scholarly journals Study Reduction of Resistance on The Flat Hull Ship of The Semi-Trimaran Model: Hull Vane Vs Stern Foil

CFD Letters ◽  
2021 ◽  
Vol 13 (12) ◽  
pp. 32-44
Author(s):  
Rahmat Azis Nabawi ◽  
Syahril ◽  
Primawati
Keyword(s):  
Froude Number ◽  
Cfd Simulation ◽  
Optimal Position ◽  
Ship Model ◽  
Resistance Reduction ◽  
Simulation Results

Flat hull ships is appraised for its superiority due to the manufacturing simplicity and lower investment costs, yet the ship has its own weakness for it requires a greater resistance. As a matter of fact, a significant reduction on the resistance can be done with foil installation but it is necessary to study the optimal position of the foil installation. This study is aimed at revealing the effectiveness of the Hull Vane and Stern Foil installation in reducing the resistance experienced by the flat hull ship of the semi-trimaran model. The research was conducted by comparing the resistance experienced by the flat hull ship of the semi-trimaran model without foil, Hull vane and Stern foil installations. In addition, the disclosure of resistance experienced by each ship model was carried out by using CFD simulation. The simulation results revealed that the installation of the Hull vane and Stern foil was able to reduce the resistance experienced by the flat hull ship of the semi-trimaran model. The largest reduction occurred in Froude number 1.1, where the Hull vane installation was able to reduce resistance by 12.44% and on the ship model with Stern foil installation the resistance reduction was 5.25%. Based on the results of this CFD simulation, it can be concluded that the Hull Vane installation is more optimal in reducing resistance on the flat hull ship of the semi-trimaran model.

scholarly journals Prediction of an Optimum Total Resistance Coefficient on Catamaran using Design of Experiment (DOE) Incorporated with CFD Approach

2020 ◽  
Vol 3 (1) ◽  
pp. 74-83
Author(s):  
Ahmad Fitriadhy ◽  
Sun Yin Lim ◽  
Adi Maimun
Keyword(s):  
Froude Number ◽  
Design Of Experiment ◽  
Cfd Simulation ◽  
Fluid Dynamic ◽  
Resistance Coefficient ◽  
Primary Objective ◽  
Design Stage ◽  
Total Resistance ◽  
Cfd Modelling ◽  
Simulation Results

In presence of complex hydrodynamic interferences between two demihulls on a catamaran ship has been prone to have a reliable prediction to her optimum total resistance. To achieve this, the author presents a Computational Fluid Dynamic (CFD) modelling incorporated with Design of Experiment (DOE) approach. Several parameters such as effect of Froude number ( ) with respect to various lateral separation ratios (S/L) of the catamaran have been taken into account. Here, the optimum total resistance coefficient (CT) has been mainly set within the range of S/L ratio 0.2 ≤ S/L ≤ 0.4 associated with Froude number 0.56 ≤  ≤ 0.66. The primary objective function of this optimization model has led towards minimizing a drag force and increased a lift force with respect to the above S/L ratios. In general, the simulation results had seemed quantitative similarity values for the optimum  of 0.6589, 0.6599 and 0.6596 with S/L ratios of 0.2, 0.3 and 0.4, respectively. In the case of  = 0.56, the optimum S/L ratios of 0.2993 and 0.3988 have resulted in insignificant reduction of CT by 0.62% and 0.32% as compared to S/L of 0.3 and 0.4, respectively. Similarly, the optimum S/L ratios of 0.2750 and 0.3750 with  = 0.66 have led to reduce by 0.14% and 0.46% as compared to S/L of 0.3 and 0.4, respectively. This CFD simulation results are very useful as preliminary data for the optimised ship resistance, which is mainly required to predict a ship powering in the early design stage.

Verification and Validation of CFD Uncertainty Analysis Based on SST K-ω Model

2020 ◽  
Author(s):  
Li Zhang ◽  
Weimin Chen ◽  
Jianting Chen ◽  
Chuanming Zhou
Keyword(s):  
Numerical Simulation ◽  
Uncertainty Analysis ◽  
Cfd Simulation ◽  
Numerical Results ◽  
Verification And Validation ◽  
Ship Model ◽  
The Past ◽  
Mesh Density ◽  
Simulation Results ◽  
Selection Of

Abstract CFD uncertainty analysis is a process to quantify the accuracy of numerical simulation results, and it is also a research hotspot in the past decades. ITTC(2017) requires uncertainty analysis of ship CFD simulation results, that is, verification and validation. In this paper, with reference to the recommended procedures by ITTC, the uncertainty of the CFD numerical simulation results of ship model resistance was analyzed. Based on the SST k-ω turbulence model, the Y+ values near the wall were set to 60,120,240, respectively. And for each and Y+ value, three different sets of grid densities were set respectively, and the uncertainty was analyzed. The results show that: 1) the results of Y+ at 60 and 120 were not validated, and the results at 240 was validated, 2) the selection of Y+ value has a significant effect on the numerical results, 3) increasing the mesh density can make the result converge, but it is not sure to get the result with the least error. Through the uncertainty analysis of CFD results, it is helpful to find a method to improve the accuracy of the numerical results.

