Calculate optimal jet size (google sheet)

Flatline

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So I created this google sheet with the help of a fluid mechanic. It calculates the optimal size of the jet inside your nozzle based on your pump specs. It however does not take the actual nozzle size into account but should give the optimal size for your pump.

Feel free to use it. Click file, make a copy and then you can edit the file.



suction nozzle.jpg
 

russau

Gold Member
May 29, 2005
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Now where is my calculator?????? :BangHead: :BangHead: And if your using a venturi Jet log instead of a suction nozzle you need to include the number of jets you want to use ! i,e. 1 ,2 , 3 or 4 nozzles ! multiple jets in a venturi jet log will help keep your material centered in the tube to keep the hi-pressure water from beating the gravels against the outside of the jet log and deforming it and eventually popping a hole there ,and RUINING your day or weekend!:coffee2:
 

Azure

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Have you tested these calculations in the real world?

I tried to calculate the optimal jet diameter using Bernoulli's principle and it didn't work in the real world, didn't move enough water. The sheet results are similar what didn't work for me, the diameter needs to be half.
 

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Flatline

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No I have not tested it yet, but i've been thinking about making myself a dredge so been looking around for the different sizes needed but thought a calculator could be nice to have.
But i asked ChatGpt to help answer some questions as I'm not an engineer and now i understand :D

"
The feedback you received brings up an important aspect of engineering design, especially when it involves fluid dynamics: theoretical calculations must ultimately be tested and validated against real-world conditions, which can include a variety of factors not accounted for in simplified models.
Bernoulli's principle and the continuity equation give us a theoretical basis for calculating flow rates and pressures in an ideal scenario. However, in practice, there are additional factors such as turbulence, friction losses inside hoses and fittings, and the interaction of the water jet with the material being dredged, all of which can affect the performance of the system.
Regarding the feedback:
  1. Jet Diameter and Water Movement: Reducing the jet diameter while keeping the pressure constant will increase the velocity of the water at the point of constriction (the jet). According to Bernoulli's principle, this should increase the suction power because the higher velocity at the jet results in lower pressure, enhancing the vacuum effect. However, there's a trade-off: a smaller jet reduces the volume of water that can pass through per unit of time, which could result in moving less material overall.
  2. Creating a Vacuum: The creation of a vacuum for suction is more about the velocity of the water than the volume. A high-velocity jet will create a stronger vacuum, but there needs to be enough water volume to carry the material away.
  3. Real-World Testing: The person who provided feedback likely encountered a scenario where the balance between jet size, water velocity, and volume did not match the demands of their specific dredging conditions. Real-world testing often reveals the need for adjustments from theoretical models. What works on paper might not work in a riverbed with variable material densities and compositions.
In summary, both the volume of water and the velocity (related to pressure) at which it moves are crucial. A smaller jet can create a higher velocity and potentially a stronger vacuum, but there must be enough water to carry the material. Conversely, a larger jet allows more water flow but at a potentially lower velocity, which could reduce suction.
Finding the optimal balance often requires field testing and adjustments based on performance. The goal is to find a jet size that offers the best combination of water velocity and volume to create sufficient suction and material transport for your specific dredging conditions.

User

You
but how can the velocity of the water increase with a smaller jet, if the pressure is the same? I'm not an engineer so i don't understand how that could work. The pressure of the water is the same and in my mind pressure is the same as the speed, just by making it smaller it would just mean less water going into the suction nozzle?


