effectiveness of small volume refugiums

[clifford513]

My three year old eats pi

[c est ma]

LOL! I love threads like these. We sure have a talented bunch here. Tagging along 'cause I'd like to add a fuge to my 5.5!

 

--Diane

 

In addition to fuge benefits, isn't there also a benefit simply from increasing the total H20 volume so significantly? But I realize the question was about fuges, not sumps...still, doesn't a fuge kinda serve both purposes?

[Mr. Fosi]

In addition to fuge benefits, isn't there also a benefit simply from increasing the total H20 volume so significantly?

 

I suppose. I would have liked to double the water volume of my 5.5g. It would have allowed me to control the temp better and would have reduced the impact of daily evap/topoff cycle.

 

Again, I am not sure I would have seen a real-world impact of the topoff concerns, but it would have made me feel better.

 

But I realize the question was about fuges, not sumps...still, doesn't a fuge kinda serve both purposes?

 

It can. It all depends on what the person uses it for.

 

Personally, I would use it for both because I wouldn't be able to resist getting rid of in-tank clutter like heaters, float switches, temp probes and most of all... my chaeto!

[ProFlatlander15]

Yea Andy! We just started turbulent and laminar flow in my fluids class. You can figure out some cool stuff with that stuff.

[jokercykoe]

Since you're an aerospace engineer I was wondering if you can answer a question for me.

 

If an airplane was on a treadmill, and the treadmill was able to match the airplanes speed, will it take off? (Huge argument on another forum about this question with supporters on both sides.)

[Mr. Fosi]

I'll post my little-informed opinion on this one: The plane isn't moving through the air and it is movement of air over the wings that creates lift, therefore the plane will not be able to take off.

 

How'd I do?

[Truck_Under_Water]

I'll post my little-informed opinion on this one: The plane isn't moving through the air and it is movement of air over the wings that creates lift, therefore the plane will not be able to take off.

 

How'd I do?

 

I concur. Airplane on treadmill = no air time. Teh wheels would get hot and get rubber in ur cheezeburgerz.

If an airplane was on a giant treadmill, theoretically it wouldn't even get the treadmill or wheels to move at all, so having a treadmill that could "match the airplanes speed" is completely irrelevant. The wheels are no means of locomotion, absolutely useless for propelling the aircraft.

 

Andy, your explanation of the boundary layer makes perfect sense to me. maybe my brain works after all. I feel so awesome since i learned something new today. They kicked me out of Mech. Eng. for no good reason. Well, other than partying every day and being hungover 7 days a week.....

[epicfish]

I'll post my little-informed opinion on this one: The plane isn't moving through the air and it is movement of air over the wings that creates lift, therefore the plane will not be able to take off.

 

How'd I do?

 

I agree with you.

 

With a little more research:

http://blog.sciam.com/index.php?title=how_...p;tb=1&pb=1

 

Sounds like whether go with Bernoulli or Newton, both opinions are based upon the the fact that there is wind travel over/under/against the winds to create a "lifting" force.

[Brian Crook]

Since you're an aerospace engineer I was wondering if you can answer a question for me.

 

If an airplane was on a treadmill, and the treadmill was able to match the airplanes speed, will it take off? (Huge argument on another forum about this question with supporters on both sides.)

 

Well, I'm only in first year engineering but I would have to say no it would not take off. Since the airplane would remain stationary during this, no matter how fast the impellers or jets were thrusting, there would be no wind under the wings of the plane and therefore it could not lift off the ground. If the plane overcame the tread mill or the tread mill stopped, then of course the plane would thrust forward and eventually take off. Perhaps the aerospace engineer can confirm or correct this.

[Truck_Under_Water]

Off topic, but Brian your avatar is effin hilarious!

[coral_addict]

Well, I'm only in first year engineering but I would have to say no it would not take off. Since the airplane would remain stationary during this, no matter how fast the impellers or jets were thrusting, there would be no wind under the wings of the plane and therefore it could not lift off the ground. If the plane overcame the tread mill or the tread mill stopped, then of course the plane would thrust forward and eventually take off. Perhaps the aerospace engineer can confirm or correct this.

 

 

It won't take off. Some Japanese guys did a testing and post it on You Tube on something similar where a normal ball gun will shoot a ball at 100MPH but when they launch it from a truck driving at 100MPH, the ball would not fly out. It would just drop to the ground.

[Mr. Fosi]

^-- Different principle but still interesting.

[andykee]

If an airplane was on a treadmill, and the treadmill was able to match the airplanes speed, will it take off? (Huge argument on another forum about this question with supporters on both sides.)

yeah, i've seen this question before too...

 

the answer is simple. no matter how fast the engines are screaming, the plane will remain motionless. no forward movement = no lift. no lift = no takeoff.

[flipteg]

i added a 5.5 gallon fuge to my 30 gallon cube just a few months back... i would have gone bigger but 5.5 gallons is the largest standard size tank i can fit inside my stand... i didn't bother with dividers and bubble traps... i don't have any problems with micro bubbles because i am only running less than about 100GPH through the fuge... the purpose of the fuge is nutrient export so the chaeto is the main attraction... i've had my tank for 2 years and this is the best upgrade i have done to the tank... it solved my excess nutrient problem but it took a few weeks before the chaeto out competed the slime and hair algae in the main display...

