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

Calculating thrust for a hollow cylinder in OpenFOAM v6"

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

Like Tree1Likes
  • 1 Post By LuckyTran

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   October 18, 2023, 23:58
Default Calculating thrust for a hollow cylinder in OpenFOAM v6"
  #1
Member
 
Niyas
Join Date: Apr 2013
Posts: 45
Rep Power: 13
niyas is on a distinguished road
Greetings everyone,

I am working on determining the thrust output of a hollow cylinder (Picture1) using OpenFOAM v6. I've added a functionObject to the controlDict file as follows:

Code:
functions
{
     forces
     {
         type                     forces;
         functionObjectLibs       ("libforces.so"); 
         patches                  ("outlet");
         origin                   (0 0 0); 
         CofR                     (0 0 0);                                                 
     }    

}
Upon implementation, I've obtained the following output in the terminal and in the postProcessing/forces/0/force.dat file as follows:

Code:
diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
diagonal:  Solving for rhoUx, Initial residual = 0, Final residual = 0, No Iterations 0
diagonal:  Solving for rhoUy, Initial residual = 0, Final residual = 0, No Iterations 0
diagonal:  Solving for rhoUz, Initial residual = 0, Final residual = 0, No Iterations 0
DILUPBiCGStab:  Solving for C2H4, Initial residual = 3.14979047753e-05, Final residual = 8.53492622127e-15, No Iterations 2
DILUPBiCGStab:  Solving for O2, Initial residual = 1.74824594395e-05, Final residual = 4.02124604301e-15, No Iterations 2
DILUPBiCGStab:  Solving for CO, Initial residual = 8.18262424705e-06, Final residual = 4.90454810226e-13, No Iterations 1
DILUPBiCGStab:  Solving for H2, Initial residual = 6.457643001e-07, Final residual = 3.87061901616e-14, No Iterations 1
DILUPBiCGStab:  Solving for O, Initial residual = 9.52133879132e-70, Final residual = 9.52133879132e-70, No Iterations 0
DILUPBiCGStab:  Solving for CO2, Initial residual = 2.35921456931e-59, Final residual = 2.35921456931e-59, No Iterations 0
DILUPBiCGStab:  Solving for OH, Initial residual = 1.83467046096e-33, Final residual = 1.83467046096e-33, No Iterations 0
DILUPBiCGStab:  Solving for H, Initial residual = 5.9672678478e-61, Final residual = 5.9672678478e-61, No Iterations 0
DILUPBiCGStab:  Solving for H2O, Initial residual = 1.00786903437e-60, Final residual = 1.00786903437e-60, No Iterations 0
diagonal:  Solving for rhoE, Initial residual = 0, Final residual = 0, No Iterations 0
min/max(T) = 200, 344.581351221
min/max(p) = 19528.5921163, 303653.998145
forces forces write:
    sum of forces:
        pressure : (0 0 78.0680166724)
        viscous  : (-6.60598318567e-10 5.56817720667e-10 -7.64502167528e-11)
        porous   : (0 0 0)
    sum of moments:
        pressure : (1.8766312015 0.141697863622 0)
        viscous  : (-7.47148938546e-11 -5.48630457733e-11 -8.40572287366e-10)
        porous   : (0 0 0)

Max Courant Numbers = 0.199907494426
deltaT = 9.98003992015e-09
Time = 0.000253373253493
I think the main value here is the pressure which is '78.0680166724'.

Now, my next step is to calculate the area of the hollow cylinder using the formula:

Area of the Hollow Cylinder (A) = Outer Area − Inner Area

Once I know the area, then by using thrust formulate,

Thrust = pressure x Area

I can calculate my thrust.

Is my approach correct? Please correct me!
Attached Images
File Type: jpg Picture1.jpg (28.4 KB, 9 views)
__________________
Regards,
Niyas
niyas is offline   Reply With Quote

Old   October 19, 2023, 01:17
Default
  #2
Senior Member
 
Lucky
Join Date: Apr 2011
Location: Orlando, FL USA
Posts: 5,760
Rep Power: 66
LuckyTran has a spectacular aura aboutLuckyTran has a spectacular aura aboutLuckyTran has a spectacular aura about
78 is Newtons is already a force

The pressure keyword identifies it is "pressure drag" obtained from the integration of pressure over the area as opposed to viscous drag

Your entry for patches should be the surfaces over which you want to obtain the force, which is not your outlet if you want to calculate drag but makes sense for your case because you are not calculating drag.

That being said, I don't really get why you are using a force tool to obtain thrust. Just calculate the streamthrust directly.
niyas likes this.
LuckyTran is offline   Reply With Quote

Old   October 19, 2023, 01:28
Default
  #3
Member
 
Niyas
Join Date: Apr 2013
Posts: 45
Rep Power: 13
niyas is on a distinguished road
Thanks for the reply.

I intend to compute the exerted thrust from the outlet of the cylinder (as shown in the attached picture).

So, in the controlDict file, should I put the patches as the outlet patch?

Like this below,

Code:
functions
{

     forces
    {
         type                        forces;
         functionObjectLibs    ("libforces.so"); 
         patches                   ("outlet");
         origin                      (0 0 0); 
         CofR                        (0 0 0);                                                 
     }    

}
Is my understanding accurate?
Attached Images
File Type: jpg Picture1.jpg (27.9 KB, 3 views)
__________________
Regards,
Niyas
niyas is offline   Reply With Quote

Old   October 20, 2023, 02:00
Default
  #4
Member
 
Niyas
Join Date: Apr 2013
Posts: 45
Rep Power: 13
niyas is on a distinguished road
Quote:
Originally Posted by LuckyTran View Post
That being said, I don't really get why you are using a force tool to obtain thrust. Just calculate the streamthrust directly.
@LuckyTran, can you please guide me how to calculate the streamthrust in OpenFoam v6 ?

My ultimate aim is to make a time vs. Thrust plot.
__________________
Regards,
Niyas
niyas is offline   Reply With Quote

Reply

Tags
cylinder, force, openfoam v6, pressure, thrust

Thread Tools Search this Thread
Search this Thread:

Advanced Search
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 Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
calculating thrust of a propeller amin.z FLUENT 5 September 15, 2023 13:51
Flow past a 2D cylinder - High Re (1E+05) - Cd too high Pervispasco OpenFOAM Running, Solving & CFD 4 March 14, 2022 03:19
OpenFOAM course for beginners Jibran OpenFOAM Announcements from Other Sources 2 November 4, 2019 09:51
OpenFOAM Training Jan-Jul 2017, Virtual, London, Houston, Berlin CFDFoundation OpenFOAM Announcements from Other Sources 0 January 4, 2017 07:15
[Other] OpenFoam Flow over a Circular Cylinder WolfgangS. OpenFOAM Meshing & Mesh Conversion 12 March 3, 2014 11:53


All times are GMT -4. The time now is 04:53.