Glossary of MCAE Terms
Please add terms - and insert them in alphabetical order.
Abstract modeling: Provide analysis data definition independent of design/concept/mesh instance, so that analysis can be defined once and applied repeatedly to data sets that can be modified between iterations, even if the topology has changed.
Acoustic:
CFD: see Computational fluid dynamics
Computational fluid dynamics: Computational fluid dynamics (CFD) is one of the branches of fluid mechanics that uses numerical methods and algorithms to solve and analyze problems that involve fluid flows. Computers are used to perform the millions of calculations required to simulate the interaction of fluids and gases with the complex surfaces used in engineering. Even with simplified equations and high-speed supercomputers, only approximate solutions can be achieved in many cases. Ongoing research, however, may yield software that improves the accuracy and speed of complex simulation scenarios such as transonic or turbulent flows. Validation of such software is often performed using a wind tunnel.
Electric and magnetic field simulation:
Explicit analysis:
Explicit dynamics:
Fluid dynamics:
Fluid dynamics is the sub-discipline of fluid mechanics dealing with fluid flow: fluids (liquids and gases) in motion. It has several subdisciplines itself, including aerodynamics (the study of gases in motion) and hydrodynamics (the study of liquids in motion). Fluid dynamics has a wide range of applications, including calculating forces and moments on aircraft, determining the mass flow rate of petroleum through pipelines, predicting weather patterns, understanding nebulae in interstellar space and reportedly modeling fission weapon detonation. Some of its principles are even used in traffic engineering, where traffic is treated as a continuous fluid.
Fluid dynamics offers a systematic structure that underlies these practical disciplines and that embraces empirical and semi-empirical laws, derived from flow measurement, used to solve practical problems. The solution of a fluid dynamics problem typically involves calculation of various properties of the fluid, such as velocity, pressure, density, and temperature, as functions of space and time.
Fluid structure interaction:
Fluid-structure interaction (FSI) occurs when a fluid interacts with a solid structure, exerting pressure on it which may cause deformation in the structure and thus alter the flow of the fluid itself. Such interactions may be stable or oscillatory, and are a crucial consideration in the design of many engineering systems, especially aircraft. Failing to consider the effects of FSI can be catastrophic, especially in large scale structures and those comprising materials susceptible to fatigue. The Tacoma Narrows suspension bridge is probably one of the most infamous examples of large-scale failure.
Aside from its destructive potential, FSI is responsible for countless useful effects in engineering. It allows fans and propellers to function; sails on marine vehicles to provide thrust; aerofoils on racecars to produce downforce, and our lungs to inflate when we breathe.
Broadly speaking, fluid-structure interactions can be classified into three groups - zero strain interactions, such as the transport of suspended solids in a liquid matrix; constant strain steady flow interactions, e.g. the constant force exerted on an oil-pipeline due to viscous friction between the pipeline walls and the fluid; and oscillatory interactions, where the strain induced in the solid structure causes it to move such that the source of strain is reduced, and the structure returns to its former state only for the process to repeat. It is the latter of these that allows reed instruments to actually produce sound, in which case the systems of equations governing their dynamics have oscillatory solutions. The act of "blowing a raspberry" is another such example.
Traditionally, fluid and solid dynamical systems have been solved independently. However, for problems where there is sufficient coupling between the two systems, such separation is not possible and the resultant systems are invariably too complex to solve analytically. Computational fluid dynamics is essential in predicting the behaviour of such systems, and extensive research is ongoing in this now well-established field.
Kinematics: (Greek κινειν, kinein, to move) is a branch of dynamics which describes the motion of objects without consideration of the circumstances leading to the motion. An example is the prediction of centripetal force in uniform circular motion, regardless of whether the circular path is due to gravitational attraction, a banked curve on a highway, or an attached string. In contrast, kinetics is concerned with the forces and interactions that produce or affect the motion.
The simplest application of kinematics is to point particle motion (translational kinematics or linear kinematics). The description of rotation (rotational kinematics or angular kinematics) is more complicated. The state of a generic rigid body may be described by combining both translational and rotational kinematics (rigid-body kinematics). A more complicated case is the kinematics of a system of rigid bodies, possibly linked together by mechanical joints. The kinematic description of fluid flow is even more complicated, and not generally thought of in the context of kinematics.
Linear static analysis: Linear static analysis allows engineers to test different load conditions and their resulting stresses and deformation. Knowing how a design will perform under different conditions allows engineers to make changes prior to physical prototyping, thus saving both time and money.
MCAD: Mechanical computer-aided design. Software used for creating engineering models and drawings.
