Mesh Shape Preservation for Flow-Induced Vibration Problems

2002 ◽  
Author(s):  
R. M. C. So ◽  
Y. Liu ◽  
Y. G. Lai
Keyword(s):  
Numerical Technique ◽  
Three Dimensional ◽  
Cross Flow ◽  
Physical Space ◽  
Shape Preservation ◽  
Structural Vibration ◽  
Flow Induced Vibration ◽  
Time Step ◽  
Dimensional Flow ◽  
Vibration Problems

This paper describes a numerical technique that can prevent the mesh from severe distortion in flow-induced vibration calculations. An orthogonal transformed space that is related to the physical space through a Laplacian equation is introduced. At each time step, the mesh may deform significantly in the physical space due to structural vibration, but the mesh nodal value in the transformed space remains constant. As long as the coordinates in the physical space can be adjusted to render the transformed space independent of time, the mesh shape in the physical space is preserved, even though the mesh area may enlarge or reduce significantly. For simplicity, a two-dimensional flow-induced vibration problem is used to illustrate this method. Two side-by-side elastic cylinders in a cross flow are considered. The Reynolds number is fixed at 200 so that a laminar wake is still available. The mass ratio is chosen to be small so that large displacements of the cylinders can be realized. The predictions with and without mesh preservation are compared. The difference between the two results could be as large as 25% in the prediction of the mean transverse displacements of the cylinders. The method could be extended to three-dimensional flow-induced vibration problems without much difficulty.

Dynamic Stability Analysis of a Flexible Rotor Filled With Liquid Based on Three-Dimensional Flow

2018 ◽  
Vol 141 (5) ◽  
Author(s):  
Guangding Wang ◽  
Huiqun Yuan
Keyword(s):  
Dynamic Stability ◽  
Numerical Technique ◽  
Fluid Dynamic ◽  
Dynamic Pressure ◽  
Three Dimensional ◽  
Frequency Equation ◽  
Fourier Series Expansion ◽  
Flexible Rotor ◽  
Three Dimensional Flow ◽  
Dimensional Flow

This paper deals with the dynamic stability of a flexible liquid-filled rotor. On the basis of three-dimensional flow, the fluid perturbation motion is analyzed and the fluid–structure interaction equation is established, combining with continuity equation, the expression of fluid force exerted on rotor is derived in terms of Fourier series expansion. Considering the complex nonlinear relationship between fluid dynamic pressure and the rotor deformation function, they are expanded in terms of the eigenfunction of a dry rotor. The whirling frequency equation of a flexible rotor partially filled with liquid is obtained based on the rotor static equilibrium equation. Finally, the numerical technique is used to analyze the dynamic stability of the rotor system, and the influences of system parameters on unstable region are discussed.

scholarly journals Investigation of the Three-Dimensional Flow Field Within a Transonic Fan Rotor: Experiment and Analysis

1985 ◽  
Vol 107 (2) ◽  
pp. 436-448 ◽  
Author(s):  
M. J. Pierzga ◽  
J. R. Wood
Keyword(s):  
Aspect Ratio ◽  
Flow Field ◽  
Numerical Technique ◽  
Pressure Ratio ◽  
Three Dimensional ◽  
Axial Flow ◽  
Data Matrix ◽  
Three Dimensional Flow ◽  
Dimensional Flow ◽  
Finite Volume Approach

An experimental investigation of the three-dimensional flow field through a low aspect ratio, transonic, axial-flow fan rotor has been conducted using an advanced laser anemometer (LA) system. Laser velocimeter measurements of the rotor flow field at the design operating speed and over a range of through flow conditions are compared to analytical solutions. The numerical technique used herein yields the solution to the full, three-dimensional, unsteady Euler equations using an explicit time-marching, finite volume approach. The numerical analysis, when coupled with a simplified boundary layer calculation, generally yields good agreement with the experimental data. The test rotor has an aspect ratio of 1.56, a design total pressure ratio of 1.629 and a tip relative Mach number of 1.38. The high spatial resolution of the LA data matrix (9 radial × 30 axial × 50 blade-to-blade) permits details of the transonic flow field such as shock location, turning distribution, and blade loading levels to be investigated an compared to analytical results.

scholarly journals Computational Study of Flow and Heat Transfer With Anti Cross-Flows (ACF) Jet Impingement Cooling for Different Heights of Corrugate

2017 ◽  
Author(s):  
Radheesh Dhanasegaran ◽  
Ssheshan Pugazhendhi
Keyword(s):  
Heat Transfer ◽  
Skin Friction ◽  
Heat Transfer Performance ◽  
Computational Study ◽  
Three Dimensional ◽  
Cross Flow ◽  
Transfer Performance ◽  
Three Dimensional Flow ◽  
Dimensional Flow ◽  
Plate Spacing

