Transonic Hull: Theory, Validation, Breakthroughs and Applications to Ships

2015 ◽  
Author(s):  
Alberto A. Calderon ◽  
Brian Maskew
Keyword(s):  
High Speed ◽  
Feasibility Studies ◽  
Hydrodynamic Characteristics ◽  
Large Magnitude ◽  
Transverse Waves ◽  
Triangular Shape ◽  
Bow Wave ◽  
Linear Drag ◽  
Speed Function ◽  
Displacement Regime

Froude laws are inductive therefore not universally applicable. The relation between Froude and Kelvin, and Froude and Wigley are made explicit. Transonic Hull (TH) has hydrodynamic characteristics not predictable by Froude’s laws. In Transonic Hydrofield (THF) Theory TH’s 3-D triangular shape induces a submerged current - subduction effect - that replaces and substantially precludes bow wave, reducing or eliminating wave making drag growth. TH’s ability to transverse waves without diminishing their energy eliminates slam. TH’s unprecedented breakthroughs with large magnitude are: substantially no bow or stern wave; full displacement regime and near zero pitch independent of speed; linear drag-speed function with greatly reduced wave making (residual) drag; accelerations in a sea that decrease with increasing speed; no slam at any speed and sea conditions. CFD studies of TH-900 vs. Fastship and TH-4022 vs. Axe Bow 4103 shows reduction of drag from 20% to 37% with gains of weight/drag from 33% to 59%. Gains originate from much smaller residual drag. Pre-feasibility studies demonstrate that TH’s triangular waterplanes houses same contents and payloads as conventional vessels provided TH has larger length and beam. TH-1200 Strategic Lift with full payload and range has exceptional high L/D at high speed in Von-Karman-Gabrielli chart.

Hydrodynamic Characteristics of Water-Entry Blades

2003 ◽  
Author(s):  
Hisashi Kamikubo ◽  
Dasisuke Ikegami ◽  
Kotaro Sato ◽  
Shinichi Mizuno ◽  
Okitsugu Furuya ◽  
...  
Keyword(s):  
High Speed ◽  
Water Entry ◽  
Hydrodynamic Characteristics ◽  
Complex Nature ◽  
Two Dimensional ◽  
Propulsive Efficiency ◽  
Triangular Shape ◽  
Speed Up

The partially submerged ventilated propeller (PSVP) is of interest to many researchers and ship builders due to its high propulsive efficiency and thrusting capability at the high sea states. As a matter of fact, it is now used for those ships of high speed up to 50 knots. However, its full capability is not totally utilized to date due to the complex nature of both hydrodynamic and material problems. It is a well known fact that PSVP fails materially after a certain period of time. The cause of the failure is not fully understood to date. Although PSVP is tested in the form of propeller for many years, the detailed ventilation phenomena, i.e., blade entry problems are not fully investigated. The paper presented herein will discuss about the results of blade entry experiments with two-dimensional blades of triangular shape used.

Some Special Aspects of Hypersonic Flow Fields

1959 ◽  
Vol 63 (585) ◽  
pp. 508-512 ◽  
Author(s):  
K. W. Mangler
Keyword(s):  
Hypersonic Flow ◽  
High Speed ◽  
Flow Fields ◽  
The Body ◽  
Lower Velocity ◽  
Bow Wave ◽  
Total Head ◽  
Bow Shocks ◽  
Lower Entropy ◽  
Subsonic Region

When a body moves through air at very high speed at such a height that the air can be considered as a continuum, the distinction between sharp and blunt noses with their attached or detached bow shocks loses its significance, since, in practical cases, the bow wave is always detached and fairly strong. In practice, all bodies behave as blunt shapes with a smaller or larger subsonic region near the nose where the entropy and the corresponding loss of total head change from streamline to streamline due to the curvature of the bow shock. These entropy gradients determine the behaviour of the hypersonic flow fields to a large extent. Even in regions where viscosity effects are small they give rise to gradients of the velocity and shear layers with a lower velocity and a higher entropy near the surface than would occur in their absence. Thus one can expect to gain some relief in the heating problems arising on the surface of the body. On the other hand, one would lose farther downstream on long slender shapes as more and more air of lower entropy is entrained into the boundary layer so that the heat transfer to the surface goes up again. Both these flow regions will be discussed here for the simple case of a body of axial symmetry at zero incidence. Finally, some remarks on the flow field past a lifting body will be made. Recently, a great deal of information on these subjects has appeared in a number of reviewing papers so that little can be added. The numerical results on the subsonic flow regions in Section 2 have not been published before.

scholarly journals Research for Space Interception Simulation under Nonlinear Time-Varied Similarity

2020 ◽  
Vol 38 (4) ◽  
pp. 715-722
Author(s):  
Xiaodong Lu ◽  
Tao Cui ◽  
Jiayao Gu
Keyword(s):  
Dimensional Analysis ◽  
High Speed ◽  
Uniform Motion ◽  
Simulation Algorithm ◽  
Large Magnitude ◽  
Small Magnitude ◽  
Whole Process ◽  
Scale Factors ◽  
Reference Motion ◽  
Spatio Temporal

