## CFD Capabilities

Under the CFD Module License of the amazing and powerful multiphysics simulation software *COMSOL Multiphysics*, we are able to:

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## Simulate any kind of fluid flow

Reynolds number define the regime of a fluid flow, which can be laminar or turbulent.

In Silico can simulate Creeping & Laminar Flows using the traditional continuity and Navier-Stokes equations.

Also, COMSOL allows us to implement RANS turbulent flow models:

k-ε, Realizable k-ε, k-ω, SST, Low-Re k-ε, Spalart–Allmaras, v2-f, Algebraic yPlus and L-VEL

COMSOL CFD Module allows us to simulate three different models for fluid compressibility:

- Incompressible flow
- Weakly Compressible flow
- Compressible flow (Ma<0.3)

The constitutive relationship between the shear rate and the shear stress in a fluid determines the fluid linearity, classifying the fluid as Newtonian or Non-Newtonian.

The dynamic viscosity o the fluid is the property reflecting the fluid linearity. The Inelastic non-Newtonian models for viscosity available in COMSOL are:

Power law, Carreu, Bingham-Papanastasiou, Herschel-Bulkley-Papanastasiou & Casson-Papanastasiou

Flows completely bounded by solid surfaces are called internal flows. Like the fluid in a piping system or in the human vascular system.

External flows are flows over bodies immersed in an unbounded fluid. Like an object in a wind tunnel or immersed in the water.

COMSOL is able to accurately simulate both internal and external flows

The flow in porous media & subsurface is also available in the CFD Module of COMSOL, which allow us to implement:

- Darcy’s law
- Brinkman Equations
- Multiphase Flow in Porous Media
- Two-Phase Darcy’s Law
- Free and Porous Media Flow

With In Silico, you can simulate one fluid flow, but also, the flow of combined fluids, which is called two-phase, three-phase or multiphase flow.

The multiphase flow models available in COMSOL CFD Module are:

Bubbly flow, mixture model, Euler-Euler, phase transport mixture model, nonisothermal mixture model, two-phase flow (moving mesh, level set and phase field), three-phase flow (phase field) & phase transport.

## Explore featured possibilities

The flow of a fluid is present in many rotating machinery applications, such as pumps, centrifuges, fans, mixers, etc.

Our COMSOL capabilities allows us to solve fluid flow equations in rotating frames, with either a full time-dependent description of the rotating system or an averaged approach based on the frozen rotor approximation.

In systems involving more than one fluid, we can use surface tracking methods to model and simulate the behavior of bubbles and droplets, as well as free surfaces

Critical or sonic flow will usually exist for most (compressible) gases or vapors discharging through the nozzle orifice of a pressure relieving valve.

Mathematically, sonic fluid flow refer to the gas flow at high Mach number. COMSOL CFD Module allows us to deal with compressible transonic and supersonic flows.

COMSOL is able to model & simulate flows in thin domains such as thin lubricating oil films between moving mechanical parts (tribology) or fractured structures.

Large Eddy Simulation (LES) one of the most promising and successful methodology for simulating turbulent flows with the improvement of computing power.

COMSOL has dedicated interfases for LES for single-phase flows:

LES RBVM, LES RBVMWV & LES Smagorinsky

## Multiphysics Coupling for CFD

There is a huge number of application involving both fluid flow and heat transfer.

COMSOL allows us to bidirectionally couple CFD and Heat Transfer.

The fluid flow affects the convection terms in the energy equation, while the fluid properties or bouyancy forces can in turn depend on temperature.

Many are the applications involvig fluid flow with diluted species. In general, the fluid flow affects the transport of species, but not viceversa.

In Silico capabilities with COMSOL, allows us to model & simulate such unidirectionally coupled phenomena by including the velocity field in the convection term of the species transport equation.

In some applications, fluid flow can be affected by the presence of electromagnetic fields.

This unidirectionally coupling can be simulated in COMSOL by making the fluid properties depend on the frequency of the electromagnetic field and/or include electric or magnetic volumetric forces acting on the fluid.

COMSOL basic license includes a mathematics interface, where both ordinary and partial differential equations can be implemented.

CFD Module can be bidirectionally coupled with custom equations through the coeficients and/or the source terms.