scholarly journals CFD Simulation of Ship Seakeeping Performance and Slamming Loads in Bi-Directional Cross Wave

2020 ◽  
Vol 8 (5) ◽  
pp. 312 ◽  
Author(s):  
Jialong Jiao ◽  
Songxing Huang
Keyword(s):  
Cfd Simulation ◽  
Wave Length ◽  
Green Water ◽  
Navier Stokes ◽  
Transverse Motion ◽  
Linear Superposition ◽  
Motion Responses ◽  
Seakeeping Performance ◽  
Ocean Environment ◽  
Cross Waves

Accurate prediction of ship seakeeping performance in complex ocean environment is a fundamental requirement for ship design and actual operation in seaways. In this paper, an unsteady Reynolds-averaged Navier–Stokes (RANS) computational fluid dynamics (CFD) solver with overset grid technique was applied to estimate the seakeeping performance of an S175 containership operating in bi-directional cross waves. The cross wave is reproduced by linear superposition of two orthogonal regular waves in a rectangle numerical wave tank. The ship nonlinear motion responses, bow slamming loads, and green water on deck induced by cross wave with different control parameters such as wave length and wave heading angle are systemically analyzed. The results demonstrate that both vertical and transverse motion responses, as well as slamming pressure of ship induced by cross wave, can be quite large, and they are quite different from those in regular wave. Therefore, ship navigational safety when suffering cross waves should be further concerned.

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.

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.

Generation of Regular and Irregular Waves in Navier-Stokes CFD Solvers by Matching With the Nonlinear Potential Wave Solution at the Boundaries

2018 ◽  
Author(s):  
Youngmyung Choi ◽  
Benjamin Bouscasse ◽  
Sopheak Seng ◽  
Guillaume Ducrozet ◽  
Lionel Gentaz ◽  
...  
Keyword(s):  
Viscous Flow ◽  
Open Source ◽  
Cfd Simulation ◽  
Irregular Waves ◽  
Navier Stokes ◽  
Wave Fields ◽  
Flow Solver ◽  
Nonlinear Potential ◽  
Simulation Parameters ◽  
2D And 3D

The capability of wave generation and absorption in a viscous flow solver becomes important for achieving realistic simulations in naval and offshore fields. This study presents an efficient generation of nonlinear wave fields in the viscous flow solver by using a nonlinear potential solver called higher-order spectral method (HOS). The advantages of using a fully nonlinear potential solver for the generation of irregular waves are discussed. In particular, it is shown that the proposed method allows the CFD simulation to start at the time and over the space of interest, retrieved from the potential flow solution. The viscous flow solver is based on the open source library OpenFOAM. The potential solvers used to generate waves are the open source solvers HOS-Ocean and HOS-NWT (Numerical Wave Tank). Several simulation parameters in the CFD solver are investigated in the present study. A HOS wrapper program is newly developed to regenerate wave fields in the viscous flow solver. The wrapper program is validated with OpenFOAM for 2D and 3D regular and irregular waves using relaxation zones. Finally, the extreme waves corresponding to the 1000 year return period condition in the Gulf of Mexico are simulated with the viscous flow solver and the wave elevation is compared with the experiments.

Study of a Wave Absorber in Various Distance Placed in a Sinusoidal Propagate Wave

2013 ◽  
Vol 302 ◽  
pp. 326-331 ◽  
Author(s):  
Zhen Zhong Yuan ◽  
Bhupendra Singh Chauhan ◽  
Hee Chang Lim
Keyword(s):  
Wind Wave ◽  
Wave Length ◽  
Ocean Waves ◽  
Floating Body ◽  
Environmental Condition ◽  
Wave Flume ◽  
Strong Source ◽  
Wave Heights ◽  
Ocean Environment ◽  
Fundamental Equations

Since there has been a rapid progress to understand the dynamics of an offshore floating body under an ocean environment, we undertake to generate the ocean waves in a lab-scale wind-wave flume. The study is aiming to observe and optimize the similar ocean environmental condition as input wave and to reduce the wall reflective wave. Several absorption methods are suggested to optimize the propagate wave by measuring the maximum and minimum of the standing wave envelope. There has been no optimized absorption method, as they highly depend on the wave period and the wave length. One of the methods - two fixed wave gauges measuring two wave heights and one wave phase - is applied in this study. In the present paper various approaches were used to analyze the results using the flume, by position of probes, with absorber and without absorber, different position, condition and angle of the wave absorber, This paper also focuses on the analysis of fundamental equations which describe the separating method of the incident and reflective wave, and finally we confirm that the wave absorber is highly efficient considering all the permutation and combination.From the study it is clear that there is a change in the wave amplitude at the receiving end then the generated end; wave absorber is a strong source to control the energy of the coming wave. With the changing the period of the wave, the reflectance is increasing when the period becomes larger.

