Numerical Simulation of the Resistance and Self-Propulsion Model Tests

2018 ◽  
Author(s):  
Adrian Lungu
Keyword(s):  
Complex Structure ◽  
Turbulence Models ◽  
Numerical Approach ◽  
Local Flow ◽  
Complex Investigation ◽  
Grid Convergence ◽  
Flow Features ◽  
Sinkage And Trim ◽  
Thrust And Torque ◽  
Resistance Coefficients

The paper proposes a series of numerical investigations performed to test and demonstrate the capabilities of a RANS solver in the area of complex ship flow simulations. Focus is on a complete numerical model for hull, propeller and rudder that can account for the mutual interaction between these components. The paper presents the results of a complex investigation of the flow computations around the hull model of the 3600 TEU MOERI containership (KCS hereafter). The resistance for the hull equipped with rudder, the POW computations as well as the self-propulsion simulation are presented. Comparisons with the experimental data provided at the Tokyo 2015 Workshop on CFD in Ship Hydrodynamics are given to validate the numerical approach in terms of the total and wave resistance coefficients, sinkage and trim, thrust and torque coefficients, propeller efficiency and local flow features. Verification and validation based on the grid convergence tests are performed for each computational case. Discussions on the efficiency of the turbulence models used in the computations as well as on the main flow features are provided aimed at clarifying the complex structure of the flow around the stern.

Numerical Simulation of the Resistance and Self-Propulsion Model Tests1

2019 ◽  
Vol 142 (2) ◽  
Author(s):  
Adrian Lungu
Keyword(s):  
Complex Structure ◽  
Turbulence Models ◽  
Open Water ◽  
Numerical Approach ◽  
Navier Stokes ◽  
Navier Stokes Equation ◽  
Local Flow ◽  
Complex Investigation ◽  
Flow Features ◽  
Thrust And Torque

Abstract The paper proposes a series of numerical investigations performed to test and demonstrate the capabilities of a Reynolds-averaged Navier–Stokes equation (RANSE) solver in the area of complex ship flow simulations. The focus is on a complete numerical model for hull, propeller, and rudder that can account for the mutual interaction between these components. The paper presents the results of a complex investigation of the flow computations around the hull model of the 3600 TEU MOERI containership (KCS hereafter). The resistance for the hull equipped with a rudder, the propeller open-water (POW hereafter) computations, as well as the self-propulsion simulation are presented. Comparisons with the experimental data provided at the Tokyo 2015 Workshop on Computational Fluid Dynamics (CFD) in Ship Hydrodynamics are given to validate the numerical approach in terms of the total and wave resistance coefficients, sinkage and trim, thrust and torque coefficients, propeller efficiency, and local flow features. Verification and validation based on the grid convergence tests are performed for each computational case. Discussions on the efficiency of the turbulence models used in the computations as well as on the main flow features are provided aimed at clarifying the complex structure of the flow around the ship stern.

Visualization and Validation of Ejector Flow Field With Computational and First-Principles Analysis

2015 ◽  
Vol 137 (5) ◽  
Author(s):  
Adrienne B. Little ◽  
Yann Bartosiewicz ◽  
Srinivas Garimella
Keyword(s):  
Flow Field ◽  
First Principles ◽  
Large Scale ◽  
Turbulence Models ◽  
Ideal Gas ◽  
Analytical Models ◽  
Local Flow ◽  
Flow Features ◽  
Flow Phenomena ◽  
Air Ejector

