# MassOutflowValue

MassOutflowValue[pred,vars,pars]

represents a mass outflow boundary condition for PDEs with predicate pred indicating where it applies, with model variables vars and global parameters pars.

MassOutflowValue[pred,vars,pars,lkey]

represents a mass outflow boundary condition with local parameters specified in pars[lkey].

# Details   • MassOutflowValue specifies a boundary condition for MassTransportPDEComponent and is used as part of the modeling equation:
• • MassOutflowValue is typically used to model a mass outlet for a convective mass transport where mass is transferred out of the domain by fluid flow.
• Typically, the mass convection outweighs the mass diffusion, and a MassOutflowValue needs to be present.
• • MassOutflowValue models the rate of mass species flowing through some part of the boundary with dependent variable in , independent variables in and time variable in .
• Stationary variables vars are vars={c[x1,,xn],{x1,,xn}}.
• Time-dependent variables vars are vars={c[t,x1,,xn],t,{x1,,xn}}.
• The non-conservative time-dependent mass transport model MassTransportPDEComponent is based on a convection-diffusion model with mass diffusivity , mass convection velocity vector , mass reaction rate and mass source term :
• • The conservative time-dependent mass transport model MassTransportPDEComponent is based on a conservative convection-diffusion model given by:
• • In the non-conservative form, MassOutflowValue with boundary unit normal models:
• • A MassOutflowValue is the implicit default boundary condition for the non-conservative model form.
• In the conservative form, MassOutflowValue models:
• • MassOutflowValue only has an effect when the flow velocity is normal to the boundary.
• Model parameters pars as specified for MassTransportPDEComponent.
• The following additional model parameters pars can be given:
•  parameter default symbol "BoundaryUnitNormal" Automatic "ModelForm" "NonConservative" • MassOutflowValue evaluates to a NeumannValue.
• The boundary predicate pred can be specified as in NeumannValue.
• If the MassOutflowValue depends on parameters that are specified in the association pars as ,keypi,pivi,], the parameters are replaced with .

# Examples

open allclose all

## Basic Examples(4)

Set up a mass outflow boundary condition in non-conservative form:

Set up a mass outflow boundary condition in conservative form:

Set up a system of mass outflow boundary conditions in non-conservative form:

Set up a system of mass outflow boundary conditions in conservative form:

## Scope(2)

Define model variables vars for a transient acoustic pressure field with model parameters pars and a specific boundary condition parameter:

Define model variables vars for a transient acoustic pressure field with model parameters pars and multiple specific parameter boundary conditions: