Preliminary Design of Mooring Systems

1982 ◽  
Vol 26 (01) ◽  
pp. 25-35
Author(s):  
Michael S. Triantafyllou
Keyword(s):  
Dynamic Performance ◽  
Static Solution ◽  
Approximate Expression ◽  
Multiple Time ◽  
Preliminary Design ◽  
Spectral Techniques ◽  
Dynamic Solution ◽  
Parametric Search ◽  
Slow Part ◽  
Selection Of

The preliminary design of mooring systems is formulated by separating the quasi-steady solution from the dynamic solution. A multiple time-scale expansion provides the appropriate equations, which are nonlinear for the quasi-steady part and linear space varying for the dynamic part. The fast dynamic solution consists of a fast varying and a slowly varying part with respect to space. An asymptotic solution is obtained by using the WKB method for the fast part, while an approximate expression is derived for the slow part. The resulting solution is simple and can be used to determine the dynamic behavior of complex systems, while permitting an extensive parametric search and the use of spectral techniques. This formulation leads to rational measures of the dynamic performance which, combined with cost considerations obtained from the static solution, permit an optimal selection of the system parameters. An example demonstrates the features of this methodology.

Numerical Optimization of Rotor-Bearing Systems

1989 ◽  
Author(s):  
J. P. Sadler ◽  
K. E. Rouch ◽  
A. S. Rani
Keyword(s):  
Numerical Optimization ◽  
Dynamic Performance ◽  
Optimal Designs ◽  
Design Parameters ◽  
Finite Element Program ◽  
Optimum Placement ◽  
Rotor Bearing ◽  
Element Program ◽  
Programming Techniques ◽  
Selection Of

Abstract Nonlinear programming techniques are combined with a finite element program for dynamic analysis of rotor-bearing systems. The resulting program provides the means for obtaining optimal designs for improved dynamic performance of a rotor through the automated selection of various design parameters of the rotor-bearing system. Both constrained and unconstrained optimizations are considered. Illustrative examples are presented for the case of optimum placement of critical speeds.

scholarly journals Critical Parameters and Influence on Dynamic Behaviours of Nonlinear Electrostatic Force in a Micromechanical Vibrating Gyroscope

2020 ◽  
Vol 2020 ◽  
pp. 1-15
Author(s):  
Shuying Hao ◽  
Yulun Zhu ◽  
Yuhao Song ◽  
Qichang Zhang ◽  
Jingjing Feng ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Bias Voltage ◽  
Electrostatic Force ◽  
Dynamic Performance ◽  
Great Influence ◽  
Critical Parameters ◽  
Multiple Time Scales ◽  
Multiple Time ◽  
Element Analysis ◽  
Dc Bias

The electrostatic force nonlinearity caused by fringe effects of the microscale comb will affect the dynamic performance of the micromechanical vibrating gyroscopes (MVGs). In order to reveal the influence mechanism, a class of four-degree-of-freedom (4-DOF) electrostatically driven MVG is considered. The influence of DC bias voltage and comb spacing on the nonlinearity of electrostatic force and the dynamic response of the MVG by using multiple time scales method and numerical simulation are discussed. The results indicate that the electrostatic force nonlinearity causes the system to show stiffness softening. The softening characteristics of the electrostatic force cause the offset of the resonance frequency and a decrease in sensitivity. Although the electrostatic nonlinearity has a great influence on the dynamic behaviour, its influence can be avoided by the reasonable design of the comb spacing and DC bias voltage. There exists a critical value for comb spacing and DC bias voltage. In this paper, determining the critical values is demonstrated by nonlinear dynamics analysis. The results can be supported by the finite element analysis and numerical simulation.

Upgrading of the STP Uithoorn: treatment of nutrient rich wastewater from horticulture

2005 ◽  
Vol 52 (4) ◽  
pp. 81-90 ◽  
Author(s):  
P. Piekema ◽  
R. Neef
Keyword(s):  
Primary Treatment ◽  
Preliminary Design ◽  
Operational Control ◽  
Tertiary Treatment ◽  
Wide Range ◽  
High Loading Rate ◽  
Stage System ◽  
Nutrient Discharge ◽  
Selection Of ◽  
System Choice

The STP Uithoorn will be upgraded to accommodate the treatment of wastewater from a growing population and to meet more stringent nutrient discharge limits in 2006. In 2003 a system choice and preliminary design was made for the upgrading. A special feature is the nutrient rich wastewater flow from the rapidly developing horticulture in the area. Since the future loads from horticulture are highly uncertain, flexibility of the STP after upgrading is an important issue. A three stage system was selected: improved physical-chemical primary treatment, secondary treatment by activated sludge, and tertiary treatment by denitrifying filters. In this way an important part of the existing infrastructure can be reused, and flexibility is assured by constructing the tertiary treatment in modules and by providing a wide range of operational control possibilities. In this paper the process of system choice and selection of type of tertiary treatment are described, as well as the optimisation of the existing treatment. In order to determine the feasibility of allowing a high loading rate on the existing secondary clarifiers, a two-dimensional hydraulic model of the clarification process was used.