Passive, heat actuated ejector pumps offer simple and energy-efficient options for a variety of end uses with no electrical input or moving parts. In an effort to obtain insights into ejector flow phenomena and to evaluate the effectiveness of commonly used computational and analytical tools in predicting these conditions, this study presents a set of shadowgraph images of flow inside a large-scale air ejector and compares them to both computational and first-principles-based analytical models of the same flow. The computational simulations used for comparison apply k-ε renormalization group (RNG) and k-ω shear stress transport (SST) turbulence models to two-dimensional (2D), locally refined rectangular meshes for ideal gas air flow. A complementary analytical model is constructed from first principles to approximate the ejector flow field. Results show that on-design ejector operation is predicted with reasonable accuracy, but accuracy with the same models is not adequate at off-design conditions. Exploration of local flow features shows that the k-ω SST model predicts the location of flow features, as well as global inlet mass flow rates, with greater accuracy. The first-principles model demonstrates a method for resolving the ejector flow field from relatively little visual data and shows the evolving importance of mixing, momentum, and heat exchange with the suction flow with distance from the motive nozzle exit. Such detailed global and local exploration of ejector flow helps guide the selection of appropriate turbulence models for future ejector design purposes, predicts locations of important flow phenomena, and allows for more efficient ejector design and operation.

Optical Validation of Ejector Flow Characteristics Predicted by Computational Analysis

2012 ◽  
Author(s):  
Adrienne B. Little ◽  
Yann Bartosiewicz ◽  
Srinivas Garimella
Keyword(s):  
Large Scale ◽  
Waste Heat ◽  
Turbulence Models ◽  
Ideal Gas ◽  
Computational Simulations ◽  
Design Data ◽  
Local Flow ◽  
Wide Range ◽  
Flow Features ◽  
Flow Phenomena

Passive, heat actuated devices can offer simple and energy-efficient options for a variety of end uses. An ejector pump is one such device that provides reasonable pressure head with no electrical input or moving parts. Useful for a wide range of applications from nuclear reactor cooling to vapor compression in waste-heat-driven heat pumping and work recovery systems, the flow phenomena inside an ejector must be understood to achieve improvements in component design and efficiency. In an effort to obtain insights into the flow phenomena inside an ejector, and to evaluate the effectiveness of commonly used computational tools in predicting these conditions, this study presents a set of shadowgraph images of flow inside a large-scale air ejector, and compares them to computational simulations of the same flow. On-design and off-design conditions are considered where the suction flow is choked and not choked, respectively. The computational simulations used for comparison apply k-ε RNG and k-ω SST turbulence models available in ANSYS FLUENT to 2D, locally-refined rectangular meshes for ideal gas air flow. Experimental and computational results show that on-design ejector operation is predicted with reasonable accuracy, but accuracy with the same models is not adequate at off-design conditions. This is attributed to an inability of turbulence models to predict shock/expansion interaction with the motive jet boundary, as well as the strength and position of flow features. Exploration of local flow features shows that the k-ω SST model predicts the location of flow features, as well as global inlet mass flow rates, with greater accuracy. It is concluded that to provide a rigorous validation of turbulence models for the application of modeling ejector flow, it is necessary to rely on off-design data where more complex phenomena occur, such as flow separation, strong boundary layer/shock interaction, and unsteady flow. Such validation will help refine turbulence models for future ejector design purposes, and allow for more efficient ejector operation.

THE PROBLEM OF IDENTIFICATION OF HYDRAULIC RESISTANCE COEFFICIENTS IN MAKISTRAL GAS PIPELINE

2021 ◽  
pp. 6-11
Author(s):  
G. Gasymov
Keyword(s):  
Hydraulic Resistance ◽  
Group Identification ◽  
Numerical Approach ◽  
Transportation Systems ◽  
Gas Pipeline ◽  
Closed Loops ◽  
Hydraulic Network ◽  
Resistance Coefficients ◽  
Operating Regimes

A numerical approach, based on obtaining design formulas for the determination of hydraulic resistance coefficients of sites in pipeline transportation systems in the presence of the results of observations over a gas pipeline operating regimes, is proposed. The representation of the hydraulic network in the form of a directed graph allows to essentially reduce the number of equations in the system down to the number of closed loops. In the software implementation of the method described, for the solution of practical problems, group identification of the hydraulic resistance coefficients is provided for every eventuality.

scholarly journals Numerical Modeling of Flow Over a Rectangular Broad-Crested Weir with a Sloped Upstream Face

