kill(all);

inner radius

ri:1;

number of subdivisions at the inner radius

n:2;

element characteristic length at the inner radius, as measured along the arc

l_ri: ri*%pi/2/n,numer;

element characteristic length, as measured along the chord
l_ri: ri*sqrt((sin(%pi/2/n)-0)^2+(cos(%pi/2/n)-1)^2),numer;

outer radius of the first element row

step_ratio:(ri+l_ri)/ri;

max outer radius of the regularly meshed area

ro:10;

rori_ratio:ro/ri;

log(rori_ratio) / log(step_ratio) ,numer;
m:floor(%);

actual outer radius of the regularly meshed area

step_ratio^m*ri;