Assigning Materials

Material assignment tells the solver which fluid fills your computational domain. LeaRes uses a single fluid per domain, chosen from a small library of validated fluids tuned for the MOEBIUS lattice-Boltzmann solver. This tutorial covers the Materials panel, the available fluids, and how the values are expressed.

The Materials Panel

The Materials / Material Properties panel controls the fluid for the current project version.

Step 1: Open the Panel

1. Make sure your project version with defined zones is loaded
2. Open the Materials (Material Properties) panel

Step 2: Check the Region

The Region field is read-only and simply reflects the project’s flow type:

• Inside geometry — shown for Internal flow: the fluid fills the interior of the geometry (blood inside a vessel)
• Outside geometry — shown for every other flow type: the fluid surrounds the geometry

To change it, change the flow type in the Simulation Types panel.

Selecting a Fluid

LeaRes provides five validated fluids. Exactly one fluid is assigned per domain.

Fluid	Typical use
Air	Respiratory and ventilation flow
Water	Generic fluid dynamics, device testing
Blood	Cardiovascular and vascular flow
Cerebrospinal	CSF dynamics, hydrocephalus, shunt analysis
Urine	Urological flow

To assign a fluid, select it in the Materials panel. Its properties are loaded and applied to the chosen region.

Tip: Pick the fluid that matches your anatomy or device context. For a coronary or aortic study, choose Blood; for an airway study, choose Air.

What the Numbers Mean

Selecting the fluid is what determines the physics. LeaRes passes only the fluid name to MOEBIUS, which then applies its own validated SI property set — for example Blood: ρ = 995.65 kg/m³, ν = 3.0 × 10⁻⁶ m²/s.

The numeric fields in the Materials panel are not used by the solver. They are stored with the project and used to tint the geometry, but editing them does not change the simulation. Do not treat them as calibrated values — some are placeholders that are not physically meaningful.

Rheology

• Air and Water are Newtonian.
• Blood, Cerebrospinal and Urine are modelled as non-Newtonian (Casson).

Single-Fluid Domains

The LeaRes/MOEBIUS engineering workflow assigns one fluid to the whole domain. Solid surfaces are represented through wall boundaries (covered in Boundary Conditions) rather than as separate solid materials. If your study needs a fluid not in the library, choose the closest available one — for example, Water as a generic Newtonian fluid.

Verification

Before continuing, confirm:

• A fluid is selected for the domain
• The region (Inside geometry or Outside geometry) matches your intent

Troubleshooting

Fluid Not in the Library

Problem: The fluid you need is not among the five available options.

Solution: Select the closest match. Water is a reasonable generic Newtonian fluid for many bench-style studies; Blood and Air cover the most common biomedical cases.

Wrong Region Applied

Problem: The fluid filled the wrong side of the geometry.

Solution: The region is not editable in the Materials panel — it follows the flow type. Change the flow type in the Simulation Types panel (Internal gives Inside geometry, the others give Outside geometry).

Next Steps

With the fluid assigned, you’re ready to configure how flow enters and leaves the domain. Continue to Setting Boundary Conditions.