Water ◽  
2018 ◽  
Vol 10 (11) ◽  
pp. 1663 ◽  
Author(s):  
Lei Jiang ◽  
Mingjun Diao ◽  
Haomiao Sun ◽  
Yu Ren
Keyword(s):  
Numerical Simulations ◽  
Discharge Coefficient ◽  
Separation Zone ◽  
Turbulence Models ◽  
Numerical Results ◽  
Upstream Face ◽  
Flow Conditions ◽  
Flow Features ◽  
The Mean ◽  
Absolute Percent Error

The objective of this study was to evaluate the effect of the upstream angle on flow over a trapezoidal broad-crested weir based on numerical simulations using the open-source toolbox OpenFOAM. Eight trapezoidal broad-crested weir configurations with different upstream face angles (θ = 10°, 15°, 22.5°, 30°, 45°, 60°, 75°, 90°) were investigated under free-flow conditions. The volume-of-fluid (VOF) method and two turbulence models (the standard k-ε model and the SST k-w model) were employed in the numerical simulations. The numerical results were compared with the experimental results obtained from published papers. The root mean square error (RMSE) and the mean absolute percent error (MAPE) were used to evaluate the accuracy of the numerical results. The statistical results show that RMSE and MAPE values of the standard k-ε model are 0.35–0.67% and 0.50–1.48%, respectively; the RMSE and MAPE values of the SST k-w model are 0.25–0.66% and 0.55–1.41%, respectively. Additionally, the effects of the upstream face angle on the flow features, including the discharge coefficient and the flow separation zone, were also discussed in the present study.

Development and Validation of a CFD Technique for the Aerodynamic Analysis of HAWT

2009 ◽  
Vol 131 (3) ◽  
Author(s):  
S. Gómez-Iradi ◽  
R. Steijl ◽  
G. N. Barakos
Keyword(s):  
Wind Tunnel ◽  
Wind Turbine ◽  
Wind Turbines ◽  
Turbine Blades ◽  
Wind Tunnel Test ◽  
Unsteady Aerodynamics ◽  
Tunnel Wall ◽  
Local Flow ◽  
Flow Angle ◽  
Thrust And Torque

This paper demonstrates the potential of a compressible Navier–Stokes CFD method for the analysis of horizontal axis wind turbines. The method was first validated against experimental data of the NREL/NASA-Ames Phase VI (Hand, et al., 2001, “Unsteady Aerodynamics Experiment Phase, VI: Wind Tunnel Test Configurations and Available Data Campaigns,” NREL, Technical Report No. TP-500-29955) wind-tunnel campaign at 7 m/s, 10 m/s, and 20 m/s freestreams for a nonyawed isolated rotor. Comparisons are shown for the surface pressure distributions at several stations along the blades as well as for the integrated thrust and torque values. In addition, a comparison between measurements and CFD results is shown for the local flow angle at several stations ahead of the wind turbine blades. For attached and moderately stalled flow conditions the thrust and torque predictions are fair, though improvements in the stalled flow regime are necessary to avoid overprediction of torque. Subsequently, the wind-tunnel wall effects on the blade aerodynamics, as well as the blade/tower interaction, were investigated. The selected case corresponded to 7 m/s up-wind wind turbine at 0 deg of yaw angle and a rotational speed of 72 rpm. The obtained results suggest that the present method can cope well with the flows encountered around wind turbines providing useful results for their aerodynamic performance and revealing flow details near and off the blades and tower.

