ON TRIM EFFECTS George Tzabiras Laboratory for Ship and Marine - PowerPoint PPT Presentation

Presentation at SNAME Greek Section November 13th, 2014 EXPERIMENTAL AND NUMERICAL STUDIES ON TRIM EFFECTS George Tzabiras Laboratory for Ship and Marine Hydrodynamics (LSMH) School of Naval Architecture and Marine Engineering NATIONAL TECHNICAL UNIVERSITY OF ATHENS

• Trim optimization is directly related to the resistance minimization and, therefore, to the overall efficiency of a ship. There are various options to face the problem. • The scope of the present work is to study the influence of trim on the hydrodynamic performance of various types ships. The studies are based on model experiments carried out in the Towing Tank of NTUA as well as on CFD calculations by methods developed at LSMH-NTUA. CRUCIAL ISSUES • Can we trust simple resistance tests (including dynamic sinkage and trim) or we should face the real problem of self-propulsion? • The optimum trim is realizable? • Can we measure accurately the benefits of trim optimization • What happens in rough seas? Trim influence is associated to bow and stern flow conditions

Bulb influence on bow wave Stern separation about (trim by bow) immersed transom

PART I : TOWING TANK TESTS The problem of scaling Equal Froude numbers ( V/(gL) 1/2 ) at model and full scale but substantially different Reynolds numbers ( VL/ ν ) Froude Hypothesis (first scale problem)          3 2 R S R C C C S V 1 2 /  S M FM FS A S S S M  effective horsepower E HP R V S S Extrapolation of self-propulsion experiments (second scale problem)  1 t      EHP R V SHP  S S R P S 1 w

The towing tank of LSMH,NTUA 90mx4.5mx3m

TOWING TANK TETS ON SIX MODELS IN ORDER TO IVESTIGATE THE TRIM INFLUENCE ON THE RESISTANCE • BULK CARRIER • PASSENGER SHIP SINGLE-SCREW • ROPAX FERRY TWIN-SCREW • SEMI-SWATH • SAILING YACHT • FISHING VESSEL Convention for “theoretical” trim angles (+) trim by bow (-) trim by stern

BULK-CARRIER (L=183m, Δ= 37,000t) Single screw, bulbous bow, wetted transom Full Load (T=10.15m) and Heavy Ballast (T=7.25m)conditions Model scale 1:35

Ship main particulars ________________________________________________ Particulars Condition _____________________________ B1 B2 B3 ________________________________________________ L WL [m] 183.295 187.320 183.785 B WL [m] 23.695 23.695 23.695 T M [m] 10.150 --------- ---------- Trim [deg] 0.000 -0.500 0.500 Δ [t] 37,177 37,177 37,177 W.S. [m 2 ] 6,885 6,902 6,860 Bulb immer. YES NO YES Transom immer. YES YES NO ________________________________________________

Model resistance vs. Froude no. at T=10.15 Trim = 0.0 deg Trim = 0.5 deg by stern Trim = 0.5 deg by bow 2,5 2 1,5 Vs Rm [Kp] (knots) Fr. No. 5.88 0.072 8.82 0.108 1 10.78 0.132 12.66 0.155 13.72 0.168 0,5 14.71 0.180 0 0,050 0,070 0,090 0,110 0,130 0,150 0,170 0,190 Froude Experiments in random sea-state show the same trends !!!

Resistance differences % at model scale (- ) corresponds to “gain” 7 T=10.15m (Even Keel vs 0.5 deg by stern) 6 T=10.15m (Even Keel vs 0.5 5 deg by bow) 4 3 Rm [%] 2 1 0 0,050 0,070 0,090 0,110 0,130 0,150 0,170 0,190 -1 -2 -3 -4 Froude

Dynamic trim and heave (sinkage) at model scale 0.80 0.00 0.050 0.070 0.090 0.110 0.130 0.150 0.170 0.190 0.210 -0.10 0.60 -0.20 0.40 -0.30 Total Trim [deg] Heave [cm] 0.20 -0.40 -0.50 0.00 T=7.25 m (Even Keel) T=7.25 m (Even Keel) 0.050 0.070 0.090 0.110 0.130 0.150 0.170 0.190 0.210 -0.60 -0.20 T=7.25 m (0.5 deg by stern) T=7.25 m (0.5 deg by stern) -0.70 T=7.25 m (0.5 deg by bow) -0.40 T=7.25 m (0.5 deg by bow) -0.80 -0.90 -0.60 Froude Froude

