Assessment of Free Surface Treatment Techniques and Turbulence Models Influence Using the Slightly Compressible Flow Simulation

2007 ◽  
Author(s):  
C. Ciortan ◽  
C. Guedes Soares ◽  
J. Wanderley
Keyword(s):  
Free Surface ◽  
Surface Treatment ◽  
Compressible Flow ◽  
Flow Simulation ◽  
Turbulence Models ◽  
Slightly Compressible ◽  
Eddy Simulation ◽  
Treatment Techniques ◽  
Flow Parameters ◽  
Wigley Hull

A free surface, finite-difference code on collocated grids, using the Slightly Compressible Flow formulation, is used for simulating turbulent flow around a Wigley hull. Two free-surface treatment techniques are compared in terms of accuracy and influence on the flow parameters. The runs were performed in standard conditions of Froude numbers and the results were compared against experimental and numerical results. The initial version of the code used an interface-tracking technique and two turbulence models (Large Eddy Simulation and Baldwin-Lomax). The numerical scheme was marched in time using the factorized Beam and Warming implicit method. The second version of the code uses an interface-capturing technique. For the time being, the code uses a fixed grid on which the kinematic free surface equation is solved. The grid is identical to the initial grid used in the first set of formulations. Other changes in the code were necessary, the most important being the switch of the time-marching method to a 2nd order, explicit Runge-Kutta. The results show good agreement with the experimental results.

Flow Computations of Rib-Roughened Cooling Channels With RANS and Scale Resolving Simulation Models

2017 ◽  
Author(s):  
İlhan Görgülü ◽  
Ender Hepkaya
Keyword(s):  
Numerical Simulations ◽  
Experimental Studies ◽  
Flow Simulation ◽  
Turbulence Models ◽  
Simulation Models ◽  
Reynolds Stress Model ◽  
Industrial Applications ◽  
Test Case ◽  
Detached Eddy Simulation ◽  
Eddy Simulation

In this research, experimental studies conducted by Casarsa [1] were used as test case to validate flow simulation methods. In the numerical simulations, four RANS turbulence models (k-ε, k-ω, V2-f and Reynolds Stress Model) and a URANS model which are widely used in industrial applications were employed for preliminary analyses. In addition, Scale-Adaptive Simulation (SAS), Detached Eddy Simulation (DES) and Large Eddy Simulation (LES) models are conducted to examine the capabilities of Scale Resolving Simulation (SRS) models. All numerical simulations were performed on two different grid resolutions. Relevance of the grid resolutions to the applied SRS methodologies have been assessed both with crude estimations obtained from the RANS simulations and examination of LES solutions. Findings were presented at various parallel and perpendicular planes with respect to the side walls and different over and inter-rib space locations in the form of mean and root mean square (rms) velocity profiles. In all comparisons, SRS results revealed an inarguable superiority over RANS models as expected. Among the SRS models, SAS model has been considered as the most promising industrial purpose model because of providing similar quality results by allowing higher time steps and coarser grid resolutions.

Free Surface Flow Around Ship Hulls Using an Interface-Capturing Method

2008 ◽  
Author(s):  
C. Ciortan ◽  
C. Guedes Soares ◽  
J. Wanderley
Keyword(s):  
Free Surface ◽  
Boundary Conditions ◽  
Compressible Flow ◽  
Numerical Scheme ◽  
Free Surface Flow ◽  
Surface Flow ◽  
Ship Hulls ◽  
Interface Capturing ◽  
Slightly Compressible ◽  
Surface Code

In the present paper, a compressible free surface code is used for simulating the flow around ship hulls. The code simulates both turbulent and laminar, free-surface flow around ship hulls, using the Slightly Compressible Flow formulation. The runs were performed for a Series60, Cb = 0.6 hull in standard conditions of Froude numbers and the results were compared against experimental and numerical results. The turbulence model used is Baldwin-Lomax. The numerical scheme was marched in time using the 2nd order, explicit Runge-Kutta. For the time being, the code uses a fixed grid on which the kinematic free surface equation is solved. Several boundary conditions were implemented and their behaviour assessed. The results show fair agreement with the experimental results.

scholarly journals Analysis of fan-stage gap-flow data to inform simulation of fan broadband noise

2019 ◽  
Vol 377 (2159) ◽  
pp. 20190080 ◽  
Author(s):  
Sheryl Grace ◽  
Ignacio Gonzalez-Martino ◽  
Damiano Casalino
Keyword(s):  
Flow Simulation ◽  
Simulated Data ◽  
Potential Effect ◽  
Broadband Noise ◽  
Navier Stokes ◽  
Time Resolved ◽  
Eddy Simulation ◽  
Flow Parameters ◽  
Gap Flow ◽  
Depth Study

