scholarly journals A Towing-tank Experiment on Dynamics of Air Bubble Introducer for Drag Reduction of Ships - Flow Visualization of Air Entrainment and Bubble Formation by the Flow Past a Cylinder beneath a Free Surface -

2009 ◽  
Vol 29-1 (2) ◽  
pp. 1009-1009
Author(s):  
Ichiro Kumagai ◽  
Naoya Nakamura ◽  
Yuichi Murai ◽  
Yuji Tasaka ◽  
Yasushi Takeda
Keyword(s):  
Free Surface ◽  
Drag Reduction ◽  
Flow Visualization ◽  
Bubble Formation ◽  
Air Entrainment ◽  
Towing Tank ◽  
Air Bubble ◽  
Tank Experiment ◽  
Flow Past A Cylinder ◽  
Towing Tank Experiment

scholarly journals Bubble formation and scale dependence in free-surface air entrainment

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Wangru Wei ◽  
Weilin Xu ◽  
Jun Deng ◽  
Zhong Tian ◽  
Faxing Zhang
Keyword(s):  
Free Surface ◽  
Bubble Formation ◽  
Air Entrainment ◽  
Scale Dependence

Towing-tank experiment and analysis of nonlinear roll damping for a drillship with different appendages

2018 ◽  
Vol 160 ◽  
pp. 324-334 ◽  
Author(s):  
Jaehoon Lee ◽  
Yonghwan Kim ◽  
Je-Eun Choi ◽  
Chuel-Hyun Kim ◽  
Young-Bum Lee
Keyword(s):  
Roll Damping ◽  
Towing Tank ◽  
Tank Experiment ◽  
Towing Tank Experiment

A Condition for an Air Entrainment by Breaking the Surface Waves at the Free Surface

2005 ◽  
Author(s):  
Ho-Yun Nam ◽  
Jong-Man Kim ◽  
Byoung-Hae Choi ◽  
Jong-Hyeun Choi
Keyword(s):  
Free Surface ◽  
Surface Wave ◽  
Water Flow Rate ◽  
Air Entrainment ◽  
Vessel Diameter ◽  
Test Facility ◽  
Critical Conditions ◽  
Air Bubble ◽  
Water Test ◽  
Entrained Air

An experimental study has been carried out to measure the critical conditions for the inception of an air entrainment by breaking the surface wave at the free surface in the water test facility. The experimental parameters are the vessel diameter, the nozzle diameter, the mean water-level and the water flow rate. More than 400 experimental data which show whether the air is entrained or not at a given experimental condition are obtained, and an experimental correlation that describes the air entrainment condition is developed. The correlation is described by the ratio between the diameter and height of the vessel, the ratio between the diameter of the nozzle and the height of the vessel, the modified Froude number and a modified Weber number. In this experiment two cases of air entrainment are observed. One case is that the air entrainment occurred due to the destruction of the surface wave from the center, and the other case is due to the crash of the water wave to the vessel wall. Theses two cases occur irregularly and the entrained air bubble distributes uniformly in the water.

scholarly journals Estimation of Forces Acting on a Sailboat Using a Kinematic Sensor

2018 ◽  
Vol 7 (02) ◽  
pp. 128-135
Author(s):  
Alan Mahne Kalin ◽  
Dejan Žagar ◽  
Peter Vidmar
Keyword(s):  
Mass Distribution ◽  
Water Resistance ◽  
Coastal Regions ◽  
Kinematic Data ◽  
Towing Tank ◽  
Tank Experiment ◽  
Open Class ◽  
Towing Tank Experiment ◽  
Boat Racing ◽  
Scale Data

Amateur keel boat racing has becoming more and more popular on coastal regions with an old sailing tradition, such as in Adriatic. Although the traditional experience is transmitted to new generations of skippers and crews that compete on national and international regattas with open class boat, the material limits of the boat are often measured subjectively, by sail or mast failure, and transmitted by a story. Most sailors know why some component failed, but often they don’t know what force was needed for the particular failure. Forces acting on a boat are usually estimated with CFD and towing tank experiment for relevant sailing conditions, but full scale data in seaway are rarely taken. Here we wanted to show a low budget method to get a rough estimate of aerodynamic and hydrodynamic forces acting on a keel sailboat using a kinematic sensor. Some approximations are taken into account to construct a simplified mathematical sailboat model, which allow to relate kinematic data to forces acting on sail, hull, keel and rudder. Some data as the geometry and mass distribution of the boat has to be known, other parameters such as water resistance instead has to be experimentally measured. Results of a series of measurements are presented and discussed. Looking on the limitations of such a method, a proposal for a new sensor is made.

scholarly journals Experimental Investigations of Free-Surface Aeration in the Developing Flow of Two-Dimensional Water Jets

