• Title/Summary/Keyword: Navier-Stokes Equations Incompressible Viscous Flow

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SENSITIVITY ANALYSIS OF A SHAPE CONTROL PROBLEM FOR THE NAVIER-STOKES EQUATIONS

  • Kim, Hongchul
    • Korean Journal of Mathematics
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    • v.25 no.3
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    • pp.405-435
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    • 2017
  • We deal with a sensitivity analysis of an optimal shape control problem for the stationary Navier-Stokes system. A two-dimensional channel flow of an incompressible, viscous fluid is examined to determine the shape of a bump on a part of the boundary that minimizes the viscous drag. By using the material derivative method and adjoint variables for a shape sensitivity analysis, we derive the shape gradient of the design functional for the model problem.

An Imprevement of the Approximate-Factorization Scheme and Its Application to the Analysis of Incompressible Viscous Flows (근사인자화법의 개량과 비압축성 유동해석에의 응용)

  • 신병록
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.19 no.8
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    • pp.1950-1963
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    • 1995
  • A modification of the approximate-factorization method is made to accelerate the convergency rate and to take sufficiently large Courant number without loss of accuracy. And a stable implicit finite-difference scheme for solving the incompressible Navier-Stokes equations employed above modified method is developed. In the present implicit scheme, the volume fluxes with contravariant velocity components and the pressure formulation in curvilinear coordinates is adopted. In order to satisfy the continuity condition completely and to remove spurious errors for the pressure, the Navier-Stokes equations are solved by a modified SMAC scheme using a staggered gird. The upstream-difference scheme such as the QUICK scheme is also employed to the right hand side. The implicit scheme is unconditionally stable and satisfies a diagonally dominant condition for scalar diagonal linear systems of implicit operator on the left hand side. Numerical results for some test calculations of the two-dimensional flow in a square cavity and over a backward-facing step are obtained using both usual approximate-factorization method and the modified one, and compared with each other. It is shown that the present scheme allows a sufficiently large Courant number of O(10$^{2}$) and reduces the computing time.

Unsteady Viscous Flow over Elliptic Cylinders At Various Thickness with Different Reynolds Numbers

  • Kim Moon-Sang;Sengupta Ayan
    • Journal of Mechanical Science and Technology
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    • v.19 no.3
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    • pp.877-886
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    • 2005
  • Two-dimensional incompressible Navier-Stokes equations are solved using SIMPLER method in the intrinsic curvilinear coordinates system to study the unsteady viscous flow physics over two-dimensional ellipses. Unsteady viscous flows over various thickness-to-chord ratios of 0.6, 0.8, 1.0, and 1.2 elliptic cylinders are simulated at different Reynolds numbers of 200, 400, and 1,000. This study is focused on the understanding the effects of Reynolds number and elliptic cylinder thickness on the drag and lift forces. The present numerical solutions are compared with available experimental and numerical results and show a good agreement. Through this study, it is observed that the Reynolds number and the cylinder thickness affect significantly the frequencies of the force oscillations as well as the mean values and the amplitudes of the drag and lift forces.

NUMERICAL STUDY ON TWO-DIMENSIONAL INCOMPRESSIBLE VISCOUS FLOW BASED ON GRIDLESS METHOD (2차원 비압축성 점성유동에 관한 무격자법 기반의 수치해석)

  • Jeong, S.M.;Park, J.C.;Heo, J.K.
    • Journal of computational fluids engineering
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    • v.14 no.4
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    • pp.93-100
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    • 2009
  • The gridless (or meshfree) methods, such as MPS, SPH, FPM an so forth, are feasible and robust for the problems with moving boundary and/or complicated boundary shapes, because these methods do not need to generate a grid system. In this study, a gridless solver, which is based on the combination of moving least square interpolations on a cloud of points with point collocation for evaluating the derivatives of governing equations, is presented for two-dimensional unsteady incompressible Navier-Stokes problem in the low Reynolds number. A MAC-type algorithm was adopted and the Poission equation for the pressure was solved successively in the moving least square sense. Some typical problems were solved by the presented solver for the validation and the results obtained were compared with analytic solutions and the numerical results by conventional CFD methods, such as a FVM.

Unsteady Lift and Drag Forces Acting on the Elliptic Cylinder

  • Kim Moon-Sang;Park Young-Bin
    • Journal of Mechanical Science and Technology
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    • v.20 no.1
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    • pp.167-175
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    • 2006
  • A parametric study has been accomplished to figure out the effects of elliptic cylinder thickness, angle of attack, and Reynolds number on the unsteady lift and drag forces exerted on the elliptic cylinder. A two-dimensional incompressible Navier-Stokes flow solver is developed based on the SIMPLER method in the body-intrinsic coordinates system to analyze the unsteady viscous flow over elliptic cylinder. Thickness-to-chord ratios of 0.2, 0.4, and 0.6 elliptic cylinders are simulated at different Reynolds numbers of 400 and 600, and angles of attack of $10^{\circ},\;20^{\circ},\;and\;30^{\circ}$. Through this study, it is observed that the elliptic cylinder thickness, angle of attack, and Reynolds number are very important parameters to decide the lift and drag forces. All these parameters also affect significantly the frequencies of the unsteady force oscillations.

