Interference Resistance of Multi-Hull Vessels in Finite-Depth Waters

2012 ◽  
Author(s):  
Alexia Aubault ◽  
Ronald W. Yeung
Keyword(s):  
Froude Number ◽  
Water Depth ◽  
High Speed ◽  
Fuel Efficiency ◽  
Finite Depth ◽  
Wave Resistance ◽  
Optimized Design ◽  
Near Shore ◽  
Geometric Variables ◽  
Depth Water

As high-speed ferry traffic is growing in near-shore areas, fuel efficiency of vessel operating in finite-depth waters becomes more critical. This can be achieved by introducing multi-hulls and minimizing the wave resistance by a proper configuration of the hulls. The wave resistance of thin-hulled vessels can be computed within Michell’s theory. Based on this principle, Yeung et al. (2004) introduced a formulation of the interference wave resistance on multi-hull vessels in deep water, after linearization of the boundary conditions. The method is generalized to any water-depth in this paper. Havelock (1921) derived the wave resistance of a single-hull vessel in finite-depth water. An expression of the interaction resistance between two hulls in finite-depth waters is derived, using a distribution of Havelock sources on the hulls. It is shown that the interference resistance may be defined as a function of geometric variables and a length-based Froude number and depth-based Froude number. The effect of sub-criticality, criticality and supercriticality of depth-based Froude number on the interference resistance is explored. The computation of the total wave resistance of two hulls is extended to vessels with any number of hulls. The application of this solution method is demonstrated. With the use of the formulation, multi-hull designs are optimized with respect to the geometric distribution of hulls as well as forward speed and water depth. The design of multi-hull vessels illustrates how an optimized design is quickly obtained. Design decisions early in the design process can therefore be facilitated by this procedure.

Disturbance During Steady and Unsteady Motion of a Two-Dimensional Pressure Distribution

2001 ◽  
Vol 45 (03) ◽  
pp. 165-176 ◽  
Author(s):  
Noriaki Okita ◽  
Iskender Sahin ◽  
Mark C. Hyman
Keyword(s):  
Pressure Distribution ◽  
Finite Depth ◽  
Unsteady Motion ◽  
Wave Resistance ◽  
Two Dimensional ◽  
Bottom Pressure ◽  
Integration Algorithm ◽  
Pressure Profiles ◽  
Principal Value ◽  
Depth Water

A two-dimensional study of flow due to a moving pressure distribution in subcritical Froude numbers over finite-depth water was conducted by a linearized ideal flow approach. A numerical integration algorithm was developed to evaluate the analytical solution given by Cauchy principal-value integrals. The surface elevation, bottom pressure profiles, and wave resistance were computed as functions of speed and water depth. The calculated results agreed well with published values.

Waves and Wave Resistance for Air-Cushion Vehicles with Time-Dependent Cushion Pressures

1978 ◽  
Vol 22 (03) ◽  
pp. 170-177
Author(s):  
H. J. Haussling ◽  
R. T. Van Eseltine
Keyword(s):  
Shallow Water ◽  
Froude Number ◽  
Water Depth ◽  
Critical Frequency ◽  
Wave Resistance ◽  
Time Dependent ◽  
Length Ratio ◽  
Wave Patterns ◽  
Air Cushion ◽  
Air Cushion Vehicles

Wave patterns and wave resistance are computed for air-cushion vehicles with time-dependent cushion pressures moving at uniform speed over deep and shallow water. The effect of beam-to-length ratio, Froude number, and water depth on the resistance is investigated. The resistance is found to exhibit a distinctive behavior at a critical frequency. This behavior corresponds to a singularity in the resistance at the critical frequency. The importance of this behavior is found to diminish with decreasing beam-to-length ratio and increasing Froude number.

scholarly journals Ship waves on uniform shear current at finite depth: wave resistance and critical velocity

2016 ◽  
Vol 791 ◽  
pp. 539-567 ◽  
Author(s):  
Yan Li ◽  
Simen Å Ellingsen
Keyword(s):  
Froude Number ◽  
Critical Velocity ◽  
Water Depth ◽  
Deep Water ◽  
Wave Resistance ◽  
Ship Motion ◽  
Ship Waves ◽  
Lateral Wave ◽  
Shear Current ◽  
Finite Water Depth

