
[Sponsors] 
Calculating thrust for a hollow cylinder in OpenFOAM v6" 

LinkBack  Thread Tools  Search this Thread  Display Modes 
October 18, 2023, 22:58 
Calculating thrust for a hollow cylinder in OpenFOAM v6"

#1 
Member
Niyas
Join Date: Apr 2013
Posts: 45
Rep Power: 13 
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); } } 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 = 3.14979047753e05, Final residual = 8.53492622127e15, No Iterations 2 DILUPBiCGStab: Solving for O2, Initial residual = 1.74824594395e05, Final residual = 4.02124604301e15, No Iterations 2 DILUPBiCGStab: Solving for CO, Initial residual = 8.18262424705e06, Final residual = 4.90454810226e13, No Iterations 1 DILUPBiCGStab: Solving for H2, Initial residual = 6.457643001e07, Final residual = 3.87061901616e14, No Iterations 1 DILUPBiCGStab: Solving for O, Initial residual = 9.52133879132e70, Final residual = 9.52133879132e70, No Iterations 0 DILUPBiCGStab: Solving for CO2, Initial residual = 2.35921456931e59, Final residual = 2.35921456931e59, No Iterations 0 DILUPBiCGStab: Solving for OH, Initial residual = 1.83467046096e33, Final residual = 1.83467046096e33, No Iterations 0 DILUPBiCGStab: Solving for H, Initial residual = 5.9672678478e61, Final residual = 5.9672678478e61, No Iterations 0 DILUPBiCGStab: Solving for H2O, Initial residual = 1.00786903437e60, Final residual = 1.00786903437e60, 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 : (6.60598318567e10 5.56817720667e10 7.64502167528e11) porous : (0 0 0) sum of moments: pressure : (1.8766312015 0.141697863622 0) viscous : (7.47148938546e11 5.48630457733e11 8.40572287366e10) porous : (0 0 0) Max Courant Numbers = 0.199907494426 deltaT = 9.98003992015e09 Time = 0.000253373253493 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!
__________________
Regards, Niyas 

October 19, 2023, 00:17 

#2 
Senior Member
Lucky
Join Date: Apr 2011
Location: Orlando, FL USA
Posts: 5,712
Rep Power: 66 
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. 

October 19, 2023, 00:28 

#3 
Member
Niyas
Join Date: Apr 2013
Posts: 45
Rep Power: 13 
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); } }
__________________
Regards, Niyas 

October 20, 2023, 01:00 

#4  
Member
Niyas
Join Date: Apr 2013
Posts: 45
Rep Power: 13 
Quote:
My ultimate aim is to make a time vs. Thrust plot.
__________________
Regards, Niyas 

Tags 
cylinder, force, openfoam v6, pressure, thrust 
Thread Tools  Search this Thread 
Display Modes  


Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
calculating thrust of a propeller  amin.z  FLUENT  5  September 15, 2023 12:51 
Flow past a 2D cylinder  High Re (1E+05)  Cd too high  Pervispasco  OpenFOAM Running, Solving & CFD  4  March 14, 2022 02:19 
OpenFOAM course for beginners  Jibran  OpenFOAM Announcements from Other Sources  2  November 4, 2019 08:51 
OpenFOAM Training JanJul 2017, Virtual, London, Houston, Berlin  CFDFoundation  OpenFOAM Announcements from Other Sources  0  January 4, 2017 06:15 
[Other] OpenFoam Flow over a Circular Cylinder  WolfgangS.  OpenFOAM Meshing & Mesh Conversion  12  March 3, 2014 10:53 