scholarly journals Numerical Prediction of Hydrodynamic Performance of Planing Trimaran with a Wave-Piercing Bow

2020 ◽  
Vol 8 (11) ◽  
pp. 897
Author(s):  
Guangsheng Su ◽  
Hailong Shen ◽  
Yumin Su
Keyword(s):  
Experimental Tests ◽  
Pressure Change ◽  
Hydrodynamic Performance ◽  
Pressure Area ◽  
Fluid Body ◽  
Sinkage And Trim ◽  
Reduction Effect ◽  
Six Degree Of Freedom ◽  
Resistance Performance ◽  
The Relationship

The central hull is the most important structure in the planing trimaran. In order to gain insight into the relationship between hydrodynamic performance and main hull shape, experimental tests and numerical simulations were carried out for volume Froude Number (FrΔ) ranging from 1.31 to 4.98. Dynamic sinkage and trim in the Dynamic Fluid Body Interaction (DFBI) six-degree-of-freedom model were considered. A validation study carried out by comparison of experimental test results with numerical results showed good consistency. To analyze the process of tunnel penetration and pressure change at the bottom of the boat, numerical simulation results for free surface, bottom streamline, and pressure distribution around the hull are given. A large triangular high-pressure area was observed in the front of the main hull for all volume Froude numbers. Consequently, the central drainage body, in reference to the profile of single planing craft with distinctive resistance performance, was redesigned into a wave-piercing shape. Total resistance, sinkage, and trim angle of the new model were then predicted by numerical method. The results show that the central drainage body has a significant impact on the hydrodynamic performance of the planing trimaran. Furthermore, the wave-piercing shaped main hull has a drag reduction effect.

scholarly journals Hydrodynamic Performance of Open-frame Deep Sea Remotely Operated Vehicles Based on Computational Fluid Dynamics Method

2022 ◽  
Vol 4 (1) ◽  
Author(s):  
Qianrong Li ◽  
Baoji Zhang
Keyword(s):  
Deep Sea ◽  
Hydrodynamic Performance ◽  
Navier Stokes ◽  
Remotely Operated Vehicles ◽  
Modeling Process ◽  
Motion Time ◽  
Force Moment ◽  
The Stability ◽  
Six Degree Of Freedom ◽  
Resistance Performance

The resistance performance and motion stability of deep sea remotely operated vehicles (ROVs) subjected to underwater motion conditions are studied on the basis of the unsteady Reynolds-averaged Navier-Stokes method combined with the six-degree-of-freedom equation of motion to quickly and accurately predict them. In the modeling process, we consider the complexity of ROV geometry and thus reduce the model to a series of regular geometries to maximize the position and weight of the original components. The grid and value slots of an ROV are divided, and the surface is reconstructed. The forward, backward, transverse, floating, and submerged resistance of ROVs are simulated and compared with existing experimental forces to determine the accuracy of the calculation method. Then, the oblique navigation of the ROV on the horizontal and vertical planes is studied. Furthermore, the motion response of the ROV to direct horizontal motion, heave, pitch, and yaw are studied. The force, moment, and motion time curves are obtained. The stability of ROV motion is analyzed to provide technical support for the safety of ROVs.

scholarly journals How Does Environmental Regulation Affect the Relationship between FDI and Technological Innovation: From the Perspective of Technology Transactions

Processes ◽  
2021 ◽  
Vol 9 (8) ◽  
pp. 1264
Author(s):  
Meng Zeng ◽  
Lihang Liu ◽  
Fangyi Zhou ◽  
Yigui Xiao
Keyword(s):  
Environmental Regulation ◽  
Technological Innovation ◽  
Pollutant Emissions ◽  
Regulatory Effect ◽  
Host Countries ◽  
Regional Heterogeneity ◽  
Industrial Sectors ◽  
Reduction Effect ◽  
The Impact ◽  
The Relationship

