scholarly journals Boundary Layer Mixture Model for a Microbubble Drag Reduction Technique

2011 ◽  
Vol 2011 ◽  
pp. 1-9 ◽  
Author(s):  
Jing-Fa Tsai ◽  
Chi-Chuan Chen
Keyword(s):  
Boundary Layer ◽  
Drag Reduction ◽  
Flat Plate ◽  
Mixture Model ◽  
Frictional Resistance ◽  
Reduction Technique ◽  
Measuring System ◽  
Water Tunnel ◽  
Towing Tank ◽  
Reduction Effect

The boundary mixture model is derived to predict the performance of the microbubble drag reduction technique for a flat plate. The flat plate with a porous material microbubble injecting system and resistance-measuring system are set up to measure the frictional resistance of the flat plate without and with injected microbubbles. The tests are conducted in a water tunnel and a towing tank. The test results show that the boundary mixture model predicts the drag reduction well for the flat plate when testing with injected microbubbles in the water tunnel. However, the boundary mixture model overestimates the drag reduction effect for the flat plate tested in the towing tank. The possible mechanism for the overestimation of drag reduction effect in the towing tank may be due to the different behaviors of microbubbles in the velocity gradient of boundary layer.

Experimental Investigation of Turbulent Boundary Layer Over Smooth Flat Plate With Towing Tank: Attempt of Measurement of Frictional Stress

2007 ◽  
Author(s):  
Kiyoto Mori ◽  
Hiroki Imanishi ◽  
Yoshiyuki Tsuji ◽  
Masashi Kashiwagi ◽  
Masaru Inada ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Flat Plate ◽  
Frictional Resistance ◽  
Reynolds Numbers ◽  
Sufficient Accuracy ◽  
Frictional Stress ◽  
Towing Tank ◽  
High Reynolds Numbers ◽  
Pressure Resistance ◽  
High Reynolds

The purpose of this study is to evaluate the frictional resistance with sufficient accuracy and to evaluate the drag coefficient at high Reynolds numbers. We have measured the resistance of flat plate with using a towing tank. Correcting the wave-making resistance, pressure resistance, and drag on turbulence simulator, it is found that the measured frictional resistance is smaller than the Karman-Schoenherr formula. But it agrees with the values suggested by Osaka et. al and Osterlund et. al.

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.

Drag Reduction by Ejecting Additive Solutions Into Pure-Water Boundary Layer

1972 ◽  
Vol 94 (4) ◽  
pp. 749-754 ◽  
Author(s):  
Jin Wu ◽  
M. P. Tulin
Keyword(s):  
Boundary Layer ◽  
Drag Reduction ◽  
Flat Plate ◽  
Pure Water ◽  
Plane Boundary ◽  
External Flows ◽  
Additive Solution

Drag reduction caused by ejecting additive solutions from a slot into a pure-water boundary layer on a flat plate has been systematically studied. Results include drag measurements for a plane boundary, smooth and rough, with various openings of the slot and with various concentrations and discharges of the ejected additive solution. Conclusions have been drawn on the additive requirement in external flows and on the ejection technique for an optimum drag reduction.

Simulation and Analysis of Flow Field Control in Bionic Jet Surface for Drag Reduction

2013 ◽  
Vol 461 ◽  
pp. 746-750
Author(s):  
Zhao Gang ◽  
Fang Li ◽  
Jun Wei Du ◽  
Muhammad Farid ◽  
Dong Yang Zang
Keyword(s):  
Boundary Layer ◽  
Flow Field ◽  
Drag Reduction ◽  
Velocity Gradient ◽  
Reverse Flow ◽  
Reduction Rate ◽  
Frictional Resistance ◽  
Longitudinal Direction ◽  
Bottom Layer ◽  
Control Behavior