Utilizing Schlieren Imaging to Visualize Heat Transfer Studies

2014 ◽  
Author(s):  
Jacob C. Kaessinger ◽  
Kramer C. Kors ◽  
Jordan S. Lum ◽  
Heather E. Dillon ◽  
Shannon K. Mayer
Keyword(s):  
Heat Transfer ◽  
Undergraduate Students ◽  
Cfd Simulation ◽  
Stokes Equations ◽  
Imaging System ◽  
Empirical Science ◽  
Navier Stokes ◽  
Schlieren Imaging ◽  
Navier Stokes Equations ◽  
Imaging Device

Convective heat transfer beyond explicit solutions to the Navier Stokes equations is often an empirical science. Schlieren imaging is one of the only fluid imaging systems that can directly visualize the density gradients of a fluid using collimated light and refractive properties. The ability to visualize fluid densities is useful in both research and educational fields. A Schlieren imaging device has been constructed by undergraduate students at the University of Portland. The device is used for professorial heat transfer and fluid dynamics research and to help undergraduates visualize and understand natural convection. This paper documents the design decisions, design process, and the final specifications of the Schlieren system. A simple 2-D heated cylindrical model is considered and evaluated using Schlieren imaging, OpenFOAM C.F.D. simulation, and convection analysis using a Nusselt correlation. Results are presented for the three analysis techniques and show excellent verifications between the CFD simulation, Nusselt correlation, and Schlieren imaging system.

scholarly journals The Numerical Diffusion Effect on the CFD Simulation Accuracy of Velocity and Temperature Field for the Application of Sustainable Architecture Methodology

2020 ◽  
Vol 12 (23) ◽  
pp. 10173
Author(s):  
Vladimíra Michalcová ◽  
Kamila Kotrasová
Keyword(s):  
Temperature Field ◽  
Cfd Simulation ◽  
Flow Direction ◽  
Three Dimensional ◽  
Stationary Flow ◽  
Navier Stokes ◽  
Ansys Fluent ◽  
Simulation Accuracy ◽  
Numerical Diffusion ◽  
Diffusion Temperature

Numerical simulation of fluid flow and heat or mass transfer phenomenon requires numerical solution of Navier–Stokes and energy-conservation equations, together with the continuity equation. The basic problem of solving general transport equations by the Finite Volume Method (FVM) is the exact calculation of the transport quantity. Numerical or false diffusion is a phenomenon of inserting errors in calculations that threaten the accuracy of the computational solution. The paper compares the physical accuracy of the calculation in the Computational Fluid Dynamics (CFD) code in Ansys Fluent using the offered discretization calculation schemes, methods of solving the gradients of the transport quantity on the cell walls, and the influence of the mesh type. The paper offers possibilities on how to reduce numerical errors. In the calculation area, the sharp boundary of two areas with different temperatures is created in the flow direction. The three-dimensional (3D) stationary flow of the fictitious gas is simulated using FVM so that only advective transfer, in terms of momentum and heat, arises. The subject of the study is to determine the level of numerical diffusion (temperature field scattering) and to evaluate the values of the transport quantity (temperature), which are outside the range of specified boundary conditions at variously set calculation parameters.

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.

scholarly journals CFD Simulation of Flow Tones From Grazing Flow Past a Deep Cavity

2006 ◽  
Author(s):  
Ted G. Bagwell
Keyword(s):  
Shear Layer ◽  
Cfd Simulation ◽  
Stokes Equations ◽  
Weak Interactions ◽  
Cavity Resonator ◽  
Navier Stokes ◽  
Flow State ◽  
Deep Cavity ◽  
Eddy Simulation ◽  
Lock In

Locked-in flow tones due to shear flow over a deep cavity are investigated using Large Eddy Simulation (LES). An isentropic from of the compressible Navier-Stokes equations (pseudo-compressibility) is used to couple the vertical flow over the cavity mouth with the deep cavity resonances (1). Comparisons to published experimental data (2) show that the pseudo-compressible LES formulation is capable of predicting the feedforward excitation of the deep cavity resonator, as well as the feedback process from the resonator to the flow source. By systematically increasing the resonator damping level, it is shown that strong lock-in results in a more organized shear layer than is observed for the locked-out flow state. By comparison, weak interactions (non-locked-in) produce no change in the shear layer characteristics. This supports the 40 dB definition of lock-in defined in the experiment.

A Transonic Compressor Stage: Part 2 — CFD Simulation

2004 ◽  
Author(s):  
G. V. Hobson ◽  
A. J. Gannon ◽  
R. P. Shreeve
Keyword(s):  
Cfd Simulation ◽  
Pressure Ratio ◽  
Internal Flow ◽  
Design Tool ◽  
Experimental Results ◽  
Navier Stokes ◽  
Experimental Program ◽  
Compressor Stage ◽  
Transonic Compressor ◽  
Cfd Method

The simulation of a transonic compressor stage is presented. This stage was designed using an Euler CFD code with the intent of minimizing the use of empirical design techniques. The stage has subsequently been built and tested. More recently an existing multi-block Navier-Stokes code with a steady averaging-plane to pass information between the blade rows was used to simulate the flow through the machine. Performance maps of stage pressure ratio and efficiency at 70, 80, 90 and 100% speeds from both the Euler and Navier-Stokes CFD codes are compared with the experimental results. Details of the internal flow from the Navier-Stokes code are presented. Comparison of the design Euler CFD and experimental results showed reasonable agreement and validated its use as a design tool. Agreement between experimental and the current Navier-Stokes CFD results was good, allowing the code to be used in the viewing of the internal flow field. Improvements to the initial design CFD method are discussed in light of the experimental program and more recent simulations.

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