Many studies have found that FDI can reduce the pollutant emissions of host countries. At the same time, the intensity of environmental regulation would affect the emission reduction effect of FDI in the host country. This study aims to reveal the internal mechanisms of this effect. Specifically, this paper studies the impact of FDI on technological innovation in China’s industrial sectors from the perspective of technology transactions from 2001 to 2019, and then analyzes whether the intensity of environmental regulation can promote the relationship. Results indicate that FDI promotes technological innovation through technology transactions. In addition, it finds that the intensity of environmental regulation significantly positively moderates the relationship between FDI and technological innovation, which is achieved by positively moderating the FDI–technology transaction relationship. Regional heterogeneity analysis is further conducted, and results show that in the eastern and western regions of China, FDI can stimulate technological innovation within regional industrial sectors through technology trading. Moreover, environmental regulation has a significant positive regulatory effect on the above relationship, but these effects are not supported by evidence in the central region of China.

scholarly journals Stability and Manoeuvrability Simulation of a Semi-Autonomous Submarine Free-Running Model SUBOFF with an Autopilot System

2021 ◽  
Vol 11 (1) ◽  
pp. 410
Author(s):  
Yu-Hsien Lin ◽  
Yu-Ting Lin ◽  
Yen-Jun Chiu
Keyword(s):  
Optimal Control ◽  
Experimental Tests ◽  
Degree Of Freedom ◽  
Line Of Sight ◽  
Pd Controller ◽  
Free Running ◽  
Simulation Results ◽  
Guidance Algorithm ◽  
Logic Operations ◽  
Six Degree Of Freedom

On the basis of a full-appendage DARPA SUBOFF model (DTRC model 5470), a scale (λ = 0.535) semi-autonomous submarine free-running model (SFRM) was designed for testing its manoeuvrability and stability in the constrained water. Prior to the experimental tests of the SFRM, a six-degree-of-freedom (6-DOF) manoeuvre model with an autopilot system was developed by using logic operations in MATLAB. The SFRM’s attitude and its trim polygon were presented by coping with the changes in mass and trimming moment. By adopting a series of manoeuvring tests in empty tanks, the performances of the SFRM were introduced in cases of three sailing speeds. In addition, the PD controller was established by considering the simulation results of these manoeuvring tests. The optimal control gains with respect to each manoeuvring test can be calculated by using the PID tuner in MATLAB. Two sets of control gains derived from the optimal characteristics parameters were compared in order to decide on the most appropriate PD controller with the line-of-sight (LOS) guidance algorithm for the SFRM in the autopilot simulation. Eventually, the simulated trajectories and course angles of the SFRM would be illustrated in the post-processor based on the Cinema 4D modelling.

scholarly journals HUBUNGAN TINGKAT PENGETAHUAN TENTANG KEBUTUHAN CAIRAN TUBUH DENGAN POLA KONSUMSI AIR MINUM PADA MAHASISWA TINGKAT I AKPER PANTI KOSALA SURAKARTA

2016 ◽  
Vol 4 (2) ◽  
Author(s):  
Budi Herminto ◽  
Risa Setia Ismandani
Keyword(s):  
Drinking Water ◽  
Design Research ◽  
P Value ◽  
First Year ◽  
Knowledge Level ◽  
First Year Students ◽  
Fluid Body ◽  
Level Of Knowledge ◽  
High Level ◽  
The Relationship

