Level set methods: an overview and some recent results

A Non-oscillatory Eulerian Approach to Interfaces in Multimaterial Flows (the Ghost Fluid Method)

▪ Abstract We provide an overview of level set methods, introduced by Osher and Sethian, for computing the solution to fluid-interface problems. These are computational techniques that rely on an implicit formulation of the interface, represented through a time-dependent initial-value partial-differential equation. We discuss the essential ideas behind the techniques, the coupling of these techniques to finite-difference methods for incompressible and compressible flow, and a collection of applications including two-phase flow, ship hydrodynamics, and ink-jet-printhead design.

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Level set methods for fluid interfaces

https://www3.nd.edu/~powers/paper.list/jcp.weno5m.05.pdf

Mapped weighted essentially non-oscillatory schemes: Achieving optimal order near critical points

An efficient ghost-cell immersed boundary method (GCIBM) for simulating turbulent flows in complex geometries is presented. A boundary condition is enforced through a ghost cell method. The reconstruction procedure allows systematic development of numerical schemes for treating the immersed boundary while preserving the overall second-order accuracy of the base solver. Both Dirichlet and Neumann boundary conditions can be treated. The current ghost cell treatment is both suitable for staggered and non-staggered Cartesian grids. The accuracy of the current method is validated using flow past a circular cylinder and large eddy simulation of turbulent flow over a wavy surface. Numerical results are compared with experimental data and boundary-fitted grid results. The method is further extended to an existing ocean model (MITGCM) to simulate geophysical flow over a three-dimensional bump. The method is easily implemented as evidenced by our use of several existing codes.

A Ghost-Cell Immersed Boundary Method for Flow in Complex Geometry

Regular Article: The Ghost Fluid Method for Deflagration and Detonation Discontinuities

This paper explains the methodology used to develop a high-resolution, multi-dimensional Euler solver that is capable of handling non-ideal equation of state and stiff chemical source terms. We have developed a pointwise implementation that has computational advantages for our intended applications, as opposed to a finite volume implementation. Our solver allows for the placement of internal reflective boundaries and the standard inflow and outflow and reflective boundaries at the edge of the domain. We discuss the spatial discretization and the temporal integration schemes, upwinding and flux splitting and the combined use of the Lax - Friedrichs and Roe schemes to solve for the required fluxes. A complete description of the pointwise internal boundary method is given. An overall summary of a representative code structure is given. We provide details on the verification of our integrated set of algorithms that resulted in an application code. We demonstrate the order of convergence for test problems. Two...

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High resolution numerical simulation of ideal and non-ideal compressible reacting flows with embedded internal boundaries

A numerical study of deflagration-to-detonation transition (DDT) in porous HMX materials is carried out. Three reactive-flow models varying from single phase to three phase formulations are chosen for the study. The GISPA model is a single-phase model and the BKS model is a simplified two-phase, gas and solid model. The SVG model is a three-phase model which is based on evolution of solid, gas and void. The modeling assumptions made in construction of the SVG model are presented with a brief description of the other two models. In addition to hydrodynamic modeling, a new reaction-kinetics model, or rate law, is presented to model energy release. The rate law accounts for autocatalytic decomposition of HMX and the pressure dependent shock-to-detonation transition kinetics. The model results are compared in detail against the DDT events observed in physical experiments. Numerical simulation of inert compaction waves and DDT is carried out for parameters suitable for powered HMX. The simulation shows that all three models can effectively predict: (a) the formation of secondary compaction wave and a high-density plug, (b) initiation of the transition to detonation in the front of the plug, and (c) survival of the plug residual after the detonation. The SVG model compares the best against the measurable data of the physical experiment and is also computationally efficient and well-posed. Therefore it is a good candidate for multi-dimensional DDT calculations.

Deflagration-to-detonation transition in porous energetic materials: A comparative model study

Economic effects evaluation and mechanism analysis of urban administrative center relocation: A case study of Qingdao City

Aiming to lack the function of soil covering in the developed orchard straw mulching machine (OSM), a kind of bilateral counter-throwing soil-covering device was developed to eliminate the orchard fire risk caused by the straw layer. The soil-covering device was suspended at the rear of the OSM. Its core component was a pair of throwing wheels installed on both sides of a frame. Hydraulic motors drove the throwing wheels to take soil on-site and cover the straw layer. The adjustment range of the space between the throwing wheels on both sides was 1.4-2.1 m. Based on analysis of soil-covering quantity, soil-covering width, thickness uniformity of soil layer, and power consumption, the key parameters such as the radius, number of the vane, and minimum rotation speed of the throwing wheels were determined. It was proved that the thickness uniformity of the soil layer by bilateral counter-throwing was better than by unilateral, and bottom throwing was better than top throwing. The blade of the soil cutter consisted of a straight blade and a curved blade, and the sliding-cutting angle was 14°-40°. The field test results showed the soil-covering device had good performance with a width of 1.4-2.2 m, a thickness of the soil-covering layer (TSL) of 23.2-40.7 mm, a standard deviation (SD) of 1.4-2.9 mm, width uniformity of 100%, and leakage rate of zero. The established model, between the thickness of soil-covering layer and trenching depth, throwing angle, and rotation speed of the throwing wheels, has a determination coefficient of 0.9757 and can be used to guide the operating parameters. The soil cutter reduced the power consumption and impact load of the throwing wheels by 64.77% and 60.88%, respectively. This work provides a type of new equipment for the mechanization technology of straw mulching in arid and semi-arid orchards. Keywords: orchard, straw mulching, mechanization, soil-covering device, counter-throwing, uniformity DOI: 10.25165/j.ijabe.20231601.7010 Citation: Zhu X H, Gao X, Li X D, Xu S J. Design and test of the bilateral throwing soil-covering device for straw mulching machine in orchards. Int J Agric & Biol Eng, 2023; 16(1): 162–171. 

Shaojie Xu

Papers

Regular Article: The Ghost Fluid Method for Deflagration and Detonation Discontinuities

High resolution numerical simulation of ideal and non-ideal compressible reacting flows with embedded internal boundaries

Deflagration-to-detonation transition in porous energetic materials: A comparative model study

Economic effects evaluation and mechanism analysis of urban administrative center relocation: A case study of Qingdao City

Design and test of the bilateral throwing soil-covering device for straw mulching machine in orchards