A nonlinear time-varied similarity(NTVS) simulation algorithm is proposed to solve the problem that the process of space interception is intractable to simulate with high precision in limited platform under the linear constant similarity(LCS). Firstly, the similarity criterions based on the dimensional analysis are given in the simulation of the interception motion at high-speed, and the disadvantage of LCS is analyzed. Then, the reference motion is introduced to establish a time-varied spatio-temporal transform system which scale factors are self-adaptive with time, and the method is proved to satisfy the similarity consistency. Finally the way that linear separation and independent mapping solve the problem that the large magnitude uniform motion in approaching directions and small magnitude overload motion in lateral directions are simulated in a limited ground platform. The results show that the NTVS can simulate the whole process of interception and perform better in accuracy comparing with that via LCS.

A Study of Transient Response of Flexible Rotors in High Speed Turbomachinery

1992 ◽  
Author(s):  
V. Pavelic ◽  
R. S. Amano
Keyword(s):  
Mathematical Model ◽  
Computer Program ◽  
Analytical Model ◽  
High Speed ◽  
Angular Speed ◽  
Journal Bearings ◽  
Hydrodynamic Characteristics ◽  
Flexible Assembly ◽  
Lagrange’S Equation ◽  
Equations Of Motions

In many applications the design operating range of the turbomachinery may be well above the rotor first critical speed which leads to the problem of insuring that the turbomachinery performs with a stable, low-level amplitude of vibration. Under certain conditions of high speed and loading the rotor system can start orbiting in its bearing at a rate which is less than the rotor angular speed, and this phenomena is commonly known as whirling or whipping action. This whipping action may produce additional undesirable dynamic loads on the overall flexible assembly and eventually destroy the rotor. Some of this action is also transient in nature. Whirling is a self-exited vibration caused mainly by the fluid bearings and by the internal friction damping of the rotor. To understand this occurrence, a general dynamic mathematical model was derived considering also the complete viscous characteristic of hydrodynamic journal bearings. The general equations of motions of the system are obtained from Lagrange’s equation of motion. The system kinetic, potential, and dissipation functions are determined based on the generalized coordinates of the system. The journal displacements are related to the overall dynamics of the rotor using deformable bearings. The loads acting at the journals of the shaft are integrated from the fluid film pressure distribution in the journal bearings using mobility method. A unique mathematical model is formulated and solved. This model includes the elastic and inertial properties of the flexible rotor, the elastic, damping and inertial properties of supports and the hydrodynamic characteristics of the journal bearings. The equations of motions result in a system of nonlinear second order differential equations which are solved by using finite difference method. The solution of the equations of motions is used to plot maps of motion of journal centers. A computer program was implemented to aid in the solution of the system of equations and to verify analytical model. The computer program used test data available in literature and the results were compared to be very good. The analytical model and results obtained in this study can be of great help to designers of high speed turbomachinery.

scholarly journals A Hydrodynamic Methodology And CFD Analysis For Performance Prediction Of Stepped Planing Hulls

2015 ◽  
Vol 22 (2) ◽  
pp. 23-31 ◽  
Author(s):  
Hassan Ghassemi ◽  
Mojtaba Kamarlouei ◽  
Sajad Taj Golah Veysi
Keyword(s):  
High Speed ◽  
Hydrodynamic Performance ◽  
Hydrodynamic Characteristics ◽  
Geometrical Parameters ◽  
Cfd Analysis ◽  
Analysis Model ◽  
Marine Coatings ◽  
Resistance Reduction ◽  
Calculation Results ◽  
Fruitful Research

AbstractNowadays all efforts in planing hull research are focused on resistance reduction for achieving the highest speed in fast planing crafts. Furthermore, many fruitful research projects have been carried out on marine coatings, planing equipment, and optimization of propeller and hull form, which revolutionized industry of high - speed crafts and made them an efficient survival vehicle in coastal areas and rivers. In this paper the hydrodynamic performance of planing hulls are investigated by means of a modified Savitsky model for both non-stepped and stepped bodies. Meanwhile, in order to meet this goal reasonably, effective geometrical parameters of planing hull are investigated and then operational hydrodynamic characteristics of the craft are predicted by using a computational program. Finally, the calculation results are verified by means of a CFD-analysis model.

Study of a Container Ship with Breaking Waves at High Froude Number Using URANS and DDES Methods

2019 ◽  
Author(s):  
Jianhua Wang ◽  
Zhen Ren ◽  
Decheng Wan
Keyword(s):  
Free Surface ◽  
Wave Breaking ◽  
High Speed ◽  
Hydrodynamic Performance ◽  
Small Scale ◽  
Breaking Wave ◽  
Container Ship ◽  
Ship Model ◽  
Bow Waves ◽  
Bow Wave

