256 



HYDRODYNAMICS IN SHIP DESIGN 



Sec. 52.12 



wave profile in side elevation should be used for 

 this purpose. 



A prediction of flow in way of the bilge keels 

 should cover the light-load or ballast condition 

 as well as that for the designed load, using the 

 appropriate speed-length quotients in each case. 

 Almost certainly the traces wiU be different, 

 unless the speeds are low, although the differ- 

 ences may be small. A decision is called for in the 

 design stage to determine which load and speed 

 condition is to be favored in positioning the bUge 

 keels on the ship. 



52.12 Probable Flow at a Distance From the 

 Ship Sixrface. At normal or lateral distances 

 from the 3-dunl ship form greater than those 

 involved in placing the roll-resisting keels, avail- 

 able data for predicting flow conditions become 

 rather rare. A few sources giving data on tests of 

 ship models, which may or may not cover the 

 distances with which a ship designer is concerned, 

 are mentioned: 



(a) Laute, W., "Untersuchungen iiber Druck- und 



Stromungsverlauf an einem Schiffsmodell (Investi- 

 gations of Pressure and Flow on a Ship Model)," 

 STG, 1933, Vol. 34, pp. 402-460; English version in 

 TMB Transl. 53, Mar 1939. See also Figs. 22.D 

 and 22.E in Sec. 22.8 of Volume I. 



(b) Lamble, J. H., "An Experimental Examination of the 



Distribution of Velocity Around a Ship's Model 

 Placed in a Turbulent Stream," IN A, 1934, pp. 

 136-143 and Pis. XV, XVI 

 (c) Hamilton, W. S., "The Velocity Pattern Around a 

 Ship Model Fixed in Moving Water," Doctorate 

 Diss., IIHR, Deo 1943. Available in TMB Ubrary, 

 number VM298.H11. 



In the present state of the art, the prediction of 

 flow conditions from available reference data 

 only, for an important part of a ship or an import- 

 ant region near the ship, is uncertain at the best. 

 Rehance upon flow tests mth a model is definitely 

 indicated. 



52.13 Estimating the Change in Flow Pattern 

 for Light or Ballast Conditions. Predicting the 

 flow pattern — and wave profile — for a ship design 

 when the vessel is assumed to be in a hght or 

 ballast condition requires modifications of the 

 rules in Sec. 66.28. In the first place, the forefoot 

 is usually well out of water, so that whether it is 

 cut away or is occupied by a bulb, the section 

 lines are by no means vertical in that region. In 

 the second place, the free surface, disturbed by 

 Velox waves, is much closer to the bottom of the 

 ship than at normal draft. The surface-wave 

 pattern may be expected, therefore, to have a 

 considerable influence on the flow pattern, at 

 least as far down as the flat floor under the ship. 



Numbers at Sides Indicate ftisitions of 

 Wave Profiles and Flow Traces at 

 Those Stotions 



U. S. Maritime Commission Design 



T2-SE-AI 



TMB Model 3867 



FULL-LOAD CONDITION 



Trim, Zero Tq = 0.684 



5 10 15 20 



l.i.i I I I I I I I I 1 I I 



Fig. 52.Xa Lines of Flow in Full-Load Condition foe U. S. Maritime Commission Design TS-SE-Al 



