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.

Improved Two-Dimensional Dynamic Stall Prediction with Structured and Hybrid Numerical Methods

2011 ◽  
Vol 56 (4) ◽  
pp. 1-12 ◽  
Author(s):  
K. Richter ◽  
A. Le Pape ◽  
T. Knopp ◽  
M. Costes ◽  
V. Gleize ◽  
...  
Keyword(s):  
Numerical Methods ◽  
Numerical Method ◽  
High Speed ◽  
Turbulence Modeling ◽  
Turbulence Models ◽  
Boundary Layer Transition ◽  
Dynamic Stall ◽  
Two Dimensional ◽  
Layer Transition ◽  
The Impact

A joint comprehensive validation activity on the structured numerical method elsA and the hybrid numerical method TAU was conducted with respect to dynamic stall applications. To improve two-dimensional prediction, the influence of several factors on the dynamic stall prediction was investigated. The validation was performed for three deep dynamic stall test cases of the rotor blade airfoil OA209 against experimental data from two-dimensional pitching airfoil experiments, covering low-speed and high-speed conditions. The requirements for spatial discretization and for temporal resolution in elsA and TAU are shown. The impact of turbulence modeling is discussed for a variety of turbulence models ranging from one-equation Spalart–Allmaras-type models to state-of-the-art, seven-equation Reynolds stress models. The influence of the prediction of laminar/turbulent boundary layer transition on the numerical dynamic stall simulation is described. Results of both numerical methods are compared to allow conclusions to be drawn with respect to an improved prediction of dynamic stall.

Numerical Study of the Pusher-Type Billet Reheating Furnace

2005 ◽  
Author(s):  
Linjiang Zou ◽  
Chaoxiang Li ◽  
Yinmei Yuan ◽  
Wei Guo ◽  
Fan Yang ◽  
...  
Keyword(s):  
Software Package ◽  
High Speed ◽  
Gas Flow ◽  
Numerical Study ◽  
Three Dimensional ◽  
Cfd Model ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
Iron And Steel ◽  
Reheating Furnace

In the present work, a commercial CFD software package, FLUENT, was used to develop a three-dimensional model of pusher-type billet reheating furnace for the second high speed wire rod plant of XiangTan Iron and steel Co. Ltd. The purpose of the study was to gain a better understanding of the gas flow and velocity and pressure distribution in the furnace. The results show that the numerical results are in agreement with the practice and the characteristics of the furnace configuration. The CFD model can be used to improve the performance and structure by analyzing and studying the behavior of the reheating furnace.

scholarly journals Minimising Numerical Ventilation in CFD Simulations of High-speed Planing Hulls

2021 ◽  
pp. 1-33
Author(s):  
Angus Gray-Stephens ◽  
Tahsin Tezdogan ◽  
Sandy Day
Keyword(s):  
Free Surface ◽  
High Speed ◽  
Volume Of Fluid Method ◽  
Cfd Simulations ◽  
Entrance Angle ◽  
Depth Analysis ◽  
Prism Layer ◽  
The Impact ◽  
Mesh Refinements ◽  
Volume Mesh

Abstract Numerical Ventilation (NV) is a well-known problem that occurs when the Volume of Fluid method is used to model vessels with a bow that creates an acute entrance angle with the free surface, as is typical for both planing hulls and yachts. Numerical Ventilation may be considered one of the main sources of error in numerical simulations of planing hulls and as such warrants an in-depth analysis. This paper sets out to bring together the available work, as well as performing its own investigation into the problem to develop a better understanding of Numerical Ventilation and present alternate solutions. Additionally, the success and impact of different approaches is presented in an attempt to help other researchers avoid and correct for Numerical Ventilation. Interface smearing caused by the simulation being unable to track the free surface is identified as the main source of Numerical Ventilation. This originates from the interface between the volume mesh and the prism layer mesh. This study investigates this interface, presenting a novel solution to prism layer meshing that was found to minimize Numerical Ventilation. Through the implementation of a modified High Resolution Interface Capture (HRIC) scheme and the correct mesh refinements, it is possible to minimize the impact of Numerical Ventilation to a level that will not affect the results of a simulation and is acceptable for engineering applications.

scholarly journals The Effect of Governance Quality on Economic Growth: Based on China’s Provincial Panel Data

