INFLUENCE OF THE DISTANCE TO THE INTERFACE AND THE SOLID COVER ON THE HYDRODYNAMIC CHARACTERISTICS OF THE WING PROFILE IN A TWO-LAYER FLOW

2021 ◽  
Author(s):  
Sergey Ivanovich Filippov ◽  
Keyword(s):  
Liquid Flow ◽  
Wave Amplitude ◽  
Hydrodynamic Characteristics ◽  
Lifting Force ◽  
Wing Profile ◽  
Layer Flow

The motion of the hydrofoil in the liquid flow between the solid cover and the interface of liquids with significantly different densities is modeled. The method of boundary singularities is applied. The results of calculations of the lifting force, hydrodynamic moment, and wave amplitude at the interface depending on the immersion of the hydrofoil are obtained and analyzed.

Keel Design for Low Viscous Drag

1987 ◽  
Author(s):  
Clifford J. Obara ◽  
C. P. van Dam
Keyword(s):  
Boundary Layer ◽  
Laminar Flow ◽  
Laminar Boundary Layer ◽  
Leading Edge ◽  
Boundary Layer Transition ◽  
Viscous Drag ◽  
Hydrodynamic Characteristics ◽  
Sweep Angle ◽  
Layer Transition ◽  
Layer Flow

In this paper, foil and planform parameters which govern the level of viscous drag produced by the keel of a sailing yacht are discussed. It is shown that the application of laminar boundary-Layer flow offers great potential for increased boat speed resulting from the reduction in viscous drag. Three foil shapes have been designed and it is shown that their hydro­dynamic characteristics are very much dependent on location and mode of boundary-Layer transition. The planform parameter which strongly affects the capabilities of the keel to achieve laminar flow is lea ding-edge sweep angle. The two significant phenomena related to keel sweep angle which can cause premature transition of the laminar boundary layer are crossflow instability and turbulent contamination of the leading-edge attachment line. These flow phenomena and methods to control them are discussed in detail. The remaining factors that affect the maintainability of laminar flow include surface roughness, surface waviness, and freestream turbulence. Recommended limits for these factors are given to insure achievability of laminar flow on the keel. In addition, the application of a simple trailing-edge flap to improve the hydrodynamic characteristics of a foil at moderate-to-high leeway angles is studied.

Evaluation of hydrodynamic characteristics of the Bosphorus regarding the performance of the marine outfall systems

1995 ◽  
Vol 32 (2) ◽  
pp. 85-93
Author(s):  
Adnan Akyarli ◽  
Yalçin Arisoy
Keyword(s):  
Environmental Impact ◽  
Impact Assessment ◽  
Black Sea ◽  
Lower Layer ◽  
Hydrodynamic Characteristics ◽  
The Black Sea ◽  
Marine Outfall ◽  
Oceanographic Data ◽  
Layer Flow ◽  
Reliable Design

Considering strong interrelations between hydrodynamic features of the Bosphorus and the tube-tunnel crossing which may affect the performance of marine outfall systems, the Institute of Marine Science and Technology (IMST) conducted a comprehensive meteo-oceanographic data acquisition campaign to collect information both for the reliable design of marine outfall systems and for the environmental impact assessment (EIA) of the railroad tunnel, on the joint request of the owners of the projects. The main objectives of this paper are to outline the results of the EIA, and also to discuss the newly adopted plan which proposes to divert the sewage collected in the Kadìköy drainage area to Riva, located along the Black Sea. Recent evaluations by the authors on the blocking of lower layer flow, and findings presented on the mixing along the Bosphorus, have been included as scientific evidences in this discussion.

Keel Design for Low Viscous Drag

1989 ◽  
Vol 33 (02) ◽  
pp. 145-155
Author(s):  
Clifford J. Obara ◽  
C. P. van Dam
Keyword(s):  
Boundary Layer ◽  
Laminar Flow ◽  
Laminar Boundary Layer ◽  
Leading Edge ◽  
Boundary Layer Transition ◽  
Viscous Drag ◽  
Hydrodynamic Characteristics ◽  
Sweep Angle ◽  
Layer Transition ◽  
Layer Flow

