Experimental Study and Hydrodynamic Performance Analysis of a Bio-Tail Fin Propellant System

2009 ◽  
Vol 419-420 ◽  
pp. 77-80 ◽  
Author(s):  
Yu Min Su ◽  
Shi Qi Zhao ◽  
Liang Yang
Keyword(s):  
Experimental Data ◽  
Lateral Force ◽  
Hydrodynamic Performance ◽  
Force Coefficient ◽  
Thrust Coefficient ◽  
Propulsion Efficiency ◽  
Design Concepts ◽  
Torque Coefficient ◽  
Precise Experimental Data ◽  
Selection Of

In order to research the bionic mechanics in unsteady flow and the hydrodynamic performance of the oscillating tail fin, in this paper, an experimental device imitating bionic tail fin were built, the design concepts and the rolling systems of the mechanical tail fins were demonstrated, including the procedures and correlated works on the selection of the servo motors, online control and signal data collecting and processing. The movements of the mechanical tail fin could be optimized by the comparisons of the propulsion efficiency, thrust coefficient, lateral force coefficient and torque coefficient at different conditions. Meanwhile, error analysis is carried out to correct the movement curves and obtain more precise experimental data and results.

Numerical Simulation of a Three Bladed Marine Propeller in Steady and Unsteady State

2014 ◽  
Vol 592-594 ◽  
pp. 1136-1141
Author(s):  
N. Prakash ◽  
A. Muthuvel ◽  
D.G. Roychowdhury
Keyword(s):  
Experimental Data ◽  
Transient Analysis ◽  
Tangential Velocity ◽  
Computational Time ◽  
Marine Propeller ◽  
Unsteady State ◽  
Thrust Coefficient ◽  
Marine Propellers ◽  
Torque Coefficient ◽  
Frame Method

In this paper the numerical analysis for an unstructured polyhedral 3bladed un-skewed propeller in steady and transient analysis is discussed and the results are compared with the experimental data. A moving reference frame method is adopted by creating an interface between the propeller and the domain for the rotation of the propeller. The hydrodynamic coefficients such as Thrust coefficient (Kt), Torque coefficient (Kq), circumferentially averaged axial, radial and tangential velocity are compared with the experimental data. The computational time for each simulation is compared and concluded that marine propellers consume less computational time in the steady analysis when compared with the unsteady analysis.

Numerical Analysis of Propeller During Heave Motion Near a Free Surface

2017 ◽  
Vol 51 (1) ◽  
pp. 40-51 ◽  
Author(s):  
Wang Lian-zhou ◽  
Guo Chun-yu ◽  
Wan Lei ◽  
Su Yu-min
Keyword(s):  
Free Surface ◽  
Coupling Effect ◽  
Hydrodynamic Performance ◽  
Navier Stokes ◽  
Grid Technology ◽  
Thrust Coefficient ◽  
Motion State ◽  
Sinusoidal Motion ◽  
Torque Coefficient ◽  
Heave Motion

AbstractThe interaction between the free surface and the propeller during heave motion near the free surface was analyzed numerically using the Reynolds-Averaged Navier-Stokes (RANS) method. The coupling effect between the rotation and heave motions of the propeller was modeled using a motion equation developed in this study; the heave motion was simplified as a periodic motion based on the sinusoidal motion law; and the transfer of numerical values for unsteady flow fields was implemented using overset grid technology. A comparative analysis of the unsteady thrust coefficient and torque coefficient under different advance coefficient conditions was conducted, and the air ingestion phenomenon of the propeller was analyzed. The research highlighted the interaction between the coupled heave and rotation motions of the propeller and the free surface. The results showed that, when the advance coefficient was low, the hydrodynamic performance of the propeller during heave motion near a free surface was strongly influenced by the free surface and that a remarkable interaction existed between the propeller and the free surface. As the advance coefficient increased, the interaction between the propeller and the free surface weakened. The air ingestion that the propeller exerts upon the free surface during heave motion is a complex coupled superposition process. This phenomenon is correlated to the motion state and working time of the propeller, as well as the distance between the propeller and the free surface.

scholarly journals Comparative analysis of the hydrodynamic performance of pre-swirl stator pump-jet propulsor under different rotational speeds

