Beginner in using Elmer

Numerical methods and mathematical models of Elmer
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Charlezyi
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Beginner in using Elmer

Post by Charlezyi »

Hi all,

I am a student at my local university. As of now, I have a presentation coming up in 2 weeks regarding "Evaluate the role computational analysis plays in the design and optimization of engineering systems. How does one ensure the accuracy and reliability of computational analysis in aiding engineering design? What could go wrong in solely relying on computational analysis to design engineering systems, and what could an engineer do to minimize it?" As such, I would like to ask how can I create a model of a slingshot shooting a projectile which can answer these questions

(1) develop a simple mathematical model from which you can connect the projectile launch velocity to
the mass of the projectile and material properties of the slingshot.
(2) develop a mathematical model for the kinematics of the projectile and express the launch velocity
appearing in this model in terms of slingshot design variables developed in part A(1).
(3) solve the trajectory of the projectile by (a) neglecting air-resistance and (b) including air-resistance
using Excel VBA. Compare and show the trajectories in a plot.
(4) estimate parameters such as maximum range and optimal angle of launch with this model.
(5) incorporate the effects of a head wind or tail wind in part A(3) and assess the effect of this on
maximum range, optimal angle of launch etc.
(6) deliberate on the limits on the stretch of the rubber band and flexibility of the frame etc on the
parameters considered in part A(4).

I hope to create a 3D simulation model which can be useful in explaining these concepts to my class. However, as I am not adept in using Elmer, I hope that some of you experienced coders can help to create one for me or guide me. I will have to do this in a week.

Thanks!
raback
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Re: Beginner in using Elmer

Post by raback »

Hi

Solving this with finite elements would be a huge overkill, and it would be a challenge within two weeks even for a seasoned Elmer user.

The natural approach for this would be to formulate it as an "ordinary differential equation". It is non-stiff and with sufficiently small timesteps you can treat all the resistance as r.h.s. terms. Now this would be ~1 hour for a seasoned Matlab user.

-Peter
mzenker
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Joined: 07 Dec 2009, 11:49
Location: Germany

Re: Beginner in using Elmer

Post by mzenker »

Hi,

I would like to add that if you don't have access to MatLab, you can use Scilab (http://www.scilab.org) which is free and as powerful as Matlab in many fields.

HTH,
Matthias
lazyTom
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Re: Beginner in using Elmer

Post by lazyTom »

Hi Charlezyi,

Another option to keep an eye on for 1D modeling and simulation is openmodelica

https://www.openmodelica.org

Here you get the bonus of 3D animation included in the simulation (some configuration required...)

In your case animation might not be a decision maker since your projectile can be seen as single point...

Good luck :)

Marco
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