Hydrodynamic Interaction Forces and Moments Prediction Methodology for the Ship Behavior Prediction During the Overtaking Maneuver

2015 ◽  
Author(s):  
Dmitry V. Nikushchenko ◽  
Anastasia A. Zubova
Keyword(s):  
Turbulence Modeling ◽  
Numerical Models ◽  
Wake Flow ◽  
Behavior Prediction ◽  
Ship Wake ◽  
Theoretical Investigations ◽  
Transverse Distance ◽  
Computational Fluid Dynamics Cfd ◽  
The Mathematical Model ◽  
Ship Behavior

Provided within current research extensive numerical and theoretical investigations include real maneuvering condition cases when ship-to-ship interaction phenomena play a significant role. General methodology for hydrodynamic forces and moments’ results analysis and further application within the mathematical model of marine simulators is implemented. Real conditions cases include: ship wake flow interaction with the overtaking ship; interaction between ships; speeds and transverse distance variations. Numerical investigations are carried out with the use of Computational Fluid Dynamics (CFD) methods; analysis of numerical models is completed based on the CFD codes used widely. A significant part of research is devoted to the turbulence modeling focused on flow specifics.

Modeling of Compressor Drum Cavities With Radial Inflow

2016 ◽  
Author(s):  
D. Amirante ◽  
Z. Sun ◽  
J. W. Chew ◽  
N. J. Hills ◽  
N. R. Atkins
Keyword(s):  
Thermal Stratification ◽  
Turbulence Modeling ◽  
Navier Stokes ◽  
Inflow Rate ◽  
Cfd Models ◽  
Flow And Heat Transfer ◽  
Rotating Discs ◽  
Computational Fluid Dynamics Cfd ◽  
Inlet Conditions ◽  
Cooling Air

Reynolds-Averaged Navier-Stokes (RANS) computations have been conducted to investigate the flow and heat transfer between two co-rotating discs with an axial throughflow of cooling air and a radial bleed introduced from the shroud. The computational fluid dynamics (CFD) models have been coupled with a thermal model of the test rig, and the predicted metal temperature compared with the thermocouple data. CFD solutions are shown to vary from a buoyancy driven regime to a forced convection regime, depending on the radial inflow rate prescribed at the shroud. At a high radial inflow rate, the computations show an excellent agreement with the measured temperatures through a transient rig condition. At a low radial inflow rate, the cavity flow is destabilized by the thermal stratification. Good qualitative agreement with the measurements is shown, although a significant over-prediction of disc temperatures is observed. This is associated with under prediction of the penetration of the axial throughflow into the cavity. The mismatch could be the result of strong sensitivity to the prescribed inlet conditions, in addition to possible shortcomings in the turbulence modeling.

Applications of Computational Fluid Dynamics (CFD) Tools for Gravity Concentrators in Coal Preparation

2007 ◽  
Vol 2 (1) ◽  
Author(s):  
Y. K. Xia
Keyword(s):  
Multiphase Flows ◽  
Coupling Effect ◽  
Numerical Models ◽  
Dense Medium ◽  
Hindered Settling ◽  
Heavy Medium ◽  
Computational Fluid Dynamics Cfd ◽  
Dimensional Simulation ◽  
Dense Medium Cyclone ◽  
Lagrange Approach

Extensive progress has been made in using CFD tool in the simulation of multiphase flows in some gravity concentrators. Several case studies for calculation of multiphase flows by different numerical models in spiral, dense medium cyclone, water only cyclones, hindered-settling bed separator, heavy medium vessel and jig are reviewed. The Euler-Lagrange approach in calculation of the particle movement and particle-liquid coupling effect are also discussed. The limitation of Euler-Euler models in the treatment of the particles with a size distribution, and disadvantages of discrete element method (DEM) in description of the jigging processes will be presented. The successful two-dimensional simulation of the hindered-settling bed separator, heavy medium vessel and jig by Euler-Lagrange approach is also addressed.