2021 ◽  
Vol 39 (5) ◽  
pp. 945-953
Author(s):  
Fuzheng LI ◽  
Qiaogao HUANG ◽  
Guang PAN ◽  
Han LI
Keyword(s):  
Maximum Error ◽  
Calculation Model ◽  
Hydrodynamic Performance ◽  
Total Force ◽  
Hydrodynamic Coefficients ◽  
Slight Effect ◽  
Force Coefficient ◽  
Rotating Speed ◽  
A Value ◽  
Torque Coefficient

The pump-jet propulsor(PJP) performances under various rotational speeds (20~50 r/s) are analyzed for further studying the influence of the Reynolds number (Re) on the hydrodynamics of PJP, before this, the calculation model is verified by using the experiment data, it proves the present numerical method is proper to make a further study. The results indicate both the hydrodynamic coefficients of PJP and PJP components and the contours with dimensionless variables are present high similarity, yet the Re has the slight effect on the components performance, among which, the force coefficient of rotor is the least affected, with a relative error no more than 1%. Followed is the force coefficient of rotor stator, the maximum error is 2.1%, since the force of duct and stator is so low that has the slight effect on PJP, the total force error is less than 2%. However, the torque coefficient error is bigger with a value of about 3%. Besides, it is found that all hydrodynamic coefficients vary monotonically with rotating speed, the higher Re caused by increasing the rotational speed will contribute to enhance the work ability of rotor, thus cause a lower pressure at vortex core, and change the trajectory of TLV.

The Research of Hydrodynamic Performance for Ducted Propeller with PBCF

2015 ◽  
Vol 733 ◽  
pp. 578-582
Author(s):  
Zhen Qiu Yao ◽  
Xin Gu ◽  
Yun Shen
Keyword(s):  
Energy Saving ◽  
Open Water ◽  
Hydrodynamic Performance ◽  
Thrust Coefficient ◽  
Rotation Direction ◽  
Ducted Propeller ◽  
Efficiency Increase ◽  
Good Energy ◽  
Torque Coefficient ◽  
Saving Effect

The Propeller Boss Cap Fins (PBCF) is often used to ordinary propeller, a good energy-saving effect being obtained. In order to study the energy-saving mechanism of ducted propeller with PBCF, in this paper, the FLUENT has been taken to simulate the distribution of thrust coefficient, torque coefficient, blade pressure and velocity vector of hub surface at different advance coefficients. By contrasting the results of numerical simulation of hydrodynamic performance of ducted propeller between with fins and without fins, we know that at the low advance coefficient, the ducted propeller with fins will increase the thrust coefficient and decrease the torque coefficient; rising the open water propeller efficiency, improving the efficiency under the premise of the efficiency increase by duct. The existence of fins has changed velocity distribution of water around the hub and made the water that flowed around the propeller hub with propeller rotation direction flow to propeller tail along the fins not gather in the cub, so it weakened the hub vortex.

scholarly journals Design Concepts for NiTiNOL Wires to Function as a Sensor

2021 ◽  
Author(s):  
D. Josephine Selvarani Ruth
Keyword(s):  
Shape Memory Alloy ◽  
Electrical Resistance ◽  
Nickel Titanium ◽  
The Other ◽  
Sensing Element ◽  
Proper Selection ◽  
Design Concepts ◽  
Mechanical Element ◽  
Selection Of ◽  
Inverse Hysteresis

AbstractNickel Titanium Naval Ordinance Laboratory (NiTiNOL) is widely called as a shape memory alloy (SMA), a class of nonlinear smart material inherited with the functionally programmed property of varying electrical resistance during the transformation enabling to be positioned as a sensing element. The major challenge to instrument the SMA wires is to suppress the wires’ nonlinearity by proper selection of two important factors. The first factor is influenced by the mechanical biasing element and the other is to identify the sensing current for the sensing device (SMA wires + biasing). This paper focuses on developing SMA wires for sensing in different orientation types and configurations by removing the non-linearity in the system’s output by introducing inverse hysteresis to the wires through the passive mechanical element.

