scholarly journals The Investigation of a Sliding Mesh Model for Hydrodynamic Analysis of a SUBOFF Model in Turbulent Flow Fields

2020 ◽  
Vol 8 (10) ◽  
pp. 744
Author(s):  
Yu-Hsien Lin ◽  
Xian-Chen Li
Keyword(s):  
Cfd Simulation ◽  
Incompressible Flows ◽  
Boussinesq Approximation ◽  
Navier Stokes ◽  
Hydrodynamic Characteristics ◽  
Sliding Mesh ◽  
Mesh Model ◽  
Straight Line ◽  
Frictional Coefficients ◽  
Predictor Corrector

A computational fluid dynamics (CFD)-based simulation using a finite volume code for a full-appendage DARPA (Defense Advanced Research Projects Agency) SUBOFF model was investigated with a sliding mesh model in a multi-zone fluid domain. Unsteady Reynolds Averaged Navier–Stokes (URANS) equations were coupled with a Menter’s shear stress transport (SST) k-ω turbulence closure based on the Boussinesq approximation. In order to simulate unsteady motions and capture unsteady interactions, the sliding mesh model was employed to simulate flows in the fluid domain that contains multiple moving zones. The pressure-based solver, semi-implicit method for the pressure linked equations-consistent (SIMPLEC) algorithm was employed for incompressible flows based on the predictor-corrector approach in a segregated manner. After the grid independence test, the numerical simulation was validated by comparison with the published experimental data and other numerical results. In this study, the capability of the CFD simulation with the sliding mesh model was well demonstrated to conduct the straight-line towing tests by analyzing hydrodynamic characteristics, viz. resistance, vorticity, frictional coefficients, and pressure coefficients.

Verification and Validation of the Caelus Library: Incompressible Turbulence Models

2017 ◽  
Author(s):  
Darrin W. Stephens ◽  
Aleksandar Jemcov ◽  
Chris Sideroff
Keyword(s):  
Incompressible Flows ◽  
Turbulence Models ◽  
Verification And Validation ◽  
Navier Stokes ◽  
Backward Facing Step ◽  
External Data ◽  
Rans Turbulence Models ◽  
Predictor Corrector ◽  
Naca 0012 ◽  
Incompressible Turbulence

In this work verification and validation of Reynolds Averaged Navier-Stokes (RANS) turbulence models for incompressible flows was performed on the numerical library, Caelus [1]. Caelus is free and open source licensed under the GNU Public License (GPL). The focus of this study is on the verification and validation of the k-ω SST [2, 3], Spalart-Allmaras [4], and realizable k-ε models [5]. The cases used in this work include the zero pressure gradient flat plate, two-dimensional bump in a channel flow, NACA 0012 airfoil, and backward facing step. All cases except the backward facing step include mesh dependency studies. A comprehensive description of the test cases and computed results are provided. The results were, in general, found to be in excellent agreement with external data suggesting that the turbulence model implementations in Caelus are correct. A companion study on verification and validation of a predictor corrector steady-state solver algorithm [6] had similar goals and results as this work.

scholarly journals Propeller Hydrodynamic Characteristics in Oblique Flow by Unsteady Ranse Solver

2020 ◽  
Vol 27 (1) ◽  
pp. 6-17
Author(s):  
Hossein Nouroozi ◽  
Hamid Zeraatgar
Keyword(s):  
Numerical Method ◽  
Navier Stokes ◽  
Hydrodynamic Characteristics ◽  
Time Step ◽  
Sliding Mesh ◽  
Oblique Flow ◽  
Ranse Solver ◽  
Ship Performance ◽  
Thrust And Torque ◽  
Good Agreement

