Table 6 Common boundary conditions for the heat and mass transfer in macroscale models.

From: Multiscale computational understanding and growth of 2D materials: a review

Navier-Stokes

 No slip on walls

u = 0

 Normal inflow velocitya

u = −U0·n

 Laminar inflowb

\({\mathrm{L}}_{{\mathrm{ent}}}\nabla _{\mathrm{t}} \cdot \left[ { - {\mathrm{p}}{\mathbf{I}} + {\upmu}\left( {\nabla _{\mathrm{t}}{\mathbf{u}} + \left( {\nabla _{\mathrm{t}}{\mathbf{u}}} \right)^{\mathrm{T}}} \right)} \right] = - {\mathrm{p}}_{{\mathrm{ent}}}{\mathbf{n}}\)

 Mass Flowc

\(\displaystyle-\,{\int}_{\partial {\mathrm{\Omega }}} {\frac{{\uprho }}{{{\uprho }}_{{\mathrm{st}}}}} - \left( {{\mathbf{u}}\, \cdot \,{\mathbf{n}}} \right){\mathrm{d}}_{{\mathrm{bc}}}{\mathrm{dS}} = {\mathrm{Q}}_{{\mathrm{sccm}}}\)

 Zero outlet pressure

\(- {\mathrm{p}}{\mathbf{I}} + {\upmu}( {\nabla {\mathbf{u}} + ( {\nabla {\mathbf{u}}} )^{\mathrm{T}}} ) - \frac{2}{3}{\upmu}\,( {\nabla \cdot {\mathbf{u}}} ){\mathbf{I}} = 0\)

Heat transfer

 Inlet

−n · q = 0

 Thermal insolation

−n · q = 0

 Inflow heat fluxd

\(- {\mathbf{n}} \cdot {\mathbf{q}} = - {\mathrm{q}}_0\frac{{{\mathrm{A}}\left( {{\mathbf{u}} \cdot {\mathbf{n}}} \right)}}{{{\int}_{\mathrm{S}} {\left| {{\mathbf{u}} \cdot {\mathbf{n}}} \right|} {\mathrm{ds}}}} + {\uprho}\left( {{\mathrm{h}}_{{\mathrm{in}}} - {\mathrm{h}}_{{\mathrm{ext}}}} \right){\mathbf{u}} \cdot {\mathbf{n}}\)

 Wall temperature

T = T(r)

Flow-assisted diffusion

 No flux at furnace walls

−n · Ni = 0

 Specified concentration

c = c0(r)

 Outflow

\(- {\mathbf{n}} \cdot {\mathrm{D}}_{\mathrm{i}}\nabla {\mathrm{c}}_{\mathrm{i}}\)

 Inflow

c = cin

  1. an is the unit normal vector of the boundary surface.
  2. bLent is the entrance length, and pent is the entrance pressure.
  3. c\({\uprho}_{{\mathrm{st}}} = \frac{{{\mathrm{P}}_{{\mathrm{st}}}{\mathrm{M}}_{\mathrm{n}}}}{{{\mathrm{RT}}_{{\mathrm{st}}}}}\); Mn is the mean molar mass, and Tst and Pst are standard temperature and pressure. Qsccm is the mass flow in the sccm units.
  4. dA is the surface area and q0 is the inward heat flux.