--- In [email protected], "Lancie Melson" <[EMAIL PROTECTED]> wrote: > Yes, this is a common "urban legend", promoted by old pictures in high school textbooks of placer mining using water cannons. The pictures plainly showed the water line coming off the mountain, getting smaller as it came down. However this was due strictly to cost savings in using a smaller high-pressure (more expensive) pipe at the bottom, and a cheaper low pressure pipe at the top. The pressure, as you pointed out, is strictly dependent on the amount of head, and is only indirectly related to the pipe size (through friction loss).
It is not just cost savings issue. By using a series of incremental size reductions, they achieved incremental velocity increases while controlling the amount of turbulence generated in the piping system. This gave them a faster and less turbulent stream that would hold together longer, resulting in a larger impact against the earth that they were trying to remove. > > > > > > ________________________________________________________________ > Sent via the WebMail system at netease.net ------------------------ Yahoo! Groups Sponsor --------------------~--> Get fast access to your favorite Yahoo! Groups. Make Yahoo! your home page http://us.click.yahoo.com/dpRU5A/wUILAA/yQLSAA/FGYolB/TM --------------------------------------------------------------------~-> Does your company feature in the microhydro business directory at http://microhydropower.net/directory ? If not, please register free of charge and be exposed to the microhydro community world wide! NOTE: The advertisements in this email are added by Yahoogroups who provides us with free email group services. The microhydro-group does not endorse products or support the advertisements in any way. More information on micro hydropower at http://microhydropower.net To unsubscribe: send empty message to [EMAIL PROTECTED] Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/microhydro/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
