# directory

DiffEqStochastic and deterministic (ordinary) differential equations.

### Contents

- Reference

This directory contains implementations of discrete time integrators for deterministic and stochastic *ordinary* differential equations. (*Ordinary* as opposed to *partial* differential equations in `src/PDE`

). At this time, all of these ordinary differential equations are used exclusively by Walker.

`Configure<eq>.[Ch]`

contain functionality related to registration and querying user-configuration information on specific equation types.

All specific equation types "inherit" from the common "base", tk::DiffEq, so that user-configured instances of multiple specific equations (as a potentially coupled system) can be integrated in a generic fashion. This is done using concept-based runtime polymorphism.

The specific equation types are registered into a factory, walker::

## Directories

- directory Beta/
- Time integrators for stochastic differential equations based on the beta PDF.
- directory Dirichlet/
- Time integrators for stochastic differential equations based on the Dirichlet PDF.
- directory Dissipation/
- Time integrators for stochastic differential equations modeling the dissipation rate of turbulent kinetic energy in turbulent flows.
- directory Gamma/
- Time integrators for stochastic differential equations based on the gamma PDF.
- directory OrnsteinUhlenbeck/
- Time integrators for stochastic differential equations based on the Ornstein-Uhlenbeck process.
- directory Position/
- Time integrators for stochastic differential equations modeling the stochastic particle positions in turbulent flows.
- directory SkewNormal/
- Time integrators for stochastic differential equations based on the skew-normal PDF.
- directory Velocity/
- Time integrators for stochastic differential equations modeling the stochastic particle velocities in turbulent flows.
- directory WrightFisher/
- Time integrators for stochastic differential equations based on the Wright-Fisher process.

## Files

- file CoupledEq.hpp
- Functionality for querying information on coupled equations.
- file DiffEq.hpp
- Differential equation.
- file DiffEqFactory.hpp
- Differential equations factory.
- file DiffEqStack.cpp
- Stack of differential equations.
- file DiffEqStack.hpp
- Stack of differential equations.
- file HydroProductions.hpp
- Hydrodynamics (turbulent kinetic energy) production divided by the dissipation rate from DNS for the homogeneous Rayleigh-Taylor instability.
- file HydroTimeScales.hpp
- Inverse hydrodynamics time scales from DNS for the homogeneous Rayleigh-Taylor instability.
- file InitPolicy.hpp
- Initialization policies.