Boat Info

Calculations

First calculate theoretical wave heights using JONSWAP Method

For this method need to know fetch (F), wind speed (U₁₀), and duration (t_d)

First we calculate F* and t*

F* = (gF)/( U₁₀)^2 where g is gravity

t* = (gt_d)/ U₁₀

next we use t* to calculate F*_eff

F*_eff= (t*/68.8)^(3/2)

If F* < F*_eff then the H* can be calculated as H*=.0016(F*)^.5

If F*_eff < F* then H* can be calculated as H*=.0016(F*_eff)^.5

From this wave height can be determined H=(H*)( U₁₀^2)/g

This method is effective to use for the wave height coming into the harbor.

In order to determine the fetch distances several degrees of wind direction were grouped together and the fetch distance estimated across Lake Michigan. Because of the large amount of data and the fact that it was measured to the closest 5 degrees, this provided the most efficient and accurate results. The following table shows fetch estimates based on degree of wind angle.

Wind Angle	Fetch (m)
0 to 30	120000
30 to 60	150000
60 to 90	100000
90 to 270	0
270 to 300	200000
300 to 330	150000
330 to 360	120000

During these calculations an assumption concerning the duration of the wind needed to be made. Since data was only available in three hour intervals, it was assumed that the wind was constant over this duration. While this is likely not the case, it provides the most reasonable estimation of the actual wind.

To check the accuracy of these calculation I checked them against the actual wave data gathered over the same time period. By comparing these two results I can determine if any adjustments need to be made to the JONSWAP results.

Additionally, in order to become good surfing waves, they would ideally break at large heights to allow for the most surfing action possible.

This is where the use of the bottom data and water level data come into play. Looking at the wave heights coming into this area we can see where they are likely to break and if this will provide for a good surfing environment.