Effect of Bilge Radius and Bilge Keel Height on Roll Damping Performance of Floating Structures

Kinetic Energy ◽

Floating Body ◽

Rectangular Section ◽

Roll Damping ◽

Floating Structures ◽

Free Decay ◽

Computational Fluid Dynamics Cfd ◽

Bilge Keel

Abstract A round bilge with a bilge keel structure is a key element which can alleviate roll motions of ships and floating structures by transferring the roll momentum of a floating body into the kinetic energy of water. This study presents a practical guide to properly designing a bilge radius and bilge keel height of a barge-shaped and tanker-shaped FPSOs. A parametric study to figure out the effect of bilge radius and bilge keel height on the roll damping performance is conducted through a series of numerical roll free decay simulations based on Computational Fluid Dynamics (CFD). The bilge radius is normalized by the half breadth of ship, and the bilge keel height is normalized by the maximum bilge keel height which is limited by the molded lines of a side shell and bottom shell. In addition, it is investigated to identify how the roll damping performance of a rectangular section differs from the result of a typical round bilge section with maximum available bilge keel height.

Morphological and Hemodynamic Changes during Cerebral Aneurysm Growth

Brain Sciences ◽

10.3390/brainsci11040520 ◽

2021 ◽

Vol 11 (4) ◽

pp. 520

Author(s):

Emily R. Nordahl ◽

Susheil Uthamaraj ◽

Kendall D. Dennis ◽

Alena Sejkorová ◽

Aleš Hejčl ◽

...

Keyword(s):

Fluid Dynamics ◽

Kinetic Energy ◽

Swirling Flow ◽

Morphological Changes ◽

Cerebral Aneurysms ◽

Patient Specific ◽

Aneurysm Wall ◽

Aneurysm Growth ◽

Computational fluid dynamics (CFD) has grown as a tool to help understand the hemodynamic properties related to the rupture of cerebral aneurysms. Few of these studies deal specifically with aneurysm growth and most only use a single time instance within the aneurysm growth history. The present retrospective study investigated four patient-specific aneurysms, once at initial diagnosis and then at follow-up, to analyze hemodynamic and morphological changes. Aneurysm geometries were segmented via the medical image processing software Mimics. The geometries were meshed and a computational fluid dynamics (CFD) analysis was performed using ANSYS. Results showed that major geometry bulk growth occurred in areas of low wall shear stress (WSS). Wall shape remodeling near neck impingement regions occurred in areas with large gradients of WSS and oscillatory shear index. This study found that growth occurred in areas where low WSS was accompanied by high velocity gradients between the aneurysm wall and large swirling flow structures. A new finding was that all cases showed an increase in kinetic energy from the first time point to the second, and this change in kinetic energy seems correlated to the change in aneurysm volume.

Analysis of an Airfoil Using a Transition and Turbulence Model

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.819.356 ◽

2016 ◽

Vol 819 ◽

pp. 356-360

Author(s):

Mazharul Islam ◽

Jiří Fürst ◽

David Wood ◽

Farid Nasir Ani

Keyword(s):

Fluid Dynamics ◽

Boundary Layer ◽

Kinetic Energy ◽

Turbulence Model ◽

Original Version ◽

Transitional Region ◽

Cfd Analysis ◽

In order to evaluate the performance of airfoils with computational fluid dynamics (CFD) tools, modelling of transitional region in the boundary layer is very critical. Currently, there are several classes of transition-based turbulence model which are based on different methods. Among these, the k-kL- ω, which is a three equation turbulence model, is one of the prominent ones which is based on the concept of laminar kinetic energy. This model is phenomenological and has several advantageous features. Over the years, different researchers have attempted to modify the original version which was proposed by Walter and Cokljat in 2008 to enrich the modelling capability. In this article, a modified form of k-kL-ω transitional turbulence model has been used with the help of OpenFOAM for an investigative CFD analysis of a NACA 4-digit airfoil at range of angles of attack.

Analysis of a Converging, Annular, Isothermal Melt Blowing Jet Using Computational Fluid Dynamics

International Nonwovens Journal ◽

10.1177/1558925005os-1400301 ◽

2005 ◽

Vol os-14 (3) ◽

pp. 1558925005os-14

Author(s):

Eric M. Moore ◽

Dimitrios V. Papavassiliou ◽

Robert L. Shambaugh

Keyword(s):

Fluid Dynamics ◽

Kinetic Energy ◽

Near Field ◽

Flow Characteristics ◽

Sectional Area ◽

Melt Blowing ◽

Mean Velocity ◽

Cross Sectional ◽

An unconventional melt blowing die was analyzed using computational fluid dynamics (CFD). This die has an annular configuration wherein the jet inlet is tapered (the cross-sectional area decreases) as the air approaches the die face. It was found that the flow characteristics of this die are different from conventional slot and annular dies. In particular, for the tapered die the near-field normalized turbulent kinetic energy was found to be lower at shallow die angles. Also, it was found that the peak mean velocity behavior was intermediate between that of conventional annular and slot dies. The centerline turbulence profiles were found to be qualitatively similar to those of annular dies; quantitatively, higher values were present for tapered dies.

