scholarly journals CFD Simulation of the Safety of Unmanned Ship Berthing under the Influence of Various Factors

2021 ◽  
Vol 11 (15) ◽  
pp. 7102
Author(s):  
Guoquan Xiao ◽  
Chao Tong ◽  
Yue Wang ◽  
Shuaishuai Guan ◽  
Xiaobin Hong ◽  
...  
Keyword(s):  
Growth Rate ◽  
Cfd Simulation ◽  
Route Planning ◽  
Lateral Force ◽  
Dominant Factor ◽  
Maximum Pressure ◽  
Vertical Force ◽  
Total Resistance ◽  
Unmanned Ship ◽  
Ship Berthing

The safety of unmanned ship berthing is of paramount importance. In order to explore the influence of wind and wave coupling, a berthing computational fluid dynamics (CFD) model was established, and the characteristics of speed field, pressure field, and vortex have been obtained under different speed, wind direction, and the quay wall distances. The results show that the total resistance of the hull against the current can be about 1.60 times higher compared to the downstream resistance, water flow resistance is the dominant factor, accounting for more than 80% of the total resistance. When changing the distance between ship and shore at fixed speed, the results found that the torque is small, but the growth rate is very large when driving below 2 m/s, and the torque growth rate is stable above 2 m/s. Based on the established coupling model, a multi-factor berthing safety study is carried out on an actual unmanned ship. The results show that when the speed increases from 4 m/s to 12 m/s, the curve slope is small, the resistance increases from 3666 N to 18,056 N, and the rear slope increases. The pressure increases with the speed, and when the speed is 24 m/s, the maximum pressure is up to 238,869 Pa. When the wind speed is fixed, the vertical force of the unmanned ship increases first and then decreases to zero and then reverses the same law change, and the maximum resistance is about 425 N at the wind angle of about 45 degrees; At 90 degrees, the maximum lateral force on an unmanned boat is about 638 N. The above results can provide control strategy for unmanned ship berthing safety, and provide theoretical basis for unmanned ship route planning and obstacle avoidance, safety design, etc.

scholarly journals Hydrodynamics of gliding penguin flipper suggests the adjustment of sweepback with swimming speeds

2021 ◽  
Author(s):  
Masateru Maeda ◽  
Natsuki Harada ◽  
Hiroto Tanaka
Keyword(s):  
Large Eddy Simulation ◽  
Cfd Simulation ◽  
Lift Coefficient ◽  
Angle Of Attack ◽  
Force Balance ◽  
Hydrodynamic Performance ◽  
Vertical Force ◽  
Sweep Angle ◽  
Eddy Simulation ◽  
Large Eddy

Hydrodynamic performance of a gliding penguin flipper (wing) considering the backward sweep was estimated with computational fluid dynamics (CFD) simulation. A flipper of a gentoo penguin (Pygoscelis papua) was 3D scanned, smoothed, and a numerical fluid mesh was generated. For accurate yet resource-saving computation, an embedded large-eddy simulation (ELES) methods was employed, where the flow near the flipper was solved with large-eddy simulation (LES) and flow far away from the flipper was solved with Reynolds-averaged Navier-Stokes (RANS). The relative flow speed was fixed at 2 m s-1, close to the typical foraging speed for the penguin species. The sweep angle was set to be 0°, 30°, and 60°, while the angle of attack was varied between -40° and 40°, both are within the realistic ranges in the wing kinematics measurement of penguins in an aquarium. It was revealed that a higher sweep angle reduces the lift slope, but the lift coefficient is unchanged at a high angle of attack. Drag coefficient was reduced across the angles of attack with increasing the sweep angles. The drag polars suggest the sweep angle may be adjusted with the change in swimming speed and anhedral (negative dihedral) angle to minimise drag while maintaining the vertical force balance to counteract the positive buoyancy. This will effectively expand the swimming envelope of the gliding penguin, similar to a flying counterpart such as swift.

scholarly journals WATER QUALITY AND ITS EFFECT ON GROWTH AND SURVIVAL RATE OF LOBSTER REARED IN FLOATING NET CAGE IN EKAS BAY, WEST NUSA TENGGARA PROVINCE

2015 ◽  
Vol 6 (2) ◽  
Author(s):  
Muhammad Junaidi ◽  
Mat Sardi Hamzah
Keyword(s):  
Water Quality ◽  
Growth Rate ◽  
Survival Rate ◽  
Quality Data ◽  
Dominant Factor ◽  
Growth And Survival ◽  
Water Quality Status ◽  
Net Cage ◽  
Quality Status ◽  
Effect On Growth