Mechanodestruction of Isoprene Rubber. Part 1. Process Kinetics

2021 ◽  
Vol 80 (3) ◽  
pp. 118-122
Author(s):  
V.P. Dorozhkin ◽  
◽  
E.G. Mokhnatkina ◽  
D.N. Zemsky ◽  
A.D. Valiev ◽  
...  
Keyword(s):  
Experimental Data ◽  
Molecular Mass ◽  
Rate Constants ◽  
Oxidative Destruction ◽  
Process Kinetics ◽  
Mass Fractions ◽  
Rubber Part ◽  
Kinetics Of ◽  
Selection Of ◽  
Isoprene Rubber

A method is proposed that allows us to obtain the values of the rate constants (CR) of the processes of mechanodestruction (mechanical cracking) of kм, oxidative destruction of kо, and recombination of kр macromolecules, as well as the mass fractions of the corresponding fractions of φм, φо, and φр,r involved in the plasticization process (P) of SKI-3 isoprene rubber. The method is based on the selection of the values of these parameters that correspond to the previously obtained experimental data, using the previously obtained recurrent equations and a specially developed program. The dependences of the CR on the time P at 30oC are obtained, which allows us to describe the kinetics of the processes accompanying P at this temperature, and the changes in molecular mass (MM) in this process. It is shown that constant values of CR are established at large times of P. Refined explanations of the nature of the kinetics of the CR change at P are proposed. The MM value of SKI-3 macromolecules that have not undergone destruction is calculated, depending on the time of plasticization.

scholarly journals Evaluation of sunflower cultivars for central Brazil

2008 ◽  
Vol 65 (2) ◽  
pp. 139-144 ◽  
Author(s):  
Willyam Stern Porto ◽  
Claudio Guilherme Portela de Carvalho ◽  
Ronald José Barth Pinto ◽  
Marcelo Fernandes de Oliveira ◽  
Ana Cláudia Barneche de Oliveira
Keyword(s):  
Experimental Data ◽  
Grain Yield ◽  
Oil Yield ◽  
Production Region ◽  
Central Brazil ◽  
Selection Of

Despite a large availability of areas suitable for sunflower cropping in Central Brazil, few adapted cultivars are available in the market. The objective of this work was to select sunflower cultivars adapted to this important production region. Experimental data from 2000 to 2004 were obtained by the National Sunflower Trials, coordinated by Embrapa Soja. The evaluated traits were grain and oil yields. Two criteria were used for selection of cultivars: i) the general mean obtained from different environments; ii) partitioning of general mean in favorable and unfavorable environments. Partitioning of the general mean allowed to detect the specific environment indicated for each cultivar. For grain yield, the cultivar Helio 251 presented general indication, Milênio and CF 17 could be indicated for favorable environments and ACA 884, ACA 885 and ACA 872 for the unfavorable ones. For oil yield, CF 13, Milênio, DK 4030, Helio 250 and ACA 872 had general indication; AG 966, GH 12, GV 26043, CF 17 and VDH 93 could be indicated for favorable environments, while VDH 488, Helio 251, ACA 884 and ACA 885 for the unfavorable conditions. In 2002, the partition of the general mean was not carried out. In this year, general mean of cultivars Exp 37, AG 962, GV 26048 and AG 967 were overweight the controls for grain yield and the cultivars AG 962, AG 967, GV 26048, AG 972, BRS 191, Guarani were overweight the controls for oil yield.

scholarly journals A hierarchical Bayesian framework for force field selection in molecular dynamics simulations

2016 ◽  
Vol 374 (2060) ◽  
pp. 20150032 ◽  
Author(s):  
S. Wu ◽  
P. Angelikopoulos ◽  
C. Papadimitriou ◽  
R. Moser ◽  
P. Koumoutsakos
Keyword(s):  
Experimental Data ◽  
Molecular Dynamics ◽  
Force Field ◽  
Computational Cost ◽  
Md Simulations ◽  
Bayesian Framework ◽  
Underlying Structure ◽  
Hierarchical Bayesian ◽  
Wide Range ◽  
Selection Of

We present a hierarchical Bayesian framework for the selection of force fields in molecular dynamics (MD) simulations. The framework associates the variability of the optimal parameters of the MD potentials under different environmental conditions with the corresponding variability in experimental data. The high computational cost associated with the hierarchical Bayesian framework is reduced by orders of magnitude through a parallelized Transitional Markov Chain Monte Carlo method combined with the Laplace Asymptotic Approximation. The suitability of the hierarchical approach is demonstrated by performing MD simulations with prescribed parameters to obtain data for transport coefficients under different conditions, which are then used to infer and evaluate the parameters of the MD model. We demonstrate the selection of MD models based on experimental data and verify that the hierarchical model can accurately quantify the uncertainty across experiments; improve the posterior probability density function estimation of the parameters, thus, improve predictions on future experiments; identify the most plausible force field to describe the underlying structure of a given dataset. The framework and associated software are applicable to a wide range of nanoscale simulations associated with experimental data with a hierarchical structure.