In the present study, a flow visualization and heat transfer investigation is carried out computationally on a flat plate with 10×1 array of impinging jets from a corrugated plate. This corrugated structure is an Anti-Cross Flow (ACF) technique which is proved to nullify the negative effects of cross-flow thus enhancing the overall cooling performance. Governing equations are solved using k-ω Shear Stress Transport (SST) turbulence model in commercial code FLUENT. The parameter variation considered for the present study are (i) three different heights of ACF corrugate (C/D = 1, 2 & 3) and (ii) two different jet-to-target plate spacing (H/D = 1 & 2). The dependence of ACF structure performance on the corrugate height (C/D) and the flow structure has been discussed in detail, therefore choosing an optimum corrugate height and visualizing the three-dimensional flow phenomena are the main objectives of the present study. The three-dimensional flow separation and heat transfer characteristics are explained with the help of skin friction lines, upwash fountains, wall eddies, counter-rotating vortex pair (CRVP), and plots of Nusselt number. It is found that the heat transfer performance is high at larger corrugate heights for both the jet-to-plate spacing. Moreover, the deterioration of the skin friction pattern corresponding to the far downstream impingement zones is greatly reduced with ACF structure, retaining more uniform heat transfer pattern even at low H/D values where the crossflow effects are more dominant in case of the conventional cooling structure. In comparison of the overall heat transfer performance the difference between C/D = 3 & C/D = 2 for H/D = 2 is significantly less, thus making the later as the optimal configuration in terms of reduced channel height.

Prevention and Cure of Flow-Induced Vibration Problems in Tubular Heat Exchangers

1980 ◽  
Vol 102 (2) ◽  
pp. 138-145 ◽  
Author(s):  
F. L. Eisinger
Keyword(s):  
Heat Exchangers ◽  
Cross Flow ◽  
Acoustic Vibration ◽  
New Method ◽  
Flow Induced Vibration ◽  
Tube Bank ◽  
Vibration Resistance ◽  
Stability Diagrams ◽  
Vibration Problems ◽  
Prevention And Cure

Various methods for predicting and solving tube and acoustic vibration problems in heat exchangers in cross flow are presented: the use of stability diagrams comprising in-service experience of heat exchangers, for a general multispan tube model; a method of selecting efficient baffle configurations for prevention of acoustic vibration, a new method of fin barriers, an alternative to conventional baffling; a new method of enhancing the vibration resistance of a tube bank based on the use of a helical spacer; these methods, singly or in combination, can be used to design against flow-induced vibration.

scholarly journals Matching experimental and three dimensional numerical models for structural vibration problems with uncertainties

2018 ◽  
Vol 417 ◽  
pp. 294-305 ◽  
Author(s):  
P. Langer ◽  
K. Sepahvand ◽  
C. Guist ◽  
J. Bär ◽  
A. Peplow ◽  
...  
Keyword(s):  
Numerical Models ◽  
Three Dimensional ◽  
Structural Vibration ◽  
Vibration Problems

Research on Cross Flow Induced Vibration of Flexible Tube Bundle

2017 ◽  
Author(s):  
Zhipeng Feng ◽  
Wenzheng Zhang ◽  
Yixiong Zhang ◽  
Fenggang Zang ◽  
Huanhuan Qi ◽  
...  
Keyword(s):  
Critical Velocity ◽  
Dynamic Equilibrium ◽  
Tube Bundle ◽  
Lift Coefficient ◽  
Three Dimensional ◽  
Cross Flow ◽  
Nonlinear Phenomena ◽  
Flow Induced Vibration ◽  
Navier Stokes Equation ◽  
Flexible Tube

When the elastic deformation of the tube bundle is considered, the interaction between the flow field and the structure becomes more complicated. In order to investigate the flow induced vibration (FIV) problems in flexible tube bundle, a numerical model for fluid-structure interaction system was presented firstly. The unsteady three-dimensional Navier-Stokes equation and LES turbulence model were solved with the finite volume approach on structured grids combined with the technique of dynamic mesh. The dynamic equilibrium equation was discretized according to the finite element theory. The configurations considered are tubes in a cross flow. Firstly, the flow-induced vibration of a single flexible tube under uniform turbulent flow are calculated when Reynolds number is 1.35× 104. The variety trends of lift, drag, displacement, vertex shedding frequency, phase difference of tube are analyzed under different frequency ratios. The nonlinear phenomena of locked-in, phase-switch are captured successfully. Meanwhile, the limit cycle and bifurcation of lift coefficient and displacement are analyzed using trajectory, phase portrait and Poincare sections. Secondly, the mutual interaction of two in-line flexible tubes is investigated. Different behaviors, bounded by critical distances between the tubes, critical velocity, and wake vortex pattern are highlighted. Finally, four tube bundle models were established to study the effect of the number of flexible tube on the FIV characteristics. Thanks to several calculations, the critical velocity of instability vibration and the effect of tube bundle configurations on fluid forces and dynamics were obtained successfully. It is therefore expected that further calculations, with model refinements and other validation studies, will bring valuable informations about bundle stability. Further comparisons with experiment are necessary to validate the behavior of the method in this configuration.

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