﻿ Solid Fluid Interface
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# Solid Fluid Interface   # Solid Fluid Interface    This boundary condition is used at the interface between two different materials. Typically, one of them is tool and the other one is the deforming material. An example is a Container and Billet in metal extrusion. The Container is the tool and the billet is the workpiece. This BC can also be used between tool and tool, as in the case of dummy block and container.

The syntax for this boundary condition is:

SolidFluidInterface SFinterface {

([X_Velocity = Ux, Y_Velocity = Uy, Z_Velocity = Uz]) |

FrictionModel = "string",

FrictionCoeff = C,

SlipVelocity_X = Uwx, SlipVelocity_Y = Uwy, SlipVelocity_Z = Uwz,

SlipVelExponent = m)

ContactBCName = "String"

Temperature = T | HeatTransferCoeff = h

Strain = e}

Here SFinterface is the name of the solid wall boundary and is specified by you. For the momentum equation, specify either velocity components, or friction coefficient and slip velocities for friction condition. For FrictionModel, the string must be inside double quotes. Even this is optional. If none are specified, the program initializes them to zero (stationary walls). On the other hand, if the velocities are specified, the program treats the problem as a moving interface problem and for each time step the program computes the grid velocities before moving the nodes. The friction at the tool-workpiece interface is computed using the specified friction model. The name of this model must be specified inside double quotes. Refer to the section on friction model to learn more about the supported friction models.

Valid data types for SolidFluidInterface boundary conditions:

### Valid Data Types

Velocity (Ui)

Velocity component (i=x,y,z)

CONSTANT, EXPRESSION f(x,y,z,t)

FrictionModel

Friction model

{SlipVelocity | Coulomb | Viscoplastic }

FrictionCoeff

Friction Coefficient

CONSTANT, EXPRESSION f(x,y,z,t)

SlipVelocity_i

Velocity vector of the boundary in the slip direction

CONSTANT, EXPRESSION f(x,y,z,t)

SlipVelExponent

Exponent of slip velocity

CONSTANT (only for PowerLaw model)

ContactBCName

Name of BC on contact surface

String

Temperature

Temperature at the boundary

CONSTANT, EXPRESSION f(x,y,z,t)

HeatTransferCoeff

Heat transfer coeff at gap between tool and workpiece

CONSTANT

Strain

Workpiece strain at boundary (Typically used at ram/dummy block and billet contact surface)

CONSTANT