Full-Scale Reynolds Number VIV Testing of Tri-Helically Grooved Drill Riser Buoyancy Module

2018 ◽  
Author(s):  
Collin Gaskill ◽  
Jie Wu ◽  
Decao Yin
Keyword(s):  
Reynolds Number ◽  
Large Scale ◽  
Hydrodynamic Force ◽  
Oscillation Amplitude ◽  
Cross Flow ◽  
Hydrodynamic Performance ◽  
Test Model ◽  
Force Coefficient ◽  
Test Cylinder ◽  
Test Models

A newly developed Tri-Helically Grooved drilling riser buoyancy module design was tested in the towing tank of SINTEF Ocean in June 2017. This new design aims to reduce riser drag loading and suppress vortex-induced vibrations (VIV). Objectives of the test program were two-fold: to assess the hydrodynamic performance of the design allowing for validation of previous computational fluid dynamics (CFD) studies through empirical measurements, and, to develop a hydrodynamic force coefficient database to be used in numerical simulations to evaluate drilling riser deformation due to drag loading and fatigue lives when subjected to VIV. This paper provides the parameters of the testing program and a discussion of the results from the various testing configurations assessed. Tests were performed using large scale, rigid cylinder test models at Reynolds numbers in the super-critical flow regime, defined as starting at a Reynolds number of Re = 3.5 × 105 – 5.0 × 105 (depending on various literatures) and continuing until Re = 3 × 106. Towing tests, with fixed and freely oscillating test models, were completed with both a bare test cylinder and a test cylinder with the Tri-Helical Groove design. Additional forced motion tests were performed on the helically grooved model to calculate lift and added mass coefficients at various amplitudes and frequencies of oscillation for the generation of a hydrodynamic force coefficient database for VIV prediction software. Significant differences were observed in the hydrodynamic performance of the bare and helically grooved test models considering both in-line (IL) drag and cross-flow (CF) cylinder excitation and oscillation amplitude. For the helically grooved model, measured static drag shows a strong independence from Reynolds number and elimination of the drag crisis region with an average drag coefficient of 0.63. Effective elimination of VIV and subsequent drag amplification was observed at relatively higher reduced velocities, where the bare test model shows a significant dynamic response. A small level of expected response for the helically grooved model was seen across the lower range of reduced velocities. However, disruption of vortex correlation still occurs in this range and non-sinusoidal and highly amplitude-modulated responses were observed.

Successful Moveable Bridges

2019 ◽  
Author(s):  
Kjeld Thomsen ◽  
Christian Riis Petersen
Keyword(s):  
Operation Time ◽  
Cost Effective ◽  
Modern Technology ◽  
Point Of View ◽  
Maintenance Cost ◽  
Hydraulic Systems ◽  
Design Concepts ◽  
Electrical Systems ◽  
Low Weight ◽  
Selection Of

<p>The present paper describes developments in the design of the most common types of movable bridges – Bascule bridges and Swing Bridges. The selection of design concepts is influenced by span, foundation conditions as well as environmental issues. Application of modern hydraulic systems and innovative bearing types for swing bridges facilitate the creation of outstanding designs. Recently built moveable bridges in Denmark exemplifies the trend and how application of modern technology and creativity can lead to outstanding solutions. There are many governing parameters such as the span, free opening height and loading conditions. Equally important issues such as surroundings, landscape, foundation conditions, requirement to low weight, achievable tolerances and from a mechanical point of view, the operation time. Risk assessment, mechanical- and electrical systems and the requirement to operation time and maintenance cost, will have influence on the selection of machinery and the architectural and structural design. For each of the moveable bridges described, it is shown how innovative application of modern bearing concepts and hydraulic systems can lead to elegant and cost-effective solutions.</p>

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