Economies ◽  
2018 ◽  
Vol 6 (4) ◽  
pp. 56 ◽  
Author(s):  
Jiandang Liu ◽  
Jie Tang ◽  
Bo Zhou ◽  
Zhijun Liang
Keyword(s):  
Economic Growth ◽  
Human Capital ◽  
Economic Development ◽  
Panel Data ◽  
High Speed ◽  
Growth Effect ◽  
Eastern Region ◽  
High Quality ◽  
Governance Quality ◽  
The Impact

This paper investigates the impact of governance quality on economic growth in China. After developing a theoretical framework for the effect of governance quality on local economic growth, this article studies the panel data in provincial regions over the period 2001–2015 by constructing a new comprehensive index of provincial governance, and checks the robustness of the empirical findings from four aspects. The results show that governance quality has a positive effect on economic growth, due to good governance strengthening the “helping hand” or weakening the “grabbing hand” of power. Governance quality presents diminishing marginal returns, which means that the high-speed economic growth effect becomes less and less, while the high-quality economic development effect becomes more and more. Higher governance quality could bring a high-speed economic growth effect in the western region, while higher governance quality could bring a high-quality economic development effect in the eastern region. Compared with fixed-asset investment, human capital has played a more important role in economic growth. In order to promote the sustainable development of China’s economy, policy makers should improve local governance quality, strengthen the capacity of independent innovation, and promote the accumulation of high-quality human capital.

Impact Resistance of Liquid Body Armor Utilizing Shear Thickening Fluids: A Computational Study

2015 ◽  
Author(s):  
Fardin Khalili ◽  
Federico De Paoli ◽  
Rasim Guldiken
Keyword(s):  
Multiphase Flow ◽  
High Speed ◽  
Volume Fraction ◽  
Computational Study ◽  
Shear Thickening ◽  
Ballistic Performance ◽  
High Quality ◽  
Liquid Body ◽  
Shear Thickening Fluids ◽  
The Impact

Since the creation of advanced knives and firearms with high rates of speed, safety has always been a vital issue for armed forces. A disadvantage of a regular fabric Kevlar is that, although it has an effective resistance against the impact of low-speed bullets, it reveals its weakness in the case of a stab wound and high-speed bullets. Under these circumstances, a new executable technology of fibers that improves the ballistic performance of the materials utilized in body armors is an essential necessity to build high quality and protective vests which are perfectly bulletproof. The purpose of this study is to investigate the physics and concepts of shear thickening fluids and perform a computational CFD simulation of liquid body armors which consist of a combination of polyethylene glycol liquid and nanoparticles of silica. A model of multiphase flow environment with STFKevlar, as a representative of the non-Newtonian shear thickening fluid (STF), is simulated in STAR-CCM+ in order to analyze the behavior of STFs under impact and performance of novel liquid body armors. In the current simulation, Eulerian multiphase flow and volume of fluid (VOF) are applied to generate three discrete regions and determine the volume fraction of each phase including gas, non-Newtonian liquid and solid which represent air, STFKevlar and bullet, respectively. Moreover, dynamic fluid body interactions (DFBI) and overset mesh are utilized to consider the interactions between the regions and forces applied. In this study, the properties of the bullet are based on characteristics of a regular pistol bullet, and it approaches the STFKevlar with the constant speed of 400 m/s. The results show that the non-Newtonian material is initially at equilibrium state and while the bullet approaches the STFKevlar, it acts like a shear thinning fluid. As a high-speed bullet nears the STFKevlar, it absorbs the significant amount of energy that is applied by the bullet. Consequently, the bullet stops penetrating the STFKevlar in a very small fraction of time due to the considerable increase in viscosity. As the shear rate increases over a certain critical value, viscosity increases remarkably which is the main characteristic of shear thickening transition and finally, it reaches to its maximum value of viscosity in approximately 8 × 10−5sec. In addition, a bullet applies a considerable amount of force on any Kevlar due to its high velocity and kinetic energy; however, the high resistant STFKevlar is approved as a high quality and protective vests which stops the bullet in 6 × 10−4sec.

scholarly journals The impact of facilities and service-based competition on Internet services provision in the Canadian Broadband Market

2021 ◽  
Author(s):  
Annemijn van Gorp ◽  
Catherine A. Middleton
Keyword(s):  
High Speed ◽  
Market Competition ◽  
Regulatory Regime ◽  
Internet Services ◽  
Policy Environment ◽  
High Quality ◽  
Early Adopters ◽  
Broadband Services ◽  
Broadband Market ◽  
The Impact

A variety of studies have focused on the effect of competition in broadband markets on increasing broadband penetration rates. Few studies however have focused on the extent to which competition also results in innovation in the marketplace, as demonstrated by increased broadband speeds, and other improvements that provide value to broadband users. This paper considers the effectiveness of market competition as a means of encouraging broadband providers to offer innovative services that meet citizens’ increasing needs for affordable high quality and high speed broadband connectivity. The study focuses on the provision of broadband services in Canada, a country where consumers were early adopters of broadband and where the policy environment has encouraged competition in the broadband market from its inception. Drawing on data from the OECD and the Canadian Radio-television and Telecommunications Commission (CRTC), the paper demonstrates that Canada’s regulatory regime does not appear to be sufficient to enable a competitive marketplace that results in the provision of innovative broadband services.