ChatGPT
Your confusion is completely understandable. Let's clarify how pressure, velocity, and jet size interact according to fluid dynamics principles.
Pressure is a measure of force exerted over an area and doesn't directly equate to speed. It's more akin to potential energy in the system. When we talk about the speed or velocity of water in this context, we're referring to how fast the water is moving, which is related to the kinetic energy of the system.
When you have a given pressure at the pump, and you reduce the size of the jet (orifice), you're forcing the same amount of energy (pressure) through a smaller area. According to Bernoulli's principle, when the same amount of water is forced through a smaller opening, it must speed up (increase in velocity) because the energy in the system is conserved. This is similar to putting your thumb over the end of a garden hose; the water sprays out faster and further, even though the pressure from the tap hasn't changed.
Here's the principle at play:
  • Larger Jet Diameter: More water can flow through, but the velocity may be lower because the water has more area to pass through.
  • Smaller Jet Diameter: Less water can flow through, but it does so at a higher velocity because the same pressure acts on a smaller area.
The increased velocity through the smaller jet creates a lower pressure area (due to the Venturi effect), which contributes to the vacuum effect that sucks material up the dredge's suction hose. However, if the jet is too small, you could indeed end up with insufficient water flow to carry the dredged material, which might be what the person giving you feedback experienced.
The ideal jet size creates a balance where the velocity is high enough to generate good suction but not so high that it reduces the overall volume of water and material that can be moved. It's this balance that's crucial in dredge design, and it's why real-world testing is essential to find the best setup for your particular conditions."
 

russau

Gold Member
May 29, 2005
7,268
6,725
St. Louis, missouri
To start off with you NEED a HI-Pressure pump for this ! Just using a water pump won't get the job done to any workable solution ! Believe me I have tried years back to no avail ! Avoid the headaches and get a HI-PRESSURE pump !
 

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Flatline

Jr. Member
Aug 31, 2021
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To start off with you NEED a HI-Pressure pump for this ! Just using a water pump won't get the job done to any workable solution ! Believe me I have tried years back to no avail ! Avoid the headaches and get a HI-PRESSURE pump !
Yep! I got a keene p180 already, but might upgrade.. need to process more material! xD
 

Reed Lukens

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Jan 1, 2013
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The P180 works good with Keene's 3/4" orifice but much better with a 1" orifice. The Proline HP400 would be the next upgrade and I run a 1⅛" Proline HP500 orifice with it. You can really feel the difference between the 2 pumps and the larger orifice makes a big difference in overall suction.
 

Azure

Jr. Member
Oct 5, 2020
23
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No I have not tested it yet, but i've been thinking about making myself a dredge so been looking around for the different sizes needed but thought a calculator could be nice to have.
But i asked ChatGpt to help answer some questions as I'm not an engineer and now i understand :D

"
The feedback you received brings up an important aspect of engineering design, especially when it involves fluid dynamics: theoretical calculations must ultimately be tested and validated against real-world conditions, which can include a variety of factors not accounted for in simplified models.
Bernoulli's principle and the continuity equation give us a theoretical basis for calculating flow rates and pressures in an ideal scenario. However, in practice, there are additional factors such as turbulence, friction losses inside hoses and fittings, and the interaction of the water jet with the material being dredged, all of which can affect the performance of the system.
Regarding the feedback:
  1. Jet Diameter and Water Movement: Reducing the jet diameter while keeping the pressure constant will increase the velocity of the water at the point of constriction (the jet). According to Bernoulli's principle, this should increase the suction power because the higher velocity at the jet results in lower pressure, enhancing the vacuum effect. However, there's a trade-off: a smaller jet reduces the volume of water that can pass through per unit of time, which could result in moving less material overall.
  2. Creating a Vacuum: The creation of a vacuum for suction is more about the velocity of the water than the volume. A high-velocity jet will create a stronger vacuum, but there needs to be enough water volume to carry the material away.
  3. Real-World Testing: The person who provided feedback likely encountered a scenario where the balance between jet size, water velocity, and volume did not match the demands of their specific dredging conditions. Real-world testing often reveals the need for adjustments from theoretical models. What works on paper might not work in a riverbed with variable material densities and compositions.
In summary, both the volume of water and the velocity (related to pressure) at which it moves are crucial. A smaller jet can create a higher velocity and potentially a stronger vacuum, but there must be enough water to carry the material. Conversely, a larger jet allows more water flow but at a potentially lower velocity, which could reduce suction.
Finding the optimal balance often requires field testing and adjustments based on performance. The goal is to find a jet size that offers the best combination of water velocity and volume to create sufficient suction and material transport for your specific dredging conditions.

