(1). Have you used the Pitot probe before? Have you had a fluid mechanics lab in college before? (2). U_i*U_i=U_x * U_x + U_y * U_y +U_z * U_z. (3). So, for the Pitot probe to measure it, it must be able to measure U_x, U_y, and U_z instantaneously. (which is not possible)

Except if the pitot tube is align with the streamline. This is used to measure the relative velocity of a plane.

John,

I think we're talking at cross-purposes and I don't think that the tone of your reply was very helpful.

David

(1). Sorry, when the question or answer is posted in the Forum, it becomes public question or answer. There is no personal connection between the message and the person's name attached to the message. (2). e-mail is an option for private communication. (3). One of the reason why Pitot probe can not measure the instantaneous total pressure or velocity is that one must align it to the flow direction instantaneously. And at the same time, the flow direction is unknown. (4). When a message is posted, even though there is a name attached to the message, in reality, the personal connection is no longer there. The message becomes public and the subject of interest is the message, not the name attached to it. (I hope we all understand that rule. "you is not you")

John,

There are lots of people out on the streets with whom I have no personal relations, but I nevertheless try to impose certain limits on my conduct towards them. Impertinence serves no positive purpose whatsoever, and there are plenty of websites where people can turn to insult one another without having to see each other in the eyes. I presume (or at least hope) most users will agree that common decensy deserves a place in this forum.

Lars Ola