Multiblock grid generation process for complex configuration analysis using Navier-Stokes solvers

1996 ◽  
Author(s):  
N. Yu ◽  
T. Su ◽  
W. Wilkinson
Keyword(s):  
Grid Generation ◽  
Complex Configuration ◽  
Navier Stokes ◽  
Generation Process ◽  
Multiblock Grid

Viscous and inviscid flows in a channel with a moving indentation

1989 ◽  
Vol 209 ◽  
pp. 543-566 ◽  
Author(s):  
M. E. Ralph ◽  
T. J. Pedley
Keyword(s):  
Flow Rate ◽  
Small Amplitude ◽  
Inviscid Flow ◽  
Finite Amplitude ◽  
Navier Stokes ◽  
Inviscid Fluid ◽  
Generation Process ◽  
Vorticity Distribution ◽  
Downstream Flow ◽  
Upstream Flow

The flow in a channel with an oscillating constriction has been studied by the numerical solution of the Navier-Stokes and Euler equations. A vorticity wave is found downstream of the constriction in both viscous and inviscid flow, whether the downstream flow rate is held constant and the upstream flow is pulsatile, or vice versa. Closed eddies are predicted to form between the crests/troughs of the wave and the walls, in the Euler solutions as well as the Navier-Stokes flows, although their structures are different in the two cases.The positions of wave crests and troughs, as determined numerically, are compared with the predictions of a small-amplitude inviscid theory (Pedley & Stephanoff 1985). The theory agrees reasonably with the Euler equation predictions at small amplitude (ε [lsim ] 0.2) as long as the downstream flow rate is held fixed; otherwise a sinusoidal displacement is superimposed on the computed crest positions. At larger amplitude (ε = 0.38) the wave crests move downstream more rapidly than predicted by the theory, because of the rapid growth of the first eddy (‘eddy A’) attached to the downstream end of the constriction. At such larger amplitudes the Navier-Stokes predictions also agree well with the Euler predictions, when the downstream flow rate is held fixed, because the wave generation process is essentially inviscid and the undisturbed vorticity distribution is the same in each case. It is quite different, however, when the upstream flow rate is fixed, as in the experiments of Pedley & Stephanoff, because of differences in the undisturbed vorticity distribution, in the growth rate of the vorticity waves and in the dynamics of eddy A. A further finite-amplitude effect of importance, especially in an inviscid fluid, is the interaction of an eddy with its images in the channel walls.

scholarly journals NUMERICAL SIMULATIONS OF LOW REYNOLDS NUMBER FLOWS PAST ELASTICALLY MOUNTED CYLINDER

2012 ◽  
Vol 11 (1-2) ◽  
pp. 61
Author(s):  
R. A. Gonçalves ◽  
P. R. F. Teixeira ◽  
E. Didier
Keyword(s):  
Vortex Shedding ◽  
Stokes Equations ◽  
Reynolds Numbers ◽  
Body Motion ◽  
Petroleum Exploration ◽  
Navier Stokes ◽  
Generation Process ◽  
Navier Stokes Equations ◽  
Eulerian Formulation ◽  
Low Reynolds

The vortex-induced vibration (VIV) phenomenon has drawn the attention of researchers in Engineering for several decades. An example is the riser used for petroleum exploration, in which it is subjected to marine flows that may cause oscillations due to vortex shedding. In this paper, numerical analyses of the phenomena that occur in the interaction among flows at low Reynolds numbers and elastically mounted cylinders are presented. The simulation is carried out by using the numerical model Ifeinco that uses a semi-implicit two-step Taylor-Galerkin method to discretize the Navier-Stokes equations and the arbitrary Lagrangean-Eulerian formulation to follow the cylinder motion. The rigid body motion description is calculated by using the Newmark method. Firstly, the characteristics of the vortex generation process for the fixed cylinder are analyzed. In this case, the Strouhal number, the mean drag and the RMS lift coefficients for Reynolds numbers ranging from 90 to 140 are shown. Afterwards, an analysis of a flexible supported cylinder (with a spring and a damper) in transverse direction subject to flows with Reynolds numbers ranging from 90 to 140 is carried out. The cylinder displacement and the vibration frequencies are studied; the synchronization between the vortex shedding and the vibration frequency (lock-in) is analyzed. Similar results to the experimental ones developed by Anagnostopoulos and Bearman (1992) were obtained in this study.

