Two-Dimensional Numerical Simulation of Flow Around Rectangular Structures With Different Aspect Ratios

2011 ◽  
Author(s):  
Xinliang Tian ◽  
Muk Chen Ong ◽  
Jianmin Yang ◽  
Dag Myrhaug
Keyword(s):  
Cross Sections ◽  
Rectangular Cross Section ◽  
Offshore Structures ◽  
Navier Stokes ◽  
Stream Velocity ◽  
Two Dimensional ◽  
Structural Components ◽  
Aspect Ratios ◽  
Two Dimensional Flow ◽  
Truss Spar

Many marine and offshore structures have structural components with square or rectangular cross-sections, e.g., columns of semi-submersibles and tension-leg platforms, heave damping plates of truss spar platforms as well as ship stabilizers. Two-dimensional flow normal to the longer edge of rectangles with different aspect ratios, i.e. from a square to a thin plate, is investigated numerically in the paper. The simulations are carried out at Re = 21400 (based on the free stream velocity and the height of the rectangular cross-section) by solving the Unsteady Reynolds-Averaged Navier-Stokes (URANS) equations with the k-ω SST (Shear Stress Transport) turbulence model by using OpenFOAM. The hydrodynamic results are compared with published experimental data and numerical results. The paper also includes further investigations on the effect of different aspect ratios.

An Exact Solution of the Unsteady Navier-Stokes Equations Resulting From a Stretching Surface

1994 ◽  
Vol 61 (3) ◽  
pp. 629-633 ◽  
Author(s):  
S. H. Smith
Keyword(s):  
Exact Solution ◽  
Stokes Equations ◽  
Limited Range ◽  
Navier Stokes ◽  
Two Dimensional ◽  
Stretching Surface ◽  
Navier Stokes Equations ◽  
Short Period ◽  
Two Dimensional Flow ◽  
Surrounding Fluid

When a stretching surface is moved quickly, for a short period of time, a pulse is transmitted to the surrounding fluid. Here we describe an exact solution in terms of a similarity variable for the Navier-Stokes equations which represents the effect of this pulse for two-dimensional flow. The unusual feature is that this solution is only valid for a limited range of the Reynolds number; outside this domain unbounded velocities result.

The flow past a rapidly rotating circular cylinder

1957 ◽  
Vol 242 (1228) ◽  
pp. 108-115 ◽  
Keyword(s):  
Boundary Layer ◽  
Circular Cylinder ◽  
Present Theory ◽  
Stream Velocity ◽  
Two Dimensional ◽  
Rotating Circular Cylinder ◽  
Flow Past ◽  
Separating Flow ◽  
Two Dimensional Flow ◽  
Uniform Stream

This paper considers the two-dimensional flow past a circular cylinder immersed in a uniform stream, when the cylinder rotates about its axis so fast that separation in suppressed. The solution of the flow in the boundary layer on the cylinder is obtained in the form of a power series in the ratio of the stream velocity to the cylinder's peripheral velocity, and expressions are deduced for the value of the circulation and the torque on the cylinder. The terms calculated explicitly are sufficient to give reliable numerical values over the whole range of rotational speeds for which the postulate of non-separating flow is justifiable. The previously accepted theory, due to Prandtl, predicted that the circulation should not exceed a certain limit, while the present theory indicates that the circulation increases indefinitely with increase of rotaional speed. Strong arguments against the older theory are put forward, but the experimental evidence available is inconclusive.

The structure of two-dimensional separation

1990 ◽  
Vol 220 ◽  
pp. 397-411 ◽  
Author(s):  
Laura L. Pauley ◽  
Parviz Moin ◽  
William C. Reynolds
Keyword(s):  
Boundary Layer ◽  
Pressure Gradient ◽  
Numerical Solutions ◽  
Stokes Equations ◽  
Adverse Pressure Gradient ◽  
Navier Stokes ◽  
Stream Velocity ◽  
Two Dimensional ◽  
Navier Stokes Equations ◽  
Shedding Frequency

The separation of a two-dimensional laminar boundary layer under the influence of a suddenly imposed external adverse pressure gradient was studied by time-accurate numerical solutions of the Navier–Stokes equations. It was found that a strong adverse pressure gradient created periodic vortex shedding from the separation. The general features of the time-averaged results were similar to experimental results for laminar separation bubbles. Comparisons were made with the ‘steady’ separation experiments of Gaster (1966). It was found that his ‘bursting’ occurs under the same conditions as our periodic shedding, suggesting that bursting is actually periodic shedding which has been time-averaged. The Strouhal number based on the shedding frequency, local free-stream velocity, and boundary-layer momentum thickness at separation was independent of the Reynolds number and the pressure gradient. A criterion for onset of shedding was established. The shedding frequency was the same as that predicted for the most amplified linear inviscid instability of the separated shear layer.