We present a comprehensive theory for linear gravity-driven ship waves in the presence of a shear current with uniform vorticity, including the effects of finite water depth. The wave resistance in the presence of shear current is calculated for the first time, containing in general a non-zero lateral component. While formally apparently a straightforward extension of existing deep water theory, the introduction of finite water depth is physically non-trivial, since the surface waves are now affected by a subtle interplay of the effects of the current and the sea bed. This becomes particularly pronounced when considering the phenomenon of critical velocity, the velocity at which transversely propagating waves become unable to keep up with the moving source. The phenomenon is well known for shallow water, and was recently shown to exist also in deep water in the presence of a shear current (Ellingsen, J. Fluid Mech., vol. 742, 2014, R2). We derive the exact criterion for criticality as a function of an intrinsic shear Froude number $S\sqrt{b/g}$ ($S$ is uniform vorticity, $b$ size of source), the water depth and the angle between the shear current and the ship’s motion. Formulae for both the normal and lateral wave resistance forces are derived, and we analyse their dependence on the source velocity (or Froude number $Fr$) for different amounts of shear and different directions of motion. The effect of the shear current is to increase wave resistance for upstream ship motion and decrease it for downstream motion. Also the value of $Fr$ at which $R$ is maximal is lowered for upstream and increased for downstream directions of ship motion. For oblique angles between ship motion and current there is a lateral wave resistance component which can amount to 10–20 % of the normal wave resistance for side-on shear and $S\sqrt{b/g}$ of order unity. The theory is fully laid out and far-field contributions are carefully separated off by means of Cauchy’s integral theorem, exposing potential pitfalls associated with a slightly different method (Sokhotsky–Plemelj) used in several previous works.

High-Speed Trimaran Drag: Numerical Analysis and Model Tests

2004 ◽  
Vol 48 (03) ◽  
pp. 248-259 ◽  
Author(s):  
Igor Mizine ◽  
Eduard Amromin ◽  
Leonard Crook ◽  
William Day ◽  
Richard Korpus
Keyword(s):  
Froude Number ◽  
Linear Theory ◽  
High Speed ◽  
Numerical Technique ◽  
Reynolds Numbers ◽  
Correlation Factor ◽  
Wave Resistance ◽  
Model Tests ◽  
Navier Stokes ◽  
Mutual Position

A numerical technique for high-speed trimaran resistance calculation is developed. The technique is based on the modified viscous-inviscid interaction concept and quasi-linear theory of wave resistance (Amromin et al 1984). The key element of this technique, which is called modified quasi-linear theory (MQLT), is an account of Froude number influence on the ship trim, transom drag, and wetted surface. This influence leads to appearance of a drag component that significantly depends on both Reynolds number and Froude number. This component has been traditionally included in residuary drag in the model test data. The presented preliminary numerical results were obtained with simplifications of the boundary layer theory that are acceptable for slender hulls. Calculated drag is in sufficient accordance with results of model tests. The MQLT computations of boundary layers are also compared with the Reynolds averaged Navier-Stokes (RANS) calculations(one-equation turbulence model by Spalart and Allmaras 1992) at model and ship scale Reynolds numbers. An analysis of the model-ship scale correlation factor for high-speed slender hulls with transom sterns and diverse mutual position of the trimaran hulls is done.

Closure of the Deep Wake Hollow of High-Speed Ships

2009 ◽  
Vol 53 (01) ◽  
pp. 1-6
Author(s):  
William S. Vorus
Keyword(s):  
Froude Number ◽  
Mathematical Theory ◽  
High Speed ◽  
Wave Resistance ◽  
Effective Length ◽  
Thin Body ◽  
Past Work ◽  
Is Development ◽  
Body Theory

Interest has developed in recent years in the length of the "wake hollow" downstream of high-speed vessels with blunt transom sterns. Past work has shown that this wake cavity appears to increase the effective length of a vessel, and thereby reduce its effective Froude number, with the result of a reduction in wave resistance. The research presented here is development and demonstration of a simple mathematical theory for the downstream wake closure characteristics of fully ventilated wakes of fast ships with transom sterns. The theory uses the linear thin body approximations with gravity in a formulation consistent with the thin body theory of wave resistance, although wave resistance is not dealt with here. The length of the wake hollow, or "trench," predicted is compared with recent experiments. Calculations of variation of the hollow length with transom shape and Froude number are presented.

