Cadence CFD Technology Update – Turbomachinery Workflow

In the design world, pushing the boundaries of traditional workflows is a constant pursuit for designers. It takes a lot of effort and expertise to achieve better performance, especially when dealing with complex and unconventional geometries. The Cadence Fidelity Flow for Turbomachinery is a unique toolset that encompasses a complete end-to-end solution: 1D to 3D design, meshing, CFD, and optimization, all in one single environment. Whether you are looking to improve simulation accuracy or reduce turnaround time for your turbomachinery applications, Fidelity Flow has the required tools to tackle even the most difficult design tasks with ease and efficiency.

Updates to Cadence Fidelity CFD Turbomachinery Workflow

The Cadence Fidelity CFD team is currently working on integrating legacy meshing features into the User Interface (UI) for turbomachinery workflow. They are also enhancing meshing algorithms and innovating the workflow with mixed meshes. The CFD solvers are frequently updated to ensure their ability to cater to various applications. The technology integrates both pressure-based and density-based approaches, effectively serving both low and high-Mach applications. Below are a few updates to the Fidelity Flow for Turbomachinery, which can ease the CFD workflow –

Memory Allocation for NLH - New Equations-Based Partitioning

The memory allocation process has been updated to calculate and utilize the necessary RAM, based on the perturbations and harmonics within the domains.

Mesh distribution ≠ equations distribution

When employing the flexibility of the Non-Linear Harmonics (NLH), optimizing memory distribution can result in a 30% speed boost and reduced RAM usage.

A New Rotor/Stator Interface in Fidelity Fine Turbo

Fine Turbo offers a wide range of Rotor/Stator interfaces, with and without non-reflecting capabilities. Another approach is to utilize Giles non-reflecting capability as well as the ability to balance flux on both sides of the interface.

Absolute Mach Number for Rotor/Stator Interface using (i) full mesh (top left), (ii) mixing plane (bottom left), (iii) new approach (2D NR+ flux balance) (top right), (iv) NLH-3 (bottom right).

New Boundary Conditions

Here are three newly added boundary conditions that can optimize your workflow:

1. Setting the pressure profile when setting the mass flow rate for an outlet.

2. Flexibility to use the temperature field results from a previous run as a boundary condition for the next simulation.

3. Setting turbulent quantities (k-eps) at an injection inlet rather than relying on automatically computed values.

Additional H Block

With an additional azimuthal block, better control over the tangential direction is achieved without increasing the number of points in the stream direction, and this feature is now available for all supported topologies.

Export Autogrid Mesh for High-Order Solvers

The unstructured CFD General Notation System (CGNS) format provides crucial information for creating high-order grids. It leverages the multigrid nature of the Autogrid mesh to generate high-order elements, enabling more accurate simulations.

Updates/New Features in Fidelity Autogrid

Fidelity Autogrid offers a wide range of functions that can be easily performed. It allows you to import hub and shroud using CAD surfaces or a geomTurbo file. Additionally, you can import the actual surfaces of the blade and create a water-tight domain by revolving the end walls and creating the necessary periodic surfaces. Lastly, Autogrid can position the seed point within the domain for an unstructured grid. Below are a few new features or updates in Fidelity Autogrid that might interest you.    

Seed point within the domain for unstructured meshing.

Surface Import for End-Walls

When importing CAD files, selecting multiple lines and segments can be a tedious task. To simplify the process, surfaces and curves can be chosen to create meridional curves. Additionally, for creating an Autogrid mesh, mechanical geometries can be effectively handled by using them as a basis.

Seed point within the domain for unstructured meshing.

Reverse End-Walls Curves Orientation

If the CAD import fails, we can reverse the hub and shroud curves and recompute the channel and inlet/outlet boundaries.

Reversing orientation of end-walls.

Improve Quality in zR-Effects

It's important to consider the degree of freedom when creating a mesh for cavities. The walls require a first cell size, whereas inlets and outlets have fewer constraints. A new algorithm has been developed to prevent a decrease in the mesh quality. The algorithm helps to establish better continuity between the hub/shroud first cell size and the cavity mesh.

Improved quality of mesh.

Updates/New Features in Fidelity Hexpress

Fidelity's Hexpress leverages surface-to-volume mesh for turbomachinery applications. Different design steps require varying fidelity levels: a fast structured grid for estimating performance and optimizing layout, blades, and end-walls. This is followed by full aero-mechanical analysis and design verification.

Preliminary aerodynamic design (left), detailed aeromechanical design (right).

Meshing with the S2V Algorithm

Turbomachinery components usually have a high surface-to-volume ratio, which means that surfaces play a more significant role than volume. Unlike the Octree algorithm, the solid-to-volume (S2V) algorithm allows the mesh to adapt better to the geometry. This means that fewer cells are required to capture the geometry accurately.

Fewer cells to capture the geometry using the S2V algorithm.

Matching Nodes on Periodic Boundaries

This feature allows for matching periodic boundaries for structured and unstructured meshes, improving geometry and mesh model accuracy, simplifying workflows, and increasing automation.

Matching mesh for improved mesh model accuracy.

Fidelity Solvers and Turbomachinery-Dedicated Post-Processing

Cadence Fidelity provides a range of solvers for low-to-high Mach applications, which include RANS and LES solvers. These solvers can be used with structured, unstructured, and mixed grids. They come equipped with Multiphysics models designed for different applications and are GPU-accelerated to enhance the solver performance.

NASA source diagnostic test (SDT) low-noise outlet guide vane (OGV), approach conditions simulated (Pt ratio ~ 1.5).

The Fidelity turbomachinery-dedicated post-processing tool can generate blade-to-blade and pitch-wise average views from structured or unstructured meshes. It also offers more flexibility for users to customize calculations.

Blade-to-blade and pitch-wise average view using Fidelity post-processing tool.

In short, Cadence Fidelity CFD offers a highly advanced turbomachinery design workflow encompassing a vast array of industrial components, made possible by the seamless integration of specialized features for turbomachinery. Our team of experts at Cadence CFD is dedicated to developing workflows that can handle even the most intricate and modern components in order to provide our customers with top-quality designs that are tailored to their unique requirements. With our comprehensive range of capabilities, we can ensure that every project is completed with the utmost precision and efficiency, delivering exceptional results every time.

If you would like to try Cadence Fidelity CFD for your turbomachinery applications, request a demo today!