Assessing the Wind-Heel Angle Relationship of Traditionally-Rigged Sailing Vessels

2009 ◽  
Author(s):  
William C. Lasher ◽  
Diana R. Tinlin ◽  
Bruce Johnson ◽  
John Womack ◽  
Jan C. Miles ◽  
...  
Keyword(s):  
Model Uncertainty ◽  
Significant Error ◽  
Future Research ◽  
Experimental Measurements ◽  
Cfd Model ◽  
Cfd Simulations ◽  
Computational Fluid Dynamics Cfd ◽  
Computationally Expensive ◽  
Experimental Values ◽  
Relationship Of

A program to assess the wind-heel relationship of traditionally-rigged sailing vessels has been undertaken with the eventual goal of being able to provide sailing guidance to the masters and crews. This program uses Computational Fluid Dynamics (CFD) with full-scale experimental measurement to develop and validate a windheel model, as well as understand the nature of how these vessels respond to different wind situations. The CFD simulations are used to assess errors in measured wind angle and direction, and the experimental data are used to establish the CFD model uncertainty. The model has been validated against a limited set of data from Pride of Baltimore II. In some cases the agreement between the model and experimental values is excellent; in other cases there is significant error. The CFD-based model is computationally expensive, so a different approach for determining the sail forces is proposed. The experimental measurements indicate that the ship is almost never in static equilibrium, which raises questions about the validity of models based on equilibrium principles. These questions have not yet been answered and are the topic of ongoing future research.

CFD Simulations of the Cold Neutron Source at the OPAL Reactor

2020 ◽  
Author(s):  
James L Spedding ◽  
Mark Ho ◽  
Weijian Lu
Keyword(s):  
Neutron Source ◽  
Cold Neutron ◽  
Operating Conditions ◽  
Convergence Time ◽  
Cfd Model ◽  
Cfd Simulations ◽  
Cold Neutron Source ◽  
Order Of Magnitude ◽  
Computational Fluid Dynamics Cfd ◽  
Polyhedral Mesh

Abstract The Open Pool Australian Light-water (OPAL) reactor Cold Neutron Source (CNS) is a 20 L liquid deuterium thermosiphon system which has performed consistently but will require replacement in the future. The CNS deuterium exploits neutronic heating to passively drive the thermosiphon loop and is cryogenically cooled by forced convective helium flow via a heat exchanger. In this study, a detailed computational fluid dynamics (CFD) model of the complete thermosiphon system was developed for simulation. Unlike previous studies, the simulation employed a novel polyhedral mesh technique. Results demonstrated that the polyhedral technique reduced simulation computational requirements and convergence time by an order of magnitude while predicting thermosiphon performance to within 1% accuracy when compared with prototype experiments. The simulation model was extrapolated to OPAL operating conditions and confirmed the versatility of the CFD model as an engineering design and preventative maintenance tool. Finally, simulations were performed on a proposed second-generation CNS design that increases the CNS moderator deuterium volume by 5 L, and results confirmed that the geometry maintains the thermosiphon deuterium in the liquid state and satisfies the CNS design criteria.

Development of a flocculation sub-model for a 3-D CFD model based on rectangular settling tanks

2011 ◽  
Vol 63 (2) ◽  
pp. 213-219 ◽  
Author(s):  
M. Gong ◽  
S. Xanthos ◽  
K. Ramalingam ◽  
J. Fillos ◽  
K. Beckmann ◽  
...  
Keyword(s):  
New York ◽  
Suspended Solids ◽  
Cfd Model ◽  
Mixed Liquor ◽  
City College ◽  
Solids Loading ◽  
Before And After ◽  
Computational Fluid Dynamics Cfd ◽  
3D Computer Model ◽  
Relationship Of

