Sample Problems > Usage > Eigenvalues > drumhole

{ DRUMHOLE_ANIMATE.PDE

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This example reads the stored output from Drumhole.pde

and shows the time-dependent oscillation of the first six modes.

The output .PG8 file can then be opened to export the desired plots using the "View->Export Movie" command.

These plots can be imported to a utility like APNGASM_GUI to create an animated PNG file.

*******************************************************************

}

title "Vibrational modes of a drumhead with a hole"

definitions

! read the transfer files from drumhole.pde

transfer("drumhole_output\ur_mode1",f1,ur1)

transfer("drumhole_output\ur_mode2",f2,ur2)

transfer("drumhole_output\ur_mode3",f3,ur3)

transfer("drumhole_output\ur_mode4",f4,ur4)

transfer("drumhole_output\ur_mode5",f5,ur5)

transfer("drumhole_output\ur_mode6",f6,ur6)

! find the lowest frequency

fmin = min(min(f1,f2,f3),min(f4,f5,f6))

! set the run length and time interval

! Here we have created 50 plots of each mode, spanning one full cycle at the lowest frequency.

t0 = 0

tlast = 2*pi/fmin

tdelt = (tlast-t0)/50

boundaries

! build the plot domain

Region 1

start(0,-1)

arc(center=0,0) angle 360

start(0,-0.4)

arc(center=0,-0.2) angle=360

! define the time range

time t0 by tdelt to tlast

! plot the oscillating drum membranes

plots

for cycle=1

surface(ur1*cos(f1*t)) fixed range(-1,1) report(f1) as "frequency"

surface(ur2*cos(f2*t)) fixed range(-1,1) report(f2) as "frequency"

surface(ur3*cos(f3*t)) fixed range(-1,1) report(f3) as "frequency"

surface(ur4*cos(f4*t)) fixed range(-1,1) report(f4) as "frequency"

surface(ur5*cos(f5*t)) fixed range(-1,1) report(f5) as "frequency"

surface(ur6*cos(f6*t)) fixed range(-1,1) report(f6) as "frequency"

! plot the combined mode 1 and mode 6 oscillation

surface(0.5*ur1*cos(f1*t)+0.5*ur6*cos(f6*t)) fixed range(-1,1) as "Mode1 + Mode6"

end "

drumhole_animate