Numerical simulation was used with SST turbulence model on the drag reduction characteristics of bionic jet surface, which clarified the reason that the bionic jet surface could reduce the frictional resistance and the control behavior to the flow field near the wall. Results show that when the area of the jet hole is constant, the higher the ratio of the length along the longitudinal direction of jet hole and that of jet surface is, the better the drag reduction effect is. With the jet speed and jet flux increasing, the drag reduction rate will increase gradually until the maximum of 35.97%. The frictional resistance of bionic jet surface will decrease by increasing the area of reverse flow and decreasing the velocity gradient of the wall; the control behavior of jet surface to boundary layer embodies the shear stress in the bottom of boundary layer caused by the reverse flow in the back flow surface is opposite to the main flow field direction when the shear flow near the wall converges the jet impedance, which causes the low speed reverse rotating vortex pair in the downstream of jet hole, the secondary vortex near the wall caused by the extent of reverse vortex towards the downstream can increase the boundary bottom layer thickness and decrease the velocity gradient and frictional resistance.

Bubble friction drag reduction in a high-Reynolds-number flat-plate turbulent boundary layer

2006 ◽  
Vol 552 (-1) ◽  
pp. 353 ◽  
Author(s):  
WENDY C. SANDERS ◽  
ERIC S. WINKEL ◽  
DAVID R. DOWLING ◽  
MARC PERLIN ◽  
STEVEN L. CECCIO
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Turbulent Boundary Layer ◽  
Drag Reduction ◽  
Flat Plate ◽  
High Reynolds Number ◽  
Friction Drag ◽  
High Reynolds ◽  
Friction Drag Reduction

The Effect of Air Lubrication on a Flat Plate at Varying Angles of Trim With Regard to Drag Reduction

2013 ◽  
Author(s):  
Sean P. Murphy ◽  
Colin T. Spillane
Keyword(s):  
Drag Reduction ◽  
Flat Plate ◽  
Fuel Consumption ◽  
Technological Development ◽  
Frictional Resistance ◽  
Flow Volume ◽  
Resistance Reduction ◽  
Flow Speeds ◽  
Air Lubrication ◽  
Air Layer Drag Reduction

One of the driving factors of technological development in ship design is the reduction of fuel consumption. One way to reduce fuel consumption is to reduce the total resistance experienced by a vessel. The methods of resistance reduction covered in this document are Air-layer-drag-reduction (ALDR) and Bubble Drag Reduction (BDR). This research, conducted in Webb Institute’s circulating flow channel, investigates the applications of ALDR and BDR to a flat plate. These tests measured frictional resistance at varying air flow volume and angles of trim over a range of flow speeds. Results from these tests offer compelling evidence that ALDR is an effective method of reducing frictional resistance.

Air Layer Drag Reduction Applied to Flat-Plate Resistance Testing

2012 ◽  
Author(s):  
Nathan T. Hagan ◽  
Jack Oczeretko
Keyword(s):  
Drag Reduction ◽  
Flat Plate ◽  
Experimental Research ◽  
Frictional Resistance ◽  
Potential Method ◽  
Conclusive Evidence ◽  
Resistance Testing ◽  
Air Entrapment ◽  
Hull Forms ◽  
Air Layer Drag Reduction

Throughout the history of naval architecture the idea of reducing frictional resistance has been the focus of extensive theoretical and experimental research. One potential method for reducing drag is the use of air on the underside of a vessel in the form of Bubble-Induced-Skin-Friction-Drag-Reduction (BDR) and Air-Layer-Drag- Reduction (ALDR). The latter, ALDR, is the focus of this thesis. This document covers flat-plate experimental research conducted using the Webb Institute Flow Channel during the spring of 2012. The objectives of this project were to demonstrate drag reduction at a variety of conditions, including varying speeds, air injection rates, and deadrise angles. A secondary objective was to map the distribution of air migration on the underside of the surface as a function of these conditions. During experimentation conclusive evidence was gathered to support the validity of the ALDR concept, although scaling has not been addressed. Some recommendations for continued work include exploring this concept in experimentation of air entrapment hull forms or analysis of performance characteristics at full scale.

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