A Simple Method for Predicting the Maximum Squat of a High-Speed Displacement Ship

2006 ◽  
Vol 43 (03) ◽  
pp. 146-151
Author(s):  
Tim Gourlay
Keyword(s):  
Satisfactory Agreement ◽  
Model Test ◽  
High Speed ◽  
Simple Formula ◽  
Test Results ◽  
Simple Method ◽  
Wide Range ◽  
Speed Range ◽  
Calm Water ◽  
Hull Forms

A simple formula is developed for predicting the maximum squat of a displacement ship as it passes through the transcritical speed range. This is given in terms of a maximum sinkage coefficient, which is almost constant across a wide range of hull forms. Satisfactory agreement is shown with model test results, and it is shown that large stern sinkages in the order of 3 to 6 meters are predicted for frigate and destroyer type hulls in shallow calm water.

CFD Simulation of Resistance of Highspeed Trimaran Hullforms

2015 ◽  
Author(s):  
Changhwan Son ◽  
Prasanta K. Sahoo ◽  
Vaibhav Aribenchi ◽  
Srikanth Asapana
Keyword(s):  
High Speed ◽  
Cfd Simulation ◽  
Accurate Determination ◽  
Cfd Analysis ◽  
Test Results ◽  
Ansys Fluent ◽  
Speed Range ◽  
Calm Water ◽  
Hull Forms

This paper attempts to carry out a CFD analysis on total resistance for trimaran hull forms based on established NPL systematic series which are high-speed round bilge hull forms. The resistance of high-speed trimaran hull forms have been determined using ANSYS FLUENT, a CFD software package. A systematic series of round bilge demi-hulls were generated, and their resistance in calm water were determined by using ANSYS FLUENT to briefly examine nature and degree of reliability of ANSYS FLUENT. The primary aim of this investigation is to determine resistance characteristics of slender round bilge trimaran hull forms in the high-speed range corresponding to Froude numbers up to 1.0. Model test results obtained from the paper Molland et al (1994) have been used to verify the efficacy of the CFD analysis. The results obtained from CFD have shown considerable promise and further analysis need to be carried out for accurate determination of resistance in trimaran configuration.

Path-Following Steering Control for Articulated Vehicles

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
B. A. Jujnovich ◽  
D. Cebon
Keyword(s):  
High Speed ◽  
Path Following ◽  
Steering Control ◽  
Active Steering ◽  
High Speeds ◽  
Wide Range ◽  
Articulated Vehicles ◽  
Speed Range ◽  
Heavy Goods Vehicles ◽  
Low Speeds

Passive steering systems have been used for some years to control the steering of trailer axles on articulated vehicles. These normally use a “command steer” control strategy, which is designed to work well in steady-state circles at low speeds, but which generates inappropriate steer angles during transient low-speed maneuvers and at high speeds. In this paper, “active” steering control strategies are developed for articulated heavy goods vehicles. These aim to achieve accurate path following for tractor and trailer, for all paths and all normal vehicle speeds, in the presence of external disturbances. Controllers are designed to implement the path-following strategies at low and high speeds, whilst taking into account the complexities and practicalities of articulated vehicles. At low speeds, the articulation and steer angles on articulated heavy goods vehicles are large and small-angle approximations are not appropriate. Hence, nonlinear controllers based on kinematics are required. But at high-speeds, the dynamic stability of control system is compromised if the kinematics-based controllers remain active. This is because a key state of the system, the side-slip characteristics of the trailer, exhibits a sign-change with increasing speeds. The low and high speed controllers are blended together using a speed-dependent gain, in the intermediate speed range. Simulations are conducted to compare the performance of the new steering controllers with conventional vehicles (with unsteered drive and trailer axles) and with vehicles with command steer controllers on their trailer axles. The simulations show that active steering has the potential to improve significantly the directional performance of articulated vehicles for a wide range of conditions, throughout the speed range.

Genetic Optimization of Geometrical Parameters of High Speed Rotor

2015 ◽  
Author(s):  
Behnam Ghalamchi ◽  
Adam Kłodowski ◽  
Jussi T. Sopanen ◽  
Aki M. Mikkola
Keyword(s):  
High Speed ◽  
Turbine Rotor ◽  
Optimization Techniques ◽  
Design Parameters ◽  
Geometrical Parameters ◽  
Campbell Diagram ◽  
Critical Speeds ◽  
Operation Speed ◽  
Wide Range ◽  
Speed Range

The main scope of this paper is optimization of high speed rotor systems by using Evolutionary Algorithm. The target of the optimization is finding geometrical parameters of the shaft, in such a way that the critical speeds are not occurring in the operation speed range. Rotating machines have a wide range of applications in industrial machinery and applying numerical optimization techniques helps engineers to improve the performance of rotor bearing systems. A schematic of a turbine rotor system is studied. The rotor is modeled using finite element method and Timoshenko beam elements having four degrees of freedom (DOF) per node — two translational and two rotational. Critical speeds are identified using Campbell diagram. The outcome of the simulation is looking to find the widest safe margin for operation speed range without any critical speed in Campbell diagram within the operation range. Design parameters for optimization are overhang shafts lengths and diameters. Several simulation runs with different variables shows a significant effect of these parameters in dynamic behavior of the system. Comparison of the results with the basic design of turbine rotor reveals that all constraints are satisfied.

