A Method to Calculate Resistance of Ship Taking the Effect of Dynamic Sinkage and Trim and Viscosity of Fluid

2011 ◽  
Vol 121-126 ◽  
pp. 1849-1857
Author(s):  
Chao Bang Yao ◽  
Wen Cai Dong
Keyword(s):  
Boundary Layer ◽  
Free Surface ◽  
Flow Field ◽  
Indirect Method ◽  
Free Surface Flow ◽  
Field Resistance ◽  
Surface Flow ◽  
Equilibrium Equations ◽  
Sinkage And Trim ◽  
Hydrodynamic Equilibrium

A method is presented to calculate the resistance of a ship taking the effect of sinkage & trim and viscosity of fluid. The free surface flow field is evaluated by solving RANS equations with VOF method. The sinkage and trim are computed by hydrodynamic equilibrium equations. The method can be divided into direct and indirect method according to the way to calculate trim of ship. The software Fluent is used to implement this method. With dynamic mesh being used, the position of a ship is updated by the motion of “ship + boundary layer” grid zone. The present methods have been applied to the INSEAN2340 hull for different Froude numbers and are found to be efficient for evaluating the flow field, resistance, sinkage and trim.

Performance characteristics of axial flow hydraulic turbine with a collection device in free surface flow field

2017 ◽  
Vol 112 ◽  
pp. 53-62 ◽  
Author(s):  
Yasuyuki Nishi ◽  
Genki Sato ◽  
Daishi Shiohara ◽  
Terumi Inagaki ◽  
Norio Kikuchi
Keyword(s):  
Free Surface ◽  
Flow Field ◽  
Axial Flow ◽  
Free Surface Flow ◽  
Hydraulic Turbine ◽  
Surface Flow ◽  
Performance Characteristics ◽  
Collection Device

The Free Surface Flow Around a TLP

2010 ◽  
Author(s):  
A. Yalpaniyan ◽  
M. Goodarzi
Keyword(s):  
Free Surface ◽  
Flow Field ◽  
Turbulent Flow ◽  
Numerical Solution ◽  
Flow Pattern ◽  
Symmetry Plane ◽  
Free Surface Flow ◽  
Inviscid Flow ◽  
Surface Flow ◽  
Wave Heights

A TLP is a buoyant platform containing four cylindrical columns. The purpose of this study was to consider the effects of different model solvers in the numerical solution on the flow pattern around the TLP. The flow around the TLP was numerically simulated with inviscid, laminar, and turbulent solvers. Three Froude numbers were run for each case. There was a symmetry plane that allowed simulating just one half of the flow field. Therefore, two columns along the symmetry plane were considered in the results discussion. Beside the generated surface waves there was a pair of vortex behind each column none of them were actually symmetric. The vortex behind the first column significantly affected the flow pattern around the second one in the manner that the vortex behind the first column was larger than the next one. In all cases the outer vortex was larger than the inner one. The obtained results showed that the generated waves of the inviscid flow were smoother than the turbulent flow, and also those of the turbulent flow were smoother than the laminar ones. Compared to the mentioned results, the influence of the flow velocity on the wave heights was more significant.

scholarly journals Influence of the hydrofoil inclination angle at free surface flow around junctions

2020 ◽  
Vol 43 ◽  
pp. 103-108
Author(s):  
Costel Ungureanu ◽  
Costel Iulian Mocanu
Keyword(s):  
Boundary Layer ◽  
Free Surface ◽  
Bluff Body ◽  
Three Dimensional ◽  
Free Surface Flow ◽  
Breaking Waves ◽  
Surface Flow ◽  
Vortex Structures ◽  
The Body ◽  
Flow Topology

"Free surface flow is a hydrodynamic problem with a seemingly simple geometric configuration but with a flow topology complicated by the pressure gradient due to the presence of the obstacle, the interaction between the boundary layer and the free surface, turbulence, breaking waves, surface tension effects between water and air. As the ship appendages become more and more used and larger in size, the general understanding of the flow field around the appendages and the junction between them and the hull is a topical issue for naval hydrodynamics. When flowing with a boundary layer, when the streamlines meet a bluff body mounted on a solid flat or curved surface, detachments appear in front of it due to the blocking effect. As a result, vortex structures develop in the fluid, also called horseshoe vortices, the current being one with a completely three-dimensional character, complicated by the interactions between the boundary layer and the vortex structures thus generated. Despite the importance of the topic, the literature records the lack of coherent methods for investigating free surface flow around junctions, the lack of consistent studies on the influence of the inclination of the profile mounted on the body. As a result, this paper aims to systematically study the influence of profile inclination in respect to the support plate."

