OIL SPREADING UNDER ICE COVERS

1989 ◽  
Vol 1989 (1) ◽  
pp. 161-166 ◽  
Author(s):  
Poojitha D. Yapa ◽  
Tamara Chowdhury
Keyword(s):  
Experimental Data ◽  
Laboratory Experiments ◽  
Stokes Equations ◽  
Constant Volume ◽  
Navier Stokes ◽  
Discharge Mode ◽  
Navier Stokes Equations ◽  
Discharge Rates ◽  
Volume Mode ◽  
Balance Of Forces

ABSTRACT A new set of equations is presented for describing oil spreading under ice in calm waters. These equations consider the constant discharge mode, constant volume mode, and termination of spreading due to a balance of forces. Therefore, a complete description of the spreading phenomena from the time of initial spill to termination of spreading is presented. The equations are derived based on a simplified form of Navier-Stokes equations. Laboratory experiments were conducted using ice covers of different roughnesses, oils of different viscosities, and varying discharge rates. The theory agrees closely with the experimental data.

Simulation of the Gap Resonance Between Two Rectangular Barges in Regular Waves by a Free Surface Viscous Flow Solver

2013 ◽  
Author(s):  
B. Elie ◽  
G. Reliquet ◽  
P.-E. Guillerm ◽  
O. Thilleul ◽  
P. Ferrant ◽  
...  
Keyword(s):  
Experimental Data ◽  
Free Surface ◽  
Viscous Flow ◽  
Stokes Equations ◽  
Resonance Phenomenon ◽  
Navier Stokes ◽  
Regular Waves ◽  
Navier Stokes Equations ◽  
Flow Solver ◽  
Gap Resonance

This paper compares numerical and experimental results in the study of the resonance phenomenon which appears between two side-by-side fixed barges for different sea-states. Simulations were performed using SWENSE (Spectral Wave Explicit Navier-Stokes Equations) approach and results are compared with experimental data on two fixed barges with different headings and bilges. Numerical results, obtained using the SWENSE approach, are able to predict both the frequency and the magnitude of the RAO functions.

scholarly journals Three-Dimensional Turbulent Vortex Shedding From a Surface-Mounted Square Cylinder: Predictions With Large-Eddy Simulations and URANS

2014 ◽  
Vol 136 (6) ◽  
Author(s):  
B. A. Younis ◽  
A. Abrishamchi
Keyword(s):  
Experimental Data ◽  
Turbulence Model ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Large Eddy Simulations ◽  
Navier Stokes ◽  
Reynolds Stresses ◽  
Mean Flow ◽  
Navier Stokes Equations ◽  
Large Eddy

The paper reports on the prediction of the turbulent flow field around a three-dimensional, surface mounted, square-sectioned cylinder at Reynolds numbers in the range 104–105. The effects of turbulence are accounted for in two different ways: by performing large-eddy simulations (LES) with a Smagorinsky model for the subgrid-scale motions and by solving the unsteady form of the Reynolds-averaged Navier–Stokes equations (URANS) together with a turbulence model to determine the resulting Reynolds stresses. The turbulence model used is a two-equation, eddy-viscosity closure that incorporates a term designed to account for the interactions between the organized mean-flow periodicity and the random turbulent motions. Comparisons with experimental data show that the two approaches yield results that are generally comparable and in good accord with the experimental data. The main conclusion of this work is that the URANS approach, which is considerably less demanding in terms of computer resources than LES, can reliably be used for the prediction of unsteady separated flows provided that the effects of organized mean-flow unsteadiness on the turbulence are properly accounted for in the turbulence model.

A Numerical Study of the Hydrodynamics of Reversing Flows Around a Cylinder

1994 ◽  
Vol 116 (4) ◽  
pp. 202-208 ◽  
Author(s):  
K. Nakajima ◽  
Y. Kallinderis ◽  
I. Sibetheros ◽  
R. W. Miksad ◽  
K. Lambrakos
Keyword(s):  
Experimental Data ◽  
Finite Element Method ◽  
Stokes Equations ◽  
Numerical Study ◽  
Offshore Structures ◽  
Two Dimensions ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Random Behavior ◽  
Marching Scheme

A numerical study of the nonlinear and random behavior of flow-induced forces on offshore structures and experimental verification of the results are presented. The numerical study is based on a finite-element method for the unsteady incompressible Navier-Stokes equations in two dimensions. The momentum equations combined with a pressure correction equation are solved employing fourth-order artificial dissipation with a nonstaggered grid, instead of the more commonly used staggered meshes. The solution is advanced in time with a combined explicit and implicit marching scheme. Emphasis is placed on study of reversing flows around a cylinder. Comparisons with experimental data evaluate accuracy and robustness of the method.

