CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > FLUENT

Rocket Nozzle problem

Register Blogs Members List Search Today's Posts Mark Forums Read

Like Tree1Likes
  • 1 Post By mrenergy

Reply
 
LinkBack Thread Tools Display Modes
Old   November 28, 2005, 12:44
Default Rocket Nozzle problem
  #1
Jeremie
Guest
 
Posts: n/a
Hello,

I am currently working on a simple convergent-divergent nozzle, with the following characteristics: -radius inlet&outlet=0,5m -radius throat =0,1m -Pin=20 bar -Tin=3424K -The fluid is water vapor (considered as ideal-gas and Cp=3225J/kg.K)

I used the coupled implicit axisymetric solver on a 2D mesh and tried to evaluate the influence of the different models (inviscid, S-A and RNG k-e) and meshes size (750, 3000 and 12000 cells), considering the fact that i have to output the mass flow rate and the velocity at the outlet and compare it with the following results: MFR=32,0893 kg/s Uex=3145,86 m/s

The Boudary Conditions are: -Pressure inlet (Po=20bar, P=19,5, To=3424K) -Pressure outlet (Pg=1bar) -Axis on the symetry edge. -Wall

I reached good comparative results with the 2 first meshes but for the last one (12000 cells) with the laminar and RNG k-e model, the Uex stabilize at 2300m/s and it seems that recirculation occurs (I have a reversed flow on the Pout and the velocity vectors show a region of recirculation near the wall at the exit). How can I obtain good results on this mesh? Do i need to refine the mesh near the recirculation? or do you think, the problem is related to the turbulence model?

If someone have any suggestions or hints,i would be very grateful. Regards

Jeremie
  Reply With Quote

Old   November 29, 2005, 03:53
Default Re: Rocket Nozzle problem
  #2
nasser
Guest
 
Posts: n/a
Hello jeremie I modeled 2D and 3D nozzle. some times your modeling is correct but your input data (e.g P out)is not correct. you can not use laminar model. your flow is turbulence.use boundary layer near your wall and you can use spallarat-almaras and K-epsilon and may be flow pressure in end of nozzle is smaller than atmosferic pressure . if your problem not solved mail me
  Reply With Quote

Old   November 29, 2005, 10:10
Default Re: Rocket Nozzle problem
  #3
Jeremie
Guest
 
Posts: n/a
Thank you very much Nasser. I put a Bounbary Condition on the wall and a lower pressure outlet (Pout=0,2bar) and it worked well with the S-A model. Regards Jeremie
  Reply With Quote

Old   February 17, 2013, 11:48
Default
  #4
New Member
 
Sami
Join Date: Sep 2012
Posts: 15
Rep Power: 4
abdul Sami is on a distinguished road
please can any one answer
why static pressure decrease in divergent section of nozzle and why total pressure and temperature remain constant througout the nozzle plz plz plz can any answer
abdul Sami is offline   Reply With Quote

Old   February 17, 2013, 12:42
Default
  #5
Member
 
Mamdouh
Join Date: Dec 2012
Location: Calgary, Alberta, Canada
Posts: 39
Rep Power: 4
mrenergy is on a distinguished road
Hi Sami,

it is basic science ...

total pressure and temperature remain constant throughout the nozzle ...

because they are the total energy ... they are constants unless shock wave occurs in the diverging part (supersonic NOZZLE)... or the nozzle is frictional


the static pressure increases in the converging section if the Mach number at throat became unity and the flow in the converging zone became supersonic ...
for supersonic flow ... the definitions of nozzle and diffuser are reversed ... according to the property relations for supersonic flow ...
and this is the reason for the name (converging - diverging NOZZLE)

Mamdouh
abdul Sami likes this.
mrenergy is offline   Reply With Quote

Old   February 18, 2013, 02:12
Default
  #6
New Member
 
Sami
Join Date: Sep 2012
Posts: 15
Rep Power: 4
abdul Sami is on a distinguished road
thanks alot dear
abdul Sami is offline   Reply With Quote

Old   February 18, 2013, 04:06
Default
  #7
New Member
 
Sami
Join Date: Sep 2012
Posts: 15
Rep Power: 4
abdul Sami is on a distinguished road
Plz tell me the terms, static pressure, total pressure, static temperature and total temperature with respect to convergent divergent nozzle I m so worried plzz help me I will be thankful i m not clear with these terms plz give detail answer
abdul Sami is offline   Reply With Quote

Old   February 18, 2013, 05:57
Default
  #8
Member
 
Mamdouh
Join Date: Dec 2012
Location: Calgary, Alberta, Canada
Posts: 39
Rep Power: 4
mrenergy is on a distinguished road
Hi Sami,

just google it, you will get many sources of information.

I did now, this is one example ...

http://www.google.ca/url?sa=t&rct=j&...MJv1DkYUMhX6Mg

try ... may you get better information

GOOD LUCK

Mamdouh
mrenergy is offline   Reply With Quote

Old   February 18, 2013, 22:29
Default
  #9
New Member
 
Sami
Join Date: Sep 2012
Posts: 15
Rep Power: 4
abdul Sami is on a distinguished road
thank you so much mamdouh
abdul Sami is offline   Reply With Quote

Old   October 8, 2014, 06:13
Default pressure ratio
  #10
Member
 
kabilan.B
Join Date: Jul 2010
Location: chennai
Posts: 77
Rep Power: 7
kabilan is on a distinguished road
hi sir,
could you please help to calculate jet pressure ratio.
in fluent pressure inlet condition total gauge pressure as 20bar,
supersonic/init pressure as 19.5 bar, and outlet pr is 1 bar,
how to calculate jet pressure ratio?
and total temperature of my inlet condition?
thank you sir..
kabilan is offline   Reply With Quote

Old   October 8, 2014, 06:16
Default
  #11
Member
 
kabilan.B
Join Date: Jul 2010
Location: chennai
Posts: 77
Rep Power: 7
kabilan is on a distinguished road
excuse me sir,
if i want to analyse into still air how can i give b.c value at outlet?
kabilan is offline   Reply With Quote

Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Gambit - meshing over airfoil wrapping (?) problem JFDC FLUENT 1 July 11, 2011 05:59
analyze a cd nozzle with fluent which designed by MOC mehrzad Main CFD Forum 0 July 6, 2011 04:33
Boundary condition on 3D Supersonic nozzle problem with atmosphere dokeun FLUENT 0 April 1, 2010 21:59
can you help me solving airfoil and nozzle problem san FLUENT 0 March 21, 2006 03:00
compressible flow in a counterflow nozzle d.vamsidhar FLUENT 0 November 24, 2005 02:45


All times are GMT -4. The time now is 17:56.