Surface Roughness Effect on the Performance of 3-lobe Symmetric Hole Entry Hybrid Journal Bearings

2014 ◽  
Vol 592-594 ◽  
pp. 1190-1194
Author(s):  
Prashant B. Kushare ◽  
Satish C. Sharama
Keyword(s):  
Surface Roughness ◽  
Journal Bearing ◽  
Dynamic Performance ◽  
Flow Equation ◽  
Longitudinal Roughness ◽  
Transverse Isotropic ◽  
Offset Factor ◽  
Rotor Dynamic ◽  
Selection Of ◽  
Effect Of Surface

The present paper, evaluates the effect of surface roughness on the performance characteristics of capillary compensated 3-lobe symmetric hole entry hybrid journal bearing. The effect of surface roughness patterns viz; transverse, isotropic, longitudinal and smooth, on bearing performance is presented for different values of offset factor. A modified form of Reynold’s equation in conjunction with restrictor flow equation is solved by using Galerkin’s technique of FEM. The numerically simulated results of the study indicate that the surface roughness orientation patterns affect the performance of 3-lobe hybrid journal bearing system significantly. Further, it is noticed that the longitudinal roughness pattern provides enhanced value of rotor dynamic coefficient.To have an improved dynamic performance, a judicious selection of offset factor and surface roughness pattern parameter is essential.

Dynamic Performance of Single-Axle Freight Trucks

1983 ◽  
Vol 105 (2) ◽  
pp. 71-74
Author(s):  
D. N. Wormley ◽  
P. A. Tombers
Keyword(s):  
Field Data ◽  
Critical Speed ◽  
Dynamic Performance ◽  
Design Parameters ◽  
Stability Field ◽  
Suspension Stiffness ◽  
The Stability ◽  
Freight Trucks ◽  
Selection Of ◽  
Wheel Track

An analysis has been developed to evaluate the stability of freight cars employing single-axle freight trucks. The analysis has been used to evaluate the influence of wheel/track contact geometry, suspension stiffness, and loading on truck stability. Field data resulting from measurement of a prototype car lateral axle accelerations have been used to identify car critical speeds as a function of suspension stiffness and loading. These data have agreed closely with the analytical calculations and provided a basis for selection of car design parameters to achieve desired values of critical speed.

scholarly journals On the Selection of Optimal Propeller Diameter for a 120m Cargo Vessel

2018 ◽  
Author(s):  
Jennie Andersson ◽  
Robert Gustafsson ◽  
Arash Eslamdoost ◽  
Rickard E. Bensow
Keyword(s):  
Open Water ◽  
Operating Conditions ◽  
Series Data ◽  
Preliminary Design ◽  
Optimum Diameter ◽  
Viscous Losses ◽  
Computational Fluid Dynamics Cfd ◽  
Propulsion Unit ◽  
Hydrodynamic Effects ◽  
Selection Of

In the preliminary design of a propulsion unit the selection of propeller diameter is most commonly based on open water tests of systematic propeller series. The optimum diameter obtained from the propeller series data is however not considered to be representative for the operating conditions behind the ship, instead a slightly smaller diameter is often selected. We have used computational fluid dynamics (CFD) to study a 120m cargo vessel with an integrated rudder bulb-propeller hubcap system and a 4-bladed propeller series, to increase our understanding of the hydrodynamic effects influencing the optimum. The results indicate that a 3-4 % smaller diameter is optimal in behind conditions in relation to open water conditions at the same scale factor. The reason is that smaller, higher loaded propellers perform better together with a rudder system. This requires that the gain in transverse kinetic energy losses thanks to the rudder overcomes the increase in viscous losses in the complete propulsion system.

scholarly journals Application of Vortex Generators in Flow Control of the Inlet

1985 ◽  
Author(s):  
Chen Xiao ◽  
Fang Liang-Wei
Keyword(s):  
Boundary Layer ◽  
Flow Field ◽  
Flow Separation ◽  
Dynamic Performance ◽  
Low Pressure ◽  
Transverse Flow ◽  
Vortex Generators ◽  
Flow Losses ◽  
Subsonic Diffuser ◽  
Selection Of

This paper introduces the features of using co-rotating vortex generators for controlling boundary layer and flow field in the inlet without flow separation. The principles of the arrangements of the blades and selection of constructional parameters of the generators that are applied to create the transverse flow between the high and low pressure regions and to reduce the secondary flow losses are analysed. The experimental results show that when the appropriate parameters of the co-rotating vortex generators are chosen for the inlet subsonic diffuser with apparent high and low pressure regions, not only the nonuniformity of the flow field is greatly improved but also the dynamic performance of the flow at exit is slightly improved.

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