[c est ma]

That's inspiring!

 

--Diane

[neanderthalman]

yeah, i've seen this question before too...

 

the answer is simple. no matter how fast the engines are screaming, the plane will remain motionless. no forward movement = no lift. no lift = no takeoff.

 

I feel like picking a fight with an aerospace engineer

 

No forward movement = no frictional force term from air resistance.

 

I don't think this is as simple as matching the speeds. In order for the plane to remain motionless, the force of the treadmill moving backwards would have to match the force of the engines. Newton's second law.

 

A plane at top speed, on a normal runway (in one dimension) has three basic forces. The force of friction from the wheels, the force of friction from air resistance, and the force from the engine. In the case of the plane at top speed, these forces are balanced. The sum of the air resistance and wheel friction forces would have to equal the forces from the engine.

 

Now, change the situation so we have the plane at full power, but at a standstill. It's now on the treadmill, moving at the plane's top speed.

 

The frictional force from the wheels is dependent on the speed of the aircraft relative to the runway/treadmill. Since this land speed is the same as before (by definition of the problem), and the plane and wheel assembly are all identical, the wheel frictional force term is the same as in the normal case.

 

The engines are again at full power, so are producing the same thrust forces as before.

 

The remaining term, the air resistance, is dependent on the wind speed of the airplane. In this case, the speed is zero, so the frictional force term from air resistance is also zero.

 

However, in the original case, this force term is necessary to balance the frictional forces against the thrust. By setting it to zero, the frictional forces are no longer in balance with the thrust force. The net thrust should cause the plane to slowly accelerate forward, not remain motionless.

 

In order for the treadmill to keep the plane at a standstill, the frictional force from the wheels would have to be the same as the sum of the friction from the wheels and air resistance in the original case. The only way to do this is to run the treadmill at a higher speed than the plane's top speed.

 

Now, lets add more complexity.

 

The wheel frictional force term is also dependent on the wind speed. The wind speed of the plane provides lift, which reduces the amount of 'weight' that the wheels are carrying. By providing lift, we reduce the force of friction from the wheels.

 

In the treadmill case, the force of friction in the wheels is the same as for the plane at virtually zero speed. In the real world case, the force of friction in the wheels is reduced by the lift generated.

 

This would allow the treadmill to operate at a lower speed than before in order to keep the plane at a standstill.

 

The question is, "does the elimination of air resistance exactly match the increase in wheel friction".

 

The answer is no. One of them will be greater than the other, though depending on the exact configuration of the plane and wheel, it's possible to design them such that they are equal. By random occurrence, it's highly unlikely for the two to match precisely.

 

 

 

Thus, I submit that the plane will move, just very slowly. It might move forward, and it might move backwards. That would depend on the exact plane and wheels.

 

 

 

 

 

One thing I have assumed is that the thrust of the plane is the same, irrespective of the windspeed. I don't think this is correct. Andy, can you tell me whether the thrust from the engines at zero windspeed is the same as at full windspeed? I think the extra windspeed should increase the thrust, from both the thermodynamic efficiency and the operation of any air-intake rams that they use.

[andykee]

so i started to type out this long complicated response going in to all sorts of nuances of aerodynamics, but i can explain it in a much simpler way. your error is in the following two paragraphs:

 

However, in the original case, this force term is necessary to balance the frictional forces against the thrust. By setting it to zero, the frictional forces are no longer in balance with the thrust force. The net thrust should cause the plane to slowly accelerate forward, not remain motionless.

 

In order for the treadmill to keep the plane at a standstill, the frictional force from the wheels would have to be the same as the sum of the friction from the wheels and air resistance in the original case. The only way to do this is to run the treadmill at a higher speed than the plane's top speed.

this is exactly correct, but top speed has nothing to do with it. the treadmill will run at whatever speed is necessary to generate enough friction between itself and the wheels to exactly offset the thrust being produced by the engine. this is, of course, assuming that the treadmill is capable of maintaining whatever speed is necessary.

 

i think you are confusing yourself by assuming that the "top speed" of the aircraft is a fixed value in all arenas. this is not true. similarly, the max thrust is also not constant.

 

the top speed of an aircraft at sea level will be much lower than the top speed of an aircraft at cruising altitude. the air is much more dense at sea level (thus, more aerodynamic drag) and the engines are less efficient.

 

The question is, "does the elimination of air resistance exactly match the increase in wheel friction".

the answer is, it really doesn't matter

 

Andy, can you tell me whether the thrust from the engines at zero windspeed is the same as at full windspeed? I think the extra windspeed should increase the thrust, from both the thermodynamic efficiency and the operation of any air-intake rams that they use.

the engine thrust is not the same at an inlet velocity of zero as it is with some cruising inlet velocity. this is largely due to the fact that an engine operating in a moving flow will have air being rammed into the inlet (ram effect), this doing some of the work of the compressor already. air will enter the compressor at a higher pressure, and less work will be necessary to compress that air up to the combustion pressure.

