White Papers

FloEFD is a unique CAD-embedded general purpose concurrent CFD software package largely automated to minimize the specialist expertise required to operate traditional CFD software. CAD-embedded CFD must simulate complex industrial turbulent flows with heat and mass transfer without simplifying the highly complex geometries. FloEFD is a mature code with over 10 years of commercial presence and a thousand man-years of development effort behind it. It's turbulence capabilities have been validated against some classic industrial CFD cases. It utilizes a modified k-ε two-equation turbulence model designed to simulate accurately a wide range of turbulence scenarios in association with its pioneering immersed boundary Cartesian meshing techniques that allow accurate flow field resolution with low cell mesh densities.

The classical two-equation k-ε empirical model for simulating turbulence effects in fluid flow CFD simulation is widely used and considered reliable for most industrial CFD simulations and it requires the minimum amount of additional information to calculate the flow field. In FloEFD the k-ε model is used with a range of additional empirical enhancements added to cover a wide range of industrial turbulent flow scenarios (such as shear flows, rotational flows etc.). For instance, damping functions proposed by Lam and Bremhorst for better boundary layer profile fit when resolving boundary layers with computational meshes have been added. This is coupled to a unique Two-Scale Wall Function (2SWF) treatment. This two-scale approach allows FloEFD to overcome the traditional CFD code restriction of having to employ a very fine mesh density near the walls in the calculation domain.

For the numerical simulation of Navier-Stokes equations, the choice of the mesh type plays a significant role. Comparative calculations on different mesh types illustrates that the best simulation precision, characterized by minimum Local Truncation Error (LTE), is obtained on Cartesian meshes. For the boundary representation the Immersed Boundary (IB) approach, which does not require a boundary-conforming mesh, is used. Use of Cartesian meshes together with Immersed Boundary approach makes it possible to efficiently: minimize approximation errors; build operators with good spectral properties, so that robustness of method is guaranteed; speed up the process of grid generation; and make grid generation robust and flexible. Many other CFD methods require a mesh that fits the boundaries of the computational domain and often complex internal geometries. The body-fitted grid generation used is time-consuming, often requiring manual intervention to modify and cleaning-up the CAD geometry as a pre-requisite.

To implement the IB approach efficiently in FloEFD, a number of issues needed to be resolved: approximation of the governing equations in cut-cells that contain the solid-fluid interface; capture of boundary layers effects irrespective of boundary layer thickness using a Two-Scale Wall Functions (2SWF) approach (see Mentor Graphics Corp., 2011); automatic mesh generation with automatic detection of initial mesh settings (octree-based mesh structure); and Solution Adaptive Refinement (SAR).

Test cases given in this paper represent a small selection of our validation examples that illustrate the IB approach precision and flexibility of FloEFD meshing technology in the wide range of industrial examples of geometry and physical formulations.

A new class of analysis software, Concurrent CFD, has proven to be very effective for performing heat, fluid and airflow analyses and optimizing the design and manufacture of automotive parts and systems including heating, cooling, fuel injection, and even body panels. Traditional CFD approaches have been difficult or cumbersome but with Concurrent CFD software, mechanical design teams can accelerate the design process and increase their productivity. This paper includes two case studies using EFD for automotive design applications.

This paper explains how Concurrent Computational Fluid Dynamics (CFD) technology has become a cornerstone for aerospace mechanical design today. Designers must perform flow analysis on a broad range of components and subsystems such as hydraulic valves and cockpit ventilation systems. Almost all aircraft elements that come into contact with liquids or gases or that conduct heat from a device will require fluid flow analysis. Thus, flow analysis will help engineers save cost, time and weight in their aerospace system design by revealing hidden design weaknesses and enabling the designer to optimize the design for greater performance.

• CFD Market Drivers—a brief review of the challenges that affect, and impacts from the early use of CFD within an overall Product Lifecycle Management (PLM) strategy
• Value of Earlier Use of CFD—a brief discussion of the benefits associated with early use of CFD
• Mentor Graphics’ Approach and CFD Solution—how FloEFD enables early use of CFD by designers
• Summary and Concluding Comments—a brief summary of the paper along with concluding remarks

This white paper describes the application of CFD to gas mixing processes, including a discussion of best practice backed up by simulation guidelines and a real world example. The paper concludes with an analysis of the financial impact of using CAD-embedded CFD for gas mixing through reduced design iteration and fewer physical prototypes based on data from Aberdeen Group.