Technology of 3D Simulation of High-Speed Damping Processes in the Hydraulic Brake Device

This chapter describes a three-dimensional simulation technology for physical processes in concentric hydraulic brakes with a throttling-groove partly filled hydraulic cylinder. The technology is based on the numerical solution of a system of Navier–Stokes equations. Free surface tracking is provided by the volume of fluid (VOF) method. Recoiling parts are simulated by means of moving transformable grids. Numerical solution of the equations is based on the finite-volume discretization on an unstructured grid. Our technology enables simulations of the whole working cycle of the hydraulic brake. Results of hydraulic brake simulations in the counter-recoil regime are reported. The results of the simulations are compared with experimental data obtained on JSC “KBP” test benches. The calculated and the experimental sets of data are compared based on the piston velocity as a function of distance. The performance of the hydraulic brake is studied as a function of the fluid mass and firing elevation of the gun

THREE-DIMENSIONAL NUMERICAL SIMULATION OF TSUNAMI WAVES BASED ON THE NAVIER-STOKES EQUATIONS

A numerical algorithm of solving the three-dimensional system of Navier-Stokes equations to simulate free surface waves and flows with gravity is presented. The main problem here is to ensure that the gravity force is properly accounted in the presence of discontinuities in the medium density. The task is made more complicated due the use of unstructured computational grids with collocated placement of unknown quantities and splitting algorithms based on SIMPLE-type methods. To obtain correctly the hydrostatic pressure, it is suggested that the contribution of the gravitational force in the equation for pressure should be distinguished explicitly; the latter being calculated by using the solution of the two-phase medium gravitational balance problem. To ensure the balance of the gravity force and the pressure gradient in the case of rest an algorithm in which the pressure gradient in the equation of motion is replaced by a modification considering the gravitational force action is suggested. This method is demonstrated by the example of tsunami wave propagation in the real water area of the World Ocean

Simulation of Turbulent Convection at High Rayleigh Numbers

The paper considers the possibility of using different approaches to modeling turbulence under conditions of highly developed convection at high Rayleigh numbers. A number of industrially oriented problems with experimental data have been chosen for the study. It is shown that, at Rayleigh numbers from 109 to 1017, the application of the eddy-resolving LES model makes it possible to substantially increase the accuracy of modeling natural convection in comparison with the linear vortex viscosity model SST. This advantage is most pronounced for cases of a vertical temperature difference with the formation of a large zone of convection of strong intensity. The use of the Reynolds stress model EARSM is shown for cases of natural convective flow in domains with dihedral angles in the simulated region and the predominance of secondary currents. When simulating a less intense convective flow, when the temperature difference is reached at one boundary, the differences in the approaches used to model turbulence are less significant. It is shown that, with increasing values of Rayleigh numbers, errors in the determination of thermohydraulic characteristics increase and, for more accurate determination of them, it is expedient to use eddy-resolving approaches to the modeling of turbulence

Modeling Object Motion on Arbitrary Unstructured Grids Using an Invariant Principle of Computational Domain Topology: Key Features

This paper uses a finite volume algorithm to address the numerical modeling of fluid flow around moving bodies. The Navier–Stokes equations, which describe the flow of viscous compressible gas, along with key boundary conditions and discretization schemes, are presented. As the motion of boundaries typically leads to changes in the control volumes, the basic discretization schemes need to be adapted. This paper provides a detailed discussion on the adaptation of the initial system to deforming boundaries while preserving communication topology. The method for calculating the boundary velocity is a crucial element of the numerical scheme. The paper proposes an approach to reconstruct the boundary velocity vector using deformation analysis and the condition of geometric conservation. This approach ensures correct simulation results for arbitrary unstructured computational grids. A comparison of two approaches to reconstructing the boundary velocity vector for characteristic aviation problems in the direct formulation is presented. It is shown that the proposed approach allows for more accurate modeling of object motion on arbitrary grids using the “invariant” principle of the computational domain topology

Numerical Approach Based on Solving 3D Navier–Stokes Equations for Simulation of the Marine Propeller Flow Problems

