Design Optimization of Subcavitating Hydrofoils for America's Cup Class Yachts

This method has been utilized by my group for many years across various applications due to its versatility. As illustrated in the contour plot from my book, which explains the aggregation process, two constraints are represented by the red lines. At their intersection, a discontinuity occurs; however, this poses no issue for Sequential Quadratic Programming (SQP). If one were to aggregate the constraints using the maximum function, this discontinuity would present a problem. The KS function effectively smooths out this discontinuity. Although it is conservative, careful tuning of the row parameter (row KS) allows for closer approximation to the desired solution.

In a sample optimization scenario, the baseline exceeded the cavitation constraint. After applying the optimization with the constraint, the results remained below the threshold. In this instance, the approach was not conservative due to the tuning of the row parameter.

Now, focusing on the conditions for AC 75 class boats, it is remarkable that these vessels can achieve speeds four times that of the wind. Depending on the angle to the wind, the speed can range from two to four times the wind speed. The performance polar demonstrates this relationship, with the vertical axis representing boat speed and the horizontal axis representing wind speed. The lines indicate different wind speeds, and it is important to note that these boats cannot sail directly into the wind; they require an angle to achieve optimal speed.

When sailing downwind, the maximum speed is limited to the wind speed, which is often insufficient. Interestingly, during upwind and downwind legs, the boats maintain a similar angle, and the sails are consistently trimmed in. Unlike smaller boats, where sails may be fully out, this is not the case for AC 75 class boats. For optimization, American Magic identified critical points that are essential for performance evaluation.