Free vs. Forced ConvectionFEFLOW ® Exercise Salt intrusion from top Vertical cross section.

Free vs. Forced Convection FEFLOW® Exercise

Salt intrusion from top

Vertical cross section


Spatial Discretization

• Automatic mesh generation (~3000 triangular elements)• Mesh refinement (via Rubberbox and Border Options)

FEFLOW Mesh Generation

Height approx. 100 m


Model Set-up

FEFLOW Basic Settings

• 2D (default)

• Problem Class:Flow and Mass (steady flow, transient

transport)

• Vertical problem projection

• Temporal and control data:Automatic time stepping, FE/BE time

integrationFinal time: 36500 days (100 years)


Flow Problem - Material parameters

• Global: Density ratio = 10-3

Input 10 [10-4]

Model Set-up

p C o 1

p po– Cs Co– ----------------------- C Co– + +=

Cs

o–o

--------------------------=


Flow Problem - Boundary Conditions

• Impermeable border (default)

• 1st-kind boundary condition at an arbitrary node, e.g., upper left: h = 0 m

Model Set-up


Mass-Transport Problem - Boundary Conditions

Implemented as 1st-kind boundary condition in the center section of the upper border (via Border-Option)

Concentration at the spill site: 100 mg/l

• C = 100 mg/l

Model Set-up


Numerical Solution

FEFLOW Options

• Direct equation solver


FEFLOW Ergebnis

Free convection

Numerical Solution


Base model – Save…


Model Extension


Horizontal hydraulic gradient (‘strong’)

Implemented as 1st-kind boundary condition along the left and right vertical borders(via Border-Option):

• left side: h = 0 m• right side:h = 0.1 m


FEFLOW Result

Flow is dominated by forced horizontal convection

Numerical Solution


Reducing the boundary-condition value on the right vertical border (via Debug option):

• right side:h = 0.01 m

Model Modification


Horizontal hydraulic gradient (‘weak’)


Combined effects of free and forced convection

FEFLOW Result

Numerical Solution

Free vs. Forced ConvectionFEFLOW ® Exercise Salt intrusion from top Vertical cross section.

Documents

mgl model setup slide

kind boundary condition

right vertical border

convection feflow

boundarycondition value

upper border

mass steady flow

border option concentration