scholarly journals Optimization of Dynamic Task Location within a Manipulator’s Workspace for the Utilization of the Minimum Required Joint Torques

Electronics ◽  
2021 ◽  
Vol 10 (3) ◽  
pp. 288
Author(s):  
Adam Wolniakowski ◽  
Charalampos Valsamos ◽  
Kanstantsin Miatliuk ◽  
Vassilis Moulianitis ◽  
Nikos Aspragathos
Keyword(s):  
High Performance ◽  
Human Robot Interaction ◽  
Optimal Position ◽  
End Effector ◽  
Joint Torques ◽  
Dynamic Task ◽  
Arbitrary Position ◽  
Simulation Results ◽  
Set Up ◽  
Task Placement

The determination of the optimal position of a robotic task within a manipulator’s workspace is crucial for the manipulator to achieve high performance regarding selected aspects of its operation. In this paper, a method for determining the optimal task placement for a serial manipulator is presented, so that the required joint torques are minimized. The task considered comprises the exercise of a given force in a given direction along a 3D path followed by the end effector. Given that many such tasks are usually conducted by human workers and as such the utilized trajectories are quite complex to model, a Human Robot Interaction (HRI) approach was chosen to define the task, where the robot is taught the task trajectory by a human operator. Furthermore, the presented method considers the singular free paths of the manipulator’s end-effector motion in the configuration space. Simulation results are utilized to set up a physical execution of the task in the optimal derived position within a UR-3 manipulator’s workspace. For reference the task is also placed at an arbitrary “bad” location in order to validate the simulation results. Experimental results verify that the positioning of the task at the optimal location derived by the presented method allows for the task execution with minimum joint torques as opposed to the arbitrary position.

scholarly journals Resistance reduction on trimaran ship model by biopolymer of eel slime

2015 ◽  
Vol 12 (2) ◽  
pp. 95-102
Author(s):  
Y. Yanuar ◽  
G. Gunawan ◽  
M. A. Talahatu ◽  
R. T. Indrawati ◽  
A. Jamaluddin
Keyword(s):  
Drag Reduction ◽  
Frictional Resistance ◽  
Skin Surface ◽  
Fish Skin ◽  
Total Drag ◽  
Towing Tank ◽  
Ship Model ◽  
Resistance Reduction ◽  
Towing Tank Test ◽  
Tank Test

Resistance reduction in ship becomes an important issue to be investigated. Energy consumption and its efficiency are related toward drag reduction. Drag reduction in fluid flow can be obtained by providing polymer additives, coating, surfactants, fiber and special roughness on the surface hull. Fish skin surface coated with biopolymers viscous fluid (slime) is one method in frictional resistance reduction. The aim of this is to understanding the effect of drag reduction using eel slime biopolymer in unsymmetrical trimaran ship model. The Investigation was conducted using towing tank test with variation of velocity. The dimension of trimaran model are L = 2 m, B = 0.20 m and T = 0.065 m. The ship model resistance was precisely measured by a load cell transducer. The comparison of resistance on trimaran ship model coated and uncoated by eel slime are shown on the graph as a function of the total drag coefficient and Froude number. It is discovered the trimaran ship model by eel slime has higher drag reduction compared to trimaran with no eel slime at similar displacement. The result shows the drag reduction about 11 % at Fr 0.35.

Optimization of Structure and Calculation of Flow-Force on Poppet Valve under Converging Flow

2011 ◽  
Vol 339 ◽  
pp. 148-151 ◽  
Author(s):  
Shu Juan Zheng ◽  
Long Quan
Keyword(s):  
Cfd Simulation ◽  
Internal Flow ◽  
Poppet Valve ◽  
Converging Flow ◽  
Simulation Results

This paper optimizes the structure of the poppet valve based on the internal flow. The flow-force on poppet valve in the case of the converging flow is simulated and studied by CFD. Simulation results represent that the traditional formula for computing the flow-force can be used only in the certain range, so the formula is modified based on the simulation result.

Numerical simulation and field test study of desulfurization wastewater evaporation treatment through flue gas

2014 ◽  
Vol 70 (7) ◽  
pp. 1285-1291 ◽  
Author(s):  
Jia-jia Deng ◽  
Liang-ming Pan ◽  
De-qi Chen ◽  
Yu-quan Dong ◽  
Cheng-mu Wang ◽  
...  
Keyword(s):  
Field Test ◽  
Flue Gas ◽  
Cfd Simulation ◽  
Electrostatic Precipitator ◽  
Negative Impact ◽  
Positive Impact ◽  
Field Tests ◽  
Gas Temperature ◽  
Simulation Results ◽  
Desulfurization Wastewater

