Thursday
May 5, 2016

# Homework Help: Turbulence

Posted by Akhtar on Tuesday, April 12, 2011 at 4:55pm.

Hi there,
In a turbulent motion the length scale (l) and the time scale (t) of the smallest eddy motions vary according to:

length scale: l/L = Re^(-0.75)

time scale t/(L/U) = Re^(-0.5)

(actually there should b tht symbol for proportionality rather than the equal sign in the above two expressions...dont know how to use tht symbol here!)

where the Reynold's no Re=(L*speed/kinematic viscosity)

Question: How do the a) number of grid nodes and b) the number of time steps required to compute the properties of a turbulent flow depend on the Reynold's number?

I tried substituing 1000 for the Re number in the above two expressions for length and time scales but am not sure wat to do after tht. I guess if someone knowldegable cud explain how the node or time scales are worked out n used for computation ill better understand the question n hopefully then work the answer out. I just think I dont know much abt how the nodes n time step things work.

Thanks,
AKHTAR