AbstractPropellers may encounter oblique flow during operation in off-design conditions. Study of this issue is important from the design and ship performance points of view. On the other hand, a propeller operating in oblique flow may sometimes result in a better propulsion efficiency. The main goal of the present study is to provide an insight on the propeller characteristics in the oblique flow condition. In this research, the performance of the DTMB 4419 propeller is studied by the numerical method based on solving Reynolds Averaged Navier–Stokes (RANS) equations in several inflow angles. The sliding mesh approach is used to model the rotary motion of the propeller. Initially, the numerical method is verified by grid and time step dependency analysis at various inflow angles. Additionally, computed results at zero inflow angle are compared with the available experimental data and good agreement is achieved. Finally, the forces and moments acting on the propeller are obtained for 0° to 30° inflow angles. It is concluded that the inflow angle up to 10° has no significant influence on the thrust and torque coefficients as well as the propeller efficiency. However, at high angles up to 30°, the thrust and torque coefficients increase as the inflow angle increases, which may result in a significant improvement of propeller efficiency.

scholarly journals Numerical Analysis on Hydrodynamic Characteristics of Surface Piercing Propellers in Oblique Flow

Water ◽  
2019 ◽  
Vol 11 (10) ◽  
pp. 2015
Author(s):  
Ren ◽  
Hua ◽  
Ji
Keyword(s):  
Experimental Data ◽  
Free Surface ◽  
Numerical Analysis ◽  
Navier Stokes ◽  
Hydrodynamic Characteristics ◽  
Planing Craft ◽  
Sliding Mesh ◽  
Oblique Flow ◽  
Thrust And Torque ◽  
Good Agreement

When a planing boat sails at the free surface, the posture changes drastically with time, so the surface piercing propellers usually work in oblique flow. In this paper, numerical simulations are performed to predict the performance of PSP-841B with Unsteady Reynolds Averaged Navier–Stokes (URANS) method coupling with sliding mesh and volume of fluid (VOF) method. The results show that the predicted thrust and torque coefficients of PSP-841B are in good agreement with the experimental data. It proves the present numerical schemes are feasible and validated. These schemes are applied in the simulations of SPP-1 that is installed to a planing craft. In oblique flow, the ventilation volume of SPP-1 increases dramatically, resulting in the postponed transition of vented status that changes from the fully dry to partially wetted; at the low advance ratios, the thrust and torque coefficients are less than that in the horizontal case. As the advance speed increases, the vented mode of SPP-1 varies from full ventilation to partially wet, and the forces and moments get closer to the results in the horizontal flow. In addition, the blockage effect of air cavity to the inflow in oblique flow is more significant than the results in the horizontal case.

Numerical solution of the reduced Navier-Stokes equations for internal incompressible flows

AIAA Journal ◽  
2000 ◽  
Vol 38 ◽  
pp. 1603-1614
Author(s):  
Martin Scholtysik ◽  
Bernhard Mueller ◽  
Torstein K. Fannelop
Keyword(s):  
Numerical Solution ◽  
Incompressible Flows ◽  
Stokes Equations ◽  
Navier Stokes ◽  
Navier Stokes Equations

scholarly journals CFD Simulation for Estimating Efficiency of PBCF Installed on a 176K Bulk Carrier under Both POW and Self-Propulsion Conditions

Processes ◽  
2021 ◽  
Vol 9 (7) ◽  
pp. 1192
Author(s):  
Dong-Hyun Kim ◽  
Jong-Chun Park ◽  
Gyu-Mok Jeon ◽  
Myung-Soo Shin
Keyword(s):  
Cfd Simulation ◽  
Open Water ◽  
Navier Stokes ◽  
Water Efficiency ◽  
Ocean Engineering ◽  
Bulk Carrier ◽  
Incompressible Viscous Flow ◽  
Korea Research Institute ◽  
Torque Coefficient ◽  
Viscous Flow Field