The KRISO container ship model is used for numerical simulations to investigate hydrodynamic performance under high speeds. Unsteady Reynolds-Averaged Navier-Stokes (URANS) and delayed detached eddy simulation (DDES) approaches are used to resolve the flow field around the ship model. High-resolution Volume of Fluid (VOF) technique in OpenFOAM is used to capture the free surface. The present work focuses on the wave-breaking phenomena of high-speed ships. To study the speed effects on the phenomenon of ship bow wave breaking, three different speeds, i.e., Fn = .26, .35, and .40, are investigated for a fixed ship model in calm water. Predicted resistance and wave patterns under Fn = .26 are validated with available experimental data, and a good agreement is achieved. The breaking wave phenomena can be observed from both URANS and DDES results for Froude numbers greater than .35. And the Fn = .40 case shows more violent breaking bow waves. The process of overturning and breaking of bow wave is more complex in the DDES results, and some small-scale free surface features are also captured. The predicted bow wave is compared with the experiment conducted at the China Ship Scientific Research Center. It shows that the DDES results are more accurate. Wave profiles and vorticity field at several cross sections are presented to illustrate the relationship between bow waves and vortices. It is found that the free surface vorticity dissipates quickly in the URANS simulation, which leads to the difference compared with the DDES results.

scholarly journals Feasibility Studies on the Use of Higher Frequency Bands and Beamforming Selection Scheme for High Speed Train Communication

2017 ◽  
Vol 2017 ◽  
pp. 1-14 ◽  
Author(s):  
Ayotunde O. Laiyemo ◽  
Petri Luoto ◽  
Pekka Pirinen ◽  
Matti Latva-aho
Keyword(s):  
High Speed ◽  
Feasibility Studies ◽  
Frame Structure ◽  
Marginal Rate ◽  
Selection Scheme ◽  
Frequency Bands ◽  
Data Rates ◽  
High Speed Trains ◽  
Increased Sensitivity ◽  
Achievable Data Rate

With increasing popularity of high speed trains and traffic forecast for future cellular networks, the need to provide improved data rates using higher frequency bands (HFBs) for train passengers is becoming crucial. In this paper, we modify the OFDM frame structure for HST, taking into account the increasing sensitivity to speed at HFBs. A lower bound on the SNR/SINR for a given rate for reliable communication was derived considering the physical layer parameters from the OFDM frame. We also analyze different pathloss models in the context of examining the required gain needed to achieve the same performance as with microwave bands. Finally, we present a time-based analogue beamforming selection approach for HST. We observed that, irrespective of the pathloss models used, the required gains are within the same range. For the same SNR/SINR at different frequency bands, the achievable data rate varies with respect to the frequency bands. Our results show the potential of the use of HFBs. However, due to the increased sensitivity of some channel parameters, a maximum frequency band of 38 GHz is suggested. Evaluation of our proposed beamforming scheme indicates a close performance to the optimal SVD scheme with a marginal rate gap of less than 2 b/s/Hz.

Hydrodynamic Characteristics of Mechanically Agitated Air - Aqueous Sucrose Solutions

2014 ◽  
Vol 35 (1) ◽  
pp. 97-107 ◽  
Author(s):  
Magdalena Cudak
Keyword(s):  
Power Consumption ◽  
High Speed ◽  
Gas Flow ◽  
Sucrose Concentration ◽  
Empirical Relationship ◽  
Experimental Studies ◽  
Hydrodynamic Characteristics ◽  
Dimensionless Numbers ◽  
Rushton Turbine ◽  
Sucrose Solutions

Abstract The aim of the research presented in this paper was determination of power consumption and gas hold-up in mechanically agitated aerated aqueous low concentration sucrose solutions. Experimental studies were conducted in a vessel of diameter 0.634 m equipped with high-speed impellers (Rushton turbine, Smith turbine or A 315). The following operating parameters were changed: volumetric gas flow rate (expressed by superficial gas velocity), impeller speed, sucrose concentration and type of impeller. Based on the experiments results, impellers with a modified shape of blades, e.g. CD 6 or A 315, could be recommended for such gas-liquid systems. Power consumption was measured using strain gauge method. The results of gas holdup measurements have been approximated by an empirical relationship containing dimensionless numbers (Eq. (2)).

Investigations on influence of groove shapes for the journal bearing in high-speed and heavy-load press system

2018 ◽  
Vol 70 (1) ◽  
pp. 230-240 ◽  
Author(s):  
Yu Chen ◽  
Yu Sun ◽  
Chunping Cao
Keyword(s):  
High Speed ◽  
Design Methodology ◽  
Journal Bearing ◽  
Computational Method ◽  
Hydrodynamic Characteristics ◽  
Hydrodynamic Behavior ◽  
Heavy Load ◽  
Content Type ◽  
Thermal Influence ◽  
Fluid Interaction

Purpose The purpose of this study is to investigate the hydrodynamic characteristics of journal bearings in a high-speed and heavy-load press system by considering thermal influence and cavitation. Design/methodology/approach A proper and effectual computational method is presented for steady-state analysis of fluid interaction in a rotor-bearing press system by combining computational fluid dynamics techniques. Findings The influences of eccentricity ratio, rotational speed and oil-film thickness on the hydrodynamic behavior of the journal bearing are studied. Originality/value The computational method can be used for creating a precise lubrication design for a journal bearing of a lubrication system.

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