Simulation of a Free Surface Flow over a Vertical Weir

2012 ◽  
Vol 256-259 ◽  
pp. 2616-2620
Author(s):  
Y. L. Liu ◽  
Y. Bai
Keyword(s):  
Numerical Simulation ◽  
Free Surface ◽  
Theoretical Analysis ◽  
Flow Field ◽  
Free Surface Flow ◽  
Surface Flow ◽  
Navier Stokes ◽  
Numerical Software ◽  
Typical Time ◽  
Time Point

In this paper the numerical simulation of a free surface flow over a vertical weir with in turns of a scour pool and a small hump weir is presented. Since in this case few of calculative examples adds scour pool and small hump weir in the model, it is meaningful to compute this example using a numerical software which is named Fluent 6.3. The numerical method used consists of Navier–Stokes turbulence solver and k-ε model together with a VOF method and PISO algorithm in pave meshes. Thus, the sketches of flow fields on each typical time point and velocity distributions on each section on 16s are provided to describe flow field accurately. A very good quantitative consequence which accords with hydraulics theoretical analysis has been obtained.

scholarly journals Stagnant peaked free surface released at a sloping beach

2021 ◽  
Vol 127 (1) ◽  
Author(s):  
Peder A. Tyvand ◽  
Jonas Kristiansen Nøland
Keyword(s):  
Free Surface ◽  
Flow Field ◽  
Free Surface Flow ◽  
Surface Flow ◽  
Single Wave ◽  
Initial Flow ◽  
Acceleration Field ◽  
Zero Velocity ◽  
Run Up ◽  
Sloping Beach

AbstractA stagnant free-surface flow is an instantaneous flow field of pure acceleration with zero velocity and a deformed surface. There exists a potential-flow acceleration field. With zero velocity and the acceleration field given, there is a limiting free-surface position which possesses one peak at its point of highest elevation. By complex analysis, it can be shown that the surface peak has a right angle. We elaborate on an elementary model of two-dimensional stagnant free-surface flow with a peak. Our model may serve to describe a situation of maximal single-wave run-up with a given energy at a uniformly sloping beach. The highest possible run-up of an incoming solitary wave corresponds to zero kinetic energy. It encompasses an idealized situation where the kinetic wave energy is converted into potential energy in a water mass piling up along the slope to become stagnant at one single moment. Multipoles with singularities outside the fluid domain may give rise to a smooth and gradual deceleration needed for a non-breaking run-up process. A pair of dipoles with an orientation perpendicular to a given slope represents the stagnant acceleration fields with the highest surface peak spatially concentrated along the slope. Thereby, a one-parameter family of surface shapes is constituted, only dependent on the slope angle. The initial flow field, the initial free surface, the initial isobars and the geometric parameters are all calculated for different slope angles.

Discharge and flow field of the circular channel along the side weir

2015 ◽  
Vol 42 (4) ◽  
pp. 273-280 ◽  
Author(s):  
Hamed Azimi ◽  
Hazhar Hadad ◽  
Zakarya Shokati ◽  
Mohammad Sajad Salimi
Keyword(s):  
Free Surface ◽  
Flow Field ◽  
Free Surface Flow ◽  
Surface Flow ◽  
Circular Channel ◽  
Side Weir ◽  
Stream Surface ◽  
Discharge Coefficients ◽  
Drainage Networks ◽  
Surface Variation

The side weir is one of the most important hydraulic structures that is used by hydraulic engineers for adjusting and controlling flow in urban waste collection systems, irrigation and drainage networks. In this study, an equation is proposed for computing side weir discharge located on circular channels. The equation computes the side weir discharge with sufficient accuracy. Then, the RNG k–ε turbulence model is used for simulating the turbulence of the flow field and the free surface flow variations are modeled using volume of fluid scheme. Comparing experimental results with numerical simulations indicates acceptable accuracy of the numerical model. Also, the side weir discharge coefficients, flow free surface variation, behavior of dividing stream surface and variations of stagnation point height for different discharges within a circular channel along a side weir were examined.

