Multiphysics problems require a variety of advanced and flexible solutions. Omnis™/Open-DBS with OpenLabs™ allows engineers to solve multi-phase, -fluid, and -species challenges with both the fastest technology on the market and a freely customizable interface that can be tailored to specific applications.

The Omnis™/Open-DBS solution includes access to the trusted FINE™/Open tool.

High-speed external flows can be a challenging endeavor, especially at transonic or supersonic to hypersonic speed.

With the Open solver and its density-based formulation, modeling flows that reach Mach numbers up to 20 for re-entry is a breeze.

The capabilities of the solver ensure fast and accurate flow solution, even for the most complex cases.

Modeling combustion applications implies handling multiple species together with complex physical and chemical reactions. Conjugate heat transfer and radiation have a large impact on the control of the temperature distribution and on combustion efficiency.

To respond to these requirements, Omnis™/Open-DBS offers several modeling strategies including the classical flamelet, the hybrid BML/flamelet method, and the Flamelet Generated Manifolds method (FGM) to analyze the range of purely non-premixed gaseous to purely premixed combustion applications.

The combustion model can be coupled with pollutant prediction, radiation, and conjugate heat transfer analysis.

Cavitation occurs in liquid flows when the pressure drops below the saturation pressure. It is observed in pumps, nozzles, injectors, marine propellers and underwater bodies and often causes loss in efficiency, increase of noise level, structural damages or erosion.

Our software offers three modelling approaches to analyze cavitation: the barotropic law, thermo-tables, and transport-equation modeling.

Cavitation inception: Left, no local refinement – Right, dynamic mesh adaptation

Our experience extends to cryogenic flow simulations, with advanced modeling for cavitation and phase change in thermo-sensitive fluids.

Multiphysics applications often involve two or more fluids of different nature or of different phases of the same fluid. These form mixtures and interactions occur between each.

The Open solver offers a wide range of multifluid modeling approaches whose domain of application depends on the physical properties, concentration and homogeneity of the mixture.

The thermo-tables fluid definition captures the phase change phenomena. The inert or reacting multispecies model describes the mixture of gases or liquid such as pollutant tracking. The Lagrangian particles model tracks the motion of dilute dispersed particles and their interaction with the main phase, for example sprays, particulate flows, cyclones. These models can be coupled with all other physical phenomena of the multiphysics environment.

The OpenLabs™ module provides a simple and easy-to-learn syntax that allows the user to customize most of the routines of the solver, including adding or editing source terms, equations, controlling the initialization, the fluid properties or the boundary conditions.

These modifications are automatically compiled, which makes them execute as fast as if they were implemented in the solver source code.

Computation of a full engine using Omnis™/Open-DBS’ NLH and combustion models

With the purpose of meeting future aircraft engine requirements in terms of low emissions, high reliability and efficiency, a novel highly efficient fully-coupled RANS-based approach has been developed, enabling the simulation of a full aero-engine within a single code.

One of the advantages of a fully coupled approach over a component-by-component approach is that the boundary conditions at the interfaces do not need to be guessed.

A Smart Interface methodology ensures a direct coupling between the different engine components, compressor- combustor-turbine, and allows the CFD models to vary between each component within the same CFD code.

For the simulation of the combustion process, the Flamelet Generated Manifold (FGM) method is applied. While the approach is superior to classical tabulated chemistry approaches and reliably captures finite-rate effects, it is also computationally inexpensive.

The Nonlinear Harmonic method is used to model the unsteady interaction between the blade rows as well as the influence of the non-homogeneities at the combustor outlet on the downstream turbine blade rows. This method is 2 to 3 orders of magnitude faster than a classical URANS simulation.

Gain 3 orders of magnitude in solving speed for unsteady simulation.

The presence of components such as hoods, collectors, or volutes can be taken into account for a better assessment of the performance of the turbomachinery. Non-axisymmetric pressure variations can be modeled with the Nonlinear Harmonic method, with domains that can be non-periodic and meshed with mixed grids.

With the Non-Linear Harmonic method, users can solve transient behavior 100 times faster than a classic unsteady analysis, capturing phenomena like clocking, blade row interactions, tonal noise, inlet distortion…

Impeller volute – Image courtesy of Liebherr

This unique technique computes the unsteady flow field by means of the Fourier decomposition of the periodic fluctuations, based on a pre-selected number of harmonics, typically associated with the blade passing frequencies and their multiples.

Fluid-Structure Interaction (FSI) occurs when a fluid flow deforms a structure which in return influences the flow field.

The significance of aeroelastic instabilities has increased substantially in the last few decades, particularly in the industry of aviation and turbomachinery. A continuous trend towards lightweight and cost-efficient design forces engineers to push the boundaries in the design phase with the risk of leading to vibratory stresses and, in the worst case, to vibratory failure. Cadence offers several approaches to predict fluid-structure interactions depending on:

• the direct coupling between the flow and the structural solvers,

• the use of the coupling server MpCCI, which manages the communication and the interpolation of coupling data between the fluid and structure solvers,

• or the modal approach in the flow solver that takes advantage of the harmonic solution of the NLH method and solves the modal equations, to compute the global deformation of the structure written as a composition of mode shapes, removing the necessity of interpolation between fluid and solid domains.

The Omnis™/Open-DBS CFD solution is optimized by scaling linearly on thousands of CPU cores, as well as on GPU.

Combined with our patented CPUBooster™ technology, a unique convergence acceleration technique, computation time is reduced even further.

The total package renders the solution up to 20 times faster than any other solution on the market.