The report presents the approach implemented in the Russian LOGOS software package for the numerical simulation of the marine propeller flow problems using unstructured computational meshes automatically generated by the mesh generator. This approach includes a computational model based on the Navier–Stokes equation system and written with respect to the physical process: the turbulent nature of flow with transient points is accounted using the Reynolds Averaged Navier–Stokes method and the k–ω SST model of turbulence by Menter along with the γ–Reθ (Gamma Re Theta) laminar-turbulent transition model; the Volume of Fluid method supplemented with the Schnerr–Sauer cavitation model is used to simulate the cavitation processes; a rotating propeller is simulated by a moving computational mesh and the GGI method to provide conformity of the solutions on adjacent boundaries of arbitrarily-shaped unstructured meshes of the two domains. The specific features of the numerical algorithms in use are described. The method validation results are given; they were obtained because of the problems of finding the performance curves of model-scale propellers in open water, namely the problems of finding the performance of propellers KP505 and IB without consideration of cavitation and the performance of propellers VP1304 and C5 under cavitation conditions. The paper demonstrates that the numerical simulation method presented allows for obtaining sufficiently accurate results to predict the main hydrodynamic characteristics for most modes of operation of the propellers

Verification of the LOGOS Software Package for Tsunami Simulations

Verification results for the LOGOS software package as applied to numerical simulations of tsunami waves are reported. The module of the LOGOS software package that is used for tsunami simulations is based on the numerical solution of three-dimensional Navier–Stokes equations. The verification included two steps. The first step involved the verification of LOGOS free-surface flow simulations on the test cases of a collapsing water column and gravity water sloshing in a tank and the known test cases of wave generation by objects falling into water or lifted out of it. The verification of LOGOS specifically for tsunami simulations was performed using a reference set of international benchmarks including the propagation and run-up of a single wave onto a flat slope and a vertical wall, the sliding of a wedge-shaped body down a slope, flow around an island and wave run-up over an obstacle. The results of the verification simulations demonstrate that LOGOS provides sufficient accuracy in numerical simulations of tsunami waves, namely, their generation, propagation and run-up

The earthquake and tsunami of November 21, 2004 at Les Saintes, Guadeloupe, lesser Antilles

http://library.lanl.gov/tsunami/231/pel.pdfA strong earthquake (mb = 6.3; Ms = 6.1; Mw = 6.3) occurred on 21 November 2004 in the Dominica Passage separating Guadeloupe and Dominica, in the Lesser Antilles, and generated a weak tsunami with maximum amplitudes of +70 and -80 cm on neighbouring islands. We conducted field surveys on the islands of “Les Saintes”, in the immediate vicinity of the epicenter on November 27, 2004 and February 12, 2005, and report here on the resulting dataset

Field survey of the 2004 tsunami occurred at Guadeloupe, Lesser Antilles

The strong earthquake (M = 6.3) occurred on 21st November 2004 in the DominicaPassage, between Guadeloupe and Dominica (Lesser Antilles), generated aweak tsunami with maximum amplitude 80 cm on neighbouring islands. Field surveyis conducted on November 27, 2004. Data of the field survey are described. Results ofthe numerical simulations in the framework of the shallow-water theory are in reasonableagreement with observed data

Tsunami generated by the volcano eruption on July 12-13 at Montserrat, Lesser Antilles

A major collapse of a lava dome occurred at the Soufrière Hills Volcano (Montserrat, Lesser Antilles), culminating late in the evening (11:35 PM local time) on July 12, 2003 (03:35 GMT on 13 July). This generated a tsunami, which was recorded on Montserrat 2-4 km from the generating area and Guadeloupe, 50 km from Montserrat. Results of field surveys are presented. Tsunami wave height on Montserrat may have been about 4 m according to the location of a strandline of charred trees and other floating objects at Spanish Point on the east coast of the island. The wave height on Guadeloupe according to “direct” witnesses was about 0.5-1 m at Deshaies and near Plage de la Perle. The tsunami at Deshaies caused the scattering of boats as confirmed by fishermen and local authorities. Data from the field survey are in agreement with the predicted tsunami scenario obtained by numerical simulation