Numerical simulation of large-scale ocean circulation based on the multicomponent splitting method

H-adaptivity is an effective tool to introduce local mesh refinement in the FEM-based numerical simulation of crack propagation. The implementation of h-adaptivity could benefit the numerical simulation of fatigue or accidental load scenarios involving large structures, such as ship hulls. Meanwhile, in engineering applications, the element deletion method is frequently used to represent cracks. However, the element deletion method has some drawbacks, such as strong mesh dependency and loss of mass or energy. In order to mitigate this problem, the element splitting method could be applied. In this study, a numerical method called ‘h-adaptive element splitting’ (h-AES) is introduced. The h-AES method is applied in FEM programs by combining h-adaptivity with the element splitting method. Two examples using the h-AES method to simulate cracks in large structures under linear-elastic fracture mechanics scenario are presented. The numerical results are verified against analytical solutions. Based on the examples, the h-AES method is proven to be able to introduce mesh refinement in large-scale numerical models that mostly consist of structured coarse meshes, which is also beneficial to the reduction of computational resources. By employing the h-AES method, very small cracks are well represented in large structures without any deletions of elements.

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Combining h-adaptivity with the Element Splitting Method for Crack Simulation in Large Structures

10.20944/preprints202111.0561.v1 ◽

2021 ◽

Author(s):

Shi Song ◽

Moritz Braun ◽

Hauke Herrnring ◽

Bjarne Wiegard ◽

Sören Ehlers

Keyword(s):

Numerical Simulation ◽

Large Scale ◽

Numerical Models ◽

Mesh Refinement ◽

Splitting Method ◽

Ship Hulls ◽

Linear Elastic ◽

Large Structures ◽

Loss Of Mass ◽

Coarse Meshes

H-adaptivity is an effective tool to introduce local mesh refinement in FEM-based numerical simulation of crack propagation. The implementation of h-adaptivity could benefit the numerical simulation of fatigue or accidental load scenarios involving large structures such as ship hulls. In engineering applications, the element deletion method is frequently used to represent cracks. However, the element deletion method has some drawbacks such as strong mesh dependency and loss of mass or energy. In order to mitigate this problem, the element splitting method could be applied. In this study, a numerical method called ‘h-adaptive element splitting’ (h-AES) is introduced. The h-AES method is applied in FEM programs by combining h-adaptivity with the element splitting method. Two examples using the h-AES method to simulate cracks in large structures under linear-elastic fracture mechanics scenario are presented. The numerical results are verified against analytical solutions. Based on the examples, the h-AES method is proven to be able to introduce mesh refinement in large-scale numerical models that consist of structured coarse meshes. By employing the mesh refinement introduced in this paper, very small cracks are well represented in large structures.

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Simulation of the Arctic – North Atlantic Ocean Circulation with a Two-Equation k-omega Turbulence Parameterization

10.20944/preprints201805.0134.v1 ◽

2018 ◽

Cited By ~ 1

Author(s):

Sergey Moshonkin ◽

Vladimir Zalesny ◽

Anatoly Gusev

Keyword(s):

General Circulation Model ◽

Ocean Circulation ◽

North Atlantic ◽

General Circulation ◽

Large Scale ◽

Splitting Method ◽

Circulation Model ◽

Dynamics Simulation ◽

The Arctic ◽

Physical Processes

A method for solving the turbulence equations embedded in the sigma ocean general ocean circulation model is proposed. Like the general circulation model, the turbulence equations are solved using the splitting method by physical processes. The turbulence equations are split into two main stages describing transport-diffusion and generation-dissipation processes. Parameterization of turbulence in the framework of equations allows, at the generation-dissipation stage, to use both numerical and analytical solutions and to ensure high efficiency of the algorithm. The results of large-scale ocean dynamics simulation taking into account the parameterization of vertical turbulent exchange are considered. Numerical experiments were carried out using k-omega turbulence model embedded to the Institute of Numerical Mathematics Ocean general circulation Model (INMOM). Both the circulation and turbulence models are solved using the splitting method with respect to physical processes. The coupled model is used to simulate the hydrophysical fields of the North Atlantic and Arctic Oceans for 1948--2009. The model has a horizontal resolution of 0.25 degree and 40 sigma-levels along the vertical. The sensitivity of the solution to the changes in mixing parameterization is studied. Experiments demonstrate that taking into account the climatic annual mean buoyancy frequency improves the reproduction of large-scale ocean characteristics. There is a positive effect of Prandtl number variations for reproducing the upper mixed layer depth. The experiments also demonstrate the computational effectiveness of the proposed approach in solving the turbulence equations.

