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Tuesday, June 12, 2001

CFD and aviation

Computational Fluid Dynamics (CFD) is
increasingly used in aerodynamic studies 
like those in the construction of the India’s Light Combat Aircraft (LCA)

In the late 80s, fire broke out at King’s Cross Underground station in London and 31 people were killed. During the investigations, computer simulations of the flow of air at the accident spot was used to explain the exact reason behind the incident. It was study of motion of fluids with aid of computers, also known as Computational Fluid Dynamics (CFD).
According to experts, the CFD is the state of the art technique for simulating fluid-flow and related heat and mass transfer by numerically solving the governing equations on a high speed digital computer. The rapid growth in computer power and the maturity of available software technology have propelled CFD from academic research to a proven, reliable analysis tool applicable not only in engineering but in every way of life including aviation, health, traffic management and pollution control.
Many aviation companies including Boeing Company and Aerospatiale are effectively using CFD techniques in the design of critical features and components in their new aircraft versions. These techniques have also been utilised in the indigenous development of Kaveri engine for India’s Light Combat Aircraft (LCA) which has already made several successful test flights with GE engine. Paris-based Transoft International, which has centre in Bangalore, has provided CFD software package - Fluidyn NS for validating design of combustor and afterburner and also for evaluating the effect of upstream disturbances and compressor performance of the LCA engines before giving the final fitness certificate.
“The toughest challenge faced by an aircraft designer is to understand the dynamics of fluid flow. This governs not only the interaction between aircraft and the external environment but also the combustion phenomenon in an aircraft engine, which is the power plant of the aircraft. These effects need high end computer models based on CFD,” S Dasgupta of Transoft International says.
In the aircraft industry, the aerodynamics of an aircraft must be determined; i.e. the lift, drag and side-forces of a design must be estimated before a prototype flies. This means information on the power required to lift and be sufficient to carry the weight of the loaded aircraft, aircraft's fuel economy and the motion of the aircraft. To obtain this aerodynamic data earlier, many models of the design were built and tested in a wind tunnel, with the model positioned in many orientations to the flow. Such tests consumed many hours of wind tunnel time and cost many millions or billions of rupees. 
But, now CFD software packages can be used, Dasgupta says. There are many devices and systems of the aircraft being difficult to prototype and CFD analysis allows the designers to know what is happening within an engine that would not otherwise visible through any other means. It also creates better products and replace physical prototypes for faster product validation besides reduces design time-cycle, he adds.
It is interesting to note that CFD is finding novel applications day by day. Some of common application areas where CFD is used extensively in missile development, dispersion of pollutants into rivers and occeans, building ventilation, air quality and comfort, fire and smoke simulation. 
Recently, the International Conference on Simulations in Biomedicine discussed about an argon laser which, when focussed on a small area of the iris in human eye, leads to tissue removal. CFD techniques have been extensively applied for modelling the conduction and convection heat transfer to the eye tissues during the surgery. Ophthalmologists are in a position now to explain possible causes of corneal burns and lens opacities and their relationship to laser surgical parameters

Rajesh Parishwad
DH News Service

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