scholarly journals Journal Bearing: An Integrated CFD-Analytical Approach for the Estimation of the Trajectory and Equilibrium Position

2020 ◽  
Vol 10 (23) ◽  
pp. 8573
Author(s):  
Franco Concli
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Pressure Distribution ◽  
Equilibrium Position ◽  
Analytical Approach ◽  
Journal Bearing ◽  
Cfd Model ◽  
Cavitation Model ◽  
Computational Fluid Dynamics Cfd ◽  
The Mathematical Model

For decades, journal bearings have been designed based on the half-Sommerfeld equations. The semi-analytical solution of the conservation equations for mass and momentum leads to the pressure distribution along the journal. However, this approach admits negative values for the pressure, phenomenon without experimental evidence. To overcome this, negative values of the pressure are artificially substituted with the vaporization pressure. This hypothesis leads to reasonable results, even if for a deeper understanding of the physics behind the lubrication and the supporting effects, cavitation should be considered and included in the mathematical model. In a previous paper, the author has already shown the capability of computational fluid dynamics to accurately reproduce the experimental evidences including the Kunz cavitation model in the calculations. The computational fluid dynamics (CFD) results were compared in terms of pressure distribution with experimental data coming from different configurations. The CFD model was coupled with an analytical approach in order to calculate the equilibrium position and the trajectory of the journal. Specifically, the approach was used to study a bearing that was designed to operate within tight tolerances and speeds up to almost 30,000 rpm for operation in a gearbox.

Turbine Airfoil Heat Transfer Predictions Using CFD

2005 ◽  
Author(s):  
Anil K. Tolpadi ◽  
James A. Tallman ◽  
Lamyaa El-Gabry
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Turbulence Modeling ◽  
Three Dimensional ◽  
Numerical Approach ◽  
Navier Stokes ◽  
Design System ◽  
Computational Fluid Dynamics Cfd ◽  
Turbine Airfoils ◽  
Typical Design

Conventional heat transfer design methods for turbine airfoils use 2-D boundary layer codes (BLC) combined with empiricism. While such methods may be applicable in the mid span of an airfoil, they would not be very accurate near the end-walls and airfoil tip where the flow is very three-dimensional (3-D) and complex. In order to obtain accurate heat transfer predictions along the entire span of a turbine airfoil, 3-D computational fluid dynamics (CFD) must be used. This paper describes the development of a CFD based design system to make heat transfer predictions. A 3-D, compressible, Reynolds-averaged Navier-Stokes CFD solver with k-ω turbulence modeling was used. A wall integration approach was used for boundary layer prediction. First, the numerical approach was validated against a series of fundamental airfoil cases with available data. The comparisons were very favorable. Subsequently, it was applied to a real engine airfoil at typical design conditions. A discussion of the features of the airfoil heat transfer distribution is included.

scholarly journals Local flow assessment of the Japan Bulk Carrier using different turbulence models

2021 ◽  
Vol 1182 (1) ◽  
pp. 012004
Author(s):  
A Bekhit ◽  
F Popescu
Keyword(s):  
Experimental Data ◽  
Viscous Flow ◽  
Turbulence Models ◽  
Wake Flow ◽  
Design Stage ◽  
Bulk Carrier ◽  
Local Flow ◽  
Special Investigation ◽  
Ship Wake ◽  
Effective Wake

