# 2.4.3.2. Bodies¶

Bodies are any physical object that is not represented as a boundary condition. They can be water, debris, structures, etc., but not, for instance, a boundary condition like a moving velocity boundary condition.

This section discusses the setup of bodies in the model.

## Material¶

Water, plastic, concrete, sand, steel, clay, rubber, etc. are some of the material presets that can be used to define the bodies. Constitutive laws are selected based on the material preset with appropriate initial values for the material properties. Constitutive laws are used to define the material behavior under different loading conditions. Options include:

1. Isotropic Fluid with Viscous Shear Stress / J-Fluid: This is used to define a basic Newtonian fluid. The material properties include density, bulk modulus, derivative of the bulk modulus with respect to pressure, and dynamic viscosity.

2. Fixed-Corotated / Neo-Hookean: This is used to define solid hyperelastic material behavior under large strains. The material properties include Young’s modulus, Poisson’s ratio, and density.

3. Drucker-Prager: This is used to define solid / granular material behavior under large strains. The material properties include Young’s modulus, Poisson’s ratio, density, and the Drucker-Prager parameters.

4. Non-Associative Cam-Clay: This is used to define solid / granular material behavior under large strains. The material properties include Young’s modulus, Poisson’s ratio, density, and the Non-Associative Cam-Clay parameters.

Material properties are defined in the `Material` tab and are specific to the chosen constitutive law / material model. The material properties include:

1. Density: This refers to the density of the material. This is defined in terms of the mass per unit volume. The units are generally in kg/m3.

2. Young’s Modulus: This refers to the stiffness of the material. This is defined in terms of the force per unit area. The units are generally in Pa.

3. Poisson’s Ratio: This refers to the ratio of the lateral strain to the longitudinal strain. This is a dimensionless quantity.

4. Bulk Modulus: This refers to the measure of the material’s resistance to uniform compression. This is defined in terms of the force per unit area. The units are generally in Pa.

5. Viscosity: This refers to the measure of the material’s resistance to flow. This is defined in terms of the force per unit area. The units are generally in Pa * sec.

## Geometries¶

There are four aspects related to the definition of geometry, namely geometry of the ocean floor or wave flume, buildings or specimens, floating bodies, and shallow water to CFD interface. This section discusses the setup of all aspects of geometry.

## Algorithm¶

The algorithm tab is used to define the algorithmic parameters for the body.

## Partitions¶

The partitions tab is used to distribute a body across the available hardware partitions, e.g. a Graphics Processing Unit or supercomputer node, for parallel computation.

## Debris¶

Currently, HydroUQ only supports floating bodies in the Material Point Method Event. This may expand to include OpenFOAM in an upcoming versions of HydroUQ app.