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Introduction to CFD

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What is CFD?

Using abacus to computers, we have certainly come a long way. It’s been more than two hundred thousand years since the first Homo sapiens appeared on earth. Life has never been faster than that of the previous century. Man learned to fly. Then man learned to fly smarter. CFD certainly has played its part in it.

Fluid dynamics is a field of engineering which studies physical laws governing flow of fluids under various conditions. An extensive amount of effort has gone into understanding the governing laws and the nature of fluids themselves, resulting in a complex yet theoretically strong field of research.

Computational Fluid Dynamics or CFD as its popularly known as is simulations of flows with the help of computers. CFD involves solution of governing laws of fluid dynamics numerically. The complex set of partial differential equations are solved on a geometrical problem divided into small volumes, commonly known as mesh (or grid).

CFD has enabled us to see the world as never before. It was never before possible to see what its like to be in a furnace. It was never before possible to see how our blood flows in our arteries and veins. It was never before that we saw the possibility of a walk into computational never-land. CFD enables analysts to simulate and understand fluid flows without the help of instruments for measuring various flow variables at desired locations.

Where CFD scores

There are various reasons why CFD is becoming popular, some of which are:

  • CFD allows numerical simulation of fluid flows, results for which are available for study even after the anaylsis is over. This is a big advantage over, say, wind tunnel testing where analysts have a shorter duration to perform flow measurements.
  • CFD allows observation of flow properties without disturbing the flow itself, which is not always possible with conventional measuring instruments.
  • CFD allows observation of flow properties at locations which may not be accessible to (or harmful for) measuring instruments. For example, inside a combustion chamber, or between turbine blades.
  • CFD can be used as a qualitative tool for discarding (or narrowing down the choices between) various designs. Designers and analysts can study different prototypes numerically and decide to experimentally test only the ones which show promise by numerical simulation.

What CFD is not

  • CFD is not yet at the level where it can be blindly used by designers or analysts without working knowledge of numerics involved.
  • Despite the increasing speed of computation available, CFD has not yet matured to a level where it can be used for real time computation. Numerical analyses require significant time to be set up and performed.
  • CFD is still an aid to other analysis and experimental tools like wind tunnel testing and is used in conjunction with them.
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