MARINE ROUGHENED CYLINDER WAVE FORCE COEFFICIENTS

John H. Nath

doi:10.9753/icce.v19.182

On Wave Force Coefficient Variability

Journal of Offshore Mechanics and Arctic Engineering ◽

10.1115/1.3257023 ◽

1987 ◽

Vol 109 (4) ◽

pp. 295-306 ◽

Cited By ~ 3

Author(s):

J. H. Nath

Keyword(s):

Phase Angle ◽

Vortex Shedding ◽

Vertical Cylinder ◽

Wave Force ◽

Maximum Force ◽

Periodic Waves ◽

Force Coefficient ◽

Ambient Flow ◽

Smooth Cylinder ◽

Phase Differences

Wave force coefficient variability for cylinders, from wave to wave in a train of periodic waves, has been shown to be dependent on the phase of the force record relative to the ambient flow. The phase varies due to vortex shedding, but the maximum force is approximately constant as seen from this work and the work of other investigators. Thus, the maximum force coefficient is tightly organized according to the Keulegan-Carpenter number and scatter is seen in the phase angle versus Keulegan-Carpenter number. On the other hand, both Cd and Cm have scatter due to these phase differences from wave to wave. For unknown reasons, even when averaged over several wave cycles there is scatter in the results for Cd and Cm. This investigation shows that the maximum force coefficients for a heavily roughened vertical cylinder are tightly arranged according to the Keulegan-Carpenter number and the period parameter. Furthermore, the phase angle is similarly much more organized than for the smooth cylinder.

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Combined Wave and Current Forces on Large-Diameter Submarine Pipelines

Marine Technology and SNAME News ◽

10.5957/mt1.1989.26.1.23 ◽

1989 ◽

Vol 26 (01) ◽

pp. 23-33

Author(s):

José M. Andrés

Keyword(s):

Large Diameter ◽

Reynolds Numbers ◽

Wave Force ◽

Frequency Domain Method ◽

Wave Forces ◽

Transfer Coefficients ◽

Mean Values ◽

Force Coefficients ◽

Force Transfer ◽

Inertia Coefficient

This paper deals with the analysis of combined wave and current forces acting on an 8.3-ft-diameter, 70-ft-long submarine pipeline mounted on a steep slope at Keahole Point on the island of Hawaii, Hawaii. Force transfer coefficients have been obtained for a large number of wave and current conditions. In the absence of strong currents, mean values of wave force coefficients calculated by a frequency-domain method have proven to predict extremely well the distribution of peak wave forces. In cases where current effects are relevant, a wave-by-wave analysis of the loads indicates that, for the range of Reynolds numbers and Keulegan Carpenter parameter covered in this study, the inertia coefficient decreases as the value of the ratio of current to maximum wave velocity increases. The same result is also found by a mean-square method in which overall force coefficients are computed for the whole record length.

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Comments on Levine: "Contingency Planning for Oil Spills: An Update Based on Experience Gained from the Port Angeles Spill"

Marine Technology and SNAME News ◽

10.5957/mt1.1989.26.1.44 ◽

1989 ◽

Vol 26 (01) ◽

pp. 44-46

Author(s):

Ricardo G. Brin

Keyword(s):

Oil Spills ◽

Reynolds Numbers ◽

Wave Force ◽

Frequency Domain Method ◽

Wave Forces ◽

Transfer Coefficients ◽

Mean Values ◽

Force Coefficients ◽

Force Transfer ◽

Inertia Coefficient

This paper deals with the analysis of combined wave and current forces acting on an 8.3-ft-diameter, 70-ft-long submarine pipeline mounted on a steep slope at Keahole Point on the island of Hawaii, Hawaii. Force transfer coefficients have been obtained for a large number of wave and current conditions. In the absence of strong currents, mean values of wave force coefficients calculated by a frequency-domain method have proven to predict extremely well the distribution of peak wave forces. In cases where current effects are relevant, a wave-by-wave analysis of the loads indicates that, for the range of Reynolds numbers and Keulegan Carpenter parameter covered in this study, the inertia coefficient decreases as the value of the ratio of current to maximum wave velocity increases. The same result is also found by a mean-square method in which overall force coefficients are computed for the whole record length.

