Development of Cartesian grid method for simulation of violent ship-wave interactions

In the present paper, a numerical method based on the constraint interpolation profile (CIP) method is applied for simulating two-dimensional violent sloshing problems. The free surface boundary value problem is considered as a multiphase problem which includes water and air. A stationary Cartesian grid system is adopted, and an interface capturing method is used to trace the shape of free surface profile. The CIP combined unified procedure (CCUP) scheme is applied for flow solver, and the tangent of hyperbola for interface capturing (THINC) scheme is used for interface capturing. Numerical simulations have been carried out for partially-filled 2D tanks under forced sway and roll motions at various filling depths and frequencies. The computational results are compared with experiments and/or the other numerical results to validate the present numerical method.

In this article, a new computational fluid dynamics simulation approach based on the constraint interpolation profile (CIP) method is applied to tackle the violent sloshing problem. The present study considers two-dimensional sloshing phenomena in a rectangular tank. By the proposed method, the sloshing problem is viewed as a multiphase problem that includes water and air flows. A stationary Cartesian grid is used and the free surface is solved by an interface capturing method. The CIP combined unified procedure (CCUP) scheme was adopted for the flow solver, and both the CIP scheme and the CIP conservative semi-Lagrangian with cubic interpolation polynomial (CIP-CSL3) scheme were used for interface capturing. For validation of the numerical method, a physical experiment was conducted with a rectangular tank for several frequencies and filling heights. A convergence check was first performed for the method. The numerical simulation results on violent sloshing show that the use of the CIP-CSL3 scheme as an interface capturing procedure gives much better results for the pressures and free-surface profiles than the conventional CIP scheme.

An interface capturing scheme for modeling atomization in compressible flows

Hydroelastic behavior of an elastic wedge impacting on calm water surface was investigated. A partitioned approach by coupling finite difference method (FDM) and finite element method (FEM) was developed to analyze the fluid structure interaction (FSI) problem. The FDM, in which the Constraint Interpolation Profile (CIP) method was applied, was used for solving the flow field in a fixed regular Cartesian grid system. Free surface was captured by the Tangent of Hyperbola for Interface Capturing with Slope Weighting (THINC/SW) scheme. The FEM was applied for calculating the structural deformation. A volume weighted method, which was based on the immersed boundary (IB) method, was adopted for coupling the FDM and the FEM together. An elastic wedge water entry problem was calculated by the coupled FDM-FEM method. Also a comparison between the current numerical results and the published results indicate that the coupled FDM-FEM method has reasonably good accuracy in predicting the impact force.

The flow field of the underwater gas jet with high temperature and high pressure is a compressible multiphase flow with strong shock waves and large deformation. In this study, establishing a two-dimensional axisymmetric five-equation multiphase flow model, and using the Tangent of Hyperbola for Interface Capturing (THINC) method. The numerical simulation of the flow field of methane-oxygen underwater detonation with different filling pressure is carried out. By building a high-speed photography system and an underwater high-pressure gas jet experimental platform, the underwater gas jet by methane oxygen detonating with different filling pressure is studied. The experimental results show that the water possessing the features of hard compressibility and huge mass inertia makes the high-pressure gas jet bubble expand rapidly to both sides of the tube at the initial stage of formation, but expand rapidly obviously in the axial direction at the end of the first expansion circulating. With the increase of filling pressure, the radial expansion of the gas jet bubble is bigger and bigger, and the rewinding distance is increasing concomitantly. The experimental results also show that the first pulsating pressure increases gradually with the increase of packing pressure.

CIP-based analysis on strongly nonlinear interaction between solitary wave and submerged flat plate

A hybrid WENO5IS-THINC reconstruction scheme for compressible multiphase flows

A unified framework for non-linear reconstruction schemes in a compact stencil. Part 1: Beyond second order

Recently, the Cartesian grid method was used on simulations of fluid flow around the complex geometry problems. In this paper, the Cartesian grid method with cut cells are used to simulate incompressible viscous flows around moving objects. In this study, the small cut cells are merged with neighboring cells. The code was developed based on Fractional Step Method on Finite Volume Method. In time integrate, the second order explicit Adams-Bashforth method was used for the convective terms and second order implicit Crank-Nicholson method was used for the diffusive terms. Some moving boundary problem are simulated using the presented code and compared with other previous numerical and experimental results.

