Work - a day in the life of a civil engineer specialised in hydraulics

Yesterday's question: if you enlarge the holes on a sewage filter distributor arm to stop them getting blocked, does it affect the uniformaity of the distribution of sewage across the filter?

I dragged a colleague's old spreadsheet out and dusted it down.  Re-arranged it to match the way my brain thinks.  Added graphical output.  Added a macro to run the tedious iteration.  Tested it with small holes and big holes.

Answer: yes, it does affect the distribution.  Obvious when you think about it.  If the holes are bigger, more will try to get out through the first hole, so there is les at the end.  Some people had said that the pressure along teh pipe would still be the same so the flow through each hole would be the same, it would just jet out less.  But the maths shows that it does mean more water is spread in the middle of the filter and less at the edges.

So this leads on to more questions:

• Is the difference enough to worry about? ( we need to ask the Process Engineer)
• This is technically outside our jurisdiction - the dsign of the distributor is the responsibility of the manufacturer, and his 'cleint' is our mechanical engineer.  So what can we do?  (We can inform the manufacturer and his client of our concerns.  we can't show them our spreadsheet, because then we would incurr a design responibility that we are not authorised to take on.  So all we can do is ask awkward questions.)