A Theoretical Approach to Bow Deck Wetness of a High-Speed Ship

1990 ◽  
Vol 34 (03) ◽  
pp. 163-171 ◽  
Author(s):  
Ken Takagi ◽  
Akihiro Niimi
Keyword(s):  
Froude Number ◽  
Theoretical Approach ◽  
Analytical Method ◽  
High Speed ◽  
Theoretical Study ◽  
Two Dimensional ◽  
Long Wavelength ◽  
High Froude Number ◽  
Self Similar ◽  
Deck Wetness

A theoretical study of the phenomenon of deck wetness is presented and effects of the flare shape are discussed. It is shown that two-dimensional (2D) self-similar flow is applicable to the analysis of deck wetness on the assumption of long wavelength and high Froude number. The 2D self-similar flow which includes effects of the deck is calculated by an analytical method. Calculated results are compared with experimental results obtained at the limit of long wavelength, that is, in still water. Calculated results are used to determine the most suitable flare angle, and it is shown that increased flare is more effective than a knuckle to reduce bow deck wetness.

scholarly journals Defect Dynamics in Graphene

2020 ◽  
Vol 5 (1) ◽  
pp. 26-34
Author(s):  
Aalim M. Malik ◽  
M. Ashraf Shah ◽  
Nikhilesh K. Dilwaliya ◽  
Vikash Dahiya
Keyword(s):  
Grain Boundary ◽  
Reference Frame ◽  
Theoretical Study ◽  
Condensed Matter ◽  
Two Dimensional ◽  
Long Wavelength ◽  
Hamiltonian Model ◽  
Different Types ◽  
Crystallographic Axes ◽  
Dirac Hamiltonian

The experimental and theoretical study of graphene, two-dimensional (2D) graphite, is an extremely rapidly growing field of today's condensed matter research. Different types of disorder in graphene modify the Dirac equation leading to unusual spectroscopic and transport properties. The authors studied one of the disorders (i.e., grain boundaries) and formulated a theoretical model of graphene grain boundary by generalizing the two-dimensional graphene Dirac Hamiltonian model. In this model only, the authors considered the long-wavelength limit of the particle transport, which provides the main contribution to the graphene conductance. In this work, they derived the Hamiltonian in a rotated side dependent reference frame describing crystallographic axes mismatching at a grain boundary junction and showed that properties like energy spectrum are an independent reference frame. Also, they showed one of the topological property of graphene.

Meandering due to large eddies and the statistically self-similar dynamics of quasi-two-dimensional jets

2012 ◽  
Vol 692 ◽  
pp. 347-368 ◽  
Author(s):  
Julien R. Landel ◽  
C. P. Caulfield ◽  
Andrew W. Woods
Keyword(s):  
Vertical Velocity ◽  
High Speed ◽  
Turbulent Jets ◽  
Theoretical Models ◽  
Maximum Speed ◽  
Two Dimensional ◽  
The Core ◽  
Self Similar ◽  
The Mean ◽  
Large Eddies

AbstractWe investigate experimentally the structure of quasi-two-dimensional plane turbulent jets discharged vertically from a slot of width $d$ into a fluid confined between two relatively close rigid boundaries with gap $W\ensuremath{\sim} O(d)$. At large vertical distances $z\gg W$ the jet structure consists of a meandering core with large counter-rotating eddies, which develop on alternate sides of the core. Using particle image velocimetry, we observe an inverse cascade typical of quasi-two-dimensional turbulence where both the core and the eddies grow linearly with $z$ and travel at an average speed proportional to ${z}^{\ensuremath{-} 1/ 2} $. However, although the present study concerns quasi-two-dimensional confined jets, the jets are self-similar and the mean properties are consistent with both experimental results and theoretical models of the time-averaged properties of fully unconfined planar two-dimensional jets. We believe that the dynamics of the interacting core and large eddies accounts for the Gaussian profile of the mean vertical velocity as shown by the spatial statistical distribution of the core and eddy structure. The lateral excursions (caused by the propagating eddies) of this high-speed central core produce a Gaussian distribution for the time-averaged vertical velocity. In addition, we find that approximately 75 % of the total momentum flux of the jet is contained within the core. The eddies travel substantially slower (at approximately 25 % of the maximum speed of the core) at each height and their growth is primarily attributed to entrainment of ambient fluid. The frequency of occurrence of the eddies decreases in a stepwise manner due to merging, with a well-defined minimum value of the corresponding Strouhal number $\mathit{St}\geq 0. 07$.

