CATAMARAN RESISTANCE WITH VARIATION DISTANCE OF DEMIHULLS

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
X- Position	Sym.Cat., S/L= 0.2		Sym.Cat., S/L= 0.3		Sym.Cat., S/L= 0.4
	Inner	Outter	Inner	Outter	Inner	Outter
Velocity
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