Foil and planform parameters which govern the level of viscous drag produced by the keel of a sailing yacht are discussed. It is shown that the application of laminar boundary-layer flow offers great potential for increased boat speed resulting from the reduction in viscous drag. Three foil shapes have been designed and it is shown that their hydrodynamic characteristics are very much dependent on location and mode of boundary-layer transition. The planform parameter which strongly affects the capabilities of the keel to achieve laminar flow is leading-edge sweep angle. The two significant phenomena related to keel sweep angle which can cause premature transition of the laminar boundary layer are crossflow instability and turbulent contamination of the leading-edge attachment line. These flow phenomena and methods to control them are discussed in detail. The remaining factors that affect the maintainability of laminar flow include surface roughness, surface waviness, and freestream turbulence. Recommended limits for these factors are given to insure achievability of laminar flow on the keel. In addition, the application of a simple trailing-edge flap to improve the hydrodynamic characteristics of a foil at moderate-to-high leeway angles is studied.

Boundary-layer flow around a submerged circular cylinder induced by free-surface travelling waves

1996 ◽  
Vol 316 ◽  
pp. 241-257 ◽  
Author(s):  
B. Yan ◽  
N. Riley
Keyword(s):  
Free Surface ◽  
Circular Cylinder ◽  
Wave Amplitude ◽  
Perturbation Methods ◽  
Travelling Waves ◽  
Inviscid Flow ◽  
Steady Streaming ◽  
Viscous Forces ◽  
Layer Flow ◽  
Streaming Motion

We consider the fluid flow induced when free-surface travelling waves pass over a submerged circular cylinder. The wave amplitude is assumed to be small, and a suitably defined Reynolds number large, so that perturbation methods may be employed. Particular attention is focused on the steady streaming motion, which induces circulation about the cylinder. The viscous forces acting on the cylinder are calculated and compared with the pressure forces which are solely responsible for the loading on the cylinder in a purely inviscid flow.

Hydrodynamic characteristics of ascending gas-liquid flow

1990 ◽  
Vol 58 (5) ◽  
pp. 576-582
Author(s):  
E. M. Shestopalov ◽  
V. V. Dil'man
Keyword(s):  
Liquid Flow ◽  
Hydrodynamic Characteristics ◽  
Gas Liquid Flow

Flow Hydrodynamic Characteristics in the Dam-Break Induced Wave Tip Region

2020 ◽  
Vol 14 (05) ◽  
pp. 2040002
Author(s):  
Danhong Wu ◽  
Jia Shen ◽  
Haijiang Liu
Keyword(s):  
Velocity Distribution ◽  
Vertical Velocity ◽  
Water Surface ◽  
Momentum Equation ◽  
Dam Break ◽  
Force Balance ◽  
Hydrodynamic Characteristics ◽  
Uniform Structure ◽  
Flow Convergence ◽  
Layer Flow

Traditional models assuming a vertically uniform structure of the horizontal flow velocity and neglecting the vertical velocity distribution cannot accurately describe the complex boundary layer flow features in the dam-break induced wave tip region. Based on the assumption that the horizontal velocity profile in the wave tip region follows a vertically parabolic distribution with shear extending to the water surface, new solutions for the hydrodynamic characteristics in the wave tip region were derived with respect to the simplified force balance or the steady momentum equation, respectively. The force balance-based models show the relation between water depth [Formula: see text] and distance from the tip [Formula: see text] in the wave tip region as [Formula: see text], whereas a complex and implicit [Formula: see text] relation is confirmed after applying the momentum equation. Comparing with other models, the present momentum equation-based model gives the best agreements with experiments, which can illustrate the general spatial distribution of the wave profile in the wave tip region. Model predicted characteristics of surface particles’ motion are consistent with the experimental observation of Baldock et al. ([ 2014 ] “Flow convergence at the tip and edges of a viscous swash front — experimental and analytical modeling,” Coast Eng. 88, 123–130). As for the vertical velocity distribution in the wave tip region (being downward direction), it increases monotonically from the bed to the water surface and its magnitude increases when approaching the wave tip. Taking into account the relative streamline distribution and total flow field feature in the wave tip region, the present model can reproduce the uniform flow convergence pattern at the wave tip front, as experimentally observed in Baldock et al. [ 2014 ].