ABSTRACT The development of lobster farming in floating net cage in Ekas Bay caused an environmental degradation such as decrease water quality due to some aquaculture wastes. The purposes of this study were to determine the status of water quality and their effect on growth and survival rate of lobster reared in floating net cages (FNC) in the Ekas Bay, West Nusa Tenggara Province. Water sample collection and handling referred to the APHA (1992). Analyses of water quality data were conducted using Principal Component Analysis. Determination of the water quality status of Ekas Bay was performed with STORET system. Multivariate analyses were used to determine the relationship between water quality, growth, and survival rate of lobster reared in FNC. Results showed that Ekas Bay water quality status was categorized in class C (medium contaminated), which exceeded some quality standard parameters such as ammonia (0.3 mg/l), nitrate (0.008 mg/l), and phosphate (0.015 mg/l). During lobster farming activities feeding with trash fish for 270 days, we obtained daily growth rate of  0.74% (lower than normal growth rate of 0.86%), survival rate of 66% (lower than normal survival rate of 86.7%), and feed conversion ratio of 11.15. Ammonia was found as a dominant factor reducing growth  and survival rate of lobster reared in FNC. Keywords: water quality, lobsters, growth, survival, Ekas Bay

Quantification of Friction Force for Dual-Axis Probe Friction Force Microscope

2009 ◽  
Author(s):  
Hiroaki Amakawa ◽  
Kenji Fukuzawa ◽  
Mitsuhiro Shikida ◽  
Hedong Zhang ◽  
Shitaro Itoh
Keyword(s):  
Friction Force ◽  
Normal Force ◽  
Calibration Method ◽  
Lateral Force ◽  
Vertical Force ◽  
Torsion Beam ◽  
Force Sensitivity ◽  
Mechanical Interference ◽  
Friction Force Microscope ◽  
Mechanical Probe

Conventional friction force microscopes (FFMs) had the disadvantage of low force sensitivity due to mechanical interference between torsion caused by friction force and deflection by normal force. In order to overcome disadvantage, we developed a dual-axis micro-mechanical probe, which measures the lateral force by the double cantilever and the vertical force by the torsion beam. However, the calibration method of the lateral force has not been established. In this study, we present a new calibration method using a step-structure.

Effects of Track Elasticity on Wheel-Rail Dynamic Performance of Heavy Haul Railway

2015 ◽  
Vol 744-746 ◽  
pp. 1249-1252 ◽  
Author(s):  
Yong Zeng
Keyword(s):  
Lateral Displacement ◽  
Dynamic Performance ◽  
Lateral Force ◽  
Vertical Force ◽  
Heavy Vehicles ◽  
Derailment Coefficient ◽  
Heavy Haul ◽  
Dynamics Models ◽  
Heavy Haul Railway ◽  
The Impact

Two vehicle-track dynamics models on heavy haul railway are established in two conditions of rigid track and elastic track. And the impact of track elasticity on the wheel-rail dynamics performance was analyzed using models. The results show that the critical speed of heavy vehicles and wheel-rail dynamic indexes, such as wheel-rail lateral force and wheel-rail vertical force decreased on elastic track compared with rigid track. However, other dynamic indexes, including derailment coefficient and lateral displacement of wheelsets increased on elastic track. And the wheel-rail wear indexes are some differences on two tracks.

scholarly journals Is Anterior Guidance a Key Factor on Planning Implant Treatment for Free-End Missing in the Posterior Mandible?

2019 ◽  
Vol 45 (2) ◽  
pp. 100-105 ◽  
Author(s):  
Mitsuharu Nagao ◽  
Chihiro Masaki ◽  
Mihoko Nakao ◽  
Yoshinori Ito ◽  
Shintaro Tsuka ◽  
...  
Keyword(s):  
Finite Element ◽  
Stress Distribution ◽  
Lateral Force ◽  
Von Mises Stress ◽  
Vertical Force ◽  
Experimental Conditions ◽  
Element Analysis ◽  
Implant Placement ◽  
Ct Data ◽  
Implant Treatment

To perform safe implant treatment, the anatomical structure and bone quality at implant placement sites are evaluated based on a patient's computerized tomography (CT) data, but there is no definite method to determine placement sites and the appropriate number of implants. The objective of this study was to investigate the influence of the number and arrangement of implants on the stress distribution in 3-unit posterior fixed partial dentures for the posterior mandible by mechanical analysis using the finite element method. Three-dimensional finite element analysis models were constructed from the CT data of a patient with missing mandibular teeth (Nos. 35, 36, 37). Implant placement was simulated under various conditions. Superstructures were connected and fixed with a titanium frame. As the loading conditions, 400 N vertical and lateral loads (45° on the lingual side and 45° on the buccal side) were applied to the upper areas of Nos. 35, 36, and 37, and the stress distribution and frame displacement were evaluated. When a vertical force was applied, no difference of the von Mises stress was noted among the 5 experimental conditions. When lateral force was applied from the lingual and buccal sides at 45°, the stress was higher than that induced by vertical force under all conditions, and it was especially high under mesial and distal cantilever conditions. When displacement of the titanium frame was measured, the displacement caused by lateral force was greater than that due to vertical force. In addition, comparison between long and short distal cantilever bridges revealed that displacement of the titanium frame tended to be smaller when the short cantilever was used. These findings suggested that the stress on peri-implant tissues and displacement of the titanium frame vary depending on the configuration and number of implants, with greater stress and more marked displacement of the titanium frame being induced by lateral force when the number of implants is reduced and a cantilever bridge is selected.

