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

Documents

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