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Modeling mass transfer and substrate utilization in the boundary layer of biofilm systems

Water Science & Technology ◽

10.2166/wst.1998.0603 ◽

1998 ◽

Vol 37 (4-5) ◽

pp. 139-147 ◽

Cited By ~ 6

Author(s):

Harald Horn ◽

Dietmar C. Hempel

Keyword(s):

Boundary Layer ◽

Mass Transfer ◽

Reynolds Number ◽

Film Theory ◽

Substrate Utilization ◽

The Other ◽

Concentration Profiles ◽

Hydrodynamic Conditions ◽

Time Axis ◽

Transfer Coefficients

The use of microelectrodes in biofilm research allows a better understanding of intrinsic biofilm processes. Little is known about mass transfer and substrate utilization in the boundary layer of biofilm systems. One possible description of mass transfer can be obtained by mass transfer coefficients, both on the basis of the stagnant film theory or with the Sherwood number. This approach is rather formal and not quite correct when the heterogeneity of the biofilm surface structure is taken into account. It could be shown that substrate loading is a major factor in the description of the development of the density. On the other hand, the time axis is an important factor which has to be considered when concentration profiles in biofilm systems are discussed. Finally, hydrodynamic conditions become important for the development of the biofilm surface when the Reynolds number increases above the range of 3000-4000.

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Effect of Integrating Metal Wire Mesh with Spray Injection for Liquid Piston Gas Compression

Energies ◽

10.3390/en14133723 ◽

2021 ◽

Vol 14 (13) ◽

pp. 3723

Author(s):

Barah Ahn ◽

Vikram C. Patil ◽

Paul I. Ro

Keyword(s):

Heat Transfer ◽

Reynolds Number ◽

Heat Transfer Enhancement ◽

Metal Wire ◽

Wire Mesh ◽

Transfer Enhancement ◽

Transfer Coefficients ◽

Heat Transfer Coefficients ◽

Gas Compression ◽

Liquid Piston

Heat transfer enhancement techniques used in liquid piston gas compression can contribute to improving the efficiency of compressed air energy storage systems by achieving a near-isothermal compression process. This work examines the effectiveness of a simultaneous use of two proven heat transfer enhancement techniques, metal wire mesh inserts and spray injection methods, in liquid piston gas compression. By varying the dimension of the inserts and the pressure of the spray, a comparative study was performed to explore the plausibility of additional improvement. The addition of an insert can help abating the temperature rise when the insert does not take much space or when the spray flowrate is low. At higher pressure, however, the addition of spacious inserts can lead to less efficient temperature abatement. This is because inserts can distract the free-fall of droplets and hinder their speed. In order to analytically account for the compromised cooling effects of droplets, Reynolds number, Nusselt number, and heat transfer coefficients of droplets are estimated under the test conditions. Reynolds number of a free-falling droplet can be more than 1000 times that of a stationary droplet, which results in 3.95 to 4.22 times differences in heat transfer coefficients.

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Heat Transfer and Friction in Channels With Very High Blockage 45° Staggered Turbulators

Volume 5: Turbo Expo 2003, Parts A and B ◽

10.1115/gt2003-38611 ◽

2003 ◽

Cited By ~ 14

Author(s):

Jeremy C. Bailey ◽

Ronald S. Bunker

Keyword(s):

Heat Transfer ◽

Reynolds Numbers ◽

Transfer Coefficients ◽

Flow Area ◽

Test Technique ◽

Heat Transfer Coefficients ◽

Smooth Channel ◽

Constant Pitch ◽

Transfer Behavior ◽

Very High

Heat transfer and friction coefficients have been measured within a rectangular passage of aspect ratio 0.4 containing 45-degree staggered turbulators of very high blockage. Using a constant pitch-to-height ratio of 10 for all geometries, turbulator height-to-channel hydraulic diameter ratios from 0.193 to 0.333 were investigated. This range of e/D creates actual channel blockage ratios e/H from 0.275 to 0.475, presenting significant flow area restrictions. A liquid crystal test technique is used to obtain both detailed heat transfer behavior on the surfaces between turbulators, as well as averaged fully developed heat transfer coefficients. Reynolds numbers from 20000 to 100000 were tested. Nusselt number enhancements of up to 3.6 were obtained over that of a smooth channel, with friction coefficient enhancements of as much as 65. In contrast to low-blockage turbulated channels, the 45-degree turbulated Nu is found to be lower than that at 90-degree orientation, given very similar e/D and e/H values.