To assess performance and evaluate alternatives to improve the efficiency of rectangular Gould II type final settling tanks (FSTs), New York City Department of Environmental Protection and City College of NY developed a 3D computer model depicting the actual structural configuration of the tanks and the current and proposed hydraulic and solids loading rates. Fluent 6.3.26™ was the base platform for the computational fluid dynamics (CFD) model, for which sub-models of the SS settling characteristics, turbulence, flocculation and rheology were incorporated. This was supplemented by field and bench scale experiments to quantify the coefficients integral to the sub-models. The 3D model developed can be used to consider different baffle arrangements, sludge withdrawal mechanisms and loading alternatives to the FSTs. Flocculation in the front half of the rectangular tank especially in the region before and after the inlet baffle is one of the vital parameters that influences the capture efficiency of SS. Flocculation could be further improved by capturing medium and small size particles by creating an additional zone with an in-tank baffle. This was one of the methods that was adopted in optimizing the performance of the tank where the CCNY 3D CFD model was used to locate the in-tank baffle position. This paper describes the development of the flocculation sub-model and the relationship of the flocculation coefficients in the known Parker equation to the initial mixed liquor suspended solids (MLSS) concentration X0. A new modified equation is proposed removing the dependency of the breakup coefficient to the initial value of X0 based on preliminary data using normal and low concentration mixed liquor suspended solids values in flocculation experiments performed.

Validation of a 2D CFD Model for Hydrodynamics' Studies in CIJ Mixers

2010 ◽  
Vol 8 (1) ◽  
Author(s):  
Ricardo J. Santos ◽  
André M. Teixeira ◽  
Ertugrul Erkoç ◽  
Mohamed Sultan ◽  
Anna M Karpinska ◽  
...  
Keyword(s):  
Flow Field ◽  
Impinging Jets ◽  
Cfd Model ◽  
Operational Parameters ◽  
3D Flow ◽  
Cfd Simulations ◽  
Mixing Chamber ◽  
Validity Range ◽  
Computational Fluid Dynamics Cfd ◽  
2D Model

A 2D model of a confined impinging jets mixer having the same geometry of the mixing chamber of a Reaction Injection Moulding, RIM, machine is introduced for the flow field simulation in a Computational Fluid Dynamics, CFD, code. From the CFD simulations the flow field structures and dynamics are clearly established. In addition, the numerical parameters affecting the 2D model simulations are studied, setting for each parameter a validity range. The 2D model is validated and used in the study of some operational parameters: the Reynolds number, the Froude number and the momentum ratio between the opposed jets. The validation of the CFD simulations is also made by comparison with experimental results. The limitations of the 2D model, for simulating the actual 3D flow field, are assessed; from the 2D/3D comparison, it is clearly shown that the introduced model can predict the main flow field features.

Multiphase Computation of Cavitation Breakdown in Model and Prototype Scale Francis Turbines

2015 ◽  
Author(s):  
Daniel J. Leonard ◽  
Jules W. Lindau
Keyword(s):  
Large Scale ◽  
Scale Model ◽  
Cfd Model ◽  
Cfd Simulations ◽  
Qualitative And Quantitative ◽  
Machine Performance ◽  
Computational Fluid Dynamics Cfd ◽  
Stage Analysis ◽  
Reduced Scale ◽  
Francis Hydroturbine

Steady-periodic multiphase Computational Fluid Dynamics (CFD) simulations were conducted to capture cavitation breakdown in a Francis hydroturbine due to large-scale vaporous structures. A reduced-scale model and a full-scale prototype were investigated to display differences in vapor content and machine performance caused by lack of Reynolds and Froude similarity. The model scale efficiencies compared favorably (within 3%) to the experimental cavitation tests. The CFD model and prototype displayed distinct qualitative and quantitative differences as σ was reduced. A stage-by-stage analysis was conducted to assess the effect of cavitation on loss distribution throughout the machine. Furthermore, a formal mesh refinement study was conducted on efficiency and volume of vapor, with three mesh levels and Richardson extrapolation, to ensure convergence.

scholarly journals Transient 3D CFD Simulation of a Stationary Vane, Oil Free, Rotary Compressor

2019 ◽  
Vol 63 (4) ◽  
pp. 308-318 ◽  
Author(s):  
Balázs Farkas ◽  
Jenő Miklós Suda
Keyword(s):  
Cfd Simulation ◽  
Piston Compressor ◽  
Working Fluid ◽  
Rotary Compressor ◽  
Heat Sources ◽  
Cfd Model ◽  
Cfd Simulations ◽  
Computational Fluid Dynamics Cfd ◽  
Rolling Piston ◽  
Good Agreement

