Thrust Force Calculation


#1

Hi,

So I ran a simulation of a 3 blade propeller model at a speed of 3000 rpm. I got the force plot outputs from the simulation. Not quite sure how to go about in calculating the thrust force generated by the blades ? Help would be appreciated. :slight_smile:

thanks & regards,
Victor


#2

Thanks a lot for the question @Targaryen!

One of the @PowerUsers_CFD may help you there.

All the best!

Jousef


#3

Hi @Targaryen, thrust is directly obtained from the force plot using the pressure force in the axial direction, this is in newtons.

Just ensure that the result control item is assigned to all blades.

Good luck,
Darren


#4

Hi @1318980 Darren,

Thanks for the clarification ! In my case, the pressure force in the z direction should give me the thrust force right ? I am getting insanely high values in the range of e18-20 which from theory is not normal. Can you help me understand the results ?

regards,
Victor


#5

Hi @Targaryen,

Could you post your project link here?

Cheers.

Regards,
Barry


#6

Hi @Get_Barried,

Sure. Here it is. https://www.simscale.com/projects/Targaryen/bladetest/. Sorry I didnt post it earlier. Cheers.


#7

Hi @Targaryen,

Looking at your simulation parameters you roughly have the right idea. Just a couple of things. The propeller itself should just be a wall boundary condition. Think of your rotating zone which you have correctly defined as the “rotating” action of the propeller. What you’re doing by defining a moving wall velocity is essentially rotating a already rotating propeller which is not what you want I assume so setting it to wall will fix that.

Next is your inlet conditions at the wall. What do you want to measure? Just the pure performance of the propeller in a static environment? Or is there some inlet you want to consider?

Thirdly and probably most importantly, what is the fluid your propeller is operating in? Currently you have set your medium to a default setting which may produce weird results. You set defined fluid mediums by selecting material and importing from the material library. After which you can adjust the density or whatever other parameters to your needs.

Lets try to fix these issue first before moving on to accuracy of the results.

Cheers.

Regards,
Barry


#8

Hi @Get_Barried,

Thanks for the quick reply !. My desired output is the performance characteristics like thrust of the propeller under static conditions initially and then move on to various inlet conditions. I have made the proposed changes regarding material parameters and have started a simulation run as I type this. Will get back to you on the results. Cheers.

Victor


#9

Hi @Get_Barried,

Changing the moving wall boundary condition certainly helped in bringing down the force value. Quick question, if I have to define an inlet velocity which boundary should I choose, the outer boundary wall or the MRF boundary wall ?
Cheers.
Regards,
Victor


#10

@Targaryen, you select the appropriate bounding wall.

Just looked at your project, few things here to add in addition to @Get_Barried.

Convergence hasn’t been reached, you will need to revisit this to ensure the result you are reading is converged results:

The mesh needs further refinement to properly capture the geometry of the blades.

Good luck,
Darren


#11

@1318980

Will do !!. Thanks.