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Old   March 30, 2011, 08:34
Default Please help! anyone know this question please help!
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ryan taylor
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Hi there,
I have got this question what i have no idea on what to do. Can anyone help.
Here it is:
Estimate computer memory in bytes and computational time required to carry out a simulation of a 10 minute fire in a room of size 4m by 5m by 3m. assume that the kolmogorov length scale is 1\mu m and the length scale of the flame thickness is about 1mm. In every grid point the fire is fully quantified with 100 of physical parametres such as gas velocity, pressure, temperature, concentartions of chemical components etc. Each of these parametres is represented in a computer with a 64 binary digit number i.e take 8 bytes of compuer memory and the computer can do 2.5*10^15 arithmetic operations per second. The computational time step (delta)t corresponds to the CFL condition (delta)t=v(delta)x with the fluid speed v of order 1m/s and 1000 arithmetic operations is needed in order to advance numerical solution per time step per grid node. Here (delta)x is the grid cell size. Provide the estiomates for 3 approaches ;
DNS resolving all possible flow features,
Fine LES on grid resolving the flame structure,
Crude LES on a grid with cell size of 1cm.

If anyone can help me with this it would be much appreciated!!
Many thanks
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