A hybrid Cartesian grid and gridless method for compressible flows

The article’s subject is to study and describe the processes in the hydrodynamic coupling during its operation. The hydrodynamic coupling is a type of hydrodynamic transmission that provides a flexible connection between the input and output shafts, in contrast to the mechanical coupling. Currently, the fluid couplings are widely used and the theoretical description of their operation has been given long before. However, in Russia these units are not produced, the theoretical model is very simple while the experimental data are scattered and non-systematized. So the problem is relevant and requires consideration. The research objective is to complement the existing theoretical model for better describing the fluid coupling operation as well as to compare the results, based on its using, with the numerical simulation results. The main part of the article contains these sections. The mathematical model shows: the equations used for theoretical description of the fluid coupling operation, the basic hydrodynamic equations converted to solve the problem in a stationary setting, and the applied turbulence model (k-ω). The author backslides from the standard jet theory in which the calculation is performed at an average trickle in order to take into consideration the non-uniformity of the velocity distribution in the fluid coupling. The article also raised the issue on the applicability of the stationary formulation of the problem for the numerical simulation. The study revealed that the solutions obtained under stationary and non-stationary calculations practically match. The verification was conducted by three points of characteristic of the hydraulic coupling. The article gives the fluid coupling dimensions, represents an image of its threedimensional model and of the computational grid. It also shows some figures to illustrate the processes in a fluid coupling obtained by its numerical modeling. During the study it was found out that the proposed theoretical model allows us to have higher precision and higher quality in representation of fluid coupling characteristics; the article shows the appropriate graphs. Then a disadvantage is a lack of experimental work. Concerning this issue, the author refers to the publications in which the verification of the results of numerical simulation and experimental results has been conducted showing that their coinciding is quite accurate.

Axial force is one of the main factors which affect the pump safety and reliability during the operation of pumps, especially in multi-stage centrifugal pumps. 150QJ20 type deep-well centrifugal pump (DCP) is selected as an example to research the pump performance and axial force with the numerical simulation and experiment method. The numerical simulation results were compared with experimental measurements, and such result was analyzed. The results show that the change trend of the pump performance and axial force acquired by numerical and experiment is similar. At rated operating point, the error of axial force between the numerical simulation and experimental measurements is less than 3%. This confirmed the feasibility of predict the pump performance by numerical simulation method.

Solitary wave interaction with an impervious house in the coastal community using a parallel three-dimensional incompressible CIP-based model

The roof water disaster of the coal seam in the western mining area has become a great threat to mine safety production. In order to study the failure evolution characteristics of mining disturbed rock, FLAC3D numerical simulation software was used to study the mining-induced rock “three zones” height of 2410 fully mechanized caving face in the Yuhua Coal Mine. The dynamic changes of stress evolution, fracture distribution, and displacement of strata in the mining field after mining are obtained by simulation analysis. The height of the bending subsidence zone is 446.4 m, the height of the fracture zone is 153.6, and the height of the caving zone is 22 m. Through the comparative analysis of the empirical formula and the numerical simulation results and the field measured “three zones” height values after mining in the mining area, the numerical simulation results are more consistent with the measured values, which indicates that the numerical simulation method of mining rock “three zones” can be used as an effective means for the study of mining rock “three zones” in the working face, and provides the necessary technical support for the safe and efficient mining of fully mechanized caving face in coal mines.

In a coal mine in the northern region of Shaanxi Province, China, a facing-mining excavating roadway exists, which is intended to be retained for subsequent working face safety services. This paper investigates the deformation and damage characteristics of the surrounding rock in different stages using FLAC 3D numerical simulation, taking the facing-mining excavating roadway of this coal mine as the research context. At 20 m ahead of the working face, a discontinuous plastic zone appears in the surrounding rock of the roadway, a phenomenon attributed to the varying hardness of the lithologyand termed 'plastic zone jumping.' The numerical simulation results have been were verified using drill hole peeping. Real-time monitoring of the roadway's stability is conducted on-site, showing that the roadway is significantly affected by mining at the 50 m point ahead of the working face. Based on the numerical simulation and on-site monitoring results, the support strength was increased at 50 m from the working face along the roadway, and a new support scheme was adopted. In the lagging section of the roadway, where mining pressure is strongly evident, differentiated reinforcement using anchor rods, anchor ropes, and W steel belts has been employed, resulting in a satisfactory on-site effect.