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Message ID: 150     Entry time: Fri Jun 21 12:57:38 2019
Author: Marie K. 
Type: Progress 
Category: BS BRDs 
Subject: Theoretical best achievable Q as a function of mass ratio 

Posting here for reference the best achievable Q for the damped BS as a function of the mass ratio of the damper mass and BS mass (see figure attached, along with the Matlab code). This is mainly based on a code from Norna (T1600259), with a line that computes the structural damping constant of the damper from the mass ratio (see Equation 12 in T1500271).

Currently we are using masses of 5g for bounce (3g for roll) for the damper. The modal masses of the BS are 27.78 kg (bounce mode) and 12.9 kg (roll mode). The mass ratio is therefore 1.8e-4 (2.3e-4). It means that we could achieve a Q ~ 120 in case of perfect tuning or Q ~ 200 for a mistuning by 0.5% for the bounce mode.

For the roll mode, we could do slightly better, with a Q~ 110 if the damper is perfectly tuned, and a Q ~170 for 0.5% detuning.

Attachment 1: Best_Q_vs_mistuning.png  115 kB  Uploaded Fri Jun 21 14:15:54 2019  | Hide | Hide all
Best_Q_vs_mistuning.png
Attachment 2: BRD_HSTS_T1600259_loop_for_graph.m  2 kB  Uploaded Fri Jun 21 14:17:27 2019  | Hide | Hide all
% Create a loop around Norna's model to reproduce Brett's graph
% from T1500271 + adjust the damping 
%
% Model from Norna concerning the BRD_HSTS
% parameters adjusted for the BS dampers v4
% MK May 2019

%model of coupled oscillator system: blade and damper
%damping in damper only
% NAR 5th May 2015
... 98 more lines ...
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