Pitching Airfoil Problem

suman91 · October 10, 2014, 19:43

Hi there,

The pitching airfoil config file has the following portion in it (by default):

% Time Step for dual time stepping simulations (s)
UNST_TIMESTEP= 0.0023555025613149587
% 24 steps per period: 0.0024536485013697488
% 25 steps per period: 0.0023555025613149587
%
% Total Physical Time for dual time stepping simulations (s)
UNST_TIME= 0.59
% 10 periods: 0.5888756403287397

Q. What does it mean by 24 steps?
Can someone please help me as to how these number came by?
Given:
PITCHING_AMPL_Z= 1.01
PITCHING_OMEGA_Z= 106.69842

suman91 · October 11, 2014, 19:50

Answer to the question above:

This config file is for a pitching airfoil that completes a pitch cycle with angular frequency PITCHING_OMEGA_Z = (2 * pi)/T, where T is the time period of one complete cycle.

If you want to resolve that complete cycle with 24 steps, then the UNST_TIMESTEP = Delta t = (T/24) = (2*pi)/(PITCHING_OMEGA_Z*24) = 0.00245

For 25 steps, divide by 25 instead of 24.

October 10, 2014, 19:43	Pitching Airfoil Problem	#1
suman91 Member Suman Chakraborty Join Date: Sep 2014 Location: Mumbai, India Posts: 42 Rep Power: 12	Hi there, The pitching airfoil config file has the following portion in it (by default): % Time Step for dual time stepping simulations (s) UNST_TIMESTEP= 0.0023555025613149587 % 24 steps per period: 0.0024536485013697488 % 25 steps per period: 0.0023555025613149587 % % Total Physical Time for dual time stepping simulations (s) UNST_TIME= 0.59 % 10 periods: 0.5888756403287397 Q. What does it mean by 24 steps? Can someone please help me as to how these number came by? Given: PITCHING_AMPL_Z= 1.01 PITCHING_OMEGA_Z= 106.69842

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October 11, 2014, 19:50		#2
suman91 Member Suman Chakraborty Join Date: Sep 2014 Location: Mumbai, India Posts: 42 Rep Power: 12	Answer to the question above: This config file is for a pitching airfoil that completes a pitch cycle with angular frequency PITCHING_OMEGA_Z = (2 * pi)/T, where T is the time period of one complete cycle. If you want to resolve that complete cycle with 24 steps, then the UNST_TIMESTEP = Delta t = (T/24) = (2pi)/(PITCHING_OMEGA_Z24) = 0.00245 For 25 steps, divide by 25 instead of 24.