Static Body Reaction¶

Introduction¶

Static body reactions represent chemical reactions that operate on scalar fields along a static body surface. The reactions are calculated on a voxel-by-voxel basis and can be a function of local fluid properties, local species concentration, local particle properties, as well as any global variables or parameters. When a thermal field is active, these reactions can also include the effects of heat of reaction (i.e., exothermic and endothermic reactions).

Static body reactions are like fluid reactions—the key difference is that static body reactions are only applied to cells adjacent to the solid surface. Moreover, static body reactions can be functions of static body variables. Used in this way, scalars can be transferred from a fluid scalar field to the static body variable. This functionality is particularly useful for modeling adsorption processes, deposition processes, reactions along catalyst surfaces, etc.

In the example below, we illustrate flow and surface reactions within a semi-batch system. Reactant enters the top of the vessel and flows over a catalyst-covered perforated plate. Interactions between the reactant and the surface catalyst create product material. The product and the excess reactant then exit through a discharge pipe near the bottom of the vessel. Within the model, the surface reaction process is rate-limited by mass transfer through the surface boundary layer.

Download Sample File: Static Body Reaction

The reaction kinetics are solved in tandem with the advection-diffusion equation, particle advection, and fluid transport algorithm. This coupling enables the code to directly predict the effects of changing species concentration on rheology near the solid surface. Moreover, the code can also predict the behavior of competing processes, such as the competition between mixing near the wall and surface reaction kinetics.

Mathematically speaking, the reactions are ordinary differential equations which describe how the local species concentration changes as a function of time. Reactions kinetics are usually written as species-specific rate equations. Within this approach, as for fluid reactions, these rate questions can be linked to a chemical equation via the law of mass action. Static body reactions can also be used to model convective species transfer between solid surfaces, although this behavior is typically modeled via appropriately tuned static body boundary conditions.

Static body reactions are solved using a 1st order Euler solver.

Property Grid¶

`General`¶

Static Body

Select the static body from the model tree which will be involved in the static body reaction.

Static Body Reaction UDF

base units | This UDF defines a scalar field reaction along a static body surface. The number of output variables is equal to the number of scalar field in the model. The names of the output variables are rate_{Scalar}, where {scalar} is the dynamic name of the scalar field. A reaction rate must be specified for each scalar field. Each output value is floating point number.

Positive values imply species production along the surface. Negative values imply species consumption. This is a local UDF, calculated on a voxel-by-voxel basis using the local fluid properties. The UDF is only applied along the cells touching the solid surface.

Download Sample File: Static Body Reaction