AbstractWater represent compound which is the necessary for all living. Consumption behaviorirrigate society not yet altogether goodness, society consume water when feel thirsty anddo not so pay attention drinking water and amount matching with requirement. Purpose ofthe study to determine the relationship between the knowledge level about fluid bodyrequirement with pattern consume drinking water at student in Academy of Nursing PantiKosala Surakarta.The subject was used as population in the study was all the first year students. The totalpopulation were 139 students, and the sample were 103 students. The samplingtechnique was simple random sampling.This research method represent analytic research with design research of corelasional toknow relationship between knowledge level about fluid body requirement with patternconsume drinking water of student.The results was the high level of knowledge about the fluid body requirment were 74(72%), moderate level of knowledge about the fluid body requirment were 29 (28%), whilethe behavior of consuming appropiate water were 69 (67%), and the behavior ofconsuming inappropiate water were 34 (33%) with a p-value 0.003 <0.05 significant 95%.There was a significant relationship between the knowledge level about fluid bodyrequirement with pattern consume drinking water at student in Academy of Nursing PantiKosala Surakarta.Keywords: knowlegde level, fluid body requirement, pattern consume drinking water.

scholarly journals Numerical Analysis on the Effect of Artificial Ventilated Pipe Diameter on Hydrodynamic Performance of a Surface-Piercing Propeller

2019 ◽  
Vol 7 (8) ◽  
pp. 240
Author(s):  
Gao ◽  
Yang ◽  
Li ◽  
Dong
Keyword(s):  
High Speed ◽  
Water Immersion ◽  
Active Role ◽  
Numerical Results ◽  
Hydrodynamic Performance ◽  
Pipe Diameter ◽  
Pressure Area ◽  
Cfd Method ◽  
Thrust And Torque ◽  
Surface Piercing Propeller

Under the condition of large water immersion, surface-piercing propellers are inclined to be heavy loaded. In order to improve the hydrodynamic performance of the surface-piercing propeller, the installation of a vent pipe in front of a propeller disc is more widely used in the propulsion device of high speed planning crafts. Based on computational fluid dynamics (CFD) method, this paper studied the influence of diverse vent pipe diameters on hydrodynamic performance of the surface-piercing propeller under full water immersion conditions. The numerical results show that, with the increase of vent pipe diameters, the thrust and torque of the surface-piercing propeller decrease after ventilation, and the efficiency of the propeller increases rapidly; the low pressure area near the back root of the blade becomes smaller and smaller gradually; and the peak of periodic vibration of thrust and torque can be effectively reduced. The numerical results demonstrate that the installation of artificial vent pipe effectively improves the hydrodynamic performance of surface piercing propeller in the field of high speed crafts, and the increase of artificial vent pipe diameter plays an active role in the propulsion efficiency of the surface-piercing propeller.

The Research of the Servovalve Noise

2013 ◽  
Vol 706-708 ◽  
pp. 1639-1643 ◽  
Author(s):  
Yuan Zhang Chen ◽  
Da Ping Gong
Keyword(s):  
Flow Field ◽  
Internal Structure ◽  
Field Distribution ◽  
Negative Pressure ◽  
Cfd Simulation ◽  
Pressure Change ◽  
Servo Valve ◽  
Pressure Zone ◽  
Circuit Structure ◽  
Pressure Area

Use Gambit and Fluent to the servo valve armature component of squeak problem undertook CFD is analyzed, simulates the flow field distribution in internal circuit structure, found in the servo valve armature component whistle when fluid in the inner of the product, produced a marked a negative pressure zone, and in this context the armature assembly stress sharply change, causing the armature assembly vibration squeal, changing the internal structure of the product again CFD simulation, negative pressure area disappeared, the pressure change tends to be steady, the structure of the product was the actual through pressure liquid servo valve test, howling problem solved.

Contact shear stresses in dowel-type joints with expansive kits of timber structures

2016 ◽  
Vol 231 (1) ◽  
pp. 140-149
Author(s):  
Jose G Fueyo ◽  
Manuel Domínguez ◽  
Jose A Cabezas
Keyword(s):  
Experimental Tests ◽  
Element Model ◽  
Shear Stresses ◽  
Load Carrying Capacity ◽  
Timber Structures ◽  
Expansion Process ◽  
Global Response ◽  
Load Carrying ◽  
Overall Performance ◽  
The Relationship