The evaluation of a newly designed oil-free rotary compressor is presented based on transient 3D Computational Fluid Dynamics (CFD) simulations. The simulations are performed at low compression ratios and low pressure ratios and low rotational speeds. To place the results into context, the data presented in related literature was processed and summarized. The methods related to the CFD model of the newly designed compressor were developed, summarized and evaluated. The accessed CFD data are in good agreement with the results of the former rolling piston compressor related investigations. The oil free operation prevents the contamination of the working fluid from lubricant. Since the compressor is planned to work in open cycle within the sensitive environment of thermal heat sources contamination free operation has to be accomplished. However, oil-free operation also results in significantly lower performance based on the modelling results.

The Impacts of Model Uncertainty on RANS CFD Simulations of a High-Speed Craft

2021 ◽  
Author(s):  
Joseph Messler ◽  
Nicholas Husser ◽  
Stefano Brizzolara
Keyword(s):  
Numerical Methods ◽  
Model Uncertainty ◽  
High Speed ◽  
Critical Element ◽  
Cfd Model ◽  
Three Dimensional Model ◽  
Cfd Simulations ◽  
High Quality ◽  
Sources Of Uncertainty ◽  
The Impact

Computational scientists frequently publish papers discussing various sources of uncertainty in numerical methods for computational fluid dynamics. The frequently discussed sources of uncertainty are round off error, discretization error, iterative error, and mathematical model uncertainty (i.e. uncertainty in turbulence modeling). While all of these sources of uncertainty are real and impact the results of a simulation, the authors have found through experience that the most critical element to achieving accurate simulation results for high-speed craft is the generation of a high quality mesh on which the numerical methods are solved. There are, in general, two requirements for a high quality mesh; refinement regions must be applied in regions where the physics of the flow are most significant, and the three dimensional model of the hull form must be appropriately defined and fair. The latter appears to be a major contributing factor to uncertainty in CFD simulations that is not often discussed in the literature. Further, in practice there are numerous sources of geometric uncertainty between a prescribed CAD geometry and physically constructed model. In this paper, simulations are performed on two models of GPPH, with and without an edge radius on the transom to evaluate the impact of including fine geometric details (like tooling radii) in a RANS CFD model. The results of the simulations show that the inclusion of the rounded edge leads to large simulation errors in resistance and running attitude. This work has concluded that inclusion of fine geometric details in a planing hull CFD model is not beneficial to the overall accuracy of the simulations relative to necessary design accuracy.

CFD Simulations of Flows in Step-up Street Canyons

2020 ◽  
Author(s):  
Soo-Jin Park ◽  
Jae-Jin Kim ◽  
Eric Pardyjak ◽  
Ji-Yoon Hong
Keyword(s):  
Wind Tunnel ◽  
Flow Characteristics ◽  
Width Ratio ◽  
Cfd Model ◽  
Wind Tunnel Experiments ◽  
Cfd Simulations ◽  
Street Canyons ◽  
Recirculation Zones ◽  
Computational Fluid Dynamics Cfd ◽  
Two Stages

<p>We analyzed the flow characteristics in strep-up street canyons using a computational fluid dynamics (CFD) model. Simulated results are validated against experimental wind-tunnel results, with the CFD simulations conducted under the same building configurations (H<sub>u</sub>/H<sub>d</sub> = 0.33, 0.6 and L/S = 1, 2, 3, and 4; H<sub>u</sub>, H<sub>d</sub>, L, and S respectively indicate the upwind, downwind building heights, the building length and street-canyon width) as those in the wind-tunnel experiments. The CFD model reproduced the in-canyon vortex, recirculation zones above the downwind buildings, and stagnation point position reasonably well. Furthermore, we analyze the flow characteristics in the step-up street canyons based on the numerical results. The in-canyon flows simulated in the shallow (H<sub>u</sub>/H<sub>d</sub> = 0.33) and deep (H<sub>u</sub>/H<sub>d</sub> = 0.6) street canyons underwent two stages (development and mature stages) as the building-length ratio increased. In the development stages, one clockwise-rotating vortex was formed in the step-up street canyons and its center was slightly tilted toward the wall of the upwind building. However, in the mature stages, two clockwise-rotating vortices were formed in the upper and lower layers. A clockwise vortex and a counterclockwise vortex were stabilized as the building width ratio increased.</p>

