Power Performance and Environmental Footprint of High-Speed Vessels in Calm Deep Water

2012 ◽  
Author(s):  
Renato Skejic ◽  
Egil Jullumstrø
Keyword(s):  
Free Surface ◽  
Deep Water ◽  
High Speed ◽  
Wave Resistance ◽  
Solid Particles ◽  
Linear Potential ◽  
Total Resistance ◽  
Environmental Footprint ◽  
Power Performance ◽  
Effective Power

This paper reports a theoretical study of the power performance and environmental footprint of high-speed vessels in calm deep water, paying particular attention to a high-speed catamaran cargo vessel Faltinsen [1]. The power analysis uses a modified version of the method of Doctors and Day [2]. One modification to their approach is that the wave resistance and free surface wave profiles, have been numerically predicted using two different linear potential flow field theories; Michell thin-ship theory (Yeung and Wan [3]) and the 3D Rankine panel method (Hess and Smith [4]), respectively. We have based the latter method on the combination of the Dawson [5] upstream finite difference operator and the ‘staggered grid’ technique (Jensen et al. [6]). In addition, this paper shows how the viscosity effects modeled on the free surface layer influence the behavior of the wave resistance curves as predicted by Michell’s thin ship theory. This was done by adopting the approaches described by Tuck [7] and Lazauskas [8]. The wave resistance models were verified and validated using the examples of Wigley monohull (Lazauskas [8], Tarafder and Suzuki [9]) and catamaran (Yeung and Wan [3], Tarafder and Suzuki [10]) analytical forms, as well as on the Tuck parabolic strut (Tuck [7]). Furthermore, the resistance models were extended using free surface profile estimates at selected Froude numbers and applied to the case of a high-speed catamaran cargo vessel. The numerical results obtained were compared with published results and their accuracy and application feasibility is discussed from the perspective of preliminary high-speed vessel design. Based on the discussion above, suitable wave resistance models were selected and combined with the modified Doctors and Day [2] method giving the total resistance of the high-speed catamaran cargo vessel in the interval of Froude numbers. Having the estimates of total resistance, enables the effective power to be found. The results were compared with known results and were found to be in good agreement. Through combination of the effective power and propulsion factors, the brake power of the generic propulsion system is predicted. Taking into account the type of vessel being analyzed, the most common type of the propulsion diesel engine was selected. Finally, knowing the indicative environmental footprint of the selected engine, emission levels of Green House Gases (GHG) and solid particles were obtained. The emission results are further discussed in an ecologically friendly high-speed vessel design perspective (IMO [11, 19]).

Effective Power and Speed Loss of Underwater Vehicles in Close Proximity to Regular Waves

2017 ◽  
Author(s):  
Stefan Daum ◽  
Martin Greve ◽  
Renato Skejic
Keyword(s):  
Free Surface ◽  
Deep Water ◽  
Water Waves ◽  
Underwater Vehicles ◽  
Total Resistance ◽  
Wave Load ◽  
Regular Waves ◽  
Effective Power ◽  
Close Proximity ◽  
Deep Water Waves

