Catamaran's resistance effect with variation of demihulls distance
I have a project to analyze the caracteristic of catamaran in it's respon to the resistance. if this ship moving on the still water she will be exposed the different effect with ship in monohull form. because of the interaction between both of demihulls. the interaction is usually called as interfency.
my proffesor have one paper that contains some experiments in towing tank. this experiment discuss the resistance of catamaran with variation distance of demihull. one of the result is shown in following paragraph.
the distance both of demihulls is described in ratio between distance of demihulls (S) and ship length waterline (L). S/L = 0.3
demihull model towing tank caracteristic is shown by :
Displacement : 7.2 kg
volume
: 7046163.8 mm3
Lwl
: 1371.8 mm
Beam
wl : 122.6 mm
Draft : 78 mm
Cb
: 0.537
Cp : 0.732
Cm : 0.79
Cwp : 0.81
WSA : 256305.9
mm2
Waterplan area : 136129.3
mm2
the towing tank test result of catamaran S/L = 0.3 is:
Froude number CV CT CW
0.187659 0.006706 0.006983 0.000277
0.281222 0.006228 0.008472 0.002244
0.374874 0.005819 0.008762 0.002943
0.468567 0.005546 0.012149 0.006603
0.561488 0.005297 0.010267 0.004970
0.654683 0.005099 0.008375 0.003276
the result has been compared with result use computerical method use CFD (Computational Fluid Dynamic) from ANSYS. the CFD results is :
click picture to enlarge
Fr= 0.47
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X- Position
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Sym.Cat., S/L= 0.2
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Sym.Cat., S/L= 0.3
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Sym.Cat., S/L= 0.4
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Inner
|
Outter
|
Inner
|
Outter
|
Inner
|
Outter
|
|
Velocity
|
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1
|
1.67971
|
1.69897
|
1.68983
|
1.70317
|
1.70569
|
1.71248
|
2
|
1.72694
|
1.72678
|
1.72233
|
1.72170
|
1.72357
|
1.72178
|
3
|
1.75828
|
1.74330
|
1.74489
|
1.73355
|
1.73744
|
1.72901
|
4
|
1.74759
|
1.73691
|
1.73868
|
1.72993
|
1.73568
|
1.72814
|
5
|
1.75094
|
1.73605
|
1.73580
|
1.72666
|
1.72656
|
1.72244
|
Pressure
|
||||||
1
|
1471.34
|
1472.29
|
1471.14
|
1471.91
|
1470.94
|
1471.53
|
2
|
1469.57
|
1472.93
|
1470.04
|
1472.18
|
1470.5
|
1471.43
|
3
|
1472.96
|
1474.09
|
1472.47
|
1473.07
|
1471.97
|
1472.05
|
4
|
1473.28
|
1472.97
|
1473.02
|
1472.61
|
1472.76
|
1472.25
|
5
|
1473.44
|
1472.69
|
1473.39
|
1472.38
|
1473.34
|
1472.06
|
