Numerical Modelling of a Planing Craft with a V-Shaped Spray Interceptor Arrangement in Calm Water

2020 ◽  
Author(s):  
Mikloš Lakatoš ◽  
Kristjan Tabri ◽  
Abbas Dashtimanesh ◽  
Henrik Andreasson
Keyword(s):  
Reaction Force ◽  
The Other ◽  
Numerical Comparison ◽  
Total Resistance ◽  
Stagnation Line ◽  
Planing Craft ◽  
Water Conditions ◽  
Calm Water ◽  
Wetted Surface Area ◽  
Novel Concept

V-shaped spray interceptors are a novel concept of spray deflection on planing craft. Conventional spray rails are positioned longitudinally on the bottom of the hull and detach the spray from hull deflecting it towards the sides or slightly down and aftward. The V-shaped spray interceptors, on the other hand, are located in the spray area forward of the stagnation line such that they would deflect the oncoming spray down and aftward, thereby producing a reaction force that reduces the total resistance. An experimental study reported that the V-shaped spray interceptors to reduce the total resistance at low planing speed by up to 4%. This paper features a numerical comparison of two planing craft, one equipped with a conventional setup of longitudinal spray rails and the other with a V-shaped spray interceptor. Both configurations were simulated in calm water conditions and were free to pitch and heave in a speed range of Fr∇ = 1.776 to 3.108. The numerical model was analyzed for grid sensitivity and numerical results were compared with experimental results. The two concepts were compared in terms of total resistance, lift, running position and wetted surface area. Conventional spray rails were shown to account for up to 5.6% of total lift and up to 6.5% of total resistance. The V-shaped spray interceptor was shown to reduce the total resistance by up to 8%. Since the V-shaped spray interceptor was located in the spray area forward of the stagnation line, it deflected the oncoming spray thereby producing a horizontal reaction force (-1.5% of RTM) in the direction of the craft’s motion. The rest of differences in the total resistance of the hulls equipped with the conventional spray rails and the V-shaped spray rails was due to absence of the resistance of the absent spray rails.

VII.–The Effect of the Transport of Heat on the Rate of Evaporation of Small Droplets I. Evaporation into a Large Excess of a Gas

1962 ◽  
Vol 66 (2) ◽  
pp. 65-80
Author(s):  
P. G. Wright
Keyword(s):  
Gaseous Phase ◽  
The Other ◽  
Total Resistance ◽  
Large Excess ◽  
Stationary Growth ◽  
In Series ◽  
Finite Period ◽  
Rate Of Evaporation ◽  
Latent Heat Of Vaporization ◽  
Algebraic Formulation

SynopsisBeginning with fundamental results obtained by Mason for the effect of self-cooling on the evaporation of drops, and by Fuchs for the diffusional retardation of evaporation for small droplets of any radius, explicit expressions for the effect of the transport of heat on the rate of quasi-stationary growth or evaporation, are discussed.The simplest algebraic formulation of the results lends itself to interpretation as expressing a resistance to evaporation, the total resistance being the sum of four resistances in series. Two of these resistances, one to diffusion and one to the conduction of heat, are offered by the gaseous phase in bulk; and there are two corresponding resistances at the interface. Corrections are formulated for the effect of the heating of the droplet by radiation. These corrections may be expressed as a (finite) resistance in parallel with the other two resistances to the transfer of heat. Simplified equations are obtained for the evaporation of a liquid whose latent heat of vaporization is very large.Some remarks are made on the formation of a monodisperse aerosol by the growth of smaller droplets. Integrated expressions are obtained for particular cases of the evaporation of a droplet over a finite period of time.

An Evaluation of Planing Boat Trim Measurements

2017 ◽  
Author(s):  
Carolyn Judge ◽  
Bill Beaver ◽  
John Zseleczk
Keyword(s):  
Performance Prediction ◽  
Measurement Methods ◽  
The Other ◽  
Test Program ◽  
Towing Tank ◽  
Calm Water

The resistance of a planing hull is known to be highly dependent on trim angle. For several reasons, trim is difficult to measure to the level of accuracy normally attained with other towing tank measurements such as resistance or speed. In a recent study intended to validate CFD methods for planing hulls, 4’ and 8’ long geosim models of the Generic Prismatic Planing Hull (GPPH) were built and tested at USNA. Significant differences were found between the trim of the two models so a separate test program was conducted which focused specifically on the trim measurement of these two models in calm water. Five different trim measurement methods were used simultaneously on one model and then used again on the other model. Trim angles were compared between measurement methods and between models. Trim measurements with the same model agreed well and are the basis for an evaluation of measurement methods. The trim measured on the two different size models did not agree well even though the same instruments were used in most cases. The paper discusses reasons for the confirmed differences in calm water running trim of the two models and suggests ways to take advantage of this knowledge to make the best use of towing tank tests for planing boat performance prediction.