The present study is focused on performance issues of underwater vehicles near the free surface and gives insight into the analysis of a speed loss in regular deep water waves. Predictions of the speed loss are based on the evaluation of the total resistance and effective power in calm water and preselected regular wave fields w.r.t. the non-dimensional wave to body length ratio. It has been assumed that the water is sufficiently deep and that the vehicle is operating in a range of small to moderate Froude numbers by moving forward on a straight-line course with a defined encounter angle of incident regular waves. A modified version of the Doctors & Days [1] method as presented in Skejic and Jullumstrø [2] is used for the determination of the total resistance and consequently the effective power. In particular, the wave-making resistance is estimated by using different approaches covering simplified methods, i.e. Michell’s thin ship theory with the inclusion of viscosity effects Tuck [3] and Lazauskas [4] as well as boundary element methods, i.e. 3D Rankine source calculations according to Hess and Smith [5]. These methods are based on the linear potential fluid flow and are compared to fully viscous finite volume methods for selected geometries. The wave resistance models are verified and validated by published data of a prolate spheroid and one appropriate axisymmetric submarine model. Added resistance in regular deep water waves is obtained through evaluation of the surge mean second-order wave load. For this purpose, two different theoretical models based on potential flow theory are used: Loukakis and Sclavounos [6] and Salvesen et. al. [7]. The considered theories cover the whole range of important wavelengths for an underwater vehicle advancing in close proximity to the free surface. Comparisons between the outlined wave load theories and available theoretical and experimental data were carried out for a submerged submarine and a horizontal cylinder. Finally, the effective power and speed loss are discussed from a submarine operational point of view where the mentioned parameters directly influence mission requirements in a seaway. All presented results are carried out from the perspective of accuracy and efficiency within common engineering practice. By concluding current investigations in regular waves an outlook will be drawn to the application of advancing underwater vehicles in more realistic sea conditions.

scholarly journals Bound Coherent Structures Propagating on the Free Surface of Deep Water

Fluids ◽  
2021 ◽  
Vol 6 (3) ◽  
pp. 115
Author(s):  
Dmitry Kachulin ◽  
Sergey Dremov ◽  
Alexander Dyachenko
Keyword(s):  
Free Surface ◽  
Deep Water ◽  
Coherent Structures ◽  
Water Waves ◽  
Nonlinear Models ◽  
Ideal Incompressible Fluid ◽  
Equation Model ◽  
System Of Nonlinear Equations ◽  
Potential Flows ◽  
Deep Water Waves

This article presents a study of bound periodically oscillating coherent structures arising on the free surface of deep water. Such structures resemble the well known bi-soliton solution of the nonlinear Schrödinger equation. The research was carried out in the super-compact Dyachenko-Zakharov equation model for unidirectional deep water waves and the full system of nonlinear equations for potential flows of an ideal incompressible fluid written in conformal variables. The special numerical algorithm that includes a damping procedure of radiation and velocity adjusting was used for obtaining such bound structures. The results showed that in both nonlinear models for deep water waves after the damping is turned off, a periodically oscillating bound structure remains on the fluid surface and propagates stably over hundreds of thousands of characteristic wave periods without losing energy.

Penetration Dynamics of Solid Particles into Liquids High-Speed Experimental Results and Modelling

2005 ◽  
Vol 473-474 ◽  
pp. 429-434 ◽  
Author(s):  
Olga Verezub ◽  
György Kaptay ◽  
Tomiharu Matsushita ◽  
Kusuhiro Mukai
Keyword(s):  
Contact Angle ◽  
Particle Size ◽  
Aqueous Solutions ◽  
Particle Velocity ◽  
Weber Number ◽  
High Speed ◽  
Solid Particles ◽  
Bulk Liquid ◽  
Distilled Water ◽  
Critical Weber Number

Penetration of model solid particles (polymer, teflon, nylon, alumina) into transparent model liquids (distilled water and aqueous solutions of KI) were recorded by a high speed (500 frames per second) camera, while the particles were dropped from different heights vertically on the still surface of the liquids. In all cases a cavity has been found to form behind the solid particle, penetrating into the liquid. For each particle/liquid combination the critical dropping height has been measured, above which the particle was able to penetrate into the bulk liquid. Based on this, the critical impact particle velocity, and also the critical Weber number of penetration have been established. The critical Weber number of penetration was modelled as a function of the contact angle, particle size and the ratio of the density of solid particles to the density of the liquid.