Time-resolved simulations present a new opportunity for studying the disturbances responsible for the broadband interaction noise created by the fan stage. In this paper, two vane configurations from the source diagnostic test at the approach rotor speed were computed with PowerFLOW's very large-eddy simulation (VLES) method using two solution strategies: a coarser mesh near the rotor and a trip to trigger turbulent transition on the rotor; and a much finer mesh near the rotor with no trip. The simulated data allow for an investigation of the potential effect from the vane configuration and an in-depth study of the mean and turbulent flow in the interstage gap. A challenge related to post-processing of high-resolution simulations is discussed. Comparison of the flow quantities with previously obtained Reynolds Averaged Navier–Stokes simulation results indicates that little advantage is gained by running a lattice Boltmann method (LBM)/VLES to simply recover the gap flow parameters for use with a lower-order fan broadband interaction noise calculation method. The true benefit of the LBM/VLES is that the noise calculation can be directly and simultaneously completed with the flow simulation. This article is part of the theme issue ‘Frontiers of aeroacoustics research: theory, computation and experiment’.

New surface treatment techniques to minimize copper alloy leaching in drinking water

2012 ◽  
Vol 7 (4) ◽  
Author(s):  
Norikazu Sugaya
Keyword(s):  
Surface Treatment ◽  
Raw Materials ◽  
Organic Film ◽  
Forming Process ◽  
Mixed Acid ◽  
Treatment Techniques ◽  
Acid Washing ◽  
Washing Process ◽  
Film Forming ◽  
Materials Used

This new surface treatment is simple and easy as well as low in cost. The processes can even be performed by hand. Pharmaceutical raw materials used for the surface treatment, such as hydrochloric acid and nitric acid used in a mixed acid washing process and vegetable oil used in an organic film forming process, are easily obtained in many countries.

scholarly journals Enhanced discrete phase model for multiphase flow simulation of blood flow with high shear stress

2021 ◽  
Vol 104 (1) ◽  
pp. 003685042110080
Author(s):  
Zheqin Yu ◽  
Jianping Tan ◽  
Shuai Wang
Keyword(s):  
Blood Flow ◽  
Shear Stress ◽  
Multiphase Flow ◽  
Experimental Verification ◽  
Flow Simulation ◽  
Turbulence Models ◽  
Phase Model ◽  
Force Model ◽  
Discrete Phase Model ◽  
Discrete Phase

Shear stress is often present in the blood flow within blood-contacting devices, which is the leading cause of hemolysis. However, the simulation method for blood flow with shear stress is still not perfect, especially the multiphase flow model and experimental verification. In this regard, this study proposes an enhanced discrete phase model for multiphase flow simulation of blood flow with shear stress. This simulation is based on the discrete phase model (DPM). According to the multiphase flow characteristics of blood, a virtual mass force model and a pressure gradient influence model are added to the calculation of cell particle motion. In the experimental verification, nozzle models were designed to simulate the flow with shear stress, varying the degree of shear stress through different nozzle sizes. The microscopic flow was measured by the Particle Image Velocimetry (PIV) experimental method. The comparison of the turbulence models and the verification of the simulation accuracy were carried out based on the experimental results. The result demonstrates that the simulation effect of the SST k- ω model is better than other standard turbulence models. Accuracy analysis proves that the simulation results are accurate and can capture the movement of cell-level particles in the flow with shear stress. The results of the research are conducive to obtaining accurate and comprehensive analysis results in the equipment development phase.

scholarly journals Comparative Study of Different Turbulence Models for Cavitational Flows around NACA0012 Hydrofoil

2021 ◽  
Vol 9 (7) ◽  
pp. 742
Author(s):  
Minsheng Zhao ◽  
Decheng Wan ◽  
Yangyang Gao
Keyword(s):  
Angle Of Attack ◽  
Large Angle ◽  
Turbulence Models ◽  
Navier Stokes ◽  
Specific Information ◽  
Cloud Cavitation ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Shedding Frequency ◽  
Reynolds Average

The present work focuses on the comparison of the numerical simulation of sheet/cloud cavitation with the Reynolds Average Navier-Stokes and Large Eddy Simulation(RANS and LES) methods around NACA0012 hydrofoil in water flow. Three kinds of turbulence models—SST k-ω, modified SST k-ω, and Smagorinsky’s model—were used in this paper. The unstable sheet cavity and periodic shedding of the sheet/cloud cavitation were predicted, and the simulation results, namelycavitation shape, shedding frequency, and the lift and the drag coefficients of those three turbulence models, were analyzed and compared with each other. The numerical results above were basically in accordance with experimental ones. It was found that the modified SST k-ω and Smagorinsky turbulence models performed better in the aspects of cavitation shape, shedding frequency, and capturing the unsteady cavitation vortex cluster in the developing and shedding period of the cavitation at the cavitation number σ = 0.8. At a small angle of attack, the modified SST k-ω model was more accurate and practical than the other two models. However, at a large angle of attack, the Smagorinsky model of the LES method was able to give specific information in the cavitation flow field, which RANS method could not give. Further study showed that the vortex structure of the wing is the main cause of cavitation shedding.

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