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Numerical Simulation of EPB Shield Tunnelling with TBM Operational Condition Control Using Coupled DEM–FDM

Applied Sciences ◽

10.3390/app11062551 ◽

2021 ◽

Vol 11 (6) ◽

pp. 2551

Author(s):

Hyobum Lee ◽

Hangseok Choi ◽

Soon-Wook Choi ◽

Soo-Ho Chang ◽

Tae-Ho Kang ◽

...

Keyword(s):

Numerical Simulation ◽

Large Scale ◽

Tunnel Boring Machine ◽

Chamber Pressure ◽

Screw Conveyor ◽

Shield Tunnel ◽

Pressure Balance ◽

Operational Conditions ◽

Shield Tunnelling ◽

Epb Shield

This study demonstrates a three-dimensional numerical simulation of earth pressure balance (EPB) shield tunnelling using a coupled discrete element method (DEM) and a finite difference method (FDM). The analysis adopted the actual size of a spoke-type EPB shield tunnel boring machine (TBM) consisting of a cutter head with cutting tools, working chamber, screw conveyor, and shield. For the coupled model to reproduce the in situ ground condition, the ground formation was generated partially using the DEM (for the limited domain influenced by excavation), with the rest of the domain being composed of FDM grids. In the DEM domain, contact parameters of particles were calibrated via a series of large-scale triaxial test analyses. The model simulated tunnelling as the TBM operational conditions were controlled. The penetration rate and the rotational speed of the screw conveyor were automatically adjusted as the TBM advanced to prevent the generation of excessive or insufficient torque, thrust force, or chamber pressure. Accordingly, these parameters were maintained consistently around their set operational ranges during excavation. The simulation results show that the proposed numerical model based on DEM–FDM coupling could reasonably simulate EPB driving while considering the TBM operational conditions.

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Optimal Design of Slit Impeller for Low Specific Speed Centrifugal Pump Based on Orthogonal Test

Journal of Marine Science and Engineering ◽

10.3390/jmse9020121 ◽

2021 ◽

Vol 9 (2) ◽

pp. 121

Author(s):

Yang Yang ◽

Ling Zhou ◽

Hongtao Zhou ◽

Wanning Lv ◽

Jian Wang ◽

...

Keyword(s):

Numerical Simulation ◽

Centrifugal Pump ◽

Large Scale ◽

Internal Flow ◽

Orthogonal Test ◽

Centrifugal Pumps ◽

Initial Model ◽

Low Specific Speed ◽

Specific Speed ◽

Four Levels

Marine centrifugal pumps are mostly used on board ship, for transferring liquid from one point to another. Based on the combination of orthogonal testing and numerical simulation, this paper optimizes the structure of a drainage trough for a typical low-specific speed centrifugal pump, determines the priority of the various geometric factors of the drainage trough on the pump performance, and obtains the optimal impeller drainage trough scheme. The influence of drainage tank structure on the internal flow of a low-specific speed centrifugal pump is also analyzed. First, based on the experimental validation of the initial model, it is determined that the numerical simulation method used in this paper is highly accurate in predicting the performance of low-specific speed centrifugal pumps. Secondly, based on the three factors and four levels of the impeller drainage trough in the orthogonal test, the orthogonal test plan is determined and the orthogonal test results are analyzed. This work found that slit diameter and slit width have a large impact on the performance of low-specific speed centrifugal pumps, while long and short vane lap lengths have less impact. Finally, we compared the internal flow distribution between the initial model and the optimized model, and found that the slit structure could effectively reduce the pressure difference between the suction side and the pressure side of the blade. By weakening the large-scale vortex in the flow path and reducing the hydraulic losses, the drainage trough impellers obtained based on orthogonal tests can significantly improve the hydraulic efficiency of low-specific speed centrifugal pumps.

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Large-scale numerical simulation of laser propulsion by parallel computing

10.1117/12.2011249 ◽

2013 ◽

Author(s):

Yaoyuan Zeng ◽

Wentao Zhao ◽

Zhenghua Wang

Keyword(s):

Numerical Simulation ◽

Parallel Computing ◽

Large Scale ◽

Laser Propulsion

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A Near-Uniform Basin-Wide Sea Level Fluctuation of the Mediterranean Sea

Journal of Physical Oceanography ◽

10.1175/jpo3016.1 ◽

2007 ◽

Vol 37 (2) ◽

pp. 338-358 ◽

Cited By ~ 56

Author(s):

Ichiro Fukumori ◽

Dimitris Menemenlis ◽

Tong Lee

Keyword(s):