Transition from Straight to Fractal Cracks due to Projectile Penetration

2013 ◽  
Vol 592-593 ◽  
pp. 765-768
Author(s):  
Zoltán Halász ◽  
Frank van Steeden ◽  
Ferenc Kun
Keyword(s):  
High Speed ◽  
Theoretical Study ◽  
Geometrical Structure ◽  
Element Model ◽  
Crack Pattern ◽  
External Boundary ◽  
Discrete Element Model ◽  
Two Dimensional ◽  
Crack Network ◽  
Fractal Cracks

We present a theoretical study of the fracture of two-dimensional disc-shaped samples due to projectile penetration focusing on the geometrical structure of the crack pattern. The penetration of a cone is simulated into a plate of circular shape using a discrete element model of heterogeneous brittle materials varying the speed of penetration in a broad range. As the cone penetrates a destroyed zone is created from which cracks run to the external boundary of the plate. Computer simulations revealed that in the low speed limit of loading two cracks are generated with nearly straight shape. Increasing the penetration speed the crack pattern remains regular, however, both the number of cracks and their fractal dimension increases. High speed penetration gives rise to a crack network such that the sample gets fragmented into a large number of pieces. We give a quantitative analysis of the evolution of the system from simple cracking through fractal cracks to fragmentation with a connected crack network.

Optimal Shape of a Planing Surface at High Froude Number

1977 ◽  
Vol 21 (01) ◽  
pp. 40-43
Author(s):  
Lu Ting ◽  
Joseph B. Keller
Keyword(s):  
Froude Number ◽  
Lift Coefficient ◽  
Optimal Shape ◽  
Two Dimensional ◽  
Flat Plates ◽  
High Froude Number ◽  
Leading Term ◽  
Ratio Dependent

A planing surface moving at high Froude number throws up a jet that is responsible for the leading term in the drag. By shaping the surface appropriately, the jet can be eliminated. The drag is thereby reduced by a factor of order (Fr)–2. The paper shows how this can be done for a two-dimensional planing surface consisting of two flat plates. It is found that the lengths of the plates must have a ratio dependent upon their angles of inclination. Then the angles that maximize the lift coefficient are determined.

An Analytical Approach to Cam-Modulated Linkage Synthesis Using Conjugate Geometry

1994 ◽  
Author(s):  
Steven B. Shooter ◽  
Paul H. Tidwell ◽  
Charles F. Reinholtz
Keyword(s):  
Mechanism Design ◽  
Infinite Number ◽  
Analytical Method ◽  
High Speed ◽  
Analytical Approach ◽  
Three Dimensional ◽  
Optimization Techniques ◽  
Synthesis Methods ◽  
Path Generation ◽  
Two Dimensional

Abstract Cam-modulated linkages are a combination of cams and traditional linkages. These mechanisms have the advantage of satisfying an infinite number of precision points for path generation and body guidance synthesis problems. It is possible to synthesize these mechanisms graphically; however, established graphical synthesis methods can be tedious and do not lend themselves to iterative mechanism design or optimization techniques. An analytical method for synthesizing cams for cam-modulated linkages using principles of conjugate geometry is presented. The method is valid for two-dimensional or three-dimensional mechanisms. The same method is used for followers undergoing complex motions. The method is applied to verify the synthesis of a high speed printing mechanism produced by Pitney-Bowes.

Rupture of Cavity Film Due to Water Entry of Horizontal Superhydrophobic Circular Cylinders

2013 ◽  
Vol 32 (1) ◽  
pp. 59-67 ◽  
Author(s):  
Y. Ueda ◽  
M. Iguchi
Keyword(s):  
Froude Number ◽  
High Speed ◽  
Water Entry ◽  
Circular Cylinders ◽  
Water Model ◽  
Inertia Force ◽  
Fluid Inertia ◽  
Contact Lines ◽  
Low Froude Number ◽  
High Froude Number

AbstractIn materials refining processes such as steelmaking process, bath-entry of agents such as CaCO3 attracts career gas around their entire surface so that the dispersion in the bath can be inhibited. To shed light on the still vague instant phenomenon, this study employs a water model experiment and carries out the visualization. Therefore, this study visually demonstrates the growth and rupture of air cavity due to water entry of horizontal superhydrophobic circular cylinders with the aid of a high-speed camera. Here, we show that the water entry of the horizontal hydrophobic cylinder forms a film of cavity behind the cylinder whereas a hydrophilic cylinder forms a cavity from both ends of the cylinder. In a high Froude number entry, once the cavity film ruptured on both sides of it, the contact lines of the cavity film abruptly move along the surface of the cylinder. In a low Froude number entry, the influence of weak fluid inertia force makes several ruptures on the cavity film which grow individually and split off the cavity. Of a particular interest is the fact that the multi-rupture regime appeals for the spanwise three-dimensionality on the cavity film against the previous studies within two-dimensional treatment. Furthermore, this report finds the trend for some range of Fr that the nondimensionalized closure depth of the cavity film zc with diameter of the cylinder obeys zc/d ∼ Fr1/3 in the range 4.7 ≤ Fr ≤ 40 although it depends on Fr in the water-entry problem of a hydrophobic sphere.

