Huang and von Kerezek 
model has been tested by many of the towing tanks in the worldasa 
standard vibration model. The streamlines on the ''double model" 
were computed by Douglas -Neuman? and slender -body ‘ potential 
flow methods. In Figure 2 good agreement between the streamlines 
computed by each method is noted. The slight difference in stream- 
lines plotted is due mainly to the fact that the starting points in the 
two computations are not exactly the same. 
A coordinate system 0'x'y' with its origin in the undis- 
turbed free surface and another coordinate system ox yz fixed in 
the ship are used, Both are right handed coordinate systems moving 
with the steady velocity of the ship. The plane o'x'z' is on the un- 
disturbed free surface, o'x' is in the direction of the ship motion 
and o'z' is upward. The plane oyz contains the midship section, 
plane oxz the center plane section and the plane oxz the design 
water plane. The locations of the shear probes and pressure taps in 
the oxyz coordinate system are tabulated in Table 1. The reference 
length used to non-dimensionalize all lengths is L/2 where L is the 
length between perpendiculars. When the model is tested in the free- 
to-trim condition, the two coordinate systems are no longer coinci- 
dent. We denoted the vertical distance from the axes o'x to ox by h(x) 
(positive above the undisturbed free surface). The sinkage is defined 
as -[h() + h(1)]/2, trim by bow by -[(h@) - h(1)} and trim angle 
by tan ~1 (ona Pn yas 
Provisions were made for sixty interchangeable shear probes 
and pressure taps spaced evenly along a total of four zero Froude 
number streamlines, designated by A, B, C, and D, on the double 
model, and along a waterline E (14% draft). These probes have to be 
mounted flush to the hull surface. At each location a one-inch dia- 
meter teflon mounting plug was .sunk into the hull with its axis paral- 
lel to the normal of the ship surface, and its face flush with the ship 
surface, the surface of the plug was carefully polished to follow the 
original contour of the hull. The hot-film shear probe penetrated the 
plug and was fastened by four screws, The depth and angle of the 
probe with respect to the hull were adjustable. A photograph of this 
arrangement is shown in Figure 3. The depth of the probe with res- 
pect to the surface was carefully set to protude less than 0.002 inches 
out of the hull surface by using a flat face pressure transducer as a 
probe-protuberance feeler. Preston tubes and static pressure taps 
were placed on the hull through the same mounting plugs. Dynasco 
pressure transducers were used to measure the pressure from the 
Preston tubes or the pressure taps. Seven-channel DISA (Franklin 
Lake, New Jersey) constant temperature anemometers were used 
for the hot-film shear probes which were manufactured by Lintronics 
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