scholarly journals ЧИСЛЕННОЕ МОДЕЛИРОВАНИЕ ВЗАИМОДЕЙСТВИЯ НЕДОРАСШИРЕННОЙ СВЕРХЗВУКОВОЙ СТРУИ ГАЗА С ПЛОСКОЙ ПРЕГРАДОЙ

2018 ◽  
Vol 26 (4) ◽  
pp. 73-80
Author(s):  
С.А. Николин ◽  
А.А. Приходько

The results of numerical modeling based on the nonstationary Reynolds-averaged Navier – Stokes equations for the interaction of an underexpanded supersonic gas jet with a flat obstacle, which was established at different distances from the nozzle exit section are presented. The results of the calculations are presented in the form of the distribution of the Mach number and the density gradient in the calculated region, and the pressure and friction coefficients over the surface of the plate. The results of the numerical calculation are compared with the experimental data.

Author(s):  
B. Elie ◽  
G. Reliquet ◽  
P.-E. Guillerm ◽  
O. Thilleul ◽  
P. Ferrant ◽  
...  

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.


2014 ◽  
Vol 136 (6) ◽  
Author(s):  
B. A. Younis ◽  
A. Abrishamchi

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.


1994 ◽  
Vol 116 (4) ◽  
pp. 202-208 ◽  
Author(s):  
K. Nakajima ◽  
Y. Kallinderis ◽  
I. Sibetheros ◽  
R. W. Miksad ◽  
K. Lambrakos

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.


1989 ◽  
Vol 1989 (1) ◽  
pp. 161-166 ◽  
Author(s):  
Poojitha D. Yapa ◽  
Tamara Chowdhury

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.


2014 ◽  
Vol 348 ◽  
pp. 88-93 ◽  
Author(s):  
S. Aggoune ◽  
El Hachemi Amara

We consider in the present work the fusion laser cutting of stainless steel sheets under a nitrogen laminar gas jet. The molten metal is treated as a laminar and steady viscous incompressible fluid. The mathematical model describing our problem is set in terms of Navier-Stokes equations, solved numerically using the finite differences method, where the effect of the gas jet velocity on the molten boundary layer is considered. The generated shear stress occurring on the gas-liquid interface and its contribution in the momentum is carried out, and it is found that when the skin friction and the shear stress decrease, the thickness and the velocity at the edge of the molten boundary layer increase along the kerf surface. The layer thickness reduces when the assisting gas velocity is increased.


Author(s):  
Hongwei An ◽  
Liang Cheng ◽  
Ming Zhao ◽  
Guohai Dong

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.


Author(s):  
Vijay K. Garg ◽  
Raymond E. Gaugler

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.


1990 ◽  
Vol 34 (03) ◽  
pp. 179-193
Author(s):  
V. C. Patel ◽  
H. C. Chen ◽  
S. Ju

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.


2021 ◽  
Vol 158 (A3) ◽  
Author(s):  
A Lavrov ◽  
C Guedes Soares

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.


2018 ◽  
Vol 8 (9) ◽  
pp. 1444 ◽  
Author(s):  
Wei Zhong ◽  
Hongwei Tang ◽  
Tongguang Wang ◽  
Chengyong Zhu

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.


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