Design and Control of Diesel and Natural Gas Engines for Industrial and Rail Transportation Applications ◽

Design and Evaluation of High Pressure Fuel Valve Nozzles Using the Method of Characteristics and CFD

10.1115/icef2003-0742 ◽

2003 ◽

Author(s):

Sangwon Kim ◽

Charles Mitchell ◽

Allan Kirkpatrick

Keyword(s):

Fluid Dynamics ◽

Kinetic Energy ◽

Method Of Characteristics ◽

Average Kinetic Energy ◽

Fuel Mass ◽

Natural Gas Engines ◽

The Method Of Characteristics ◽

Computational Fluid Dynamics Cfd ◽

Energy And Momentum

The topic of this paper is the design of fuel valve nozzles for natural gas engines that maximize the kinetic energy and momentum of the injected fuel and maintain a required mass flow rate. The nozzle design used both the method of characteristics and computational fluid dynamics (CFD). Three types of nozzles were designed: a converging-diverging nozzle, three conical nozzles and an aerospike nozzle. The evaluation of the performance of the nozzle designs was conducted using Computational Fluid Dynamics. CFD simulations were used to calculate the average axial momentum per unit fuel mass and the average kinetic energy per unit fuel mass in the jets emanating from each nozzle. The performance was computed in off-design conditions (2.9MPa, 3.1MPa) as well as for the nominal design supply pressure of 3 MPa. Results showed that for the new nozzle designs, the average axial momentum per unit mass was improved by 17 to 24% and the average kinetic energy per unit fuel mass was improved by 30 to 80% compared with a standard shrouded poppet valve. Of the candidate designs, the converging-diverging nozzle gave the best performance, and the simple 15 degree conical nozzle also performed very well.

CFD Simulation of Flow in a Circular Pipe With Percina Rex Fish

Volume 7: Fluid Flow, Heat Transfer and Thermal Systems, Parts A and B ◽

10.1115/imece2010-39973 ◽

2010 ◽

Author(s):

Sreekanth Bangaru ◽

Jie Cui

Keyword(s):

Fluid Dynamics ◽

Kinetic Energy ◽

Cfd Simulation ◽

Fish Passage ◽

Fish Behavior ◽

Circular Pipe ◽

Streamwise Direction ◽

Computational Fluid Dynamics Cfd ◽

Roanoke Logperch

We tried to correlate the fish behavior observed in the laboratory during the development of the exhaustion threshold curves with flow field in the fish passage with culverts and other impediments. In particular, we focused on aspects of fish behavior which may have exploited the velocity and turbulence fields in a circular passage. Roanoke logperch ( Percina rex ), the largest of the Virginia’s darters are federally endangered species. Logperch of different sizes were tested during the development of the exhaustion threshold curves at different velocities ranging from 40 to 70 cm/s in the laboratory in a circular pipe. The pipe was divided into four quadrants in the streamwise direction. Simulations were run at velocities 40 and 70 cm/s using Computational Fluid Dynamics (CFD) software Fluent with fish at center and bottom of the pipe. The velocity and turbulence kinetic energy contours of all the positions of the fish were compared to correlate the fish behavior observed in the laboratory.

Spray Pattern of Aluminum Coatings with the Rectangular Cross-Section Nozzle Calculated by the Computational Fluid Dynamics (CFD) in High-Pressure Cold Spray

Thermal Spray 2021: Proceedings from the International Thermal Spray Conference ◽

10.31399/asm.cp.itsc2021p0214 ◽

2021 ◽

Author(s):

Kazuhiko Sakaki ◽

Tomiki Tsubata ◽

Hikaru Isogami ◽

Koki Matsuda

Keyword(s):

Fluid Dynamics ◽

High Pressure ◽

Cold Spray ◽

Aluminum Particles ◽

Rectangular Section ◽

Cross Sectional ◽

Spray Pattern ◽

Rectangular Nozzle ◽

Abstract In the cold spray process; cross-sectional shape of the nozzle has a significant effect on spray pattern of coatings. The circular exit nozzle is parabolic in shape. So; spray pattern with the rectangular nozzle is wider than that with the circular spray nozzle. The goal of this investigation is to establish a design for the cold spray gun nozzle to gain more uniform spray profile of coatings. We have investigated the influence of expansion ratio; nozzle total length and the ratio of nozzle length of divergent section and parallel section of rectangular nozzle on behaviors of gas and particle by the computational fluid dynamics (CFD) in high pressure cold spraying. We have studied copper particles so far. In this study; we will examine aluminum particles. First; we investigate the influence of the size and shape of the rectangular section nozzle on the velocity; temperature; and particle distribution of aluminum particles by CFD. After that; the rectangular section nozzles were fabricated and coating formation experiments were conducted; spray patterns and coating cross-sectional structures were observed; and coating adhesion was also evaluated. The nozzle material was polybenzimidazole resin; which is difficult for aluminum particles to attach to nozzle walls.