User

You
but how can the velocity of the water increase with a smaller jet, if the pressure is the same? I'm not an engineer so i don't understand how that could work. The pressure of the water is the same and in my mind pressure is the same as the speed, just by making it smaller it would just mean less water going into the suction nozzle?


ChatGPT
Your confusion is completely understandable. Let's clarify how pressure, velocity, and jet size interact according to fluid dynamics principles.
Pressure is a measure of force exerted over an area and doesn't directly equate to speed. It's more akin to potential energy in the system. When we talk about the speed or velocity of water in this context, we're referring to how fast the water is moving, which is related to the kinetic energy of the system.
When you have a given pressure at the pump, and you reduce the size of the jet (orifice), you're forcing the same amount of energy (pressure) through a smaller area. According to Bernoulli's principle, when the same amount of water is forced through a smaller opening, it must speed up (increase in velocity) because the energy in the system is conserved. This is similar to putting your thumb over the end of a garden hose; the water sprays out faster and further, even though the pressure from the tap hasn't changed.
Here's the principle at play:
  • Larger Jet Diameter: More water can flow through, but the velocity may be lower because the water has more area to pass through.
  • Smaller Jet Diameter: Less water can flow through, but it does so at a higher velocity because the same pressure acts on a smaller area.
The increased velocity through the smaller jet creates a lower pressure area (due to the Venturi effect), which contributes to the vacuum effect that sucks material up the dredge's suction hose. However, if the jet is too small, you could indeed end up with insufficient water flow to carry the dredged material, which might be what the person giving you feedback experienced.
The ideal jet size creates a balance where the velocity is high enough to generate good suction but not so high that it reduces the overall volume of water and material that can be moved. It's this balance that's crucial in dredge design, and it's why real-world testing is essential to find the best setup for your particular conditions."

The pressure energy is converted into kinetic energy, which results in a low pressure area on the other side of the jet. When the low pressure area is less than atmospheric pressure, more water comes in towards the area to equalize the pressure difference, creating the suction (venturi effect).

From what i've seen, 1/4 -> 1/5 restriction of inlet water cross section area is what has worked.
 

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Flatline

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The P180 works good with Keene's 3/4" orifice but much better with a 1" orifice. The Proline HP400 would be the next upgrade and I run a 1⅛" Proline HP500 orifice with it. You can really feel the difference between the 2 pumps and the larger orifice makes a big difference in overall suction.
I got the 3" hydro that i use with it with the biggest gold hog highbanker.. and it produces almost too much water for the hopper, so i need a bigger high banker.. thinking about making a version of the gold hog but like 2" wider or such.
 

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OP
F

Flatline

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Aug 31, 2021
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The pressure energy is converted into kinetic energy, which results in a low pressure area on the other side of the jet. When the low pressure area is less than atmospheric pressure, more water comes in towards the area to equalize the pressure difference, creating the suction (venturi effect).

From what i've seen, 1/4 -> 1/5 restriction of inlet water cross section area is what has worked.
Thanks!
 

Reed Lukens

Silver Member
Jan 1, 2013
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I would bypass the hopper and run it directly into the top of the box. So, you're running a Raptor? I ran a Raptor up at the Blue Bucket in Eastern Oregon, it's a great box. It will handle a 2½ ok but a 16" or wider box with dredge riffles would be best for a 3" for a maxed out P180.

IMG_20180529_123419.jpg
 

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Flatline

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I would bypass the hopper and run it directly into the top of the box. So, you're running a Raptor? I ran a Raptor up at the Blue Bucket in Eastern Oregon, it's a great box. It will handle a 2½ ok but a 16" or wider box with dredge riffles would be best for a 3" for a maxed out P180.