EHP vs. Froude no. (ship, T=10.15m)) 6000 T=10.15m (Even Keel) T=10.15m (0.5 deg by stern) 5000 T=10.15m (0.5 deg by bow) 4000 EHP [PS] 3000 2000 1000 0 0,050 0,070 0,090 0,110 0,130 0,150 0,170 0,190 Froude

EHP differences % vs. Froude no. (ship) 10 T=10.15m (Even Keel vs 0.5 deg by stern) 8 T=10.15m (Even Keel vs 0.5 deg by bow) 6 4 ΕΗΡ [%] 2 0 0,050 0,070 0,090 0,110 0,130 0,150 0,170 0,190 -2 -4 -6 Froude

Heavy Ballast Condition Ship T=7.25m Model Characteristics Test conditions A1 A2 A3 A4 L WL m 5.11 5.362 5.082 5.024 L BULB m 5.116 5.361 5.096 5.09 B WL m 0.677 0.677 0.677 0.677 t deg 0.000 -0.500 0.500 1.500 Δ mt 589.42 556.84 592.46 599.32 m 2 W.S. 4.669 4.677 4.676 4.696 Cb 0.820 0.808 0.824 0.834 Bulb immersion NO NO NO NO Transom immersion NO YES NO NO

Model Resistance vs. Froude no. 3,5 T=7.25 m (Even Keel) 3 T=7.25 m (0.5 deg by stern) 2,5 T=7.25 m (0.5 deg by bow) 2 T=7.25 m (1.5 deg by bow) Rm [Kp] 1,5 1 0,5 0 0,050 0,070 0,090 0,110 0,130 0,150 0,170 0,190 0,210 0,230 0,250 Froude

Resistance differences % vs. Froude no. (model) 5 3 1 -1 0,050 0,070 0,090 0,110 0,130 0,150 0,170 0,190 0,210 0,230 0,250 -3 Rm [%] -5 -7 T=7.25 m (Even Keel vs 0.5 deg by stern) -9 T=7.25 m (Even Keel vs 0.5 deg by bow) -11 T=7.25 m (Even Keel vs 1.5 deg by bow) -13 -15 Froude

Total trim and heave (sinkage) vs. Froude no. (model) 2,00 0,00 0,050 0,070 0,090 0,110 0,130 0,150 0,170 0,190 0,210 1,50 -0,20 1,00 -0,40 Total Trim [deg] Heave [cm] 0,50 -0,60 T=7.25 m (Even Keel) T=7.25 m (Even Keel) 0,00 -0,80 T=7.25 m (0.5 deg by stern) T=7.25 m (0.5 deg by stern) 0,050 0,070 0,090 0,110 0,130 0,150 0,170 0,190 0,210 T=7.25 m (0.5 deg by bow) T=7.25 m (0.5 deg by bow) -0,50 -1,00 T=7.25 m (1.5 deg by bow) T=7.25 m (1.5 deg by bow) -1,00 -1,20 Froude Froude

EHP vs. Froude number (ship, T=7.25m) 14000 T=7.25 m (Even Keel) 12000 T=7.25 m (0.5 deg by stern) 10000 T=7.25 m (0.5 deg by bow) T=7.25 m (1.5 deg by bow) 8000 EHP [PS] 6000 4000 2000 0 0,050 0,070 0,090 0,110 0,130 0,150 0,170 0,190 0,210 0,230 0,250 Froude

EHP differences % vs. Froude no. (ship) 10 5 0 0,050 0,070 0,090 0,110 0,130 0,150 0,170 0,190 0,210 0,230 0,250 ΕΗΡ [%] -5 -10 T=7.25 m (Even Keel vs 0.5 deg by stern) T=7.25 m (Even Keel vs 0.5 deg by bow) T=7.25 m (Even Keel vs 1.5 deg by bow) -15 Froude

