Optimization of Underwater Cavity's Shape

2011 ◽  
Vol 291-294 ◽  
pp. 1925-1928
Author(s):  
De Xin Zhang ◽  
Xue Bo Shao ◽  
Li Lou ◽  
Lei Liu
Keyword(s):  
Drag Reduction ◽  
Cavitation Bubble ◽  
Decisive Role ◽  
Basic Research ◽  
Experimental Results ◽  
Bubble Shape ◽  
Cavitation Resistance ◽  
Cavity Shape ◽  
Submerged Body

The steady bubble shape as one of the basic research, plays a decisive role in the cavitation’s study, To study it clearly will be not only basis for the study of non-steady cavitation, but also provide the necessary basis for the design of the control for cavitation bubble. In this paper, cavity shape produced by submerged body is studied, and related to the use of foreign experimental results, super-cavitation resistance, drag reduction is discussed.

Multi-Modal Medical Image Registration of by Combining Improved Mean Shift and RPM

2012 ◽  
Vol 239-240 ◽  
pp. 1472-1475
Author(s):  
Dan Ai ◽  
Jing Li Shi ◽  
Jun Jun Cao ◽  
Hong Yan Zhong
Keyword(s):  
Image Registration ◽  
Medical Image ◽  
Mean Shift ◽  
Decisive Role ◽  
Experimental Results ◽  
Medical Image Registration ◽  
Image Content ◽  
Point Matching ◽  
Target Mode ◽  
Convergence Process

Landmark correspondence plays a decisive role in the landmark-based multi-modality image registration. We combine RPM (Robust Point Matching) and improved Mean Shift to estimate the correspondence of landmarks in images. We improve the target mode and bandwidth used in Mean Shift, and we also perform RPM to estimate the initial landmark correspondence. Next, we use improved Mean Shift to adjust corresponding relations between points. Our method is benefit to make corresponding relations between points more accurate and impels the convergence process of RPM to be related to the image content. Experimental results show that our method can achieve accurate registration of the multi-modal images.

Basic Research for the UV Fixed Abrasive Lapping Plate

2013 ◽  
Vol 371 ◽  
pp. 95-100
Author(s):  
Ioan Marinescu ◽  
Lei Guo ◽  
Peng Wei
Keyword(s):  
Surface Roughness ◽  
Basic Property ◽  
Basic Research ◽  
Experimental Results ◽  
Work Piece ◽  
Machining Efficiency ◽  
Fixed Abrasive

The traditional lapping procedure is based on a slurry process. This paper describes the development of a novel fixed abrasive lapping plate (UV-plate) and investigates the basic property of ultraviolet-cured resins. The primary lapping experiments are carried out. Experimental results show that the lapping process performed with UV-plate significantly increases machining efficiency. It is proved that the surface roughness of machined work-piece by UV-plate is better compared with the conventional slurry lapping plate.

VIV Control and Drag Reduction Using the Guided Porosity Concept

2008 ◽  
Author(s):  
Antonio C. Fernandes ◽  
Fabio M. Coelho ◽  
Ricardo Franciss ◽  
Severino F. S. Neto
Keyword(s):  
Drag Reduction ◽  
Potential Theory ◽  
Experimental Tests ◽  
Experimental Results ◽  
Mass Ratio ◽  
Vortex Induced Vibrations ◽  
Low Mass ◽  
Low Mass Ratio ◽  
Moving Parts

This paper aims to discuss the effectiveness of a new passive kind of VIV (Vortex Induced Vibrations) suppression. Moreover, the proposed solutions leads to a significant drag reduction when compared with conventional proposals (strakes for instance). The concept of guided porosity is applied in experimental tests conducted with low mass ratio cylindrical models. The works also shows that the job (VIV control and drag reduction) is achieved without moving parts, in contrast with segmented fairings. It also advances in terms of the omnidirectional solution. Initially, the concept is discussed in terms of the potential theory. Then experimental results are presented in terms of displacements and forces.

scholarly journals Drag Reduction by Microvortexes in Transverse Microgrooves

2014 ◽  
Vol 6 ◽  
pp. 734012 ◽  
Author(s):  
Bao Wang ◽  
Jiadao Wang ◽  
Gang Zhou ◽  
Darong Chen
Keyword(s):  
Drag Reduction ◽  
High Speed ◽  
Bottom Layer ◽  
Experimental Results ◽  
Dynamics Simulation ◽  
Surface Drag ◽  
Flow Shear ◽  
Detailed Simulation ◽  
Flow Shear Stress ◽  
Microgrooved Surface