Template-Based Hexahedral Mesh Generation for Turbine Cooling Geometries

2020 ◽  
Author(s):  
Muting Hao ◽  
Feng Wang ◽  
Joshua Hope-Collins ◽  
Max E. Rife ◽  
Luca di Mare
Keyword(s):  
Turbine Blades ◽  
Size Control ◽  
Grid Generation ◽  
General Purpose ◽  
Poisson System ◽  
Hexahedral Mesh ◽  
Turbine Cooling ◽  
Control Functions ◽  
Elliptic Smoothing ◽  
Multiblock Grid

Abstract This paper describes a multiblock grid generation method for turbine cooling geometries. The method is based on the observation that cooling films are essentially branches inserted on a large trunk, represented by the passage or by the cooling duct. The small size of the films compared to the overall size of turbine blades allows simplifications to be introduced with respect to general-purpose trunk and branch algorithms. The grid generation starts from an existing layout for the passage or cooling duct grid and operates on a Cartesian patch of the trunk surface. The patch is hollowed and a templated branch layout is inserted. Padding blocks are created to connect the two layouts into a single, boundary conforming layout. The resulting multiblock grid is then smoothed using a modification of Thompson’s Poisson system. The boundary mesh distribution is not prescribed. Instead, boundary orthogonality is enforced and elliptic smoothing is performed on the boundaries as well as inside the volume. The grid size control relies on a novel Newton-like update for the control functions of the Poisson system. The smoothing step is essential in achieving good grid quality throughout and determines, in part, the template for a given configuration. The algorithm is particularly suitable for large arrays of films or other cooling decoration and results show that the proposed method can produce grids of better quality than existing methods.

scholarly journals 3D Rans Calculations of Flow Through Turbine Volutes

1998 ◽  
Author(s):  
R. G. M. Hasan ◽  
J. J. McGuirk
Keyword(s):  
Grid Generation ◽  
Point Of View ◽  
Navier Stokes ◽  
Cross Sectional ◽  
Flow Recirculation ◽  
Outflow Boundary Condition ◽  
Flow Features ◽  
Outflow Boundary ◽  
Radial Outflow ◽  
Sectional Shape

Due to their complex shape and complicated flow configuration, the volutes of turbocharger compressors and turbines appear to be a difficult component for both numerical modelling and experimental measurements. This paper presents some 3-D Reynolds Averaged Navier-Stokes (RANS) calculations for a volute with a trapezoidal cross-sectional shape. Flow recirculation under the ‘tongue’ and treatment of radial outflow boundary condition are two important aspects of the current calculations. The results are compared with available experimental data and the reasons for the discrepancies are discussed. The flow features highlight the fact that very strong secondary velocities are present and hence the conventional one-dimensional analyses are not adequate for design purposes. The paper also highlights the typical problems faced by a numerical analyst from grid generation point of view and briefly describes a procedure for handling the problems. Generated grids for two different volutes are presented here in order to show the capability of the grid generation method.

scholarly journals Introduction. Computational aerodynamics

2007 ◽  
Vol 365 (1859) ◽  
pp. 2379-2388 ◽  
Author(s):  
Paul G Tucker
Keyword(s):  
Complex Geometry ◽  
Weak Link ◽  
Turbulence Models ◽  
Grid Generation ◽  
Aircraft Design ◽  
Design Tool ◽  
Turbulence Modelling ◽  
Navier Stokes ◽  
Turbulence Control ◽  
Wide Range

The wide range of uses of computational fluid dynamics (CFD) for aircraft design is discussed along with its role in dealing with the environmental impact of flight. Enabling technologies, such as grid generation and turbulence models, are also considered along with flow/turbulence control. The large eddy simulation, Reynolds-averaged Navier–Stokes and hybrid turbulence modelling approaches are contrasted. The CFD prediction of numerous jet configurations occurring in aerospace are discussed along with aeroelasticity for aeroengine and external aerodynamics, design optimization, unsteady flow modelling and aeroengine internal and external flows. It is concluded that there is a lack of detailed measurements (for both canonical and complex geometry flows) to provide validation and even, in some cases, basic understanding of flow physics. Not surprisingly, turbulence modelling is still the weak link along with, as ever, a pressing need for improved (in terms of robustness, speed and accuracy) solver technology, grid generation and geometry handling. Hence, CFD, as a truly predictive and creative design tool, seems a long way off. Meanwhile, extreme practitioner expertise is still required and the triad of computation, measurement and analytic solution must be judiciously used.

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