Passenger Ship Single screw, bulbous bow, wetted transom Scale 1:15 Lines plan Main particulars Particulars Condition A1 A2 A3 A4 A5 __________________________________________________ L WL [m] 55.155 55.050 52.500 53.595 56.550 B WL [m] 10.500 10.500 10.500 10.500 10.500 T M [m] 3.150 3.15 0 3.150 3.150 3.150 A1 A2 A3 A4 A5 Trim [deg] 0.000 -0.500 -1.000 0.500 1.000 Bulb immersion YES YES NO YES YES Δ [t] 1,135 1,135 1,135 1,135 1,135 Transom immers. YES YES YES NO NO W.S. [m 2 ] 665,1 672,3 694,1 649,4 641,9

Bow wave at low speed Bow wave at high speed

Model resistance vs. Froude number Trim = 0.0 deg Trim = 0.5 deg by stern Trim = 1.0 deg by stern Trim = 0.5 deg by bow Trim = 1.0 deg by bow 5 5 4 Vs(Knots) Fr. No. 4 6.95 0.151 8.33 0.181 10.16 0.221 3 11.13 Rm [Kp] 0.242 12.37 0.269 3 14.45 0.314 2 2 1 1 0 0,100 0,150 0,200 0,250 0,300 0,350 Froude

Resistance differences % (model) 20 T=3.15m (Even Keel vs 0.5 deg by stern) T=3.15m (Even Keel vs 1 deg by stern) 15 T=3.15m (Even Keel vs 0.5 deg by bow) T=3.15m (Even Keel vs 1 deg by bow) 10 5 Rm [%] 0 0,100 0,150 0,200 0,250 0,300 0,350 -5 -10 -15 Froude

Total trim angle and heave vs. Froude number 0,00 1,50 0,150 0,200 0,250 0,300 0,350 0,400 -0,20 1,00 -0,40 T=3.15 m (Even Keel) T=3.15 m (0.5 deg by stern) -0,60 0,50 T=3.15 m (1 deg by stern) Total Trim [deg] T=3.15 m (0.5 deg by bow) Heave [cm] -0,80 T=3.15 m (1 deg by bow) 0,00 -1,00 0,150 0,200 0,250 0,300 0,350 0,400 T=3.15 m (Even Keel) T=3.15 m (0.5 deg by stern) -1,20 -0,50 T=3.15 m (1 deg by stern) -1,40 T=3.15 m (0.5 deg by bow) -1,00 T=3.15 m (1 deg by bow) -1,60 -1,50 -1,80 Froude Froude

EHP vs. Froude number (ship) 1400 T=3.15 m (Even Keel) 1200 T=3.15 m (0.5 deg by stern) T=3.15 m (1 deg by stern) T=3.15 m (0.5 deg by bow) 1000 T=3.15 m (1 deg by bow) 800 EHP [PS] 600 400 200 0 0,100 0,150 0,200 0,250 0,300 0,350 Froude

EHP differences % vs. Froude number (ship) 20 T=3.15m (Even Keel vs 0.5 deg by stern) 15 T=3.15m (Even Keel vs 1 deg by stern) T=3.15m (Even Keel vs 0.5 deg by bow) 10 T=3.15m (Even Keel vs 1 deg by bow) 5 EHP [%] 0 0,100 0,150 0,200 0,250 0,300 0,350 -5 -10 -15 Froude

ROPAX PASSENGER-FERRY (Twin-screw, bulbous bow, wetted transom) Scale 1:35 Particulars Condition _______________________________ A1 A2 A3 A4 A5 L WL [m] 153.65 154.80 153.09 138.00 137.55 B WL [m] 22.60 22.60 22.60 22.60 22.60 T M [m] 4.00 ----- ----- ----- ----- Trim [deg] 0.00 -1.00 -2.00 1.00 2.00 Δ [t] 6832 7078 7797 6724 6738 W.S. [m 2 ] 2748 2889 3187 2703 2706 Bulb NO NO NO NO NO immersion Transom NO YES YES NO NO immersion