Would drop riffles work in deep water?

[Goldfreak]

Probably more a question relating to physics but think you alluvial fellas can answer it.
Would drop riffles work in deep water like more than a meter the same way they work in a sluice that only has a couple of centimeters assuming the water was moving at the same speed over the riffles?

 

[Pogo]

Thats the way crevices in a stream bed work, so Im guessing yes

 

[robmoto]

look up submersible dredges

 

[Mungoman]

Flow dynamics Goldfreak.

 

[Goldfreak]

I was wondering this because some diagrams say drop riffles work because if low pressure, others say its because of the eddy or vortex and in this in the picture below it has a bit of both. If you increase the weight of water above by making it deeper would it have any effect on these things?

I understand this isn't a drop riffle but it describes a similar process.

 

[mudgee hunter]

I just had my fluid bed sluice running 400mm below the water working perfectly

 

[Pogo]

Should work fine,

Problem will be feeding it

And getting it back out again without washing out the cons

 

[limpalot]

I use a 20 - 30 mm drop from the feed level in, to the bottom of my riffle area, so with mat and riffles all material has to drop down into the sluice area. This means I can catch the gold quicker and in a shorter length of riffle.

 

[limpalot]

I use a 20 - 30 mm drop from the feed level in, to the bottom of my riffle area, so with mat and riffles all material has to drop down into the sluice area. This means I can catch the gold quicker and in a shorter length of riffle. Gold wants to drop down, with normal sluices Gold has to push up over the riffles, mats. with the drop down you are using gravity to help sort the material, the lighter material keep moving forward and out.

 

[Goldtarget]

Saw it on Berring Sea Gold, an underwater dredge, the bloke claimed he was a genius who built it and used it..... my guess is yes.

Like first or second season.

 

[Goldfreak]

I will have a look at that. Cheers.

 

[casper]

..... drop riffles ain't a new concept, mother nature has been doin' it for eons and Mackirk perfected it in ABS plastic. I use an elevated feed for my home brew Dream mat sluice and it's a "gold grabber" and in low flow situations I substitute with a Mackirk Sluice.

 

[casper]

..... drop riffles ain't a new concept, mother nature has been doin' it for eons and MacKirk perfected it in ABS plastic. I use an elevated feed for my home brew Dream mat sluice and it's a "gold grabber" and in low flow situations I substitute with a MacKirk Sluice.

 

[Goldfreak]

I used to run a letrap sluice box that was quite effective too, added a frame and pump then turned it into a high banker and later sold it. Similar riffle shape to Mackirks.