1998 ◽  
Vol 120 (4) ◽  
pp. 738-744 ◽  
Author(s):  
T. Brattberg ◽  
H. Chanson ◽  
L. Toombes
Keyword(s):  
Free Surface ◽  
Flow Region ◽  
Air Entrainment ◽  
Experimental Investigations ◽  
Two Dimensional ◽  
Air Bubble ◽  
Surface Aeration ◽  
Water Jets ◽  
Developing Flow ◽  
Air Diffusion

Turbulent water jets discharging into the atmosphere are often characterized by a substantial amount of free-surface aeration. The effects can be detrimental or beneficial. In any case, the knowledge of the air entrainment mechanisms is essential for an optimum design. New experimental data are presented in the developing flow region of two-dimensional water jets discharging into air. The results indicate that the air diffusion takes place rapidly downstream of the nozzle and it is nearly independent of the momentum transfer process. Further, the distribution of air bubble frequency may be related to the air content distribution by a parabolic relationship.

A comparison of 2 cementing techniques in hip resurfacing using human femoral heads

2021 ◽  
pp. 112070002199706
Author(s):  
Sarah J Shiels ◽  
Martin Williams ◽  
Gordon C Bannister ◽  
Richard P Baker
Keyword(s):  
Femoral Head ◽  
Femoral Component ◽  
Bubble Formation ◽  
Young Male ◽  
Cement Mantle ◽  
Hip Resurfacing ◽  
Air Bubble ◽  
Low Viscosity ◽  
Femoral Heads ◽  
Group 2

Introduction: Hip resurfacing remains a valid option in young male patients. The creation of the optimum cement mantle aids fixation of the femoral component. If the cement mantle is too thick the prosthesis can remain proud leading to early failure or if it penetrates too far into the femoral head, it may cause osteonecrosis. Method: 18 of 96 femoral heads collected from patients undergoing total hip arthroplasty were matched for their surface porosity. They were randomly allocated into 2 different cementing groups. Group 1 had the traditional bolus of cement technique, while group 2 had a modified cementing technique (swirl) where the inside of the femoral component was lined with an even layer of low viscosity cement. Results: The traditional bolus technique had significantly greater cement mantle thickness in 3 of 4 zones of penetration ( p = 0.002), greater and larger air bubble formation (6 of 9 in bolus technique vs. 1 in 9 in swirl technique, p = 0.05) and more incomplete cement mantles compared with the swirl technique. There was no relationship to femoral head porosity. Conclusion: The swirl technique should be used to cement the femoral component in hip resurfacing. Long-term clinical studies would conform if this translates into increased survivorship of the femoral component.

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.

Competition of roller rotation and horizontal crossflow to control the free surface cusp-induced air entrainment

2021 ◽  
Vol 33 (11) ◽  
pp. 112114
Author(s):  
Santosh Kumar Panda ◽  
Basanta Kumar Rana ◽  
Parmod Kumar
Keyword(s):  
Free Surface ◽  
Air Entrainment

Mixing Characteristics of a Two-Phase Flow (Gas-Liquid) Microchannel Mixer

2011 ◽  
Author(s):  
Tarek Abdel-Salam ◽  
Srikanth Pidugu
Keyword(s):  
Reynolds Number ◽  
Two Phase Flow ◽  
Bubble Formation ◽  
Width Ratio ◽  
Phase Flow ◽  
Two Phase ◽  
Bubble Generation ◽  
Air Bubble ◽  
And Performance ◽  
Actual Shape

Multiphase phase flows occur in many engineering and bio-medical applications. Bubble formation in microchannels can be beneficial or harmful depending upon their influence on the operation and performance of microfludic devices. Potential uses of bubble generation found in many applications such as microreactors, micropump, and micromixers. In the present work the flow and mixing process in a passive microchannel mixer were numerically investigated. Effects of velocity, and inlet width ratio (Dgas/Dliquid) on the two phase flow were studied. Numerical results are obtained for 2-dimensional and 3-dimesional cases with a finite volume CFD code and using structured grids. Different liquid-gas Reynolds number ratios (Reliquid/Regas) were used ranging from 4 to 42. In addition, three values of the inlet width ratio (Dgas/Dliquid) were used. Results for the 3-D cases capture the actual shape of the air bubble with the thin film between the bubble and the walls. Also, increasing Reliquid increases the rate of the development of the air bubble. The bubble length increases with the increase of Dgas/Dliquid. For the same values of Re, the rate of growth of the bubble increases with the increase of Dgas/Dliquid. Finally, a correlation is provided to predict the length of the bubble with liquid-gas Reynolds number ratio (Reliquid/Regas) and tube width.

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