An Empirical Formula to Estimate the Resistance of a Convoy in a Restricted Waterway

1996 ◽  
Vol 40 (02) ◽  
pp. 107-111
Author(s):  
J.L.J. Marchal ◽  
Y.-D. Shen ◽  
D. Kicheva
Keyword(s):  
Cross Section ◽  
Empirical Formula ◽  
The Other ◽  
Total Resistance ◽  
Empirical Methods ◽  
Joint Research ◽  
Ship Hydrodynamics ◽  
Joint Research Project ◽  
Length Width ◽  
The Subject

An examination of the literature produced very few references related to the subject of estimating the resistance of a convoy navigating in a waterway of limited cross section. This paper reports the findings of one such study—a joint research project undertaken by Belgium's University of Liege and the Bulgarian Ship Hydrodynamics Centre. A polynomial is presented here for evaluating the total resistance of a convoy moving in a restricted waterway. The resistance was found to depend on Froude number and on the relative dimensions (length, width and depth) between the convoy and the channel. The results obtained by the suggested polynomial are compared with those obtained by the other three existing empirical methods.

Katena gleb mułowo-madowych w okolicy Suraża w Dolinie Górnej Narwi / Muddy-alluvial soils catena near Suraż in the Upper Narew Valley

2013 ◽  
Vol 64 (2) ◽  
pp. 34-40 ◽  
Author(s):  
Sławomir Roj-Rojewski ◽  
Marek Walasek
Keyword(s):  
Physical Properties ◽  
Plant Community ◽  
Plant Communities ◽  
Vegetation Cover ◽  
Ash Content ◽  
The Other ◽  
Alluvial Soils ◽  
Water Conditions

Abstract The aim of the study was the recognition of profile structure and main physical properties of humus-rich endogley soils, which form muddy-alluvial habitats, and soils appearing together with them in a catena developed in the Upper Narew Valley near Sura¿. Plant communities growing on these soils were also recognized. Typological development of the analysed soils is clearly connected with microrelief of flood terrace, water conditions and vegetation cover. The most moisture positions taken by humus-rich endogley soils are overgrown by Glycerietum maximae community. Typic czernozemic alluvial and mucky-like soils with Phalaridetum arundinaceae community are found slightly higher. In the highest and the most dried parts of the analysed terrain mucky soils overgrown by plant community with domination of Alopecurus pratensis appears. Due to lower ash content physical properties of humus-rich endogley soils and peaty-like deposits considerably distinguish from properties of the other soils and deposits founded on the study area.

Numerical Study on the Maneuvering of a Ship in Waves Based on Unified State Space Model

2016 ◽  
Author(s):  
Rameesha Thayale Veedu ◽  
Parameswaran Krishnankutty
Keyword(s):  
State Space ◽  
Numerical Study ◽  
State Space Model ◽  
Container Ship ◽  
Regular Waves ◽  
Ship Maneuvering ◽  
Space Model ◽  
Water Conditions ◽  
Calm Water ◽  
Early Design Stages

Ship maneuvering performance is usually predicted in calm water conditions, which provide valuable information about ship’s turning ability and its directional stability in the early design stages. Investigation of maneuvering simulation in waves is more realistic since the ship usually sails through waves. So it is important to study the effect of waves on the turning ability of a ship. This paper presents the maneuvering simulation for a container ship in presence of regular waves based on unified state space model for ship maneuvering. Standard maneuvers like turning circle and zigzag maneuver are simulated for the head sea condition and the same are compared with calm water maneuvers. The present study shows that wave significantly affects the maneuvering characteristics of the ship and hence cannot be neglected.

scholarly journals III. On unequal electric conduction-resistance at cathodes

1884 ◽  
Vol 37 (232-234) ◽  
pp. 35-36
Keyword(s):  
Small Extent ◽  
The Other ◽  
Total Resistance ◽  
Electric Conduction ◽  
Thermo Electric ◽  
Contact Potential ◽  
Chemical Action ◽  
Negative Plate ◽  
Action Films ◽  
New Phenomena

During some experiments which I have been making on the unequal resistance to the deposition of a metal upon cathodes of different metals in the same solution by the same current (see “Some New Phenomena of Electrolysis”), I have been led to investigate the resistance of cathodes of different metals to the passage of the current into them. I have found that by taking a good conducting electrolyte, immersing in it a positive sheet of zinc, and a smaller negative one of another metal, connecting the plates with a galvanometer of low resistance, reducing all the other resistances in the circuit to the minimum except that of the negative plate; then making a series of measurements of strengths of current of different couples formed by the zinc and about twelve other metals, during removal of polarisation by stirring the liquid; also making another series of measurements of the electromotive forces of the same couples during stirring; calculating from these data the total resistance in each case, then deducting the portion of resistance due to the galvanometer, also that due to the liquid itself, and to opposing contact-potential, and thermo-electric and voltaic action at the cathode and external junction, very different amounts of resistance, large in some cases, remain, and are exercised by different metals as cathodes, and those differences of resistance are only to a small extent due to heat and current absorbed in liberating hydrogen, and can only in a few cases be partly accounted for by chemical action, films, or absorption of gases at the cathode.