Analyzing of UVLC system considering the effect of water depth

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Mustafa B. Al-Deen ◽  
Mazin Ali A. Ali ◽  
Zeyad A. Saleh
Keyword(s):  
Coastal Water ◽  
Water Depth ◽  
Bit Error Rate ◽  
Multiple Input Multiple Output ◽  
Visible Light Communications ◽  
New Approach ◽  
Multiple Input ◽  
Input Multiple Output ◽  
Depth Water

Abstract This paper presents a new approach to discover the effect of depth water for underwater visible light communications (UVLC). The quality of the optical link was investigated with varying water depth under coastal water types. The performance of the UVLC with multiple input–multiple output (MIMO) techniques was examined in terms of bit error rate (BER) and data rate. The theoretical result explains that there is a good performance for UVLC system under coastal water.

Optimum air-demand ratio for maximum aeration efficiency in high-head gated circular conduits

2014 ◽  
Vol 70 (5) ◽  
pp. 871-877 ◽  
Author(s):  
Fahri Ozkan ◽  
M. Cihat Tuna ◽  
Ahmet Baylar ◽  
Mualla Ozturk
Keyword(s):  
Froude Number ◽  
High Speed ◽  
Water Mixture ◽  
High Speed Flow ◽  
Mixture Flow ◽  
Speed Flow ◽  
Aeration Efficiency ◽  
High Head ◽  
Closed Conduit ◽  
Air Vent

Oxygen is an important component of water quality and its ability to sustain life. Water aeration is the process of introducing air into a body of water to increase its oxygen saturation. Water aeration can be accomplished in a variety of ways, for instance, closed-conduit aeration. High-speed flow in a closed conduit involves air-water mixture flow. The air flow results from the subatmospheric pressure downstream of the gate. The air entrained by the high-speed flow is supplied by the air vent. The air entrained into the flow in the form of a large number of bubbles accelerates oxygen transfer and hence also increases aeration efficiency. In the present work, the optimum air-demand ratio for maximum aeration efficiency in high-head gated circular conduits was studied experimentally. Results showed that aeration efficiency increased with the air-demand ratio to a certain point and then aeration efficiency did not change with a further increase of the air-demand ratio. Thus, there was an optimum value for the air-demand ratio, depending on the Froude number, which provides maximum aeration efficiency. Furthermore, a design formula for aeration efficiency was presented relating aeration efficiency to the air-demand ratio and Froude number.

Integrated Vehicle Comparison of Turbo-Ramjet Engine and Pulsed Detonation Engine

2002 ◽  
Vol 125 (1) ◽  
pp. 257-262 ◽  
Author(s):  
T. Kaemming
Keyword(s):  
Life Cycle Cost ◽  
High Speed ◽  
Fuel Efficiency ◽  
Pressure Rise ◽  
Propulsion System ◽  
Cross Sectional ◽  
Pulsed Detonation Engine ◽  
Pulsed Detonation ◽  
Large Matrix ◽  
Detonation Engine

The pulsed detonation engine (PDE) is a unique propulsion system that uses the pressure rise associated with detonations to efficiently provide thrust. A study was conducted under the direction of the NASA Langley Research Center to identify the flight applications that provide the greatest potential benefits when incorporating a PDE propulsion system. The study was conducted in three phases. The first two phases progressively screened a large matrix of possible applications down to three applications for a more in-depth, advanced design analysis. The three applications best suited to the PDE were (1) a supersonic tactical aircraft, (2) a supersonic strike missile, and (3) a hypersonic single-stage-to-orbit (SSTO) vehicle. The supersonic tactical aircraft is the focus of this paper. The supersonic, tactical aircraft is envisioned as a Mach 3.5 high-altitude reconnaissance aircraft with possible strike capability. The high speed was selected based on the perceived high-speed fuel efficiency benefits of the PDE. Relative to a turbo-ramjet powered vehicle, the study identified an 11% to 21% takeoff gross weight (TOGW) benefit to the PDE on the baseline 700 n.mi. radius mission depending on the assumptions used for PDE performance and mission requirements. The TOGW benefits predicted were a result of the PDE lower cruise specific fuel consumption (SFC) and lower vehicle supersonic drag. The lower vehicle drag resulted from better aft vehicle shaping, which was a result of better distribution of the PDE cross-sectional area. The reduction in TOGW and fuel usage produced an estimated 4% reduction in life cycle cost for the PDE vehicle. The study also showed that the simplicity of the PDE enables concurrent engineering development of the vehicle and engine.

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