# file

PositionCoeffPolicy.hParticle position equation coefficients policies.

### Contents

- Reference

This file defines coefficients policy classes for the Lagrangian particle position equation defined in DiffEq/

General requirements on position equation coefficients policy classes:

- Must define a
*constructor*, which is used to initialize the SDE coefficients. Required signature:`CoeffPolicyName( std::array< tk::real, 9 >& dU );`

where*dU*is an optionally prescribed mean velocity gradient. Must define the static function

*type()*, returning the enum value of the policy option. Example:static ctr::CoeffPolicyType type() noexcept { return ctr::CoeffPolicyType::INSTANTANEOUS_VELOCITY; }

which returns the enum value of the option from the underlying option class, collecting all possible options for coefficients policies.

## Namespaces

- namespace walker
- Walker declarations and definitions.

## Classes

- class walker::Position_InstantaneousVelocity
- Position equation coefficients policy given by the instantaneous velocity.
- class walker::Position_ConstShear
- Position equation coefficients policy using a prescribed constant mean velocity gradient for homogeneous shear flow.