The growth of scleractinian corals is strongly influenced by the effect of water motion. Corals are known to have a high level of phenotypic variation and exhibit a diverse range of growth forms, which often contain a high level of geometric complexity. Due to their complex shape, simulation models represent an important option to complement experimental studies of growth and flow. In this work, we analyzed the impact of flow on coral's morphology by an accretive growth model coupled with advection-diffusion equations. We performed simulations under no-flow and uni-directional flow setup with the Reynolds number constant. The relevant importance of diffusion to advection was investigated by varying the diffusion coefficient, rather than the flow speed in Péclet number. The flow and transport equations were coupled and solved using COMSOL Multiphysics. We then compared the simulated morphologies with a series of Computed Tomography (CT) scans of scleractinian corals Pocillopora verrucosa exposed to various flow conditions in the in situ controlled flume setup. As a result, we found a similar trend associated with the increasing Péclet for both simulated forms and in situ corals; that is uni-directional current tends to facilitate asymmetrical growth response resulting in colonies with branches predominantly developed in the upstream direction. A closer look at the morphological traits yielded an interesting property about colony symmetry and plasticity induced by uni-directional flow. Both simulated and in situ corals exhibit a tendency where the degree of symmetry decreases and compactification increases in conjunction with the augmented Péclet thus indicates the significant importance of hydrodynamics.

We have simulated the two-dimensional growth of fractal aggregates produced in electrodeposition experiments with axial symmetry in the presence of electric and magnetic fields. A modified diffusion-limited aggregation algorithm based on the Monte Carlo method is used in order to simulate cluster growth under the action of Coulomb and Lorentz forces, taking into account the thermal energy. The ion-particle movement has each step biased by the resultant force; in the algorithm, it is mediated by the Boltzmann term. The electric voltage between the electrodes tends to compact the aggregates and reduce the effect of screening. The Lorentz force provides a spiral form for aggregates which twists according to the magnetic field direction and intensity. A function was defined to measure the chirality of the system. The fractal dimension was also calculated to measure the influence of the electric and magnetic fields as well as the temperature during the growth process. Good agreement with experimental results was observed.

The quasi-two-dimensional deposition of ferromagnetic materials by electrochemical process under the influence of a magnetic field applied in the plane of the growth leads to a surprising symmetry breaking in the dendritic structures found. The reasons for these features are still not completely understood. The original dense circular envelope becomes rectangular, as well as the sparse figures have their shapes elongated. This paper reports the results of a diffusion-limited aggregation (DLA) -like simulation. The model proposed here, a modification of the original DLA model, can deal with ferromagnetic particles under the influence of an electric field and the dipolar interactions between particles, submitted to an applied magnetic field in the plane of growth of such structures. The results were produced varying the applied magnetic field and the magnetic moment of the particles and show that the balance between these interactions is an important mechanisms that can be responsible for the changes in shape of the aggregates observed in the experiments.

We are studying the effect of a magnetic field normal to the cell in electrodeposition of zinc arborescences. When the cell thickness is reduced, the MHD convection, responsible for morphology changes, spiraling, etc. is suppressed, but in a high magnetic field there is still an effect maybe due to small-scale hydrodynamic convection or to the Lorentz force on the growing metallic branches, the "Laplace" force.

Biosilicification occurs in many organisms. Sponges and diatoms are major examples of them. In this chapter, we introduce a modeling approach that describes several biological mechanisms controlling silicification. Modeling biosilicification is a typical multiscale problem where processes at very different temporal and spatial scales need to be coupled: processes at the molecular level, physiological processes at the subcellular and cellular level, etc. In biosilicification morphology plays a fundamental role, and a spatiotemporal model is required. In the case of sponges, a particle simulation based on diffusion-limited aggregation is presented here. This model can describe fractal properties of silica aggregates in first steps of deposition on an organic template. In the case of diatoms, a reaction-diffusion model is introduced which can describe the concentrations of chemical components and has the possibility to include polymerization chain of reactions.