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.

scholarly journals The impact of facilities and service-based competition on Internet services provision in the Canadian Broadband Market

2021 ◽  
Author(s):  
Annemijn van Gorp ◽  
Catherine A. Middleton
Keyword(s):  
High Speed ◽  
Market Competition ◽  
Regulatory Regime ◽  
Internet Services ◽  
Policy Environment ◽  
High Quality ◽  
Early Adopters ◽  
Broadband Services ◽  
Broadband Market ◽  
The Impact

A variety of studies have focused on the effect of competition in broadband markets on increasing broadband penetration rates. Few studies however have focused on the extent to which competition also results in innovation in the marketplace, as demonstrated by increased broadband speeds, and other improvements that provide value to broadband users. This paper considers the effectiveness of market competition as a means of encouraging broadband providers to offer innovative services that meet citizens’ increasing needs for affordable high quality and high speed broadband connectivity. The study focuses on the provision of broadband services in Canada, a country where consumers were early adopters of broadband and where the policy environment has encouraged competition in the broadband market from its inception. Drawing on data from the OECD and the Canadian Radio-television and Telecommunications Commission (CRTC), the paper demonstrates that Canada’s regulatory regime does not appear to be sufficient to enable a competitive marketplace that results in the provision of innovative broadband services.

scholarly journals Transportation Infrastructure Construction and High-Quality Development of Enterprises: Evidence from the Quasi-Natural Experiment of High-Speed Railway Opening in China

2021 ◽  
Vol 13 (23) ◽  
pp. 13316
Author(s):  
Tianjiao Zhao ◽  
Xiang Xiao ◽  
Qinghui Dai
Keyword(s):  
Information Disclosure ◽  
High Speed ◽  
Natural Experiment ◽  
Quality Development ◽  
High Quality ◽  
Quality Of Information ◽  
High Speed Railway ◽  
Business Environments ◽  
The Impact

High-quality development of the economy is an important guarantee for economic and business sustainability, and the construction of transportation infrastructure is an important channel to achieving high-quality development. Thus, we take the opening of China’s high-speed railway (HSR) as a quasi-natural experiment and use the difference-in-difference model to explore the impact and mechanism of HSR on firms’ high-quality development. By using the total factor productivity of enterprises as the proxy for high-quality development, the empirical results show that: (1) the opening of the HSR can significantly promote high-quality development of enterprises; (2) the quality of information disclosure plays a mediating role in such relationships; and (3) the impact of HSR on enterprises’ high-quality development is more significant for enterprises that are located in cities with better business environments. Overall, this research indicates that local infrastructure construction is an important factor to achieve high-quality development of enterprises as well as economic sustainability that cannot be ignored, and this conclusion will be helpful for corporate managers in enhancing the quality of information disclosure, as well as for local governments to attach more importance to optimizing business environments to achieve high-quality development and economic sustainability.

Structural changes in silicon-on-insulator material during post-implantation annealing

1986 ◽  
Vol 44 ◽  
pp. 736-737
Author(s):  
C. O. Jung ◽  
S. J. Krause ◽  
S.R. Wilson
Keyword(s):  
Integrated Circuits ◽  
Oxide Layer ◽  
High Speed ◽  
Structural Changes ◽  
Device Fabrication ◽  
Silicon On Insulator ◽  
High Quality ◽  
Radiation Hardened ◽  
Post Implantation ◽  
Very High

Silicon-on-insulator (SOI) structures have excellent potential for future use in radiation hardened and high speed integrated circuits. For device fabrication in SOI material a high quality superficial Si layer above a buried oxide layer is required. Recently, Celler et al. reported that post-implantation annealing of oxygen implanted SOI at very high temperatures would eliminate virtually all defects and precipiates in the superficial Si layer. In this work we are reporting on the effect of three different post implantation annealing cycles on the structure of oxygen implanted SOI samples which were implanted under the same conditions.

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