A transverse microgrooved surface was employed here to reduce the surface drag force by creating a slippage in bottom layer in turbulent boundary layer. A detailed simulation and experimental investigation on drag reduction by transverse microgrooves were given. The computational fluid dynamics simulation, using RNG k- ε turbulent model, showed that the vortexes were formed in the grooves and they were a main reason for the drag reduction. On the upside of the vortex, the revolving direction was consistent with the main flow, which decreased the flow shear stress by declining the velocity gradient. The experiments were carried out in a high-speed water tunnel with flow velocity varying from 17 to 19 m/s. The experimental results showed that the drag reduction was about 13%. Therefore, the computational and experimental results were cross-checked and consistent with each other to prove that the presented approach achieved effective drag reduction underwater.

A direct numerical simulation of laminar and turbulent flow over riblet-mounted surfaces

1993 ◽  
Vol 250 ◽  
pp. 1-42 ◽  
Author(s):  
Douglas C. Chu ◽  
George Em Karniadakis
Keyword(s):  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Turbulent Flow ◽  
Drag Reduction ◽  
Complex Geometry ◽  
Fourier Method ◽  
Experimental Results ◽  
Shear Stresses ◽  
Smooth Wall ◽  
Turbulent Statistics

The flow in a channel with its lower wall mounted with streamwise riblets is simulated using a highly efficient spectral element-Fourier method. The range of Reynolds numbers investigated is 500 to 3500, which corresponds to laminar, transitional, and turbulent flow states. A complete study is presented for V-groove riblets; the effect of rounded riblets is also investigated. Our results suggest that in the laminar regime there is no drag reduction, while in the transitional and turbulent regimes drag reduction exists (approximately 6 % at Reynolds number 3500) for the riblet-mounted wall in comparison with the smooth wall of the channel. For the first time, we present detailed turbulent statistics (turbulence intensities, Reynolds shear stresses, skewness and flatness) as well as a temporal analysis using a numerical analog of the VITA technique. The flow structure over the riblet-mounted wall is also analysed in some detail and compared with the corresponding flow over the smooth wall in an attempt to identify the physical mechanisms that cause drag reduction. The accuracy of the computation is established by comparing flow quantities corresponding to the smooth wall with previous direct numerical simulation results as well as with experimental results; on the riblet-mounted wall comparison is made with available experimental results. The agreement is very good for both cases. The current computation is the first direct numerical simulation of turbulence in a complex geometry domain.

scholarly journals Aerodynamic Study of a Tricycle Wheel Subsystem for Drag Reduction

2012 ◽  
Author(s):  
Thomas Driant ◽  
Lakhdar Remaki ◽  
Stéphane Moreau ◽  
Alain Desrochers ◽  
Hachimi Fellouah
Keyword(s):  
Wind Tunnel ◽  
Drag Reduction ◽  
Numerical Simulations ◽  
Experimental Results ◽  
Flow Conditions ◽  
Commercial Code ◽  
Drag Analysis

This paper deals with a CFD and experimental drag analysis on an isolated rotating wheel subsystem (including its accessories: tire, suspension, A-arms and fender) of a tricycle vehicle. The main goal of the present work is to study the effect of the fender on the wheel subsystem drag and its optimization. The Star CCM+ commercial code was used for the numerical simulations. Different flow conditions were simulated and some results were validated by comparison to wind tunnel experimental results. To perform drag optimization, several aerodynamic fender shapes were designed and simulated as part of the subsystem. A drastic drag reduction up to 30.6% compared to the original wheel subsystem was achieved through numerical simulations.

The Flat Solitary Waves Due to a Submerged Moving Body in a Two-Layer Fluid With a Free Surface

2005 ◽  
Author(s):  
Gang Wei ◽  
Xiao-Bing Su ◽  
Yun-Xiang You
Keyword(s):  
Free Surface ◽  
Theoretical Analysis ◽  
Solitary Wave ◽  
Solitary Waves ◽  
Experimental Results ◽  
Stable System ◽  
Weakly Nonlinear ◽  
Submerged Body ◽  
Moving Body

The flat solitary wave with the behavior of conjugate flow, generated by a submerged body moving in a two-layer fluid, is investigated. A criteria about the existence of weakly nonlinear weakly dispersive flat solitary wave is given. The condition of the stable system of conjugate flow is obtained. The solution of the flat solitary wave satisfying the criteria is numerically verified to be unique. Theoretical analysis is qualitatively consistent with the experimental results obtained by the authors.

