TPK is not a linear function. Submarine propellers are designed to most efficient at maximum speed. Data collected on the same hull on the same day indicates TPK values of 9.54 at 26.06 knots, 9.61 at 14.1 knots and 10.25 at 8.08 knots.
At speeds below about five knots - and especially at speeds as low as 2-3 knots, TPK values will "decay"
significantly. Although none were derived at such speeds for the above case, other data indicates TPK values as high as 12-15 may have applied for that hull at 2-3 knots. I don't think you will find many submarine COs pleased to have to operate at speeds lower than or as low as three knots.
The battle about linearity was fought - and won - against the US submarine community many years ago; however, the results probably are still not well known, i.e., most will tell you TPK is linear, i.e., does not change as a function of speed. That assessment was the result of not being able to measure speed with the accuracy required to identify variations such as those noted above.
Thanks Bruce. I am very familiar with computing TPK. I had a Large Yacht for years and the curve was BRUTAL at WOT. The hull problem is much different with a submarine. Thanks for your posts.