MODELING OF THE COMPLETE MECHANISM OF OXIDATION OF PHENYL RADICAL UNDER COMBUSTION CONDITIONS

2020 ◽  
Author(s):  
G. I. Tolstov ◽  
◽  
I. A. Medvedkov ◽  
D. P. Porfiriev ◽  
M. V. Zagidullin ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
High Temperature ◽  
Quantum Chemical ◽  
Experimental Measurements ◽  
Phenyl Radical ◽  
Flow Tube ◽  
Cfd Simulations ◽  
Computational Fluid Dynamics Cfd ◽  
Mechanism Of Oxidation

Quantum chemical calculations, computational fluid dynamics (CFD) simulations, and isothermal approximation were applied for the interpretation of experimental measurements of the reaction of С6Н5 + O2 in the high-temperature microreactor and of the pressure drop in the flow tube of the reactor.

Poststall Behavior of a Multistage High Speed Compressor at Off-Design Conditions

2018 ◽  
Vol 140 (12) ◽  
Author(s):  
Fanzhou Zhao ◽  
John Dodds ◽  
Mehdi Vahdati
Keyword(s):  
High Speed ◽  
Transient Flow ◽  
Axisymmetric Flow ◽  
Axial Compressor ◽  
Transient Behavior ◽  
Rotating Stall ◽  
Navier Stokes ◽  
Experimental Measurements ◽  
Cfd Simulations ◽  
Computational Fluid Dynamics Cfd

Stall followed by surge in a high speed compressor can lead to violent disruption of flow, damage to the blade structures and, eventually, engine shutdown. Knowledge of unsteady blade loading during such events is crucial in determining the aeroelastic stability of blade structures; experimental test of such events is, however, significantly limited by the potential risk and cost associated. Numerical modeling, such as unsteady computational fluid dynamics (CFD) simulations, can provide a more informative understanding of the flow field and blade forcing during poststall events; however, very limited publications, particularly concerning multistage high speed compressors, can be found. The aim of this paper is to demonstrate the possibility of using CFD for modeling full-span rotating stall and surge in a multistage high speed compressor, and, where possible, validate the results against experimental measurements. The paper presents an investigation into the onset and transient behavior of rotating stall and surge in an eight-stage high speed axial compressor at off-design conditions, based on 3D Reynolds-averaged Navier–Stokes (URANS) computations, with the ultimate future goal being aeroelastic modeling of blade forcing and response during such events. By assembling the compressor with a small and a large exit plenum volume, respectively, a full-span rotating stall and a deep surge were modeled. Transient flow solutions obtained from numerical simulations showed trends matching with experimental measurements. Some insights are gained as to the onset, propagation, and merging of stall cells during the development of compressor stall and surge. It is shown that surge is initiated as a result of an increase in the size of the rotating stall disturbance, which grows circumferentially to occupy the full circumference resulting in an axisymmetric flow reversal.

Numerical Simulation of Biodiesel Production Using Waste Cooking Oil

2013 ◽  
Author(s):  
A. K. M. Mohiuddin ◽  
Nabeel Adedapo Adeyemi
Keyword(s):  
Waste Cooking Oil ◽  
Reynolds Stress Model ◽  
Biodiesel Production ◽  
Cfd Simulations ◽  
Piv Measurements ◽  
Image Velocimetry ◽  
Dissipation Model ◽  
Computational Fluid Dynamics Cfd ◽  
Experimental Values ◽  
Cfd Method

The goal of this work was to carry out transesterification using computational fluid dynamics (CFD) method and obtain yield comparable to experimental values. First of all, the single–phase flow field was simulated and compared with experimental data obtained by means of particle image velocimetry (PIV) measurements. The velocities calculated from the RSM approach agreed quite well with those from PIV. The CFD simulations of biodiesel production were performed using the Reynolds stress model (RSM) coupled with the eddy dissipation model (EDM). CFD analysis of biodiesel yield compared fairly well with the experimental results available.

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