Gusts that are statistical?
Yes. They happens for a wide range of reasons. Ivanpah is a dry lake bed surrounded by low hills. As the wind behind those hills builds up pressure, it spills onto the plain. There can be several streams from many directions that mix to produce variations of speed and direction. In cities, buildings can do the same. There can be changes of 20m/s in a second because of that effect. The lake is hot because it is open, and the Sun can easily add 400W sq meter, and winds sheer over that. The BB is tall, so can dip into that stream, while at ground level, there is not much going on.
There are more general effects that can be estimated by standard deviation, if gust length is known. Meteorology is complicated. I may write that up, but the vane dynamics is more important.
Ivanpah is suitable for testing Greenbird, because it is up to the pilot to choose the best course. It's his loss if he doesn't. But ddw is specific, and that means the wind must be specific to meet that situation. It isn't.
NALSA have no experience of ddw testing, nor the appropriate instruments.
The instruments promised for the cart, including pitot tubes, never eventuated, and only the GPS was fitted to the cart and the rest on the CV, leaving huge scope for error. When Spork wanted to wager me, I said that pitot tubes must be used, along with high speed data capture. It was not a whim.
I think you are saying that the cart might speed up during a gust and then coast when the wind drops, thereby recording a higher speed during the low windspeed than would be achieved in a steady wind. Is that what you mean?
Partially. The wind gusts are moving air mass, so that influences the energy density over a short period. the mass of the cart will integrate the energy form the gusts. Mass makes for poor acceleration, but allows for big storage.
Acceleration is not an issue - it went fast enough to do the job - but would be if competing against other carts.
The question of ddw is one of thermodynamics, and that is why it is disputed. The claim was that >WS would be achieved in a wind tunnel, and that it more like a closed system, but Ivanpah is far from that. It's not much of a challenge to gain energy, if the wind is energetic.
The evidence of that would be that the cart would slow down during the measured run, wouldn't it? The chart shows the cart continuing to accelerate throughout the measured period.
Well, the TM does not predict constant acceleration, so the model and the cart don't match, but the wind changes for the entire run, so why wouldn't it accelerate? That is no substitute for steady state. A great deal of the details of the test were held back. Had I known of them, I would have objected, but all were denied that choice.
Harold Bricer produced a calculation that said the cart would reach 50-60% of WS at best, in a steady tailwind. That is what happens.
That can be seen from the chart. At the start, the wind travels in the same direction for about 10 seconds (the CV is moving about so the data before that is lost), but the cart does not accelerate until the wind changes South.
If the speed data is differentiated, it can be seen that acceleration falls when the cart approaches ddw, as the wind changes in that sinus pattern.
The Jenkin's video shows the cart doing much the same. It travels at 2m/s for quite a long time, but takes off when the wind changes.
That is evidence that Harold is right, but it is not seen as an outcome.