Studies on Design Optimization of Coronary Stents

2008 ◽  
Vol 2 (1) ◽  
Author(s):  
K. Srinivas ◽  
T. Nakayama ◽  
M. Ohta ◽  
S. Obayashi ◽  
T. Yamaguchi
Keyword(s):  
Design Optimization ◽  
Cross Sections ◽  
Latin Hypercube Sampling ◽  
Coronary Stents ◽  
Point Of View ◽  
Two Dimensional ◽  
Reattachment Length ◽  
Design Variables ◽  
Two Dimensional Flow ◽  
The Relationship

The stent design itself seems to be one of the factors responsible for restenosis. As a remedy, the present work attempts to perform a design optimization of coronary stents from a hemodynamic point of view. For the purpose, we have applied the principles of modern exploration of design space restricting ourselves to two-dimensional considerations. Width, thickness, and spacing of the struts of the stent formed the design variables. The objectives chosen for optimization were the vorticity generated, length of recirculation zone, and the reattachment distance in between the struts. Both semicircular and rectangular cross sections of stents were included. Starting with the range of design variables, sample stent cases were generated using Latin hypercube sampling. Objective functions were calculated for each of these by computing the two-dimensional flow using software FLUENT under the assumption of a steady, Newtonian flow considering a model stent with three struts. This was followed by Kriging to construct a response surface, which gives the relationship between the objectives and the design variables. The procedure gave nondominated fronts, which consist of optimized designs. Stents with minimum vorticity, with minimum recirculation distance, and the ones with maximum reattachment length in between struts were generated. The procedure is capable of producing the optimum set of design variables to achieve the prescribed objectives.

scholarly journals A Study of Glacier Flow for an Open-Pit Mine: An Exercise in Applied Glaciology

1974 ◽  
Vol 13 (69) ◽  
pp. 401-414 ◽  
Author(s):  
S. C. Colbeck
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Greenland Ice Sheet ◽  
Field Work ◽  
Open Pit Mine ◽  
Open Pit ◽  
Two Dimensional ◽  
Ice Flow ◽  
Two Dimensional Flow ◽  
Glacier Flow

As part of the feasibility study for the development of an open-pit mine at the edge of the Greenland ice sheet, a study is made of the ice flow toward the proposed pit. The flow is analyzed by considering the two-dimensional flow along seven cross-sections. The most favorable profile is determined for each cross-section and its flow calculated. The excavation necessary to expose the ore is 106 × 106 m3 of ice. 66 × 106 m3 of ice will have to be removed in order to establish favorable profiles and an additional 7.9 × 106 m3 of ice will have to be removed each year in order to prevent the glacier from thickening and advancing into the mine. Many other glaciological problems must be considered, and field work continues in order to provide more information about the area.

scholarly journals Two-Dimensional Computational Model for Wave Rotor Flow Dynamics

1997 ◽  
Vol 119 (4) ◽  
pp. 978-985 ◽  
Author(s):  
G. E. Welch
Keyword(s):  
Stokes Equations ◽  
Flow Simulation ◽  
Navier Stokes ◽  
Two Dimensional ◽  
Wave Rotor ◽  
Navier Stokes Equations ◽  
Flow Features ◽  
Rotor Experiment ◽  
Two Dimensional Flow ◽  
Rotor Flow

A two-dimensional (θ, z) Navier–Stokes solver for multiport wave rotor flow simulation is described. The finite-volume forms of the unsteady thin-layer Navier–Stokes equations are integrated in time on multiblock grids that represent the stationary inlet and outlet ports and the moving rotor passages of the wave rotor. Computed results are compared with three-port wave rotor experimental data. The model is applied to predict the performance of a planned four-port wave rotor experiment. Two-dimensional flow features that reduce machine performance and influence rotor blade and duct wall thermal loads are identified.

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