CFD Modelling and Validation of Newtonian and Non-Newtonian Fluids in Curved Conduits

2015 ◽  
Vol 786 ◽  
pp. 181-187
Author(s):  
Abdulrahman Yousif ◽  
Azuraien Japper-Jaafar
Keyword(s):  
Pressure Drop ◽  
Drag Reduction ◽  
Reynolds Stress ◽  
Tap Water ◽  
Newtonian Fluids ◽  
Experimental Results ◽  
Polymer Additives ◽  
Centrifugal Forces ◽  
Cfd Modelling

CFD modelling of drag reduction agents (also called Flow Improvers) polymer additives dissolved in a newtonian solvent (UTP tap Water) was carried out in a curved conduit, A 7 equation Reynolds stress set of equations was used to simulate this flow. The purpose of this simulation is validate experimental results that show unusual pressure drop behaviour. CFD experiments show that there is pressure build-up near the end of the curved conduit due to severe centrifugal forces produced by the fluid, confirming the validity of the experimental results.

scholarly journals Grafted natural polymer as new drag reducing agent: An experimental approach

2012 ◽  
Vol 18 (3) ◽  
pp. 361-371 ◽  
Author(s):  
Hayder Abdulbari ◽  
Nuraffini Kamarulizam ◽  
A.H. Nour
Keyword(s):  
Drag Reduction ◽  
Closed Loop ◽  
Reducing Agent ◽  
Water Soluble ◽  
Experimental Results ◽  
Circulation System ◽  
Additive Concentration ◽  
Gas Oil ◽  
Media Type ◽  
Type Water

The present investigation introduces a new natural drag reducing agent which has the ability to improve the flow in pipelines carrying aqueous or hydrocarbon liquids in turbulent flow. Okra (Abelmoschus esculentus) mucilage drag reduction performance was tested in water and hydrocarbon (gas-oil) media after grafting. The drag reduction test was conducted in a buildup closed loop liquid circulation system consists of two pipes 0.0127 and 0.0381 m Inside Diameter (ID), four testing sections in each pipe (0.5 to 2.0 m), tank, pump and pressure transmitters. Reynolds number (Re), additive concentration and the transported media type (water and gas-oil), were the major drag reduction variables investigated. The experimental results show that, new additive drag reduction ability is high with maximum percentage of drag reduction (%Dr) up to 60% was achieved. The experimental results showed that the drag reduction ability increased by increasing the additive concentration. The %Dr was found to increase by increasing the Re by using the water-soluble additive while it was found to decrease by increasing the Re when using the oil-soluble additive. The %Dr was higher in the 0.0381 m ID pipe. Finally, the grafted and natural mucilage showed high resistance to shear forces when circulated continuously for 200 seconds in the closed-loop system.

Effects of Interfacial Position on Drag Reduction in a Superhydrophobic Microchannel

2008 ◽  
Author(s):  
Ryan Enright ◽  
Tara Dalton ◽  
Tom N. Krupenkin ◽  
Paul Kolodner ◽  
Marc Hodes ◽  
...  
Keyword(s):  
Pressure Drop ◽  
Drag Reduction ◽  
Flow Rate ◽  
Contact Line ◽  
Superhydrophobic Surface ◽  
Parallel Plate ◽  
Laser Scanning ◽  
Liquid Interface ◽  
Experimental Results ◽  
Superhydrophobic Surfaces

The use of superhydrophobic surfaces in confined flows is of particular interest as these surfaces have been shown to exhibit a drag reduction effect that is orders of magnitude larger than those due to molecular slip. In this paper we present experimental results of the pressure-driven flow of water in a parallel-plate microchannel having a no-slip upper wall and a superhydrophobic lower wall. Pressure-drop versus flow-rate measurements characterize the apparent slip behavior of the superhydrophobic surfaces with varying pillar-to-pillar pitch spacing and pillar diameter. The superhydrophobic surface consists of a square array of cylindrical pillars that are fabricated by deep reactive ion etching on silicon and coated with a hydrophobic fluoropolymer. A major challenge, in correlating our experimental results with existing theoretical predictions, is uncertainty in the location of the gas/liquid interface and the associated gas/liquid/solid contact line within the pillar features comprising the superhydrophobic surface. We present experimental results, from laser-scanning confocal microscopy, that measure the location of the gas-liquid interface and associated contact line for fluid flowing through a parallel-plate microchannel. Knowledge of the contact line location is then used to correlate experimental pressure-drop versus flow-rate data with a theoretical model based on porous-flow theory that takes into account partial penetration of liquid into a superhydrophobic surface.

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