MassOutflowValue
✖
MassOutflowValue
represents a mass outflow boundary condition for PDEs with predicate pred indicating where it applies, with model variables vars and global parameters pars.
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 allBasic Examples (4)Summary of the most common use cases
Set up a mass outflow boundary condition in non-conservative form:

https://wolfram.com/xid/0b7ekq06log851iy-vw7olo

Set up a mass outflow boundary condition in conservative form:

https://wolfram.com/xid/0b7ekq06log851iy-8qyb5o

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

https://wolfram.com/xid/0b7ekq06log851iy-waq93h

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

https://wolfram.com/xid/0b7ekq06log851iy-i6ww43

Scope (2)Survey of the scope of standard use cases
Define model variables vars for a transient acoustic pressure field with model parameters pars and a specific boundary condition parameter:

https://wolfram.com/xid/0b7ekq06log851iy-glqeii

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

https://wolfram.com/xid/0b7ekq06log851iy-uwpzeb

https://wolfram.com/xid/0b7ekq06log851iy-hwq3hg


https://wolfram.com/xid/0b7ekq06log851iy-zk0k6a

Wolfram Research (2020), MassOutflowValue, Wolfram Language function, https://reference.wolfram.com/language/ref/MassOutflowValue.html.
Text
Wolfram Research (2020), MassOutflowValue, Wolfram Language function, https://reference.wolfram.com/language/ref/MassOutflowValue.html.
Wolfram Research (2020), MassOutflowValue, Wolfram Language function, https://reference.wolfram.com/language/ref/MassOutflowValue.html.
CMS
Wolfram Language. 2020. "MassOutflowValue." Wolfram Language & System Documentation Center. Wolfram Research. https://reference.wolfram.com/language/ref/MassOutflowValue.html.
Wolfram Language. 2020. "MassOutflowValue." Wolfram Language & System Documentation Center. Wolfram Research. https://reference.wolfram.com/language/ref/MassOutflowValue.html.
APA
Wolfram Language. (2020). MassOutflowValue. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/MassOutflowValue.html
Wolfram Language. (2020). MassOutflowValue. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/MassOutflowValue.html
BibTeX
@misc{reference.wolfram_2025_massoutflowvalue, author="Wolfram Research", title="{MassOutflowValue}", year="2020", howpublished="\url{https://reference.wolfram.com/language/ref/MassOutflowValue.html}", note=[Accessed: 06-June-2025
]}
BibLaTeX
@online{reference.wolfram_2025_massoutflowvalue, organization={Wolfram Research}, title={MassOutflowValue}, year={2020}, url={https://reference.wolfram.com/language/ref/MassOutflowValue.html}, note=[Accessed: 06-June-2025
]}