Two-dimensional planing at high Froude number

1958 ◽  
Vol 4 (5) ◽  
pp. 466-478 ◽  
Author(s):  
E. Cumberbatch
Keyword(s):  
Integral Equation ◽  
Pressure Distribution ◽  
Flat Plate ◽  
Froude Number ◽  
Water Surface ◽  
Flow Characteristics ◽  
Iteration Process ◽  
Leading Edge ◽  
Two Dimensional ◽  
High Froude Number

This paper examines the flow characteristics of a body of small slope planing at high Froude number over a water surface. An equation is obtained relating the slope of the planing surface to an integral containing the pressure distribution on the planing surface. The equation is expanded for large Froude number and a solution is obtained by an iteration process. At each stage of the iteration process the integral equation of ordinary thin aerofoil theory is solved. The pressure distribution on the planing surface is derived as a series in inverse powers of the Froude number F, as far as the F−4 term. Computations are performed for the planing of a flat plate, a parabolic surface, and a suitable linear combination of these shapes which results in a flow without a splash at the leading edge.

High speed theory for the planing of a flat plate at high Froude number

2007 ◽  
Vol 34 (11-12) ◽  
pp. 1552-1560 ◽  
Author(s):  
Y.K. Chung ◽  
H.H. Chun
Keyword(s):  
Flat Plate ◽  
Froude Number ◽  
High Speed ◽  
High Froude Number

scholarly journals The merger of two-dimensional radially stratified high-Froude-number vortices

2007 ◽  
Vol 582 ◽  
pp. 133-151 ◽  
Author(s):  
LAURENT JOLY ◽  
JEAN N. REINAUD
Keyword(s):  
Froude Number ◽  
Large Scale ◽  
Separation Distance ◽  
Critical Distance ◽  
Uniform Density ◽  
Two Dimensional ◽  
Large Scale Structures ◽  
Initial Separation ◽  
High Froude Number ◽  
Observed Behaviour

We investigate the influence of density inhomogeneities on the merger of two corotating two-dimensional vortices at infinite Froude number. In this situation, buoyancy effects are negligible, yet density variations still affect the flow by pure inertial effects through the baroclinic torque. We first re-address the effects of a finite Reynolds number on the interaction between two identical Gaussian vortices. Then, by means of direct numerical simulations, we show that vortices transporting light fluid in a heavier counterpart merge from further distances than vortices in a uniform density medium. On the other hand, heavy vortices only merge from small separation distances. We measure the critical distance a/b0 of the vortex radii to their initial separation distance. It departs from the homogeneous threshold of 0.22 in response to increasing density contrasts between the vortices and their surroundings. An analysis of the contribution of the baroclinic vorticity to the dynamics of the flow is detailed and explains the observed behaviour. This analysis is completed by a simple model based on point vortices that mimics the flow. It is concluded that vortices carrying light fluid are more likely to generate large-scale structures than heavy ones in an inhomogeneous fluid.

Load Spectrum Compiling and Fatigue Life Estimation of the Automobile Wheel Hub

2020 ◽  
Vol 13 ◽  
Author(s):  
Xintian Liu ◽  
Yang Qu ◽  
Xiaobing Yang ◽  
Yongfeng Shen
Keyword(s):  
Fatigue Life ◽  
High Speed ◽  
Two Dimensional ◽  
Load Spectrum ◽  
One Dimensional ◽  
Life Estimation ◽  
Load Spectra ◽  
Fatigue Life Estimation ◽  
Program Load Spectrum ◽  
Program Load

Background:: In the process of high-speed driving, the wheel hub is constantly subjected to the impact load from the ground. Therefore, it is important to estimate the fatigue life of the hub in the design and production process. Objective:: This paper introduces a method to study the fatigue life of car hub based on the road load collected from test site. Methods:: Based on interval analysis, the distribution characteristics of load spectrum are analyzed. The fatigue life estimation of one - dimensional and two - dimensional load spectra is compared by compiling load spectra. Results:: According to the S-N curve cluster and the one-dimensional program load spectrum, the estimated range fatigue life of the hub is 397,100 km to 529,700 km. For unsymmetrical cyclic loading, each level means and amplitude of load were obtained through the Goodman fatigue empirical formula, and then according to S-N curve clusters in the upper and lower curves and two-dimensional program load spectrum, estimates the fatigue life of wheel hub of the interval is 329900 km to 435200 km, than one-dimensional load spectrum fatigue life was reduced by 16.9% - 17.8%. Conclusion:: This paper lays a foundation for the prediction of fatigue life and the bench test of fatigue durability of auto parts subjected to complex and variable random loads. At the same time, the research method can also be used to estimate the fatigue life of other bearing parts or high-speed moving parts and assemblies.

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