Atlantic Ocean ◽

Mediterranean Sea ◽

Sea Level ◽

Ocean Circulation ◽

Large Scale ◽

Circulation Model ◽

Level Fluctuation ◽

Strait Of Gibraltar ◽

Sea Level Fluctuation ◽

The Mediterranean

Abstract A new basin-wide oscillation of the Mediterranean Sea is identified and analyzed using sea level observations from the Ocean Topography Experiment (TOPEX)/Poseidon satellite altimeter and a numerical ocean circulation model. More than 50% of the large-scale, nontidal, and non-pressure-driven variance of sea level can be attributed to this oscillation, which is nearly uniform in phase and amplitude across the entire basin. The oscillation has periods ranging from 10 days to several years and has a magnitude as large as 10 cm. The model suggests that the fluctuations are driven by winds at the Strait of Gibraltar and its neighboring region, including the Alboran Sea and a part of the Atlantic Ocean immediately to the west of the strait. Winds in this region force a net mass flux through the Strait of Gibraltar to which the Mediterranean Sea adjusts almost uniformly across its entire basin with depth-independent pressure perturbations. The wind-driven response can be explained in part by wind setup; a near-stationary balance is established between the along-strait wind in this forcing region and the sea level difference between the Mediterranean Sea and the Atlantic Ocean. The amplitude of this basin-wide wind-driven sea level fluctuation is inversely proportional to the setup region’s depth but is insensitive to its width including that of Gibraltar Strait. The wind-driven fluctuation is coherent with atmospheric pressure over the basin and contributes to the apparent deviation of the Mediterranean Sea from an inverse barometer response.

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Prognostic criteria for Polar Lows

10.5194/egusphere-egu21-12282 ◽

2021 ◽

Author(s):

Natalia Vazaeva ◽

Otto Chkhetiani ◽

Michael Kurgansky

Keyword(s):

Numerical Simulation ◽

Wind Velocity ◽

Large Scale ◽

Satellite Image ◽

Development Stage ◽

Mature Stage ◽

Initial Development ◽

Polar Lows ◽

Prognostic Criteria ◽

Main Challenge

Polar lows (PLs) are important mesoscale (horizontal diameter up to 1000 km) maritime weather systems at high latitudes, forming pole ward from the polar front. We consider the possible prognostic criteria of PLs, in particular, the kinematic helicity as a quadratic characteristic related to the integral vortex formations and the kinematic vorticity number (KVN). To calculate such characteristics we use reanalysis data and the results of numerical simulation with the WRF-ARW model (Version 4.1.) for the PLs over the Nordic (Norwegian and Barents) seas. For comparison, experimental data are used.Our estimate of helicity is based on the connection of an integral helicity (IH) in the Ekman layer with the geostrophic wind velocity, due to the good correlation between IH and half the sum of the wind velocity squared. We have chosen IH averaged over preselected area covering the locality of PLs genesis. This area was moving along with the centre of PL during the numerical simulation.The genesis of PLs can be divided into three stages: (i) an initial development stage, in which a number of small vortices appear in a shear zone; (ii) a late development stage, characterized by the merger of vortices; (iii) a mature stage, in which only a single PL is present. Approximately one day before PL formation, a significant increase in helicity was observed. The average helicity bulk density of large-scale motions has values of 0.3 &#8211; 0.4 ms-2. The local changes in helicity are adjacent to the front side of the PLs. The IH criterion described facilitates the identification of the PLs genesis area. For a more detailed analysis of the PL genesis, it is recommended to apply KVN, which is the additional indicator of PL size and intensity. At the moment of maximum intensity of PLs KVN can reach values of 12 &#8211; 14 units. The advantage of using KVN is also in its clear change directly in the centre of the emerging PLs, which allows to precisely indicates the limits of the most intense part of PLs.The main challenge is to make the operational forecast of PLs possible through the selection of the prognostic integral characteristics of PLs, sufficient for PLs identification and for analysis of their size and intensity in a convenient, usable and understandable way. The criteria associated with vorticity and helicity are reflected in the PLs genesis and development quite clearly. At this time, such a claim is only a hypothesis, which must be tested using a larger set of cases. Future work will need to extend these analyses to other active PL basins. Also, it would be interesting to compare the representation of PLs by using any other criteria. It is intended to use our combined criteria as a precursor to machine learning-based PLs identification procedure where satellite image analysis and capture of particular cloud patterns are currently applied in most of the cases. It would eliminate the time consuming first stage of collecting data sets.This work was supported by the Russian Science Foundation (project No. 19-17-00248).

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