DEM Model for Soot Restructuring

Developing a discrete element model for restructuring of soot aggregates. Aggregates are represented as a collection of rigid spherical particles. Various contact models are added to create a realistic system.

Binary interactions

Elastic contact force between two rigid spherical particles can be modeled with Hertz theory:


In order to simulate kinetic energy loss during a collision, a damping component is added to the normal force:


Van der Waals attraction between small particles can be modeled with the Hamaker equation:

\mathbf{F}_{vw}=\frac{Ad}{(\lvert \mathbf{r}_i-\mathbf{r}_j\rvert-d)^2}\mathbf{n}\\
\mathrm{if}\ \lvert \mathbf{r}_i-\mathbf{r}_j\rvert>r_0
\end{multline*}\] \[\begin{multline*}
\mathrm{if}\ \lvert \mathbf{r}_i-\mathbf{r}_j\rvert\leq r_0

Tangential contact force resulting from an oblique collision can be calculated with the following equation:


Tangential damping force can be modeled in a manner similar to normal damping:


The torque arising from the tangential forces can then be expressed as:


Finally, the torque generated by rolling friction can be modeled with the equation:


Stable aggregates

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