This paper studies the shear stresses appearing in the contact zones of dowel-type joints of timber structures using expansive kits. To achieve this goal, a finite element model capable of determining the effect of using these kits on the global response of the joint has been prepared. For its development, different tools have been used to model the expansion process, the contact between the different parts of the joint, the compression pressures triggered by this contact, the resulting shear stresses caused by friction and, finally, the effect of all these circumstances on the overall performance of the joint, especially on the relationship between the applied load and the related displacement. The design of the model has been checked for correctness using experimental tests. The results obtained show that the use of expansive kits slightly improves the load-carrying capacity of the dowel through the rope effect.

scholarly journals Finding a signal hidden among noise: how can predators overcome camouflage strategies?

2020 ◽  
Vol 375 (1802) ◽  
pp. 20190478 ◽  
Author(s):  
James A. M. Galloway ◽  
Samuel D. Green ◽  
Martin Stevens ◽  
Laura A. Kelley
Keyword(s):  
Visual Processing ◽  
Signal Detection Theory ◽  
Experimental Tests ◽  
The Past ◽  
Substantial Progress ◽  
Recognition Systems ◽  
The Relationship ◽  
Evolving Models ◽  
Made In ◽  
Detection And Recognition

Substantial progress has been made in the past 15 years regarding how prey use a variety of visual camouflage types to exploit both predator visual processing and cognition, including background matching, disruptive coloration, countershading and masquerade. By contrast, much less attention has been paid to how predators might overcome these defences. Such strategies include the evolution of more acute senses, the co-opting of other senses not targeted by camouflage, changes in cognition such as forming search images, and using behaviours that change the relationship between the cryptic individual and the environment or disturb prey and cause movement. Here, we evaluate the methods through which visual camouflage prevents detection and recognition, and discuss if and how predators might evolve, develop or learn counter-adaptations to overcome these. This article is part of the theme issue ‘Signal detection theory in recognition systems: from evolving models to experimental tests'.

scholarly journals Design of a Compliant Mechanism Based Four-Stage Amplification Piezoelectric-Driven Asymmetric Microgripper

Micromachines ◽  
2019 ◽  
Vol 11 (1) ◽  
pp. 25
Author(s):  
Xiaodong Chen ◽  
Zilong Deng ◽  
Siya Hu ◽  
Jinhai Gao ◽  
Xingjun Gao
Keyword(s):  
Compliant Mechanism ◽  
Experimental Tests ◽  
Element Analysis ◽  
Output Displacement ◽  
Amplification Ratio ◽  
Output Force ◽  
Characteristics Analysis ◽  
The Relationship ◽  
Two Sides ◽  
Theoretical Results

The existing symmetrical microgrippers have larger output displacements compared with the asymmetrical counterparts. However, the two jaws of a symmetrical microgripper are less unlikely to offer the same forces on the two sides of a grasped micro-object due to the manufacture and assembly errors. Therefore, this paper proposes a new asymmetric microgripper to obtain stable output force of the gripper. Compared with symmetrical microgrippers, asymmetrical microgrippers usually have smaller output displacements. In order to increase the output displacement, a compliant mechanism with four stage amplification is employed to design the asymmetric microgripper. Consequently, the proposed asymmetrical microgripper possesses the advantages of both the stable output force of the gripper and large displacement amplification. To begin with, the mechanical model of the microgripper is established in this paper. The relationship between the driving force and the output displacement of the microgripper is then derived, followed by the static characteristics’ analysis of the microgripper. Furthermore, finite element analysis (FEA) of the microgripper is also performed, and the mechanical structure of the microgripper is optimized based on the FEA simulations. Lastly, experimental tests are carried out, with a 5.28% difference from the FEA results and an 8.8% difference from the theoretical results. The results from theoretical calculation, FEA simulations, and experimental tests verify that the displacement amplification ratio and the maximum gripping displacement of the microgripper are up to 31.6 and 632 μm, respectively.

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