• Title, Summary, Keyword: Navier-Stokes equation

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A Comparison Study Between Navier-Stokes Equation and Reynolds Equation in Lubricating Flow Regime

  • Song, Dong-Joo;Seo, Duck-Kyo;William W. Schultz
    • Journal of Mechanical Science and Technology
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    • v.17 no.4
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    • pp.599-605
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    • 2003
  • For practical calculations, the Reynolds equation is frequently used to analyze the lubricating flow. The full Navier-Stokes Equations are used to find validity limits of Reynolds equation in a lubricating flow regime by result comparison. As the amplitude of wavy upper wall increased at a given average channel height, the difference between Navier-Stokes and lubrication theory decreased slightly : however, as the minimum distance in channel throat increased, the differences in the maximum pressure between Navier-Stokes and lubrication theory became large.

Thermodynamic Study on the Limit of Applicability of Navier-Stokes Equation to Stationary Plane Shock-Waves (정상 평면충격파에 대한 Navier-Stokes 방정식의 적용한계에 관한 열역학적 연구)

  • Ohr, Young Gie
    • Journal of the Korean Chemical Society
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    • v.40 no.6
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    • pp.409-414
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    • 1996
  • The limit of applicability of Navier-Stokes equation to stationary plane shock-waves is examined by using the principle of minimum entropy production of linear irreversible thermodynamics. In order to obtain analytic results, the equation is linearized near the equilibrium of downstream. Results show that the solution of Navier-Stokes equation which fits the boundary condition of far downstream flow is consistent with the thermodynamic requirement within the first order when the solution is expanded around the M=1, where M is the Mach number of upstream speed.

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COMPARISON OF COUPLING METHODS FOR NAVIER-STOKES EQUATIONS AND TURBULENCE MODEL EQUATIONS (Navier-Stokes 방정식과 난류모델 방정식의 연계방법 비교)

  • Lee, Seung-Soo;Ryu, Se-Hyun
    • 한국전산유체공학회:학술대회논문집
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    • pp.111-116
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    • 2005
  • Two coupling methods for the Navier-Stokes equations and a two-equation turbulence model equations are compared. They are the strongly coupled method and the loosely coupled method. The strongly coupled method solves the Navier-Stokes equations and the two-equation turbulence model equations simultaneously, while the loosely coupled method solves the Navier-Stokes equation with the turbulence viscosity fixed and subsequently solves the turbulence model equations with all the flow quantities fixed. In this paper, performances of two coupling methods are compared for two and three-dimensional problems.

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A Comparative Study of the Navier-Stokes Equation & the Reynolds Equation in Spool Valve Analysis (스풀밸브 해석에서 Navier-Stokes 방정식과 Reynolds 방정식에 의한 비교 연구)

  • Hong, Sung-Ho;Son, Sang-Ik;Kim, Kyung-Woong
    • Tribology and Lubricants
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    • v.28 no.5
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    • pp.218-232
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    • 2012
  • In a spool valve analysis, the Reynolds equation is commonly used to investigate the lubrication characteristics. However, the validity of the Reynolds equation is questionable in a spool valve analysis because cavitation often occurs in the groove and the depth of the groove is much higher than the clearance in most cases. Therefore, the validity of the Reynolds equation in a spool valve analysis is investigated by comparing the results obtained from the Reynolds equation and the Navier-Stokes equation. Dimensionless parameters are determined from a nondimensional form of the governing equations. The differences between the lateral force, friction force, and volume flow rate (leakage) obtained by the Reynolds equation and those obtained by the Navier-Stokes equation are discussed. It is shown that there is little difference (less than 10%), except in the case of a spool valve with many grooves where no cavitation occurs in the grooves. In most cases, the Reynolds equation is effective for a spool valve analysis under a no cavitation condition.

Comparative Study of the Navier-Stokes Equation & the Reynolds Equation in Spool Valve Analysis Considering Cavitation (캐비테이션을 고려한 스풀밸브 해석에서 Navier-Stokes 방정식과 Reynolds 방정식에 의한 비교 연구)

  • Hong, Sung-Ho;Son, Sang-Ik;Kim, Kyung-Woong
    • Tribology and Lubricants
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    • v.29 no.5
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    • pp.275-285
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    • 2013
  • The Reynolds equation is commonly used to investigate the lubrication characteristics of a spool valve. However, the applicability of the Reynolds equation is questionable for analyzing a spool valve because cavitation often occurs in the grooves of the valve and the depth of a groove is much higher than the clearance in most cases. In this study, the validity of the Reynolds equation in the spool valve analysis is investigated by comparing the results obtained from the Reynolds equation and those obtained from the Navier-Stokes equation. The results are compared in terms of the lateral forces, friction forces, and volume flow rates (leakages). A significant difference of more than 20% is found in the lateral forces in cases where cavitation occurs and there are many grooves. Therefore, the Navier-Stokes equation should be used to investigate the lubrication characteristics of a spool valve when cavitation occurs and when the spool valve contains many grooves.

Parallel Preconditioner for the Domain Decomposition Method of the Discretized Navier-Stokes Equation (이산화된 Navier-Stokes 방정식의 영역분할법을 위한 병렬 예조건화)

  • Choi, Hyoung-Gwon;Yoo, Jung-Yul;Kang, Sung-Woo
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.27 no.6
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    • pp.753-765
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    • 2003
  • A finite element code for the numerical solution of the Navier-Stokes equation is parallelized by vertex-oriented domain decomposition. To accelerate the convergence of iterative solvers like conjugate gradient method, parallel block ILU, iterative block ILU, and distributed ILU methods are tested as parallel preconditioners. The effectiveness of the algorithms has been investigated when P1P1 finite element discretization is used for the parallel solution of the Navier-Stokes equation. Two-dimensional and three-dimensional Laplace equations are calculated to estimate the speedup of the preconditioners. Calculation domain is partitioned by one- and multi-dimensional partitioning methods in structured grid and by METIS library in unstructured grid. For the domain-decomposed parallel computation of the Navier-Stokes equation, we have solved three-dimensional lid-driven cavity and natural convection problems in a cube as benchmark problems using a parallelized fractional 4-step finite element method. The speedup for each parallel preconditioning method is to be compared using upto 64 processors.

DERIVATION OF THE g-NAVIER-STOKES EQUATIONS

  • Roh, Jaiok
    • Journal of the Chungcheong Mathematical Society
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    • v.19 no.3
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    • pp.213-218
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    • 2006
  • The 2D g-Navier-Stokes equations are a certain modified Navier-Stokes equations and have the following form, $$\frac{{\partial}u}{{\partial}t}-{\nu}{\Delta}u+(u{\cdot}{\nabla})u+{\nabla}p=f$$, in ${\Omega}$ with the continuity equation ${\nabla}{\cdot}(gu)=0$, in ${\Omega}$, where g is a suitable smooth real valued function. In this paper, we will derive 2D g-Navier-Stokes equations from 3D Navier-Stokes equations. In addition, we will see the relationship between two equations.

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