Experimental Investigation of Boundary Layer Instabilities on the Free Surface of Non-Turbulent Jet

2012 ◽  
Author(s):  
Matthieu A. Andre ◽  
Philippe M. Bardet
Keyword(s):  
Boundary Layer ◽  
Free Surface ◽  
High Speed ◽  
Particle Tracking Velocimetry ◽  
Capillary Waves ◽  
Wave Growth ◽  
Image Velocimetry ◽  
Planar Laser ◽  
Surface Visualization ◽  
The Waves

Shear instabilities induced by the relaxation of laminar boundary layer at the free surface of a high speed liquid jet are investigated experimentally. Physical insights into these instabilities and the resulting capillary wave growth are gained by performing non-intrusive measurements of flow structure in the direct vicinity of the surface. The experimental results are a combination of surface visualization, planar laser induced fluorescence (PLIF), particle image velocimetry (PIV), and particle tracking velocimetry (PTV). They suggest that 2D spanwise vortices in the shear layer play a major role in these instabilities by triggering 2D waves on the free surface as predicted by linear stability analysis. These vortices, however, are found to travel at a different speed than the capillary waves they initially created resulting in interference with the waves and wave growth. A new experimental facility was built; it consists of a 20.3 × 146.mm rectangular water wall jet with Reynolds number based on channel depth between 3.13 × 104 to 1.65 × 105 and 115. to 264. based on boundary layer momentum thickness.

AlGaN/GaN HEMTs: RECENT DEVELOPMENTS AND FUTURE DIRECTIONS

2008 ◽  
Vol 18 (04) ◽  
pp. 913-922 ◽  
Author(s):  
SIDDHARTH RAJAN ◽  
UMESH K. MISHRA ◽  
TOMÁS PALACIOS
Keyword(s):  
Field Effect ◽  
High Speed ◽  
Digital Circuits ◽  
Field Effect Transistors ◽  
Rf Power ◽  
Power Performance ◽  
Future Directions ◽  
Recent Developments ◽  
Gan Hemts ◽  
State Of Art

This paper provides an overview of recent work and future directions in Gallium Nitride transistor research. We discuss the present status of Ga -polar AlGaN / GaN HEMTs and the innovations that have led to record RF power performance. We describe the development of N -polar AlGaN / GaN HEMTs with microwave power performance comparable with state-of-art Ga -polar AlGaN / GaN HEMTs. Finally we will discuss how GaN -based field effect transistors could be promising for a less obvious application: low-power high-speed digital circuits.

Linear and non-linear potential-flow calculations of free-surface waves with lift and induced drag

2000 ◽  
Vol 214 (6) ◽  
pp. 801-812
Author(s):  
C-E Janson
Keyword(s):  
Free Surface ◽  
Potential Flow ◽  
Lift Force ◽  
Radiation Condition ◽  
Linear Potential ◽  
Surface Boundary ◽  
Model Approximation ◽  
Non Linear ◽  
Lifting Surfaces ◽  
The Waves

A potential-flow panel method is used to compute the waves and the lift force from surface-piercing and submerged bodies. In particular the interaction between the waves and the lift produced close to the free surface is studied. Both linear and non-linear free-surface boundary conditions are considered. The potential-flow method is of Rankine-source type using raised source panels on the free surface and a four-point upwind operator to compute the velocity derivatives and to enforce the radiation condition. The lift force is introduced as a dipole distribution on the lifting surfaces and on the trailing wake, together with a flow tangency condition at the trailing edge of the lifting surface. Different approximations for the spanwise circulation distribution at the free surface were tested for a surface-piercing wing and it was concluded that a double-model approximation should be used for low speeds while a single-model, which allows for a vortex at the free surface, was preferred at higher speeds. The lift force and waves from three surface-piercing wings, a hydrofoil and a sailing yacht were computed and compared with measurements and good agreement was obtained.