Numerical Simulation of Oscillatory Flow Around Two Circular Cylinders of Different Diameters

2006 ◽  
Author(s):  
Hongwei An ◽  
Liang Cheng ◽  
Ming Zhao ◽  
Guohai Dong
Keyword(s):  
Experimental Data ◽  
Vortex Shedding ◽  
Oscillatory Flow ◽  
Stokes Equations ◽  
Circular Cylinders ◽  
Navier Stokes ◽  
Oscillatory Flows ◽  
Navier Stokes Equations ◽  
Different Diameters ◽  
Small Cylinder

A detailed study of oscillatory flow around two circular cylinders of different diameters is carried out numerically. The Reynolds-averaged Navier-Stokes equations are solved using a finite element method (FEM) with a k–ω turbulence closure. The numerical model is validated against oscillatory flows past a single circular cylinder where the experimental data are available in literature. Then it is employed to simulate the flow around two circular cylinders. It’s found that the fluid flow field around two cylinders is different from the single cylinder case, especially when the small cylinder diameter increases. The orientation of the small cylinder and the gap between two cylinders have significant effects on the vortex shedding process and force coefficients on the cylinders.

Heat Transfer in Film-Cooled Turbine Blades

1993 ◽  
Author(s):  
Vijay K. Garg ◽  
Raymond E. Gaugler
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Film Cooling ◽  
Stokes Equations ◽  
Turbine Blades ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Explicit Finite Difference ◽  
Control Volumes

In order to study the effect of film cooling on the flow and heat transfer characteristics of actual turbine blades, a three-dimensional Navier-Stokes code has been developed. An existing code (Chima and Yokota, 1990) has been modified for the purpose. The code is an explicit finite difference code with an algebraic turbulence model. The thin-layer Navier-Stokes equations are solved using a general body-fitted coordinate system. The effects of film cooling have been incorporated into the code in the form of appropriate boundary conditions at the hole locations on the blade surface. Each hole exit is represented by several control volumes, thus providing an ability to study the effect of hole shape on the film-cooling characteristics. Comparison with experimental data is fair. Further validation of the code is required, however, and in this respect, there is an urgent need for detailed experimental data on actual turbine blades.

Computations of Ship Stern and Wake Flow and Comparisons with Experiment

1990 ◽  
Vol 34 (03) ◽  
pp. 179-193
Author(s):  
V. C. Patel ◽  
H. C. Chen ◽  
S. Ju
Keyword(s):  
Experimental Data ◽  
Shear Flow ◽  
Numerical Method ◽  
Stokes Equations ◽  
Ship Hull ◽  
Wake Flow ◽  
Navier Stokes ◽  
Turbulent Shear ◽  
Turbulent Shear Flow ◽  
Navier Stokes Equations

A numerical method for the solution of the Reynolds-averaged Navier-Stokes equations has been employed to study the turbulent shear flow over the stern and in the wake of a ship hull. Detailed comparisons are made between the numerical results and available experimental data to show that most of the important overall features of such flows can now be predicted with considerable accuracy.

MODELLING THE HEAVE OSCILLATIONS OF VERTICAL CYLINDERS WITH DAMPING PLATES

2021 ◽  
Vol 158 (A3) ◽  
Author(s):  
A Lavrov ◽  
C Guedes Soares
Keyword(s):  
Experimental Data ◽  
Laminar Flow ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Moving Mesh ◽  
Navier Stokes ◽  
Morison Equation ◽  
Navier Stokes Equations ◽  
Vertical Cylinders ◽  
Semi Empirical

The laminar flow around heaving axisymmetric and three-dimensional cylinders with damping plates is numerically studied for various Keulegan-Carpenter numbers. The Navier-Stokes equations are solved using OpenFOAM, which is applied to the flow on a moving mesh. For processing of results the semi-empirical Morison equation is used. Calculations are conducted for one cylinder, one cylinder with one disk, one cylinder with two disks, and one cylinder with one pentagonal plate. The calculated values are compared against experimental data.

scholarly journals Accurate RANS Simulation of Wind Turbine Stall by Turbulence Coefficient Calibration

2018 ◽  
Vol 8 (9) ◽  
pp. 1444 ◽  
Author(s):  
Wei Zhong ◽  
Hongwei Tang ◽  
Tongguang Wang ◽  
Chengyong Zhu
Keyword(s):  
Experimental Data ◽  
Wind Turbine ◽  
Stokes Equations ◽  
Navier Stokes ◽  
Maximum Torque ◽  
Simulation Accuracy ◽  
Navier Stokes Equations ◽  
Pressure Distributions ◽  
Sst Turbulence Model ◽  
Better Than