In this paper, the efficiency of Propeller Boss Cap Fins (PBCF) installed at the bulk carrier was estimated under both Propeller Open Water (POW) and self-propulsion conditions. For this estimation, virtual model-basin tests (resistance, POW, and self-propulsion tests) were conducted through Computational Fluid Dynamics (CFDs) simulation. In the resistance test, the total resistance and the wake distribution according to ship speed were investigated. In the POW test, changes of thrust, torque coefficient, and open water efficiency on the propeller according to PBCF installation were investigated. Finally, the International Towing Tank Conference (ITTC) 1978 method was used to predict the effect of PBCF installation on self-propulsive coefficient and brake horsepower. For analyzing incompressible viscous flow field, the Reynolds-Averaged Navier–Stokes (RANS) equation with SST k-ω turbulence model was calculated using Star-CCM+ 11.06.010-R8. All simulation results were validated by comparing the results of model tests conducted at the Korea Research Institute of Ships and Ocean Engineering (KRISO). Consequently, for the self-propulsion test with the PBCF, a 1.5% reduction of brake horsepower was estimated in the simulation and a 0.5% reduction of the brake horsepower was estimated in the experiment.

Analysis of Hydrodynamic Characteristics in the Process of Autonomous Underwater Vehicle Docking

2015 ◽  
Author(s):  
Xiaoxu Du ◽  
Huan Wang
Keyword(s):  
Drag Coefficient ◽  
Autonomous Underwater Vehicle ◽  
Simple Algorithm ◽  
Underwater Vehicle ◽  
Navier Stokes ◽  
Hydrodynamic Characteristics ◽  
Successful Operation ◽  
Underwater Docking ◽  
Computational Fluid Dynamics Cfd ◽  
Volume Method

The successful operation of an Autonomous Underwater Vehicle (AUV) requires the capability to return to a dock. A number of underwater docking technologies have been proposed and tested in the past. The docking allows the AUV to recharge its batteries, download data and upload new instructions, which is helpful to improve the working time and efficiency. During the underwater docking process, unsteady hydrodynamic interference occurs between the docking device and an AUV. To ensure a successful docking, it is very important that the underwater docking hydrodynamics of AUV is understood. In this paper, numerical simulations based on the computational fluid dynamics (CFD) solutions were carried out for a 1.85m long AUV with maximum 0.2 m in diameter during the docking process. The two-dimensional AUV model without fin and rudder was used in the simulation. The mathematical model based on the Reynolds-averaged Navier-Stokes (RANS) equations was established. The finite volume method (FVM) and the dynamic structured mesh technique were used. SIMPLE algorithm and the k-ε turbulence model in the Descartes coordinates were also adopted. The hydrodynamics characteristics of different docking states were analyzed, such as the different docking velocity, the docking device including baffle or not. The drag coefficients of AUV in the process of docking were computed for various docking conditions, i.e., the AUV moving into the docking in the speed of 1m/s, 2m/s, 5m/s. The results indicate that the drag coefficient increases slowly in the process of AUV getting close to the docking device. When the AUV moves into the docking device, the drag coefficient increases rapidly. Then the drag coefficient decreases rapidly. The drag coefficient decreases with the increase of velocity when AUV enters the docking device. It was also found that the drag coefficient can be effectively reduced by dislodging the baffle of docking device.

A Verification and Validation Study of CFD Simulation of Wind-Induced Ventilation on Building with Single-Sided Opening

2014 ◽  
Vol 554 ◽  
pp. 696-700 ◽  
Author(s):  
Nur Farhana Mohamad Kasim ◽  
Sheikh Ahmad Zaki ◽  
Mohamed Sukri Mat Ali ◽  
Ahmad Faiz Mohammad ◽  
Azli Abd Razak
Keyword(s):  
Open Source Software ◽  
Natural Ventilation ◽  
Cfd Simulation ◽  
Previous Experiment ◽  
Experimental Methods ◽  
Verification And Validation ◽  
Navier Stokes ◽  
Navier Stokes Equation ◽  
Computational Fluid Dynamics Cfd ◽  
Model Approach

Wind-induced ventilation is widely acknowledged as one of the best approaches for inducing natural ventilation. Computational fluid dynamics (CFD) technique is gaining popularity among researchers as an alternative for experimental methods to investigate the behavior of wind-driven ventilation in building. In this present paper, Reynolds averaged Navier-Stokes equation (RANS) k-ε model approach is considered to simulate the airflow on a simplified cubic building with an opening on a single façade. Preliminary simulation using models from previous experiment indicates the reliability of OpenFOAM, the open source software that will be used in this study. The results obtained in this study will better define options for our future study which aims to explore how different buildings arrays modify the airflow inside and around a naturally ventilated building.