scholarly journals Pavlovian Control of Intraspinal Microstimulation to Produce Over-Ground Walking

2019 ◽  
Author(s):  
Ashley N Dalrymple ◽  
David A Roszko ◽  
Richard S Sutton ◽  
Vivian K Mushahwar
Keyword(s):  
Learning Strategy ◽  
Control Strategies ◽  
Reaction Force ◽  
The Other ◽  
State Transitions ◽  
Intraspinal Microstimulation ◽  
Cord Injury ◽  
Sensor Signals ◽  
Cat Model ◽  
Over Ground Walking

ABSTRACTObjectiveNeural interface technologies are more commonly used in people with neural injury. To achieve a symbiotic relationship between device and user, the control system of the device must augment remaining function and adapt to day-to-day changes. The goal of this study was to develop predictive control strategies to produce alternating, over-ground walking in a cat model of hemisection spinal cord injury (SCI) using intraspinal microstimulation (ISMS).ApproachEight cats were anaesthetized and placed in a sling over a walkway. The residual function of a hemisection SCI was mimicked by manually moving one hind-limb through the walking cycle over the walkway. ISMS targeted motor networks in the lumbosacral enlargement to activate muscles in the other limb using low levels of current (< 130 µA). Four different people took turns to move the “intact” limb. Two control strategies, which used ground reaction force and angular velocity information about the manually moved limb to control the timing of the transitions of the other limb, were compared. The first strategy, reaction-based control, used thresholds on the sensor values to initiate state transitions. The other strategy used a reinforcement learning strategy, Pavlovian control, to learn predictions about the sensor values. Thresholds on the predictions were used to initiate transitions.Main ResultsBoth control strategies were able to produce alternating, over-ground walking. Reaction-based control required manual tuning of the thresholds for each person to produce walking, whereas Pavlovian control did not. We demonstrate that learning occurs quickly during walking. Predictions of the sensor signals were learned quickly, initiating transitions in no more than 4 steps. Pavlovian control was resilient to transitions between people walking the limb, between cat experiments, and recovered from mistakes during walking.SignificanceThis work demonstrates that Pavlovian control can augment remaining function and allow for personalized walking with minimal tuning requirements.

scholarly journals Evaluation of design methods for side resistance only rock socketed piles

2021 ◽  
Author(s):  
Ian Johnston
Keyword(s):  
Design Methods ◽  
Full Scale ◽  
The Other ◽  
Total Resistance ◽  
The Third ◽  
Components Of Resistance ◽  
Side Resistance

The ability of three methods to predict the load-settlement response of rock socketed piles was examined in a recent paper. The piles considered were complete piles in which both the side and base of the piles contribute to the total resistance. For a range of reasons, it is sometimes necessary to consider rock socketed piles for which the resistance is provided only by the side of the socket. This paper extends the earlier paper by comparing predictions for side resistance only piles with the load-settlement response of a suite of full-scale side resistance only pile tests. Only two of the methods of the earlier paper are used for this comparison as the third method could not decouple the two components of resistance. It is demonstrated that one of the methods produces reasonable predictions of performance whereas the other appears to underpredict performance.

scholarly journals The Effect of Workplace Spirituality on Innovative Work Behavior

2019 ◽  
Vol 12 (12) ◽  
pp. 29
Author(s):  
Vimansha R. Ranasinghe ◽  
Samantha M. Samarasinghe
Keyword(s):  
Intrinsic Motivation ◽  
Organizational Performance ◽  
Workplace Spirituality ◽  
Mediating Effect ◽  
Work Behavior ◽  
The Other ◽  
Innovative Work Behavior ◽  
Innovative Work ◽  
Novel Concept ◽  
Positive Effect

Workplace spirituality is a novel concept and it has been identified as a unique way to improve organizational performance. On the other hand, many organizations are experiencing undesirable consequences of lack of workplace spirituality, such as employee stress, turnover, absenteeism, and lack of employee creativity. Hence, organizations are now focusing on developing workplace spirituality in the workplaces as it offers many advantages to organizations. Despite the growing interest on workplace spirituality, there is still a dearth of research on the topic of workplace spirituality. Literature suggests that employee innovative work behavior directly leads to enhance organizational performance and workplace spirituality leads to increase innovativeness and creativity of employees. Hence, the purpose of this paper is to fill the gap in literature, to a certain extent by proposing a conceptual model to examine the effect of workplace spirituality on employee innovative work behavior. Thus, it proposed that there is a positive effect of workplace spirituality on employee innovative work behavior. Consequently, intrinsic motivation from componential theory of creativity was integrated to identify the mediating effect of intrinsic motivation on the effect of workplace spirituality on innovative work behavior.

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