Enhanced understanding of leakage in mechanical seals with elliptical dimples based on CFD simulation

2019 ◽  
Vol 72 (1) ◽  
pp. 24-30
Author(s):  
Sen Jiang ◽  
Hua Ji ◽  
Tianhao Wang ◽  
Donglin Feng ◽  
Qian Li
Keyword(s):  
Cfd Simulation ◽  
Three Dimensional ◽  
Leakage Rate ◽  
Geometric Feature ◽  
Maximum Pressure ◽  
Mechanical Seals ◽  
Ansys Fluent ◽  
Content Type ◽  
Surface Textures ◽  
Influencing Mechanism

Purpose The shapes of surface textures have been designed to control the leakage of mechanical seals in recent years. The purpose of this paper is to demonstrate the influence of geometric properties of elliptical dimples on the leakage rate. Design/methodology/approach A new geometric feature point is expressed using an analytical solution to locate the high-pressure zones. Furthermore, a numerical model of the three-dimensional flow field for the mechanical seal with elliptical dimples is developed using ANSYS Fluent to demonstrate the influencing mechanism. Findings The location of the proposed geometric converging point coincides with the maximum pressure point under different orientation angles. An inward flow on the leakage section observed from the simulation results is responsible for decreasing the leakage rate. Originality/value The influencing mechanism of the elliptical dimple on the leakage rate is demonstrated, which can facilitate the design of surface textures.

Force Exertion during Lifting with Light Loads

1974 ◽  
Vol 18 (4) ◽  
pp. 393-396
Author(s):  
Ronald Perkins ◽  
Stephan Konz
Keyword(s):  
Male Subject ◽  
Peak Stress ◽  
Lateral Force ◽  
The Body ◽  
Vertical Force ◽  
Final Position ◽  
Single Male ◽  
Object Weight ◽  
Before And After ◽  
Body Center

A single male subject lifted a tote box 12 times at each of 24 conditions while standing on a force platform. The 24 conditions were 6 combinations of initial and final position (floor to 12,24 and 36 in. shelf, floor plus 12 in. to 24 and 36 in. shelf, and floor plus 24 in. to 36 in. shelf) x 2 box weights (11 and 22 lbs.) and 2 distances of the box from the body center of gravity (16 and 20 in.). Averaged over all 24 conditions, peak vertical force was 46 lbs., frontal force was 6 lbs., lateral force was 2 lbs., somersault torque was 417 in.-lbs., cartwheel torque was 75 in.-lbs., twist torque was 59 in.-lbs. and peak box acceleration was .3 g. For lifting with light loads, object weight has much less effect on stress than might be expected. Peak forces occurred in the .5 sec. before and after grasping the box. In fact, peak stress occurred before the box was grasped in 66% of the lifts.

ANALYSIS OF THE WATER IMPACT OF SYMMETRIC WEDGES WITH A MULTI- MATERIAL EULERIAN FORMULATION

2021 ◽  
Vol 154 (A4) ◽  
Author(s):  
S Wang ◽  
C Guedes Soares
Keyword(s):  
Pressure Distribution ◽  
Impact Velocity ◽  
Pressure Coefficient ◽  
Time History ◽  
Maximum Pressure ◽  
Vertical Force ◽  
Force Coefficient ◽  
Explicit Finite Element ◽  
Eulerian Formulation ◽  
The Impact

The two-dimensional hydrodynamic problem of a symmetric wedge vertically impacting in calm water is analysed by using an explicit finite element method based on a multi-material Eulerian formulation. The slam-induced loads on wedges with different deadrise angle at a constant velocity are calculated, including pressure distribution, maximum pressure coefficient, force coefficient and time history of vertical force, which are compared with available theoretical and analytical results. The time evolution of pressure distribution and free surface elevation are presented. Furthermore, the effects of impact velocity are investigated. It shows that this method is capable of predicting the local slamming loads, and as well assessing the effects of the deadrise angle and the impact velocity on the slamming pressure for the wedge-shape section.

Sign in / Sign up

Export Citation Format

Share Document