A New Pressure-Based PISO-Finite Element Method for Navier-Stokes Equations in All Speed Range (Navier-Stokes 점성유동의 전속도 영역 해석을 위한 새로운 압력기반 PISO-유한요소법)

  • Shim E. B.;Chang K. S.
    • Journal of computational fluids engineering
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    • v.1 no.1
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    • pp.112-122
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    • 1996
  • A finite element scheme using the concept of PISO method has been developed to solve the Navier-Stokes viscous flows in all speed range. This scheme includes development of new pressure equation that retains both the hyperbolic term related with the density variation and the elliptic term reflecting the incompressibility constraint. The present method is applied to the incompressible two-dimensional driven cavity flow problems(Re=100, 400 and 1,000). For compressible flows, the Carter plate problem(M=3 and Re=1,000) is computed. Finally, we have simulated the shock-boundary layer interaction(M=2 and Re=2.96×10/sup 5/), a more difficult problem, and compared its results with the experiment to demonstrate the shock capturing capability of the present solution algorithm.

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PENALIZED APPROACH AND ANALYSIS OF AN OPTIMAL SHAPE CONTROL PROBLEM FOR THE STATIONARY NAVIER-STOKES EQUATIONS

  • Kim, Hong-Chul
    • Journal of the Korean Mathematical Society
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    • v.38 no.1
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    • pp.1-23
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    • 2001
  • This paper is concerned with an optimal shape control problem for the stationary Navier-Stokes system. A two-dimensional channel flow of an incompressible, viscous fluid is examined to determine the shape of a bump on a part of the boundary that minimizes the viscous drag. by introducing an artificial compressibility term to relax the incompressibility constraints, we take the penalty method. The existence of optima solutions for the penalized problem will be shown. Next, by employing Lagrange multipliers method and the material derivatives, we derive the shape gradient for the minimization problem of the shape functional which represents the viscous drag.

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Nodeless Variables Finite Element Method and Adaptive Meshing Teghnique for Viscous Flow Analysis

  • Paweenawat Archawa;Dechaumphai Pramote
    • Journal of Mechanical Science and Technology
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    • v.20 no.10
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    • pp.1730-1740
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    • 2006
  • A nodeless variables finite element method for analysis of two-dimensional, steady-state viscous incompressible flow is presented. The finite element equations are derived from the governing Navier-Stokes differential equations and a corresponding computer program is developed. The proposed method is evaluated by solving the examples of the lubricant flow in journal bearing and the flow in the lid-driven cavity. An adaptive meshing technique is incorporated to improve the solution accuracy and, at the same time, to reduce the analysis computational time. The efficiency of the combined adaptive meshing technique and the nodeless variables finite element method is illustrated by using the example of the flow past two fences in a channel.

Steady and Unsteady flows with Pressure-based Unstructured-grid Navier-Stokes Solver PUNS (비정렬격자 압력기준 유동해석기법을 이용한 정상 및 비정상 유동해석)

  • Kim Jongtae
    • 한국전산유체공학회:학술대회논문집
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    • 1999.05a
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    • pp.98-105
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    • 1999
  • The Pressure-based Unstructured-grid Navier-Stokes Solver PUNS-2/3D for incompressible steady and unsteady viscous flows has been developed. It is based on nonstaggered cell-centered finite volume method. Second-order upwind scheme with least-square reconstruction is used for convective fluxes. The SIMPLE method is implemented to couple the pressure and velocity fields. And the time derivatives in the momentum equations are discretised using a second-order Euler backward-differencing scheme. The discretised linear equations are solved by the preconditioned Biconjugate Gradient Stabilized method(Bi-CGSTAB). The developed solver is applied to validation problems using hybrid meshes.

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Numerical Simulation of Cascade Flows with Rotor-Stator Interaction Using the Multiblocked Grid (중첩 격자계를 이용한 동익과 정익의 상호작용이 있는 익렬 유동해석)

  • Jung, Y. R.;Park, W. G.;Lee, S. W.
    • 유체기계공업학회:학술대회논문집
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    • 1999.12a
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    • pp.163-169
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    • 1999
  • The numerical procedure has been developed for simulating incompressible viscous flow around a turbine stage with rotor-stator interaction. This study solves 2-D unsteady incompressible Navier-Stokes equations on a non-orthogonal curvilinear coordinate system. The Marker-and-Cell concept is applied to efficiently solve continuity equation. To impose an accurate boundary condition, O-H multiblocked grid system is generated. O-type grid and H-type grid is generated near and outer rotor-stator The cubic-spline interpolation is applied to handle a relative motion of a rotor to the stator. Turbulent flows have been modeled by the Baldwin- Lomax turbulent model. To validate present procedure, the time averaged pressure coefficients around the rotor and stator are compared with experiment and a good agreement obtained.

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