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Incidence of bloodstream infection among patients on hemodialysis by central venous catheter

Revista Latino-Americana de Enfermagem ◽

10.1590/s0104-11692010000100012 ◽

2010 ◽

Vol 18 (1) ◽

pp. 73-80 ◽

Cited By ~ 14

Author(s):

Cibele Grothe ◽

Angélica Gonçalves da Silva Belasco ◽

Ana Rita de Cássia Bittencourt ◽

Lucila Amaral Carneiro Vianna ◽

Ricardo de Castro Cintra Sesso ◽

...

Keyword(s):

Central Venous Catheter ◽

Bloodstream Infection ◽

Severe Infection ◽

Venous Catheter ◽

Central Venous Catheter Insertion ◽

Central Venous ◽

Double Lumen ◽

One Year ◽

Very High

This study evaluated the incidence and risk factors of bloodstream infection (BSI) among patients with a double-lumen central venous catheter (CVC) for hemodialysis (HD) and identified the microorganisms isolated from the bloodstream. A follow-up included all patients (n=156) who underwent hemodialysis by double-lumen CVC at the Federal University of São Paulo - UNIFESP, Brazil, over a one-year period. From the group of patients, 94 presented BSI, of whom 39 had positive cultures at the central venous catheter insertion location. Of the 128 microorganisms isolated from the bloodstream, 53 were S. aureus, 30 were methicillin-sensitive and 23 were methicillin-resistant. Complications related to BSI included 35 cases of septicemia and 27 cases of endocarditis, of which 15 cases progressed to death. The incidence of BSI among these patients was shown to be very high, and this BSI progressed rapidly to the condition of severe infection with a high mortality rate.

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Low First Wave COVID-19 cases and health seeking behaviors across the six geopolitical zones of Nigeria

Nigerian Journal of Parasitology ◽

10.4314/njpar.v42i1.1 ◽

2021 ◽

Vol 42 (1) ◽

pp. 1-8

Author(s):

C.N. Ukaga ◽

S.O. Sam-Wobo ◽

R.H. Muhammed ◽

H.O. Mogaji ◽

O.A. Surakat ◽

...

Keyword(s):

Laboratory Testing ◽

Management Strategies ◽

Demographic Characteristics ◽

Community Level ◽

Health Seeking ◽

Routine Testing ◽

Home Management ◽

Health Seeking Behaviors ◽

Very High ◽

Age Category

This study was carried out across the six geopolitical zones to assess knowledge and health seeking behaviors of Nigerians during the first wave of COVID-19 pandemic lockdown in order to understand the seemingly low cases of COVID-19 in Nigeria. Structured and pretested short questionnaires were employed to obtain information electronically and physically across the six geopolitical zones on socio-demographic characteristics of participants; the knowledge of participants on COVID-19 disease; availability and accessibility to testing and isolation centers in the communities, attitudes and health seeking behaviors. Atotal of 1023 respondents; 705 (68.9%) males and 318 (31.1%) females across the six geopolitical zones in Nigeria participated in this study with 477(46.6%) within the 26-45 years age category, and 6(0.6%) above 66 years. Atotal of 985(96.3%) had heard about COVID-19 at the time of survey while a total of 859(84.0%) of the respondents were aware of the presence of COVID-19 laboratory testing centers. Across the geopolitical zones, majority of the respondents 487(47.6%) claimed there are no routine testing for COVID-19 at their community level, while 303 (29.6%) affirmed otherwise and 216(21.1%) did not know if there were routine testing going on or not. On health seeking behaviors across the country, majority of the respondents 558(54.5%) affirmed they would visit the hospital as the first point of contact if the opportunitypresented itself, 244(23.9%) claimed they would call the NCDC toll line, 2(0.2%) said they would use prayers, while 1(0.1%) respectively claimed they would use home management strategies through visiting chemist stores and checking the internet for solutions. Findings from this study confirm that there is very high awareness of the COVID-19 disease across the country, and limited number of testing centers at the community level. The implications include the possibility of unreported COVID19 cases in the cities as well as in the communities. Keywords: COVID-19, knowledge, health seeking behaviors, community level