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 Bedform Morphology in the Area of the Confluence of the Negro and Solimões-Amazon Rivers, Brazil

Water ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 1630 ◽  
Author(s):  
Carlo Gualtieri ◽  
Ivo Martone ◽  
Naziano Pantoja Filizola Junior ◽  
Marco Ianniruberto
Keyword(s):  
Wave Height ◽  
Complex Structure ◽  
Acoustic Doppler Current Profiler ◽  
Low Flow ◽  
Flow Conditions ◽  
Average Value ◽  
Flow Features ◽  
Current Profiler ◽  
Converging Flow ◽  
Riverine Systems

Confluences are common components of all riverine systems, characterized by converging flow streamlines and the mixing of separate flows. The fluid dynamics of confluences possesses a highly complex structure with several common types of flow features observed. A field study was recently conducted in the area of the confluence of the Negro and Solimões/Amazon Rivers, Brazil, collecting a series of Acoustic Doppler Current Profiler (ADCP) transects in different flow conditions. These data were used to investigate the morphology of the bedforms observed in that area. First, the bedforms were mostly classified as large and very large dunes according to Ashley et al. (1990), with an observed maximum wavelength and wave height of 350 and 12 m, respectively. Second, a comparison between low flow and relatively high flow conditions showed that wavelength and wave height increased as the river discharge increased in agreement with previous literature studies. Third, the lee side angle was consistently below 10°, with an average value of about 3.0°, without flow separation confirming past findings on low-angle dunes. Finally, a comparison between the bedform sizes and past literature studies on large rivers suggested that while several dunes were in equilibrium with the flow, several largest bedforms were found to be probably adapting to discharge changes in the river.

Benchmark Studies Using Virtual Model Basin for Resistance and Diffraction: A RANS CFD Approach

2008 ◽  
Author(s):  
Balasubramanyam Sasanapuri
Keyword(s):  
Experimental Data ◽  
Free Surface ◽  
Diffraction Problem ◽  
Turbulence Models ◽  
General Purpose ◽  
Virtual Model ◽  
Ansys Fluent ◽  
Vof Model ◽  
Flow Features ◽  
Surface Combatant

Virtual Model Basin (VMB) developed based on RANS CFD Approach along with VOF model to simulate free-surface has been used to perform benchmark studies and the results are presented in this paper. The VMB based on general purpose CFD solver ANSYS FLUENT has been used to simulate resistance and diffraction problems for a Navy surface combatant hull and the results are validated against experimental data. The resistance simulations are done to assess two turbulence models and best among the two is used to solve the diffraction problem. The validation results suggest that the VMB approach reproduces the flow features, forces and moments accurately.

scholarly journals Numerical study on the hydrodynamic performance of the semi-spade rudder and propeller

2019 ◽  
Vol 11 (1) ◽  
pp. 168781401882310 ◽  
Author(s):  
Xiao Yang ◽  
Yong Yin ◽  
Jing-Jing Lian
Keyword(s):  
Stokes Equations ◽  
Numerical Study ◽  
Turbulence Models ◽  
Suction Side ◽  
Hydrodynamic Performance ◽  
Computational Grids ◽  
Hydrodynamic Characteristics ◽  
Thrust Coefficient ◽  
Ship Maneuverability ◽  
Thrust And Torque

The semi-spade rudder and KP458 propeller of the KVLCC2 (KRISO very large crude carrier) model tanker are adopted by ITTC maneuvering technical committee in the comparative study of ship maneuverability. The incompressible viscous flow around semi-spade rudder and KP458 propeller is investigated using Reynolds-averaged Navier–Stokes equations, the computational grids are generated using ICEM software, and finite volume method is employed to discretize the governing equations. Combined with turbulence model, the hydrodynamic performance of semi-spade rudder is analyzed at different rudder angles, and the result provides a reference for the estimation of the hydrodynamic characteristics of semi-spade rudder. The multi-reference framework method is employed to carry out the numerical simulation of the flow field around the propeller. The thrust and torque of propeller under different turbulence models are calculated in the simulation. The thrust coefficient curve, torque coefficient curve, and efficiency curve are present. The pressure distributions of the pressure side and suction side of propeller blades are studied at different advance coefficient. Based on the study of the hydrodynamic performance of the semi-spade rudder and propeller, the propeller–rudder interaction is simulated and analyzed at different advance coefficient.

Sign in / Sign up

Export Citation Format

Share Document