Hydraulic Investigations on Free Surface Flow of ADS Windowless Target

2017 ◽  
Author(s):  
Chen Hu
Keyword(s):  
Free Surface ◽  
Flow Field ◽  
Flow Velocity ◽  
Simulation Models ◽  
Free Surface Flow ◽  
Surface Flow ◽  
Water Model ◽  
Critical System ◽  
Inlet Flow ◽  
Outlet Pressure

The formation and control of free surface flow is one of the most essential parts in the studies of windowless target in acceleration driven sub-critical system (ADS). Water model experiments and 360° full scale three dimensional simulations are conducted in this page. The free surface motion is significantly affected by the inlet flow velocity and outlet pressure. The length of free surface decrease in the second order with the inlet flow velocity, while it decreases linearly with the outlet pressure. The structure and feature of flow field are investigated. The results show that the free surface is vulnerable to the vortex movement. Transient simulations are performed with volume of fluid (VOF) method, large eddy simulation (LES) and the pressure implicit with splitting of operators (PISO) algorithm. The simulation results agree qualitatively well with the experimental data related to both free surface flow and flow field. These simulation models and methods are proved to be practicable in the hydraulic simulations of liquid heavy metal target.

scholarly journals Vortex-Induced Vibration Characteristics of a PTC Cylinder with a Free Surface Effect

Energies ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 907
Author(s):  
Dahai Zhang ◽  
Lei Feng ◽  
Hao Yang ◽  
Tianjiao Li ◽  
Hai Sun
Keyword(s):  
Free Surface ◽  
Flow Field ◽  
Surface Effect ◽  
Amplitude Ratio ◽  
Free Surface Flow ◽  
Surface Flow ◽  
Water Tunnel ◽  
Vortex Induced Vibration ◽  
Turbulence Control ◽  
Moving Cylinder

The experimental study of vortex induced vibration needs to be carried out in water tunnel, but in previous associated simulation work, the water tunnel was treated as an infinite flow field in the depth direction with the effect of the free surface neglected. In the paper, the dynamic characteristics and physical mechanisms of a passive turbulence control (PTC) cylinder in a flow field with a free surface is studied, and the combined technique of a volume of fluid (VOF) method and vortex-induced vibration (VIV) was realized. In the range of Reynolds number studied in this paper (3.5 × 104 ≤ Re ≤ 7.0 × 104), the dynamic parameters (lift and drag coefficients), vortex structures, VIV response (amplitude and frequency ratios), and energy harvesting characteristics of a PTC cylinder under different flow conditions were obtained. The study found that: (1) the shear layer was made more unstable behind the cylinder by the free surface, which made it quicker to reach periodic stability, and the asymmetry shortened the initial stage of vibration of the oscillator, which made it easier to produce dynamic control of the motion of the oscillator; (2) the presence of the free surface only affected the positive amplitude ratio, but had almost no effect on the negative amplitude ratio; (3) the frequency ratio in the free surface flow was closer to the experimental data; (4) the presence of the free surface did not affect the detached vortex pattern in the flow around the stationary cylinder, but in the VIV, the lower the free surface height Z, the more vortices that were shed from the moving cylinder.

Flow of Wall Jet Near Channel Exit at Moderate Reynolds Number

2010 ◽  
Author(s):  
Md. Abul Kalam Azad ◽  
Roger E. Khayat
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Free Surface ◽  
Boundary Conditions ◽  
Free Surface Flow ◽  
Surface Flow ◽  
Wall Jet ◽  
Channel Exit ◽  
Moderate Reynolds Number ◽  
Layer Region

The wall jet flow near channel exit at moderate Reynolds Number, emerging from a two-dimensional channel, is examined theoretically in this study. Poiseuille flow conditions are assumed to prevail far upstream from the exit. The problem is solved using the method of matched asymptotic expansions. The small parameter involved in the expansions is the inverse Reynolds number. The flow and stress fields are obtained as composite expansions by matching the flow in the boundary-layer region near the free surface, flow in the outer layer region and the flow in the core region. The fluid is assumed to be Newtonian and it is found that the jet contracts downstream from the channel exit. The influence of inertia on the shape of free surface, the velocity and stress is emphasized and the higher order boundary layer is explored. To leading order, the problem is similar to the case of the free jet (Tillett) [1] with different boundary conditions. A similarity solution can be carried out using a similarity variable problem which is then solved as an initial-value problem, where the equation is integrated subject to the boundary conditions and a guessed value of the slope at the origin. The slope is adjusted until reasonable matching is achieved between the solution and the asymptotic form at large θ. The level of contraction is essentially independent of inertia, but the contraction moves further downstream with increasing Reynolds number. The present work provides the correct conditions near exit, which are required to determine the jet structure further downstream. If the jet becomes thin far downstream, a boundary layer formulation can be used with the presently predicted boundary conditions for steady and possibly transient flows.

Sign in / Sign up

Export Citation Format

Share Document