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Decision Support System Based on Fuzzy Logic for Assessment of Expected Corporate Income Performance

International Journal of Computational Intelligence and Applications ◽

10.1142/s1469026821500097 ◽

2021 ◽

pp. 2150009

Author(s):

Arthur Yosef ◽

Eli Shnaider ◽

Rimona Palas ◽

Amos Baranes

Keyword(s):

Fuzzy Logic ◽

Decision Support ◽

Operating Income ◽

Explanatory Variables ◽

Section Model ◽

Evaluation Mechanism ◽

One Year ◽

High Degree ◽

Decision Support Method ◽

Very High

This study presents a decision-support method to estimate the next year performance of corporate Operating Income Margin (OIM). It is based on a unique combination of cross-section model and the rules-based evaluation mechanism. The estimate is done in terms of broad categories, and not precise numerical values. The model is constructed as follows: its dependent variable (OIM) is one year ahead vs. the corresponding explanatory variables. This structure of the model allows us to view explanatory variables as reflecting financial potential of corporations. The evaluation component consists of a set of rules designed to identify the companies whose “potential” clearly points to an opportunity to invest. For the method presented here to succeed, it is necessary to utilize a highly reliable modeling method, even if it is “Fuzzy”. We apply Soft Regression (SR), which is a Soft Computing modeling tool based on Fuzzy Logic, and utilize all available proxy variables by creating intervals of values. Advantages of utilizing SR, and the intervals’-based modeling are extensively discussed. Modeling results for five consecutive years are consistent and stable, thus indicating high degree of reliability. Testing indicates very high success rate for the stock market related domain, the lowest being 87.9%.

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Experimental Investigation of Local Heat Transfer Distribution on Smooth and Roughened Surfaces Under an Array of Angled Impinging Jets

10.1115/imece2001/htd-24320 ◽

2001 ◽

Author(s):

Lamyaa A. El-Gabry ◽

Deborah A. Kaminski

Keyword(s):

Heat Transfer ◽

Reynolds Number ◽

Cross Flow ◽

Local Heat Transfer ◽

Reynolds Numbers ◽

Local Heat ◽

Impinging Jets ◽

Transfer Coefficients ◽

Heat Transfer Coefficients ◽

Roughened Surface

Abstract Measurements of the local heat transfer distribution on smooth and roughened surfaces under an array of angled impinging jets are presented. The test rig is designed to simulate impingement with cross-flow in one direction which is a common method for cooling gas turbine components such as the combustion liner. Jet angle is varied between 30, 60, and 90 degrees as measured from the impingement surface, which is either smooth or randomly roughened. Liquid crystal video thermography is used to capture surface temperature data at five different jet Reynolds numbers ranging between 15,000 and 35,000. The effect of jet angle, Reynolds number, gap, and surface roughness on heat transfer efficiency and pressure loss is determined along with the various interactions among these parameters. Peak heat transfer coefficients for the range of Reynolds number from 15,000 to 35,000 are highest for orthogonal jets impinging on roughened surface; peak Nu values for this configuration ranged from 88 to 165 depending on Reynolds number. The ratio of peak to average Nu is lowest for 30-degree jets impinging on roughened surfaces. It is often desirable to minimize this ratio in order to decrease thermal gradients, which could lead to thermal fatigue. High thermal stress can significantly reduce the useful life of engineering components and machinery. Peak heat transfer coefficients decay in the cross-flow direction by close to 24% over a dimensionless length of 20. The decrease of spanwise average Nu in the crossflow direction is lowest for the case of 30-degree jets impinging on a roughened surface where the decrease was less than 3%. The decrease is greatest for 30-degree jet impingement on a smooth surface where the stagnation point Nu decreased by more than 23% for some Reynolds numbers.

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