MCAE: Mechanical computer-aided engineering. A category of software encompassing a variety of tools for engineering analysis including:
• Stress and strain;
• Modes of vibration;
• Thermal and fluid-flow;
• Computational fluid dynamics (CFD);
• Kinematics;
• Mechanical event simulation (MES);
• Analysis tools for process simulation for operations such as casting, molding, and die press forming;
• Electric and magnetic field simulation;
• Optimization of products or processes.
• RAVDA: Rapid analysis and validation of design alternatives.
Mechanical event simulation:
MES: see Mechanical Event Simulation
Model Fidelity: CAE tools are used at various levels of model fidelity starting from models formed with equations solved using tools such as Excel, MATLAB, MathCAD, etc., to full 3-D model fidelity solved using methods such as FEA using meshes. There is a huge chasm that separates the world of engineering analysis without CAD geometry and analysis that starts with CAD geometry. The former includes general math tools such as Excel (used extensively in the aerospace industry) and specialized systems engineering tools such as Easy5 (originally from Boeing and purchased by MSC). There is a significant amount of analysis done with these sorts of tools. The data generated by the first category are completely segregated from the CAD-based CAE data. People/expertise is also segregated.
Modes of vibration: A normal mode of an oscillating system is a pattern of motion in which all parts of the system move sinusoidally with the same frequency. The frequencies of the normal modes of a system are known as its natural frequencies or resonant frequencies. A physical object, such as a building or bridge, has a set of normal modes (and frequencies) that depend on its structure and composition.
It is common to use a spring-mass system to illustrate a deformable structure. When such a system is excited at one of these natural frequencies, all of the masses move at the same frequency. The phases of the masses are either exactly the same or exactly opposite. The practical significance of this can be illustrated by a mass-spring model of a building. If an earthquake excites the system near one of the natural frequencies, the displacement of one floor with respect to another will be maximum. Obviously, buildings can only withstand this displacement up to a certain point. Modeling a building by finding its normal modes is an easy way to check the safety of the building's design. The concept of normal modes also finds application in wave theory, optics and quantum mechanics.
Multiphysics: This treats simulations that involve multiple physical models or multiple simultaneous physical phenomena. For example, combining chemical kinetics and fluid mechanics or combining finite elements with molecular dynamics. Multiphysics typically involves solving coupled systems of partial differential equations.
Almost any physical simulation involves coupled systems, like E and B (electric and magnetic) fields for electromagnetism or pressure and velocity for sound or the real and the imaginary part of the quantum mechanical wave function. Or consider the mean field approximation for the electronic structure of atoms, where the electric field and the electron wave functions are coupled.
Abaqus, ANSYS Multiphysics, CFD-ACE+, CFD-FASTRAN, COMSOL Multiphysics, LS-DYNA, NEi Nastran and OOFELIE are some examples of commercially available software packages for simulating multiphysics models. These software packages mainly rely on the Finite Element Method or similar commonplace numerical methods for simulating coupled physics: thermal stress, electromechanic interaction, fluid structure interaction (FSI), fluid flow with heat transport and chemical reactions, electromagnetic fluids (magnetohydrodynamics or plasma), electromagnetically induced heating. In many cases, to get accurate results, it is important to include mutual dependencies where the material properties significant for one field (such as the electric field) vary with the value of another field (such as temperature) and vice versa.
Nonlinear Static:
Nonlinear coupled physics:
Optimization: The design and operation of a system or process to make it as good as possible in some defined sense.
PIDO: process integration and design optimization software. The “process
integration” portion involves capturing and automating processes using graphical
symbolism, facilitating the combining of disparate tools into a single workflow. Thus,
everything from specifications through manufactured and delivered products is linked, so
that changes in any aspect of the process are reflected in all other aspects.
Process simulation for operations: such as casting, molding, and die press forming
RAVDA: Rapid analysis and validation of design alternatives
Stochastic CAE: based on Monte Carlo techniques. These approaches have not received the attention they deserve. Instead of getting results based on nominal dimensions and characteristic values for material properties, they simulate the statistical variability that actually occurs and interpret the results statistically.
Stress and strain: Stress is a measure of the average amount of force exerted per unit area. It is a measure of the intensity of the total internal forces acting within a body across imaginary internal surfaces, as a reaction to external applied forces and body forces.
Strain is the deformation of materials caused by the action of stress. Strain is calculated by first assuming a change between two body states: the beginning state and the final state. Then the difference in placement of two points in this body in those two states expresses the numerical value of strain. Strain therefore expresses itself as a change in size and/or shape.
Thermal and fluid-flow:
Voxel approach: