Fire Sprinkler simulation
 

Hi all,
I am very new to this Ansys CFX software. As the title, i want to simulate water distribution for fire sprinkler in a room. I have done through some tutorial in the example but i cant manage to get my simulation right.

i am using multiphase for domain combination of water and air. for the input, the fraction of water is 1 while for the air is 0. output is at the floor.

the streamline result only show velocity at the sprinkler but not reaching the floor of the room.

i hope anybody can enlighten me in this simulation. is there any important setting that i left out? if there is a tutorial close to this simulation, let me know.

thanx.

How are you modelling the multiple phases? Particle tracking or eularian?

i believe it is particle tracking..

Can you post an image of what you are seeing?

finally i solved the problem.. it is due to the initial condition of the domain..
but now my problem is the flow of the water is like bended.. its not falling in a straight line.. any idea what causes it?

http://img6.imageshack.us/img6/3718/54970788.jpg
http://img190.imageshack.us/img190/3482/33391457.jpg

Umm, isn't that why you are doing a CFD model? Isn't it bending because the air flow bends it?

but the condition of the air speed has been set to 0.. plus i only want to study the design of sprinkler distribution cap neglecting the air movement..
im still exploring cfx to get better result presentation..
thanx alot.. :)

The water droplet will drive a flow. If you want to disable the flow then use an expert parameter "solve fluids=f" then it will not update the fluid flow field.

hi..
 

very nice work. will you help me for simulation in tunnel fire. how i start in CFX ?
thanks with best regards

Do the tutorials, do some training, read the textbooks and do a literature search. And every once in a while put a post on the forum and we will try to help too.

hi
 

plz suggest some text books..

Any text book with "introduction" and "CFD" is a good start.

Here's a few, there are many more: http://www.cfd-online.com/Books/brow...?category_id=1

thanks for suggestion...

I'm new with CFX. Modelling a simple water sprinkler in air. Actually i used Lagrangian particle tracks but my simulation goes in error (floating) every time...
I've tried different solutions to solve this problem but without any effects (mesh, timescale, increase particle injection, decrease particle speed and flow rate, ecc).

I select no turbulence, isothermal and no inlet, so no speed, for air considered as countinous fluid.

Initial condition has been setted to zero for every parameter.

Geometry is actually small (about 3 x 2 x 2 m). Sprinkler inlet is modelled as a cilindrical surface.

Water speed is about 10 m/s and flow rate abou 10 kg/s.

Sprinkler direction is from top to bottom.

I want to start from this basic and easy system in order to study later the behaviour of a water "wall" generated by a sprinkler on a gas release.

I would compare particle track and fluid disperded different results.

Any idea on how to solve this simulation solver error? RMS and imbalance are so oscillating...

Is this an unsteady simulation? Does it converge if you set the particle number to zero?

These are FAQs:
Floating point error: https://www.cfd-online.com/Wiki/Ansy...do_about_it.3F

Poor convergence:
https://www.cfd-online.com/Wiki/Ansy...gence_criteria

Thank you for your suggestion...

This is a steady simulation.

If i put 0 as number of positions for particle solver goes immediately in error.

I noticed that:
particle entered the domain: 10000
particle left domain: 9950
exceeded distance limit:50

I expect that particle will be accumulated on walls (floor). I've tried to reduce also speed and flow rate but nothing changed...

I made a simulation with only 1 particle and RMS still oscillating...less...

It is very strange because it a very simple simulation...no wind, no turbulence, isothermal...i want only to see the water! please help me...

mesh is ok and fitted enough in my opinion...

on the sprinker inlet i have about 4mm size against 0.5mm particle diameter...is it ok?

another strange things... particle seems not to go out normal to inlet surface but with casual angles...

Hi,
in case of interest i found the solution of my problem...

It is related to particle speed.

I noticed that if the speed is too low < 30m/s i have oscillating on RMS and particle seems coming from inlet at casual angle.
If i put a speed > 40 m/s this problems are solved.
Speed are related also with particle diameter. With smaller diameter i have to increase speed.
Can anybody explain this strange behaviour?
Is there any equation for calculating "correct" speed?

I leave flow rate fixed because this is coming form my physics. But basically this should be also for speed...

Any comment?