Stall, a complex phenomenon related to flow separation, is difficult to be predicted accurately. The motivation of the present study is to propose an approach to improve the simulation accuracy of Reynolds Averaged Navier–Stokes equations (RANS) for wind turbines in stall. The approach is implemented in three steps in simulations of the S809 airfoil and the NREL (National Renewable Energy Laboratory) Phase VI rotor. The similarity between airfoil and rotor simulations is firstly investigated. It is found that the primary reason for the inaccuracy of rotor simulation is not the rotational effect or the 3-D effect, but the turbulence-related problem that already exists in airfoil simulation. Secondly, a coefficient of the SST turbulence model is calibrated in airfoil simulation, ensuring the onset and development of the light stall are predicted accurately. The lift of the airfoil in the light stall, which was overestimated about 30%, is reduced to a level consistent with experimental data. Thirdly, the calibrated coefficient is applied to rotor simulation. That makes the flow patterns on the blade properly simulated and the pressure distribution of the blade, as well as the torque of the rotor, are predicted more accurately. The relative error of the predicted maximum torque is reduced from 34.4% to 3.2%. Furthermore, the procedure of calibration is applied to the MEXICO (Model Experiments in Controlled Conditions) rotor, and the predicted pressure distributions over blade sections are better than the CFD (Computational Fluid Dynamics) results from the Mexnext project. In essence, the present study provides an approach for calibrating rotor simulation using airfoil experimental data, which enhances the potential of RANS in accurate simulation of the wind turbine aerodynamic performance.

Investigation of Several Turbulence Models in Simulation of an Axial PAT for a Small Hydropower Using as Renewable Source of Energy

2011 ◽  
Author(s):  
A. Bozorgi ◽  
A. Riasi ◽  
A. Nourbakhshi
Keyword(s):  
Experimental Data ◽  
Stokes Equations ◽  
Turbulence Models ◽  
Navier Stokes ◽  
Small Hydropower ◽  
Software Environment ◽  
Navier Stokes Equations ◽  
Reverse Mode ◽  
Energy Demands ◽  
Environment Characteristic

Small hydropower stations as one of the clean and renewable resources of energy have great capacity to generate electricity and with increasing energy demands, using such potentials is quite necessary. One of the suitable choices for utilizing small hydropower resources is using pump as turbine (PAT), which means using pump in reverse mode. Pumps are relatively simple and inexpensive machines, easy to maintain and readily available in many of developing countries. Several methods have been developed to predict operation of pumps running as turbines but their results are not in good coincidence with experimental data for all pumps. Therefore, study and investigation of hydraulic behavior of pumps in reverse mode can be useful. In this work, an axial pump is simulated in reverse mode by computational fluid dynamics. Reynolds-Averaged Navier–Stokes equations are solved using different turbulence models in NUMECA software environment. Characteristic curves of the reverse pump are obtained for each turbulence model and results are compared with experimental data. The results show that Spallart-Allmaras can predict operation of the axial PAT better than other models.

The development of concentrated vortices: a numerical study

1971 ◽  
Vol 48 (1) ◽  
pp. 1-21 ◽  
Author(s):  
L. M. Leslie
Keyword(s):  
Steady State ◽  
Numerical Experiment ◽  
Laboratory Experiments ◽  
Body Force ◽  
Stokes Equations ◽  
Navier Stokes ◽  
Quasi Steady State ◽  
Navier Stokes Equations ◽  
Flow Parameters ◽  
Axis Of Rotation

Amongst the more important laboratory experiments which have produced concentrated vortices in rotating tanks are the sink experiments of Long and the bubble convection experiments of Turner & Lilly. This paper describes a numerical experiment which draws from the laboratory experiments those features which are believed to be most relevant to atmospheric vortices such as tornadoes and waterspouts.In the numerical model the mechanism driving the vortices is represented by an externally specified vertical body force field defined in a narrow neighbourhood of the axis of rotation. The body force field is applied to a tank of fluid initially in a state of rigid rotation and the subsequent flow development is obtained by solving the Navier–Stokes equations as an initial-value problem.Earlier investigations have revealed that concentrated vortices will form only for a restricted range of flow parameters, and for the numerical experiment this range was selected using an order-of-magnitude analysis of the steady Navier–Stokes equations for sink vortices performed by Morton. With values of the flow parameters obtained in this way, concentrated vortices with angular velocities up to 30 times that of the tank are generated, whereas only much weaker vortices are formed at other parametric states. The numerical solutions are also used to investigate the comparative effect of a free upper surface and a no-slip lid.The concentrated vortices produced in the numerical experiment grow downwards from near the top of the tank until they reach the bottom plate whereupon they strengthen rapidly before reaching a quasi-steady state. In the quasi-steady state the flow in the tank typically consists of the vortex at the axis of rotation, strong inflow and outflow boundary layers at the bottom and top plates respectively, and a region of slowly-rotating descending flow over the remainder of the tank. The flow is cyclonic (i.e. in the same sense as the tank) in the vortex core and over most of the bottom half of the tank and is anticyclonic over the upper half of the tank away from the axis of rotation.

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