Integrated Dynamic Thermo-Mechanical Modeling of High Speed Spindles, Part 2: Solution Procedure and Validations

2004 ◽  
Vol 126 (1) ◽  
pp. 159-168 ◽  
Author(s):  
Hongqi Li ◽  
Yung C. Shin
Keyword(s):  
High Speed ◽  
Solution Procedure ◽  
Operating Conditions ◽  
Test Results ◽  
Mechanical Modeling ◽  
Spindle Bearing ◽  
Wide Range ◽  
Bearing Stiffness ◽  
Models Validation ◽  
Validation Tests

This paper presents a new solution procedure for an integrated thermo-dynamic spindle model and validation results. Based on the model presented in Part 1 of this paper, a computer program has been developed to generate comprehensive solutions for high speed spindle-bearing systems, such as bearing stiffness, contact load and temperature, spindle dynamic characteristics and response, temperature distributions, and thermal expansions. The model and the solution procedure are modular such that solutions for different spindle set-ups can be easily generated by combining a given spindle model with different toolholder models. Validation test results for thermal and dynamic predictions are presented for four different spindle systems, including the thermal and dynamic validation tests on a specially constructed spindle testbed. The validation results show the model has accurate predictive capabilities for a wide range of operating conditions and various spindle designs.

scholarly journals Hull Forms of High Speed Craft having smallest Total Resistance at High Speed Range

1976 ◽  
Vol 1976 (140) ◽  
pp. 51-57
Author(s):  
Yasushi Yoshida ◽  
Hirotsugu Tanaka ◽  
Tamotsu Nagai
Keyword(s):  
High Speed ◽  
Total Resistance ◽  
Speed Range ◽  
Hull Forms

Experimental appraisal of hydrodynamic performance and motion of a single-stepped high-speed vessel in calm water and regular waves

2020 ◽  
pp. 095440622096812
Author(s):  
Sayyed Mahdi Sajedi ◽  
Parviz Ghadimi ◽  
Aliakbar Ghadimi ◽  
Mohammad Sheikholeslami
Keyword(s):  
High Speed ◽  
Single Step ◽  
Hydrodynamic Performance ◽  
Sea Waves ◽  
Regular Waves ◽  
Height Range ◽  
Step Model ◽  
Speed Range ◽  
Calm Water ◽  
Laboratory Models

High-speed vessels exhibit various motions and accelerations in calm water and sea waves. For examining the behavior of high-speed vessels, it is possible to examine these movements in laboratory models. In this paper, a single-step model in calm water is experimentally tested and compared with a model of no step. The speed range of these vessels is 1 m/s to 9 m/s equivalent to Beam Froude numbers of 0.43 to 3.87. During these experiments, the resistance parameters, trim, bow, and stern rise-up as well as the center of the gravity are measured. The non-step model has longitudinal instability at a speed of 8 m/s. This instability is avoided when the vessel is equipped by a transversal step. The vessel's trim and resistance are also reduced in the planing mode in calm water. Subsequently, hydrodynamic performance and its seakeeping condition in the planing regime are investigated for both vessels in regular waves. The single-step and non-step vessels are tested in the wavelength range of [Formula: see text], and the wave height range of 6 to 18 centimeters. It is observed that stepped vessel experiences lower motions and bow accelerations and less added resistance in comparison to the non-stepped vessel.

A New Type Laser Imaging System of Underwater Wake Bubbles

2014 ◽  
Vol 543-547 ◽  
pp. 2505-2508
Author(s):  
Xi Zhan Liu ◽  
Yan Bo Xue
Keyword(s):  
High Speed ◽  
Imaging System ◽  
Laser Sheet ◽  
High Speed Photography ◽  
Test Results ◽  
Laser Imaging ◽  
Technical Requirements ◽  
Wide Range ◽  
New Type ◽  
Wake Zone

Considering the difficulties in the wake bubbles imaging, a wake bubbles measurement system was presented based on the combination of high speed photography and laser sheet scanning technology. In this system, laser sheet was used to illuminate the wake zone to avoid the image stacking of bubbles. Because the particle size of bubbles was in a wide range (10~500um), three switchable magnification lenses were designed for the bubbles imaging. the test results show that the image quality is good and this system satisfies technical requirements.

Development of a Direct Drive Servo Valve With Flow Force Compensated Spool

2003 ◽  
Author(s):  
Weongyu Shin ◽  
Hyunyoung Choi ◽  
Hyopil Shin ◽  
Euijoon Moon
Keyword(s):  
High Speed ◽  
Performance Test ◽  
Cfd Analysis ◽  
Test Results ◽  
Direct Drive ◽  
High Speed Flow ◽  
Simple Method ◽  
Servo Valve ◽  
Speed Flow ◽  
Force Compensation

This paper is on the development of a Direct Drive servo Valve (DDV) with flow force compensated spool. In valves with spool, flow force is caused by the unbalance of pressure exerted on each land of spool when high-speed flow passes through very narrow orifices. A simple method for flow force compensation using a stepped spool is presented in this paper. It is easy to manufacture the stepped spool of the presented method because the shape of it is simple. The method has another merit that the size of valve need not be increased. Actuating force required for driving the spool can be decreased through the compensation of flow force. The effectiveness of the proposed method is predicted through CFD analysis. The results of the CFD analysis are also utilized for the optimization of step shape. Prototypes of flow force compensated DDV are manufactured and the measurements of flow force are carried out. The measured effectiveness of flow force compensation is very similar to that from the CFD analysis. Performance test results of prototype DDV satisfy required specifications.

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