaluated for a range of Reynolds numbers between 60 and 200 with opposite body configurations respectively. The diffusion scheme based on the particle strength exchange(PSE) is used to account far the viscous effect accurately. And the vorticity generation algorithm to enforce the no-slip boundary conditions is employed. In order to redistribute particles efficiently on the distorted Lagrangian grid the particle distribution technique is adaptively revised, while maintaining the uniform resolution. The results of the simulations are compared to other experimental results.

  • PDF