View attachment 2115232
No raptor is small ;D I got the Super Hog :D
 

Reed Lukens

Silver Member
Jan 1, 2013
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Then try running it as is with the P180. Run the suction hose right into the head of the lower box and run a - ¼" to ⅜" thick damper in the entire 12" wide section and then another ¼" damper a couple feet or more down the beginning of the 18" section. In the upper section, consider running 1½" expanded metal riffles with non-backed miners moss over the top of the stock Gold Hog mat because the water will need to be steep enough to not overfow the upper box if you aren't seeing any gold in the upper box from the scrubbing action of the fast water.
The upper section will make a nice nugget catch and the old Friesen 3" dredges back in the late 70's ran a 12" box on their 3". We've come a long way since then and I had 2 Friesen dredges back in the day. Run it as low to the water as possible.
Lets see a video when you get it running 🤠
 

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Flatline

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Then try running it as is with the P180. Run the suction hose right into the head of the lower box and run a - ¼" to ⅜" thick damper in the entire 12" wide section and then another ¼" damper a couple feet or more down the beginning of the 18" section. In the upper section, consider running 1½" expanded metal riffles with non-backed miners moss over the top of the stock Gold Hog mat because the water will need to be steep enough to not overfow the upper box if you aren't seeing any gold in the upper box from the scrubbing action of the fast water.
The upper section will make a nice nugget catch and the old Friesen 3" dredges back in the late 70's ran a 12" box on their 3". We've come a long way since then and I had 2 Friesen dredges back in the day. Run it as low to the water as possible.
Lets see a video when you get it running 🤠
Yes that could work, unless i upgrade.. i plan to maybe upgrade to at least a 4" or even make my own 5" as midwest prospector who makes the hydro doesn't seem to answer his emails. I need to move more material!! :D But if i do upgrade to a 5" i would definitely need a wider box.
 

Reed Lukens

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Yup, 22" is a nice width for a 5". Keene has theirs at 20" but being that you can run a 6" with the 2 P180s also, you might as well go with a 6". You could run your Super Hog as a 4" but put in their dredge mat because you would need taller & steeper riffles.
I made this old video back in 2005, it has a lot of good pump info, etc.
 

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Flatline

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Yup, 22" is a nice width for a 5". Keene has theirs at 20" but being that you can run a 6" with the 2 P180s also, you might as well go with a 6". You could run your Super Hog as a 4" but put in their dredge mat because you would need taller & steeper riffles.
I made this old video back in 2005, it has a lot of good pump info, etc.

Yep, seen that one :D
 

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Flatline

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I made an update to the sheet, it now does calculate the optimal size of your nozzle based on the pump and takes into account that the jet should be 1/4 roughly of the nozzle size. So it seems my pump is somewhat too small to run a 5" :(
*Edit* ok scrap that, something is wrong with this new calculation.. the lower pressure i have the bigger the nozzle i can use lol
 

russau

Gold Member
May 29, 2005
7,268
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St. Louis, missouri
That "Midwest" prospector is : Chuck Lassiter from Indiana and I "think" he stopped making these BUT I'm not sure ,I haven't talked to him in year's . I know there are people close to him that view this site and maybe they could pass a message to him ???
 

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Flatline

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That "Midwest" prospector is : Chuck Lassiter from Indiana and I "think" he stopped making these BUT I'm not sure ,I haven't talked to him in year's . I know there are people close to him that view this site and maybe they could pass a message to him ???
Well they are still sold on his webpage but maybe he has inventory still, and also some resellers sell them. But i'm leaning against making my own potentially.
 

N-Lionberger

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Well they are still sold on his webpage but maybe he has inventory still, and also some resellers sell them. But i'm leaning against making my own potentially.
It’s fairly simple to modify an existing suction nozzle.
 

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