Development and Assessment of a Total Resistance Optimized Bow for the AE 36

1994 ◽  
Vol 31 (02) ◽  
pp. 149-160
Author(s):  
Donald C. Wyatt ◽  
Peter A. Chang
Keyword(s):  
Experimental Data ◽  
Optimization Procedure ◽  
Wave Resistance ◽  
Scale Model ◽  
Optimization Approach ◽  
Nonlinear Constraints ◽  
Total Resistance ◽  
Hull Form ◽  
Final Design ◽  
Resistance Data

A numerically optimized bow design is developed to reduce the total resistance of a 23 000 ton ammunition ship (AE 36) at a speed of 22 knots. An optimization approach using slender-ship theory for the prediction of wave resistance is developed and applied. The new optimization procedure is an improvement over previous optimization methodologies in that it allows the use of nonlinear constraints which assure that the final design remains within practical limits from construction and operational perspectives. Analytic predictions indicate that the AE 36 optimized with this procedure will achieve a 40% reduction in wave resistance and a 33% reduction in total resistance at 22 knots relative to a Kracht elliptical bulb bow design. The optimization success is assessed by the analysis of 25th scale model resistance data collected at the David Taylor Research Center deepwater towing basin. The experimental data indicate that the optimized hull form yields a 51% reduction in wave resistance and a 12% reduction in total resistance for the vessel at 22 knots relative to the Kracht bulb bow design. Similarly encouraging results are also observed when comparisons are made with data collected on two other conventionally designed AE 36 designs.

scholarly journals DESIGN OF A MOBILE BIO-DIESEL PRODUCTION FACILITY

2011 ◽  
Author(s):  
B. J. Drake ◽  
M. Jacques ◽  
D. Binkley ◽  
S. Barghi ◽  
R. O. Buchal
Keyword(s):  
Particulate Matter ◽  
Vegetable Oil ◽  
Diesel Fuel ◽  
High Speed ◽  
Solid Particles ◽  
Vacuum Filter ◽  
Production Facility ◽  
Operational Life ◽  
Used Vegetable Oil ◽  
Diesel Production

In 2004/2005, a team of mechanical engineering students undertook an interdisciplinary capstone design project to design a mobile bio-diesel production facility capable of converting 500 L/h of used vegetable oil or animal tallow into bio-diesel fuel. Bio-diesel fuel has negligible sulfur content and significantly reduces the emission of particulate matter, e.g. soot and carbon monoxide, compared to the combustion of conventional diesel fuel. Furthermore, bio-diesel fuel is biodegradable, nontoxic, and can be produced from renewable feedstock. The mobile facility is capable of taking used vegetable oil from different sources and processing the oil while in motion, eliminating costs associated with transportation, land use and construction. A special filter was designed to remove any major particulate matter as well as wax-like substances formed by heating of the cooking oil during its operational life. A rotary vacuum filter was designed to continuously of remove wax and solid particles accumulated on the filter cloth. The wax and solid wastes, which are organic compounds, are readily converted to useful light organic molecules through a subsequent gasification process. A transesterification process was applied using methanol as a solvent and sodium hydroxide as a catalyst. A mix of unrefined bio-diesel fuel and glycerol, which is produced by transestrification, is sent to a glycerol separating tower. The separator was designed to efficiently separate bio-diesel fuel from glycerol. The bio-diesel fuel is neutralized by weak acid solution and washed by water to remove impurities. High-speed mixers were designed to create maximum contact between phases for efficient separation. The mobile facility is subject to vibration, which was considered in every aspect of the design. The facility will be powered by bio-diesel fuel, and heat recovery and water recycling were considered to minimize energy requirements. The project culminated in a final design report containing detailed engineering analysis and a comprehensive set of working drawings.

scholarly journals MASS TRANSPORT IN VOCOIDAL THEORY

1982 ◽  
Vol 1 (18) ◽  
pp. 22
Author(s):  
J.W. Gonsalves ◽  
D.H. Swart
Keyword(s):  
Free Surface ◽  
Mass Transport ◽  
Deep Water

The concept of mass transport is theoretically discussed within the framework provided by Vocoidal theory. The Lagrangian mass transport is divided into two parts; firstly treating the fluid as being inviscid and secondly, incorporating viscosity by means of the free surface and bottom boundaries. Eulerian mass transport is defined and is shown to correspond, in deep water, to the net flow predicted by Stokes and others.

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