Computers in Engineering

A look at computer simulation

Various simulation products have been developed by companies such as LMS Intl., AEA Technology plc., and Flomerics, with the goal of improving processing speed and development time.

As processing speeds and capacity increase, so will engineers' use of computer software. Much innovation has been packed into in various CAD software used by the engineering community, but the advantages of simulation have only just begun to be realized. With product development cycles shrinking in the midst of improving time-to-market, far less initial testing is being performed in favor of computer simulation.

Various types of simulation are found in the aerospace industry. Most obvious is the use of Computational Fluid Dynamics (CFD), a numerical analysis of fluid flow, heat transfer, and related phenomena. There are also packages designed to simulate loading, acoustics, and kinematics.

In this month's Computers in Engineering feature story, Aerospace Engineering Online takes a closer look at a few of these simulation software packages.

LMS DADS 9.6 and SYSNOISE 5.5
LMS International has recently announced the release of its mechanical simulation software, LMS DADS 9.6, as well as its plans to deliver its vibro-acoutics simulation software, LMS SYSNOISE 5.5, worldwide.

LMS DADS 9.6's dynamic and static solvers feature several improvements that have resulted in a simulation speed 10-100 times quicker than previous versions.

Many manufacturers already are using DADS virtual prototyping software to predict and analyze the dynamic behavior of vehicles, aircraft, and other mechanical systems during the design phase. The latest release is part of a comprehensive suite of physical and digital prototyping tools from LMS that enable engineers to integrate actual test data with virtual prototypes to optimize the durability, acoustic, vibration, and dynamic performance of its products, reduce engineering costs, and shorten time to market.

DADS 9.6 provides significant customer-driven enhancements in both the Dynamic and Static Solvers resulting in solution speed improvements of 10-100 times for certain applications. The software's open architecture allows template-based interfaces to be designed that capture engineering knowledge through parameterized forms for specific simulation applications such as engines, timing belts, landing gear, motorcycles, and vehicle suspensions. Additionally, improved interfaces to other LMS Test and CAE products for durability, vibro-acoustics, and optimization are making it possible to analyze multiple design concepts and optimize product performance for multiple attributes in a single day.

The new release features several enhancements such as increased dynamic and static solver speeds. In some applications, solution speeds have been improved by a factor of 10-100 without any loss in accuracy. This is made possible through enhanced support for the Harwell Sparse Matrix Solver and Analytical Jacobians for all elements, which results in increased solver stability and speed.

Dynamic simulation results include forces, accelerations, velocities, positions, and photo-realistic animation.

Another benefit of the software is its durability and vibro-acoustics interface. Improved use of load time histories results as inputs to fatigue studies with LMS TecWare and LMS FALANCS. Additionally, surface velocities can be exported for vibro-acoustic studies with LMS SYNOISE.

Other software improvements include:

• Optimization interface - Enables users to perform design of experiments and response surface modeling of mechanical system design parameters quickly and esily with the state-of-the-art technology of LMS Optimus.
• Expression simplification - Simplifies using custom equations to represent complex system behavior. These elements can now be applied as a force directly to flexible bodies.
• Differential equations element - Streamlines the process of using first order differential equations as force inputs to the mechanical system so that users are able to define custom forces such as hydraulic actuators or shock absorbers.
• Drivers reference expression - Driver elements are able to reference user-defined equations in an expression element. This allows a custom equation to define kinematic relationships in a system without the need to write a user-defined subroutine.
• Force expression - Equations defined by the user in an expression element to apply forces onto a system can now include terms that are measured from other force elements in the model.

LMS SYSNOISE 5.5 is part of a comprehensive suite of physical and digital prototyping tools offered by the company that enables engineers to optimize their products for motion, ride and handling, structural integrity, noise and vibration, acoustics, and durability. This latest product release represents another step toward the company's goal of making its products faster and easier to operate. While previous releases have brought considerable progress in terms of user interface, solution capabilities, and solver speed, Revision 5.5 introduces a revolutionary acoustic transfer vector (ATV) concept as the technology basis of four new solution sequences that are available as add-on capabilities - Acoustic Transfer Vector Response, Numerical Engine Acoustics, Inverse Numerical Acoustics, and Panel Acoustic Contribution Analysis.

In the past, manufacturers have studied noise, vibration, and harshness by testing physical prototypes late in the development process. At this stage, design changes are expensive and time-consuming to implement. With the ATV concept, LMS SYSNOISE enables engineers to predict noise levels of their designs early on in the design cycle and fully concurrent with other simulation tasks.

The CFX family
AEA Technology has released a new version of its CFD software designed to significantly shorten computing time. CFX-5 combines direct CAD import, automatic adaptive meshing, and CFX's unique Coupled Algebraic Multigrid solver, which solves flow equations simultaneously.

Pressure contours of the F-22 Raptor were analyzed using CFX-5.

The new version extends CFX-5's capabilities to multiphase flows. According to AEA Technology, the multiphase flow module provides a technology that is an order of magnitude faster in predicting chemical engineering process flows over other products.