 

 

 

 

 

hope this answers your questions and thoroughly refutes your submission. if not, ask away!

[travisurfer]

lol andy, here are my experiences with fuges:

 

I ran an AC500 on my 20H for about 6-8 months or so and took it off for some reason or another that I can't seem to remember now. Anyway, here is a quick recap from what I noticed:

- my water always seemed to be much clearer

- the rocks had absolutely no growth on them while there are now small fibrous growths all over the place

- i never had any algae outbreaks shy of the occasional cyano

- there was always an abundance of pods and mini brittles not to mention regular snail spawning and tons of baby ceriths

and now for the minuses

- the chaeto grew incredibly fast consuming way too many nutrients depleting my calcium and so slowing the growth rates of the corals

- the fuge had to be cleaned quite often. otherwise a strange grayish sludge would form(not detritus)

-when i cleaned it out, if found some crazy stuff in there. anything from strange worms topping 6" long to little crabs and whatnot. not sure if this is good or bad but it was some crazy looking stuff nonetheless

 

and thats about it. all-in-all, i regret taking the fuge off the tank and should probably find a suitable replacement. anyway, hope that helps.

[adinsxq]

WARNING---WARNING---WARNING

 

THIS THREAD HAS TOO MUCH NERD

 

WARNING---WARNING---WARNING

[Alastair]

Umm... maybe I missed something, but.. .

 

Plane on treadmill.

 

Plane turns engines on.

 

Treadmill is irrelevant.. . why? Never came across a plane that used rotary motion of the wheels to accelerate.

 

Outcome - Treadmill stays where it is, plane exits stage left.. .

 

 

Maybe you build planes different in the US?

[travisurfer]

Umm... maybe I missed something, but.. .

 

Plane on treadmill.

 

Plane turns engines on.

 

Treadmill is irrelevant.. . why? Never came across a plane that used rotary motion of the wheels to accelerate.

 

Outcome - Treadmill stays where it is, plane exits stage left.. .

Maybe you build planes different in the US?

The arguement is that, as the prop pushes or pulls the plane forward on the pavement, the treadmill's opposing velocity prohibits the plane from moving forward therefore preventing any lift from being generated.

[andykee]

Umm... maybe I missed something, but.. .

 

Plane on treadmill.

 

Plane turns engines on.

 

Treadmill is irrelevant.. . why? Never came across a plane that used rotary motion of the wheels to accelerate.

 

Outcome - Treadmill stays where it is, plane exits stage left.. .

Maybe you build planes different in the US?

think of hit s way... you run on a treadmill. treadmill spins "backwards" under you. assuming that the treadmill is free to spin at any speed, no matter how fast you run, you will not be able to run off the treadmill. same principle. think of your feet as the wheels of the plane and your legs as the engines.

[Alastair]

think of hit s way... you run on a treadmill. treadmill spins "backwards" under you. assuming that the treadmill is free to spin at any speed, no matter how fast you run, you will not be able to run off the treadmill. same principle. think of your feet as the wheels of the plane and your legs as the engines.

 

But I generate forward motion by pushing against the ground (or treadmill) with my feet. A planes engines are pushing against the air, not the ground, in order to generate forward motion. The ground is merely supporting the weight of the aircraft with some energy losses due to rolling resistance and friction in the wheel hubs. If you're going to rotate the treadmill fast enough that these friction forces equal the thrust of a couple of Spey jet engines then my guess is that you are going to pull the undercarriage off long before you match their output.

 

You can't compare legs with undercarriage in terms of their purpose in providing motive force. Using that argument would suggest putting a treadmill in the bottom of your tank would prevent your fish from swimming.

[neanderthalman]

so i started to type out this long complicated response going in to all sorts of nuances of aerodynamics, but i can explain it in a much simpler way. your error is in the following two paragraphs:

this is exactly correct, but top speed has nothing to do with it. the treadmill will run at whatever speed is necessary to generate enough friction between itself and the wheels to exactly offset the thrust being produced by the engine. this is, of course, assuming that the treadmill is capable of maintaining whatever speed is necessary.

 

hope this answers your questions and thoroughly refutes your submission. if not, ask away!

 

It really doesn't answer my point.

 

I am assuming a "top speed", but by your explanation that the "treadmill will run a whatever speed is necessary" implies that it will have to move at a different speed than the plane at top speed (in those conditions).

 

That was sortof the heart of my argument. If, under the exact conditions (still wind, sea level, 70F, 65% humidity, etc.), the plane has a top speed of 200mph, the treadmill would have to move at, say, 210mph to hold the plane still.

 

The question was that the two were at the same speed - which wouldn't work.

 

Is it possible to have a treadmill operate at the necessary speed to keep the plane still? Absolutely. Would it be the same as the top speed of the plane at those same conditions? No.

 

 

 

 

Now, if one were to put the plane on a treadmill at 200mph, and in a wind tunnel at 200mph, then yeah, the plane would stay still.

[bdare]

Se habla engles?

 

You guys are getting WAY to into this....