Investigating Gas Turbine Internal Cooling Using Supercritical CO2 at High Reynolds Numbers for Direct Fired Cycle Applications

2021 ◽  
Author(s):  
Matthew Searle ◽  
Arnab Roy ◽  
James Black ◽  
Doug Straub ◽  
Sridharan Ramesh
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Gas Turbines ◽  
Cfd Simulation ◽  
Reynolds Numbers ◽  
Navier Stokes ◽  
Process Conditions ◽  
Internal Cooling ◽  
Air Breathing

Abstract In this paper, experimental and numerical investigations of three variants of internal cooling configurations — dimples only, ribs only and ribs with dimples have been explored at process conditions (96°C and 207bar) with sCO2 as the coolant. The designs were chosen based on a review of advanced internal cooling features typically used for air-breathing gas turbines. The experimental study described in this paper utilizes additively manufactured square channels with the cooling features over a range of Reynolds number from 80,000 to 250,000. Nusselt number is calculated in the experiments utilizing the Wilson Plot method and three heat transfer characteristics — augmentation in Nusselt number, friction factor and overall Thermal Performance Factor (TPF) are reported. To explore the effect of surface roughness introduced due to additive manufacturing, two baseline channel flow cases are considered — a conventional smooth tube and an additively manufactured square tube. A companion computational fluid dynamics (CFD) simulation is also performed for the corresponding cooling configurations reported in the experiments using the Reynolds Averaged Navier Stokes (RANS) based turbulence model. Both experimental and computational results show increasing Nusselt number augmentation as higher Reynolds numbers are approached, whereas prior work on internal cooling of air-breathing gas turbines predict a decay in the heat transfer enhancement as Reynolds number increases. Comparing cooling features, it is observed that the “ribs only” and “ribs with dimples” configurations exhibit higher Nusselt number augmentation at all Reynolds numbers compared to the “dimples only” and the “no features” configurations. However, the frictional losses are almost an order of magnitude higher in presence of ribs.

Low-Pressure Compressor Near-Stall Predictions Using Unsteady CFD Methods

2021 ◽  
Author(s):  
David Vanpouille ◽  
Dimitrios Papadogiannis ◽  
Stéphane Hiernaux
Keyword(s):  
Low Pressure ◽  
Navier Stokes ◽  
Phase Lag ◽  
Sliding Mesh ◽  
Tip Leakage ◽  
Eddy Simulation ◽  
Surge Margin ◽  
Large Eddy ◽  
Unsteady Rans ◽  
Pressure Compressor

Abstract Surge margin is critical for the safety of aeronautical compressors, hence predicting it early in the design process using CFD is mandatory. However, close to surge, steady-state Reynolds Averaged Navier-Stokes (RANS) simulations are proven inadequate. Unsteady techniques such as Unsteady RANS (URANS) and Large Eddy Simulation (LES) can provide more reliable predictions. Nevertheless, the accuracy of such methods are dependent on the method used to handle the rotor/stator interfaces. The most precise method, the sliding mesh, requires simulating the full annulus or a periodic sector, which can be very costly. Other techniques to reduce the domain exist, such as the phase-lagged approach or geometric blade scaling, but introduce restrictive assumptions on the flow at near-stall conditions. The objective of this paper is to investigate the near-stall flow of a low-pressure compressor using unsteady methods of varying fidelity: URANS with the phase lag assumption, URANS on a periodic sector and a high-fidelity LES on a smaller periodic sector achieved using geometric blade scaling. Results are compared to experimental measurements. An overall good agreement is found. Results show that the tip leakage vortex is not the origin of the stall on the studied configuration and a hub corner separation is initiated. LES further validates the (U)RANS flow predictions and brings additional insight on unsteady flow separations.

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