06-05-2014, 04:11 PM
Introduction to Computational Fluid Dynamics
Computational Fluid Dynamics.ppt (Size: 1.08 MB / Downloads: 23)
Learning Objectives
Make the student understand the role of C in FD, its applicability, potential and limitations
Give a basic foundation in numerical analysis, by teaching the relevance of accuracy and stability
Give a working idea of the various choices of numerical methods and discretization schemes by applying them to simple model equations. In doing this, always remind them of the connection with the big picture.
Make the student knowledgeable about the various terminologies in practical CFD (Grids, BCs, Approximations, Schemes etc)
Ingrain the basics of good CFD practice (be aware of the applicability/feasibility of a particular model, its limitations, choose the right boundary conditions, ascertain grid/time independence, verification/validation)
By the end of the class, the student should be in a position to set up simple aerodynamic problems and analyze them
What is CFD/FD ?
CFD is a branch of Fluid dynamics
So what really is Engineering Fluid Dynamics in the first place? Lets look at some examples:
We are interested in the forces (pressure , viscous stress etc.) acting on surfaces (Example: In an airplane, we are interested in the lift, drag, power, pressure distribution etc)
We would like to determine the velocity field (Example: In a race car, we are interested in the local flow streamlines, so that we can design for less drag)
We are interested in knowing the temperature distribution (Example: Heat transfer in the vicinity of a computer chip)
Roughly put, in Engineering fluid dynamics, we would like to determine certain flow properties in a certain region of interest, so that the information can be used to predict the behaviour of systems, to design more efficient systems etc..
Words of wisdom
(To be taken with a huge helping of salt
Theoretical Fluid dynamics: Most important. Everyone HAS to learn it.
Experimental Fluid dynamics: Important. Usually, everyone believes it except the person that conducted the experiment.
Computational Fluid dynamics: Also important. Usually, no one believes it except the person that performed the calculations.
A good engineer understands the pro’s and con’s of all three methods, and should be in a position to assess which one is best under the circumstances
More importantly, should not be prejudiced against any of the three approaches
Procedures in CFD
Identification of right approximation (Viscous/Inviscid, Laminar/Turbulent, Incompressible / compressible, Single-phase/multi-phase)
Identification of right solution method (Finite Element / Difference/Volume, Structured/Unstructured mesh, Order of accuracy)
Pre-processing (Generate computational grid, assign boundary conditions, set initial conditions, compile code, prepare input parameters)
Solution (Run the code, monitor the solution)
Post-processing (Collect and organize data, analyze results)
Verification (Do the results make sense? Are the trends right? Does it agree with previous calculations on similar configurations?)
Validation (Does the result (or an aspect of the result)) agree with theory/experiment?)
At every step, good understanding of theoretical fluid dynamics is essential!!!