Abstract Ship resistance and powering represent the most important aspects in the initial design stage of the ship. Based on their estimation the basic milestone for selecting the main engine and the propulsion system is established. The majority of ships in the international fleet nowadays rely on the screw propeller working in the wake zone behind the ship. The wake flow of the ship has a direct impact on the propeller performance and the propulsion efficiency. Accurate prediction of the nominal and effective wake is crucially important to provide a proper understanding of the flow where the propeller will perform. From this point of view, the wake flow of the Capesize Japan Bulk Carrier (JBC) is assessed using a viscous flow Computational Fluid Dynamics (CFD) method. Numerical simulations are performed to predict the nominal and effective wake of the ship by making use of the viscous flow solver ISIS_CFD of the FINETM/Marine software provided by NUMECA. The solver is based on the finite volume method to build the spatial discretization of the transport equation to resolve the Reynolds-Averaged Navier-Stokes (RANS) equations. Closure to turbulence is achieved using different turbulence models in order to investigate their accuracy in predicting the complex wake flow of the ship. Two-phase flow approach is used to model the air-water interface where the Volume of Fluid method is implemented to capture the free-surface. The results for both nominal and effective wake are assessed against the experimental data provided by the National Maritime Research Institute (NMRI) and Yokohama National University in Japan that were presented in the seventh Workshop on CFD in ship hydrodynamics (Tokyo2015). The results validation showed a reasonable agreement compared to the experimental data for both nominal and effective wake. As it was expected, some turbulence models showed to be more accurate in predicting ship wake, especially the Shear Stress Transport (K-ω SST) and Explicit Algebraic Reynolds Stress (EASM) Models. A special investigation of the flow vortices is also taken into consideration.

scholarly journals Emergency measure of soft isolation controlling pollution diffusion response to sudden water pollution accidents

2019 ◽  
Vol 80 (7) ◽  
pp. 1238-1248
Author(s):  
Fanghui Pan ◽  
Youbao Wang ◽  
Xinxi Zhang
Keyword(s):  
Water Pollution ◽  
Water Environment ◽  
Quality Model ◽  
Complete Purification ◽  
Emergency Measure ◽  
Pollutant Source ◽  
Computational Fluid Dynamics Cfd ◽  
Sudden Water Pollution ◽  
Stage 1 ◽  
The Mathematical Model

Abstract The frequent occurrence of sudden water pollution accidents has become a major threat to water environment safety. Although most researches have focused on constructing a pollutant source identification model and risk assessment methods for dealing with sudden water pollution accidents, a real-time, effective emergency measure for controlling pollutant diffusion, isolating and removing the pollutant, aiming at sudden water pollution accidents, has not been emphasized. Therefore, in this paper, a novel emergency approach of soft isolation was investigated to control pollution diffusion and decrease damage as soon as the accident occurred. In stage 1, the feature of pollution diffusion regarding a sudden water accident was predicted through a water quality model using computational fluid dynamics (CFD). Then, a design scheme of soft isolation was constructed in stage 2 to isolate the polluted zone and attention was paid to optimizing the parameters of soft isolation. Ultimately, the mathematical model of complete purification was formulated in stage 3 to remove the pollution from the impacted zone. The results indicated that the emergency measure of soft isolation could have significant potential to control and isolate pollution occurring in a sudden water pollution accident in the future.

Truss Spar Vortex Induced Motions: Benchmarking of CFD and Model Tests

2006 ◽  
Author(s):  
John Halkyard ◽  
Sampath Atluri ◽  
Senu Sirnivas
Keyword(s):  
Fluid Dynamics ◽  
Best Practices ◽  
Turbulence Modeling ◽  
Production Systems ◽  
Model Tests ◽  
The Past ◽  
Helical Strakes ◽  
Truss Spar ◽  
Computational Fluid Dynamics Cfd ◽  
Riser Design

Spar production systems are subject to Vortex Induced Motions (VIM) which may impact mooring and riser design. Helical strakes are employed to mitigate VIM. Model tests are typically required to validate the performance of the strakes. This paper will report on the results of benchmarking studies that have been conducted over the past few years to compare model tests with computational fluid dynamics (CFD). The paper discusses comparisons of CFD with model tests, “best practices” for the use of CFD for these classes of problems and issues related to turbulence modeling and meshing of problems at large Reynold’s numbers. This work is ongoing.

