格子で解像できる空間的に

03:39 Jul 10, 2016
This question was closed without grading. Reason: No acceptable answer

Japanese to English translations [PRO]
Tech/Engineering - Ships, Sailing, Maritime / Naval Architecture
Japanese term or phrase: 格子で解像できる空間的に
The following piece is from a chapter discussing the methods of estimating the viscous resistance of the hull.

How does one translate '格子で解像できる空間的に'?

乱流に対する実用的な計算方法としては、格子で解像できる空間的に大きなスケールの流れとそれよりも小さいスケールの流れに分解して、大きなスケールの流れに対する方程式を解くラージ・エディ・シミュレーション(LES)と呼ばれる方法と、元の方程式に対して平均化を行うことで得られるレイノルズ平均ナビエ・ストークス方程式(Reynolds Averaged Navier-Stokes equation ; RANS)を支配方程式とする方法とがある。
Lekhika
Local time: 18:47


Summary of answers provided
3numerical grid
Erzsébet Czopyk


Discussion entries: 10





  

Answers


31 mins   confidence: Answerer confidence 3/5Answerer confidence 3/5
numerical grid


Explanation:
Viscous-Flow Computations of Two Existing Vessels at Model - MARIN
www.marin.nl/web/file?uuid=ee4d7d74-64af-4c93-88b7...
full-scale ship flows including both the effect of viscosity and the free surface ... In the computations, the RaNS equations are solved until the steady state is .... However, even on a very fine grid the resistance coefficients will show large ... resistance estimation, the hull rougness, and the roughness of the propeller blades.

INTRODUCTION
The use of viscous-flow calculations in ship design is gradually becoming more widespread.
However, the majority of such calculations is for model scale; and making computations directly for the full-scale ship has often been considered a major challenge. Recently, simulations of full-scale ship flows including both the effect of viscosity and the free surface were performed by Chen et al. [1], Schweighofer [6], Tzabiras [7] and Raven et al. [4]. In most of the cases, the computations were performed for a simple geometry, the one of the Series 60 ship. However, real ships have a much more complicated geometry, which makes the respective full-scale
computations much more difficult.
The European-Union project EFFORT (European Full-Scale Flow Research and Technology) [9] focusses on the applicability of different RANS methods to full-scale viscous flow computations performed for real ships. Full-scale flow measurements are being done and existing data have been collected; CFD methods have been further developed; and extensive validations with full-scale data are now being done.

The used approaches and computations are briefly described. An evaluation of the grid influence on the results is given. Convergence is documented by giving the respective convergence criterion used

NUMERICAL METHODS
In the computations, the RaNS equations are solved until the steady state is reached. The turbulence is treated by different turbulence models. The free surface is evaluated either by solving the potential flow around the hull or taking the influence of viscosity into account by surface tracking methods. The boundary layer is either resolved entirely or wall functions are applied.

https://books.google.hu/books?id=MsCbAgAAQBAJ&pg=PA952&lpg=P...

Numerical simulation of ship stern flows with a space ... - MARIN
www.marin.nl/web/file?uuid=0e75a4ce-05e6-40a2-91b0-79262b39...
Navier-Stokes (RANS) equations has become feasible for many flow .... of numerical damping of the ship-generated waves requires a grid resolution that is.

time-domain simulation of propeller-ship interactions under ... - ABS
https://www.eagle.org/.../Time-DomainSimulationPropeller-Shi...
Keywords: Propeller-Ship Interactions, RANS Equations, Chimera Method, Turning .... The ship grids (blocks 1 & 2) are identical to those used in Chen and Lee ...

Download PDF file [1135KB] - (www.simman2008.dk).
www.simman2008.dk/PDF/QM4.9-04-02-01.pdf
2.2 Grids. 2.3 Verification and Validation of Integral Variable: Resistance ... computational ship hydrodynamics. The. RANS equations are solved using higher-.

2.2 Computational Grids
Grid studies were conducted using four grids (m=4), which enables two separate grid studies to be performed and compared. Grid study 1 gives estimates for grid errors and uncertainties on grid 1 using the three finest
grids 1-3 while grid study 2 gives estimates for grid errors and uncertainties on grid 2 using the three coarsest grids 2-4. The results for grid study 1 are given in detail and the differences for grid study 2 are also mentioned. The grids were generated using the commercial code GRIDGEN (Pointwise, Inc.) with consideration to topology; number of points and grid refinement ratio rG; nearwall spacing and k-w turbulence model requirement that first point should be at y+<1; bow and stern spacing; and free-surface spacing.

http://www.simman2008.dk/PDF/QM4.9-04-02-01.pdf


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Note added at 36 mins (2016-07-10 04:15:38 GMT)
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Download as Adobe PDF - Edinburgh Research Explorer - University ...
www.research.ed.ac.uk/portal/files/.../Viola_etal_2013IJSCT...
ON THE USE OF CFD FOR THE DESIGN OF YACHT HULLS ... flow. Therefore, the wave resistance can be computed but the viscous resistance must ... scales, and thus the higher the needed spatial resolution .... index to estimate the uncertainty due to the spatial and ... grids and too large time steps lead to non-converging.

In the 1970s, greatly improved computers allowed potential flow theory to be successfully applied in marine applications. This theory assumes the flow to be inviscid and irrotational, and allows modelling of non-dissipative flows. For instance, the lift generated by airfoils at angle
of attack below the stall angle and the wave pattern generated by a vessel can be modelled with potential flow. Therefore, the wave resistance can be computed but the viscous resistance must be estimated with other methods.

This example clearly shows that the spatial resolution used in RANS applications will certainly increase in the future together with the grown of the computational capability. The higher the number of cells of the grid, the higher is the spatial resolution and thus the less the
simulation relies on the turbulence model, which is a non-universal semi-empirical formulation.
The increase in the spatial and time resolutions will also allow different techniques for solving the Navier-Stokes equations to be efficiently used in the design process, such as Detached Eddy Simulation (DES) and Large Eddy Simulations (LES), which are too time consuming at the current state of the art.

http://www.research.ed.ac.uk/portal/files/14079256/Viola_eta...

Erzsébet Czopyk
Hungary
Local time: 14:17
Native speaker of: Native in HungarianHungarian
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