Hydrodynamic characteristics of a dispersely annular gas-liquid flow in annular channels

1984 ◽  
Vol 56 (2) ◽  
pp. 120-123 ◽  
Author(s):  
G. V. Alekseev ◽  
N. A. Gromov ◽  
Yu. I. Dzarasov ◽  
S. Yu. Orlov
Keyword(s):  
Liquid Flow ◽  
Hydrodynamic Characteristics ◽  
Annular Channels ◽  
Gas Liquid Flow

scholarly journals Influence of Hydrodynamic Conditions on the Type and Area of Occurrence of Gas–Liquid Flow Patterns in the Flow through Open–Cell Foams

Materials ◽  
2020 ◽  
Vol 13 (15) ◽  
pp. 3254
Author(s):  
Roman Dyga ◽  
Małgorzata Płaczek
Keyword(s):  
Flow Pattern ◽  
Liquid Flow ◽  
Flow Patterns ◽  
Metal Foams ◽  
Hydrodynamic Characteristics ◽  
Internal Diameter ◽  
Open Cell ◽  
Flow Through ◽  
Open Cell Foams ◽  
Gas Liquid Flow

This paper reports the results of a study concerned with air−water and air−oil two–phase flow pattern analysis in the channels with open–cell metal foams. The research was conducted in a horizontal channel with an internal diameter of 0.02 m and length of 2.61 m. The analysis applied three foams with pore density equal to 20, 30 and 40 PPI (pore per inch) with porosity, typical for industrial applications, changing in the range of 92%–94%. Plug flow, slug flow, stratified flow and annular flow were observed over the ranges of gas and liquid superficial velocities of 0.031–8.840 m/s and 0.006–0.119 m/s, respectively. Churn flow, which has not yet been observed in the flow through the open–cell foams, was also recorded. The type of flow patterns is primarily affected by the hydrodynamic characteristics of the flow, including fluid properties, but not by the geometric parameters of foams. Flow patterns in the channels packed with metal foams occur in different conditions from the ones recorded for empty channels so gas−liquid flow maps developed for empty channels cannot be used to predict analyzed flows. A new gas−liquid flow pattern map for a channel packed with metal foams with the porosity of 0.92–0.94 was developed. The map is valid for liquids with a density equal to or lower than the density of water and a viscosity several times greater than that of water.

Experimental Investigation and Numerical Modeling of Hydrodynamic Characteristics of a Heaving Sea Cage

2009 ◽  
Author(s):  
Sho Ito ◽  
Tomoyuki Tsunoda ◽  
Hiroshi Itakura ◽  
Weiguang Bao ◽  
Daisuke Kitazawa ◽  
...  
Keyword(s):  
Wave Amplitude ◽  
Forced Oscillation ◽  
Oscillation Amplitude ◽  
Exciting Force ◽  
Hydrodynamic Characteristics ◽  
Offshore Area ◽  
Aquaculture System ◽  
Cultured Fish ◽  
Offshore Aquaculture ◽  
Sea Cage

With the increasing world demand for seafood and environmental problems in coastal aquaculture, offshore area has been increasingly expected to be utilized for aquaculture. The offshore aquaculture system has fewer effects on the surrounding marine environment through the rapid diffusion of organic wastes from the cultured fish than the coastal one. The offshore area then provides clean waters for cultured fish. On the other hand, the offshore aquaculture system is subject to the severe natural condition such as typhoon attack. Actually, in the current aquaculture system, the offshore fish cages are always submerged around 10m below the sea surface to avoid the effects of high waves and strong currents. However, the safety of the sea cage against the incident wave has seldom been examined, while that against the water current has been analyzed by model tests in tank and numerical simulation. In the present study, therefore, we investigated hydrodynamic property of a heaving sea cage as the first step. Forced oscillation tests and wave exciting force tests have been carried out, and numerical modeling have also been made to estimate hydrodynamic characteristics theoretically and to estimate the drag and mass coefficients. Results of the forced oscillation tests show that the added mass and damping coefficient of sea cage models depend on forced oscillation amplitude. This dependence may be mainly attributed to the deformation of net, and we successfully reduce the dependence on the forced oscillation amplitude in the result of reanalysis which takes into account the deformation of net. Results of measured wave exciting force show that wave exciting forces are not linear in wave amplitude. This may be due to the viscous drag effects as well as the deformation of net. On the other hand, we calculated the flow around a sea cage. This is based on velocity potential and supplemented the effect of viscosity by equivalent linearization. In the boundary condition on the sea cage surface, the vertical velocity to the surface is not equal to zero, but determined by the permeate coefficient of the surface. This permeate coefficient is a function of wave amplitude, wave period and porosity of the net. In the future works, deformation of net should be also taken into account in this calculation.

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