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Thread: Solidworks transient simulation

  1. #1

    Solidworks transient simulation

    Hello everyone

    My name is BSHER and I am a member of JUST racing team. I am writing this to seek some answers to some problems I faced the other day while preparing our intake system for transient flow simulation by solidworks.
    I searched over the internet on how to perform such analysis, eventually I managed to learn how to it. After running the simulation and setting a sequence for the intake strokes for the runners, I got some unreasonable results as it was assumed that the runners were opened to the atmosphere and acted as inlets during the intervals where they should be closed. So please, if there is anyone who encountered such a setback can help me?
    Thank you for time.
    P.S.: I used a polynomial function to describe the pressure drop throughout the intake stoke.

  2. #2
    Junior Member
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    Mansoura, Egypt
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    Did you checked "Time dependent" option in the wizard tool?

    and please can you discuss how did you managed to get a relation between time intervals and pressure?
    Kareem
    Mansoura Formula Student

  3. #3
    Can't help you with the software since I have never used SW Flow Simulation. But considering the not-so-great Static Simulation by SW, I would recommend using a better sofware like ANSYS or else.


    But on a more general question, what is your goal with this simulation? What to you want to optimize? Do you already have a car that can move by it's own?
    Daniel Schwind
    UFF - Universidade Federal Fluminense (Rio de Janeiro, Brazil)

    2015 - Mechanical Systems Leader - Faraday Racing Formula SAE-E
    2014 - Powertrain Consultant - Buffalo Formula SAE-C
    2013 - Powertrain Leader - Buffalo Formula SAE-C
    2012 - Brake System Co-Designer - Buffalo Formula SAE-C
    2011 - Newbie/Do everything - Buffalo Formula SAE-C

  4. #4
    Did you analyze the rest of the manifold first?

    I can think of a few better uses for simulation time/effort than looking at transient flows in a manifold.

    A transient flows simulation is 3-d. In general, you add dimensions as they are actually needed, and start from 0 dimensions.

    You will get nearly the same performance by calculating the required runner lengths (INTAKE AND EXHAUST!!) in a spreadsheet, using good engineering judgement in preventing sharp turns and tapers around the restrictor.


    Overall, the total volume between the restrictor and the valves is far more important than the shape of that volume. You can find the required volume with 1-D simulation or an exceptional spreadsheet.


    If you did 1-D simulation of the engine as a whole, you would be able to look at the valve flow vs crank angle in your chosen simulator and copy that into the 3-D tool.
    Andrew Palardy
    Kettering University - Computer Engineering, FSAE, Clean Snowmobile Challenge
    Williams International - Commercial Turbofan Controls and Accessories

    "Sometimes, the elegant implementation is a function. Not a method. Not a class. Not a framework. Just a function." ~ John Carmack

    "Any sufficiently advanced technology is indistinguishable from magic" ~Arthur C. Clarke

  5. #5
    I agree with Andrew, that is what I was going to suggest after you answered my question

    I strongly advise you to focus your simulation efforts on a reliable and solid 1-D simulation, using either Ricardo WAVE or GT-Power (or any other good software), since the overall benefits of it are far greater than those of a 3-D simulation in that case. You can use the 3-D simulation later to improve your design, but do not focus solely on it.
    Daniel Schwind
    UFF - Universidade Federal Fluminense (Rio de Janeiro, Brazil)

    2015 - Mechanical Systems Leader - Faraday Racing Formula SAE-E
    2014 - Powertrain Consultant - Buffalo Formula SAE-C
    2013 - Powertrain Leader - Buffalo Formula SAE-C
    2012 - Brake System Co-Designer - Buffalo Formula SAE-C
    2011 - Newbie/Do everything - Buffalo Formula SAE-C

  6. #6
    Dear Kareem,
    Thank you for your response. The answer to your first question is: Yes, of course.
    The answer to your second question is:
    1- Determine certain rpm you want (let's say 3000 rpm),this means there are 1500 complete cycles in 1 minute, this means that one cycle needs (60/1500) seconds to be completed.
    2- From your engine's catalog or from the internet, determine the intake stroke interval in degrees (in my case 284 degrees).
    3- To find the pressure distribution over the 720 degrees of the crank angle, I assumed that the function of the pressure drop during the intake interval is polynomial (as the cam profile).
    4- Find the expression.
    5- The rest of the interval is assumed to be constant (closed).
    6- Repeat it for each cylinder.
    I hope that helps.

  7. #7
    Dear Daniel,
    Thank you for your response. We are performing this kind of study in order to produce a high quality intake system for future designs (class 2). We want to study and optimize each parameter of the intake system and its effect on the mass flow rate and its distribution.
    Regarding our car, we still work on it.
    I tried to use the Ansys earlier today instead of solidworks. I followed the instructions of a detailed youtube video, but I also get unreasonable results as it acted as if there is only one runner and stayed that way throughout the entire run.
    So, please if you have some advice, I would appreciate it.
    The link of the youtube video:
    https://www.youtube.com/watch?v=xsZleJdmGp8

  8. #8
    Dear Andrew and Daniel,
    We are doing this study as a research and also we have untraditional configuration for the intake system in mind that differs than the configurations that are used.
    May I ask you about Ricardo wave? Is it accurate? Is it easy to learn? And most importantly does it accept complicated 3d models (from solidworks or creo)? Or just it deals with straight pipes and elbows?

  9. #9
    Beshr,

    I am not too much into WAVE, but since it has most of the capabilities of GT-Power, I guess yes, you can use complex 3-D models in it. The problem comes with the discretization of such geometries, since it will be regarded as being made of multiple equal-volume cubes.

    This "untraditional configuration" is just an odd geometry or there is more to it?

    The models in 1-D simulation is as accurate as you dedicate time to build it. You need of course some sort of validation for your model, either being with an in-cylinder pressure sensor or comparing the expected torque curve with the real one you can get from a dyno. Of course there will be many differences in both curves, but if your valleys and peaks are kinda in the same RPM range you have a close model.
    If you dedicate enough time and efforts, you can make it very very accurate. I've seen a model of a real engine in GT-Power having a average error of around 5%, it was pretty good.

    It is not hard to learn. What is hard sometimes is to measure the entire engine to create the model, but if you already have the cam-profile and such, it will be way easier.

    Are you inputing acoustic effects in your runner simulation?
    Daniel Schwind
    UFF - Universidade Federal Fluminense (Rio de Janeiro, Brazil)

    2015 - Mechanical Systems Leader - Faraday Racing Formula SAE-E
    2014 - Powertrain Consultant - Buffalo Formula SAE-C
    2013 - Powertrain Leader - Buffalo Formula SAE-C
    2012 - Brake System Co-Designer - Buffalo Formula SAE-C
    2011 - Newbie/Do everything - Buffalo Formula SAE-C

  10. #10
    Daniel,

    You can say it has an odd geometry (of course for specific reasons).

    Regarding the last question, if you mean (Ansys), I just selected "transient" and define functions and expressions from an excel sheet (as mentioned before) as the outlet boundary conditions then I started the run.

    If this isn't what you are asking about, please explain further more.

    Thanks

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