Within the software's solver, linearized momentum and continuity equations are solved simultaneously for velocity and pressure. This greatly increases the robustness of the product, requiring far fewer iterations to achieve convergence and minimizing user intervention to achieve that convergence. The use of coupled algebraic multigrid to solve the coupled linear system provides a scalable algorithm in the sense that CPU time increases linearly with problem size rather than exponentially compared to traditional technology.

AEA Technology has also announced that major improvements have been performed on its blade design software, CFX-BladeGen. As its name suggests, the software is a specialized 3-D software tool for the rapid design of rotating machinery components. A unique feature of the product is its Plus module, which enables rapid 3-D viscous flow screening of the design through an embedded and fully automated CFD solver. This permits early pre-selection of profiles and reduces the number of iterations needed to deliver an optimum design.

"This is a major improvement in blade design software," explained George Bache of AEA Technology. "Designers can now evaluate realistic geometry and physics in timeframes that fit well within typical design cycles. Used appropriately, it can save time and money in both design and manufacturing processes. Engineers are able to fully integrate 3-D blade design, computational fluid dynamics, and CAD."

A turbine blade internal cooling passage was modeled with CFX-5.

Functions such as 3-D-model generation and post-processing are simplified and automated, allowing engineers with minimal CFD experience to operate the tool effectively. More complex applications are also possible with the software, allowing the most minute details in blade design to be evaluated. The software can be used for axial, mixed-flow, and radial blades in applications such as pumps, compressors, fans, blowers, turbines, expanders, turbochargers, and inducers.

A variety of data sources can be used with this software, including line drawings, IGES, and generic data files. CFX-BladeGen exports to CAD/CAM through IGES, DXF, or ibl.

AEA Technology has also developed other products aimed at improving the design process of aircraft engines. CFX-TASCflow enables engineers to understand the interaction of the physical processes beforehand and reduce design time and cost. The latest version of the software, CFX-TASCflow 2.10, features several new enhancements:

• Advanced turbulence models - A number of state-of-the-art turbulence models have been added, including a second moment closure model and a k-omega model.
• Rotating machinery pre-processing - A new pre-processing function provides a unified environment for setting up rotating machinery analysis.
• Cavitation - The model allows cavitation predictions that are critical to certain liquid flow applications.
• Moving grid - This capability makes it possible to model situations such as moving piston flows, solid/fluid interaction, and relative motion between components and free surfaces.
• Pre-processing speed - This release provides 10-100 times faster pre-processing speed than previous versions.

CFX-BladGenPlus was used to design and evaluate performance of a turbine stator.

CFX-TurboGrid 1.5 also features some enhancements aimed at improving development time such as a new viewer, tandem vane template, double-precision accuracy mesh creation, and mesh optimization. The software's new post-processing viewer provides options for assessing mesh quality in 3-D, blade-to-blade, and meridional views. The double-precision feature offers more robustness during mesh creation, with a slight increase in processing time over the single-precision option. To reduce the time needed to optimize mesh quality, templates have been enhanced in their initial placements of control points.

Flotherm
Flomerics has finished the latest edition of its electronics thermal analysis software, Flotherm Version 3.1. The software features an "Explorer-style" browser for increased ease of use and new solver technology offering significantly faster solution times. Also added to the software were MCAD interface enhancements; "SmartParts" for IC packages, heat sinks, and heat exchangers; and a new "CommandCenter" module that provides fast, efficient parametric studies and distributed processing.

Temperature variations in a handheld cellphone virtual prototype are shown in Flotherm.

"All our development efforts are focused on improving speed and simplicity, and hence maximizing design productivity for our customers," said Mike Reynell, Director of Marketing at Flomerics. "At the same time, we are moving rapidly towards a new, broader solution for designers of electronic equipment, which we are calling 'integrated physical design' in which thermal analysis is linked to mechanical stress and electromagnetic analysis via common data models."

Several enhancements made with Version 3.1 include:

• Command center module - This enables engineers to create multiple design variations on an initial baseline model and quickly determine the optimum design.
• "SmartPart" compact package library - The library enables users to quickly, efficiently, and accurately solve complex designs featuring numerous onboard packages. It also uses a new integrated network solver for quick interaction between resistance network and Flotherm's resident CFD solver.
• "SmartPart" compact heat sink library - This features detailed or compact representations of plate or pin fin heat sinks that take considerable time to model manually. These are now available for incorporation into designs, making the modeling process more efficient.
• Heat exchanger "SmartPart" - The module allows users to define a thermostat at a point in space, which can be used to turn a heat exchanger on or off at a specific point in time.
• Multi-grid solver - This has been added to the software to further enhance solution times and remove any dependency on block correction for conjugate heat transfer problems.
• Parallel solver - The solver is responsible for controlling the number of processors used to solve a problem.
• Simplified gridding - The gridding of designs required to solve heat transfer and airflow across the model has been simplified to provide greater control for more detailed calculations.
• FLO/MCAD module - This intelligently filters geometric data from MCAD software to produce a simplified "thermal equivalent model," thus reducing the time required to perform thermal analysis.

The latest version of Flotherm is designed to run on NT, HP, SUN, IBM, and SGI platforms.