Three-Dimensional Strain-Based Model for the Severity Characterization of Dented Pipelines

2018 ◽  
Vol 1 (3) ◽  
Author(s):  
Chike Okoloekwe ◽  
Muntaseer Kainat ◽  
Doug Langer ◽  
Sherif Hassanien ◽  
J.J. Roger Cheng ◽  
...  
Keyword(s):  
Oil And Gas ◽  
Numerical Models ◽  
Three Dimensional ◽  
Strain Analysis ◽  
Computation Time ◽  
Order Continuity ◽  
Element Analysis ◽  
The Mathematical Model ◽  
Derivatives Of

Oil and gas pipelines traverse long distances and are often subjected to mechanical forces that result in permanent distortion of its geometric cross section in the form of dents. In order to prioritize the repair of dents in pipelines, dents need to be ranked in order of severity. Numerical modeling via finite element analysis (FEA) to rank the dents based on the accumulated localized strain is one approach that is considered to be computationally demanding. In order to reduce the computation time with minimal effect to the completeness of the strain analysis, an approach to the analytical evaluation of strains in dented pipes based on the geometry of the deformed pipe is presented in this study. This procedure employs the use of B-spline functions, which are equipped with second-order continuity to generate displacement functions, which define the surface of the dent. The strains associated with the deformation can be determined by evaluating the derivatives of the displacement functions. The proposed technique will allow pipeline operators to rapidly determine the severity of a dent with flexibility in the choice of strain measure. The strain distribution predicted using the mathematical model proposed is benchmarked against the strains predicted by nonlinear FEA. A good correlation is observed in the strain contours predicted by the analytical and numerical models in terms of magnitude and location. A direct implication of the observed agreement is the possibility of performing concise strain analysis on dented pipes with algorithms relatively easy to implement and not as computationally demanding as FEA.

scholarly journals 1D, 2D and 3D Collapse of Interstellar Clouds

1980 ◽  
Vol 58 ◽  
pp. 235-246
Author(s):  
W.M. Tscharnuter
Keyword(s):  
Star Formation ◽  
Gravitational Instability ◽  
Numerical Models ◽  
Young Stellar Objects ◽  
Stellar Objects ◽  
Interstellar Clouds ◽  
B Stars ◽  
Theoretical Investigations ◽  
2D And 3D

This review is concerned with recent theoretical investigations and numerical models of star formation with varions symmetries. Observations strongly support the fact that stars condense out of cool (≈10 K) and dense (103-104 atoms/cm3) interstellar clouds due to gravitational instability and collapse. Bright, young stellar objects (0- and B-stars are always found in the vicinity of coloud complexes.

An Experimental Assessment of Numerical Predictive Accuracy for Electronic Component Heat Transfer in Forced Convection—Part II: Results and Discussion

2003 ◽  
Vol 125 (1) ◽  
pp. 76-83 ◽  
Author(s):  
Peter J. Rodgers ◽  
Vale´rie C. Eveloy ◽  
Mark R. Davies
Keyword(s):  
Heat Transfer ◽  
Forced Convection ◽  
Printed Circuit Board ◽  
Predictive Accuracy ◽  
Numerical Models ◽  
Circuit Board ◽  
Junction Temperature ◽  
Electrical Performance ◽  
Test Cases ◽  
Computational Fluid Dynamics Cfd

Numerical predictive accuracy is assessed for component-printed circuit board (PCB) heat transfer in forced convection using a widely used computational fluid dynamics (CFD) software. In Part I of this paper, the benchmark test cases, experimental methods and numerical models were described. Component junction temperature prediction accuracy for the populated board case is typically within ±5°C or ±10%, which would not be sufficient for temperature predictions to be used as boundary conditions for subsequent reliability and electrical performance analyses. Neither the laminar or turbulent flow model resolve the complete flow field, suggesting the need for a turbulence model capable of modeling transition. The full complexity of component thermal interaction is shown not to be fully captured.

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