Aimed at cost saving and pollution reduction, a novel desulfurization wastewater evaporation treatment system (DWETS) for handling wet flue gas desulfurization (WFGD) wastewater of a coal-fired power plant was studied. The system's advantages include simple process, and less investment and space. The feasibility of this system has been proven and the appropriate position and number of nozzles, the spray droplet size and flue gas temperature limitation have been obtained by computational fluid dynamics (CFD) simulation. The simulation results show that a longer duct, smaller diameter and higher flue gas temperature could help to increase the evaporation rate. The optimal DWETS design of Shangdu plant is 100 μm droplet sprayed by two nozzles located at the long duct when the flue gas temperature is 130 °C. Field tests were carried out based on the simulation results. The effects of running DWETS on the downstream devices have been studied. The results show that DWETS has a positive impact on ash removal efficiency and does not have any negative impact on the electrostatic precipitator (ESP), flue gas heat exchanger and WFGD. The pH values of the slurry of WFGD slightly increase when the DWETS is running. The simulation and field test of the DWETS show that it is a feasible future technology for desulfurization wastewater treatment.

CFD Simulation of Large Dust Collection Cyclones Positioned Vertically in Staggered Downward Cascade Arrangement

2013 ◽  
Author(s):  
Eugen-Dan Cristea ◽  
Pierangelo Conti
Keyword(s):  
Cfd Simulation ◽  
Solid Phase ◽  
Phase Particle ◽  
High Mass ◽  
Cfd Modeling ◽  
Cement Kiln ◽  
Dust Collection ◽  
Dry Process ◽  
Cascade Arrangement ◽  
Simulation Results

Three dimensional, time dependent Euler-Euler simulation approach for numerical calculation of multiphase strongly swirling turbulent gas-heavy laden particulate flow in large industrial collection cyclones, positioned vertically, in staggered downward cascade arrangement has been performed. The multiphase flow was featured high mass loading. This paper specifically addresses a CFD modeling of a “suspension preheater”, typical equipment for dry process cement kiln. Big sized cyclone separator is a key component of this device. The simulation case study was developed in the frame of the commercial general-purpose code ANSYS-Fluent R13. In cyclone separators the swirling gas motion induces a centrifugal force on the solid particulate phase which is the driving force behind the separation process. The turbulence disperses the solid particulates and enhances the probability that particles are discharged, as reject. Both phenomena are related to solid phase particle size distribution (PSD) and flow pattern into the collection cyclones. The multiphase turbulence was modeled using the RSM Mixture Turbulence Model. The simulation results were validated against industrial measurements carried out on an industrial suspension preheater, in the frame of heat and mass balance of cement kiln energy audit. The numerical simulation results were found in reasonable agreement with the collected industrial measurements. This CFD simulation represents a powerful engineering tool on behalf of the cement process engineer either for new cutting-edge design or for performance verification of an existing plant.

An Experimental Examination of the 2D+T Approximation

2009 ◽  
Vol 53 (02) ◽  
pp. 59-67
Author(s):  
Mostafa Shakeri ◽  
Eric Maxeiner ◽  
Thomas Fu ◽  
James H. Duncan
Keyword(s):  
Froude Number ◽  
Longitudinal Wave ◽  
Contact Line ◽  
Three Dimensional ◽  
Maximum Height ◽  
Hull Form ◽  
Ship Model ◽  
Wave Maker ◽  
Acceleration Of Gravity ◽  
Good Agreement

Measurements of contact line height and longitudinal wave profiles from experiments with a three-dimensional naval ship model and experiments using a 2D+T wave maker with motions approximating the three-dimensional hull form are compared. The shape and maximum height of the contact line in the bow region are nearly the same in the two experiments, and the distance downstream along the hull over which the two measurements agree increases with increasing Froude number, Fn = Um/√gLm, where Um is the ship model speed, g is the acceleration of gravity, and Lm is the ship model waterline length. The comparison of the longitudinal wave profile (wave cut) data from the two experiments shows fairly good agreement for wavelengths and amplitudes at the highest Froude number and the measurement position closest to the hull.

scholarly journals Study of the nozzle check valve with respect to its operating characteristics

2018 ◽  
Vol 180 ◽  
pp. 02044 ◽  
Author(s):  
Roman Klas ◽  
Vladimír Habán ◽  
Pavel Rudolf
Keyword(s):  
Cfd Simulation ◽  
Check Valve ◽  
Operating Characteristics ◽  
Valve Design ◽  
Pressure Fields ◽  
Valve Disc ◽  
Unsteady Operation ◽  
Simulation Results ◽  
2D And 3D ◽  
Main Operating

Several modifications were developed when designing the nozzle valve. This study offers an assessment of the properties of new modifications of the nozzle valve design. The main operating characteristics, such as loss and flow coefficients, were determined using a CFD methods. Besides mentioned coefficients, the forces acting on the valve disc are also decisive for the behavior of the valve, both in its steady and unsteady operation. It is important to examine the possible simplification and matching of CFD simulation results from 2D and 3D geometries in terms of subsequent dynamic analysis of the valve. This will be taken into consideration by comparing the above-mentioned operating characteristics, by analyzing the forces acting on the valve disc and comparing the velocity and pressure fields.

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