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Questions from Oral Presentations (9.30)


This creates a problem because the mechanical concept of the AED is that it ... rather then as the quantum physics topic of ... For our next presentation, ... – PowerPoint PPT presentation

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Title: Questions from Oral Presentations (9.30)

Questions from Oral Presentations (9.30)

Electromechanical Questions
  • What is the effect of relocating the position of
    the magnet/inductor?
  • Changing the location of the magnet effects the
    distance the magnet oscillates. In order to
    capture the most flux as possible one must keep
    the distance between the magnet and coils to a
    minimum, in order to operate in the high density
    flux lines. This means locating the magnet on
    the ends where belt displacement is low. If it
    were put further away from the ends it would
    generate less current as the fewer flux lines
    would pass through our coils and it would cause
    greater disturbance in flow over the belt.

Electromechanical Questions
  • If the magnets are taking out energy, wont they
    be dampening the vibrations thus changing the
    natural frequency calculated?
  • The magnets will take energy out of the system
    due to the effects of Lorenz forces induced by
    the current flow in the stationary coils. This
    will affect the dynamics of belt operation but
    does not affect its natural frequency which are
    governed by the mass, stiffness and length of the

Electromechanical Questions
  • Where/what are these electrodynamic equations?
    You keep talking about them but you dont show or
    actually explain them.
  • When the presentation was made the specific
    equations for magnetic flux where not know by the
    ARES team. Shortly after the presentation the
    equations which are used to determine the flux of
    a magnet (of specified shape) with respect to
    distance have been found. Currently the
    electrodynamic equations used by the ARES team
    include Faradays Law, Coulombs Law, and the
    magnet flux equations for a permanent magnet.
    These equations will be in much greater detail in
    the next ARES presentation.

Electromechanical Questions
  • Are these models time realistic? It seems that
    electromechanics are a large (missing) part of
    this project so without this area of knowledge
    one expect to prod reasonable amount of
  • The equation referred to in this question is
    Faradays law, in which the induced voltage in a
    coil of wires is governed directly by the
    derivative of the flux density experienced by the
    coils with respect to time. Our magnet will be
    oscillating and will then generate a varying flux
    density experienced by the coils thus inducing a
    voltage that is time based.
  • In terms of if were going to complete these
    models in the allotted time for Senior Design, it
    is the intention of our project. We have some
    time considering the difficulties presented by
    this project and feel confident that we will
    successfully complete this project on time
    through the careful planning and hard work of the
    team as a whole. Gantt charts and timelines are
    available, but as always, are susceptible to the
    learning curve that is presented by this project.

Belt Materials and Manufacturing Questions
  • How is belt length determined?
  • This variable will primarily be determined by the
    dimensional limits of the wind tunnel test
    section, if we choose to take a path where we
    test everything in the wind tunnel. Otherwise,
    the length will probably just be "picked" as one
    close to the Humdinger's belt length. A seemingly
    "arbitrary" selection will help lower the number
    of parameters that we will have to optimize.

Belt Materials and Manufacturing Questions
  • What is the material of the belt going to be?
  • Several differnet types are being explored
    including the Mylar coated taffeta that Humdinger
  • Composite belts, similar to Humdinger's taffeta
    belt, are a big possibility. Using stiff fabrics
    laminated by thin flexible films will allow us to
    stiffen the belt in twisting directions, which
    may be beneficial to power generation.
  • Elastomers would also make good belt materials as
    they typically have an exceptional resistance to
    cyclic fatigue.

Belt Materials and Manufacturing Questions
  • What is the final deliverable?
  • Our final deliverable will be an optimized
    prototype AED that can operate under the
    conditions specified by our objectives. Our main
    goal is to make this AED as efficient as

Belt Materials and Manufacturing Questions
  • How will fatigue of the belt affect performance?
  • We will be choosing materials that under our
    operating conditions will not plastically deform
    because having the belt under a specific tension
    is important for efficient operation. Materials
    will also have enough strength to not fail due to
    the intense forces caused by resonance in the
    belt. Our main concern will be cyclic fatigue,
    which would result in a failure in the belt.
    Cyclic fatigue is being considered in the design
    and one design criteria is the ease of belt

Belt Materials and Manufacturing Questions
  • If constant changing of the belt is required, how
    will it be cost effective?
  • We are going to design the device so that the
    belt does not require constant changing and
    instead only requires periodic changing. The belt
    is actually one of the cheapest parts of the
    entire device and so replacing belts is not

Belt Materials and Manufacturing Questions
  • How do you intend to manufacture a composite belt
    with multiple layers of the size described? (ie,
    very small)
  • We will use thin fabrics laminated with flexible
    films (like Mylar) with the use of flexible
    ahesives. Secondly there are manufacturing
    techniques such as vacuum bagging that greatly
    reduce the thickness of the composite.

Aerodynamics Questions
  • How will you compare plate vibration to a
  • We intend to model a cylinder first because it is
    the simplest case for analysis. By using a
    cylinder as a starting point for our
    calculations, we can assume various parameters
    that will allow us to output useful data that we
    can compare to our experimental data. Once we
    have completed the model for a cylinder, then the
    model for a flat plate can be completed. The
    same basic principles still apply to both cases,
    but more studies have been done on cylinders and
    hence there is more data to which we can compare
    our models.

Aerodynamics Questions
  • Unclear as to what Slide 20 equations are for
    physically as in the amplitude
  • Slide 20 from our presentation discussed the
    minimum velocity required to induce vortex
    shedding along the membrane, and thus the
    equation was a displacement function of the belt
    in the y-direction

Aerodynamics Questions
  • Are your calculations going to be determined by
    analytical or experimental results?
  • Our calculations are going to be determined using
    both analytical and experimental data first we
    will analytically determine how our belt will
    perform, and then experimentally discover how our
    belt actually performed to validate our
    mathematical calculations

Aerodynamics Questions
  • Are there any equations out there that relate
    wind velocity to belt vibration already?
  • There are equations that already exist. However,
    they are systems of equations with unknown
    variables at this time, and that is currently
    what our team is working on to develop and
    understand through research and mathematical
    manipulation. Once we can find a way to calculate
    the unknown variables (analytical or
    experimental) we can then solve the system of
    equations giving a solution for our aeroelastic
    model. Non-dimensional analysis is currently
    underway and will be complete very shortly, as a
    main goal of this is to produce some
    non-dimensional specifications to which the wind
    belt should be manufactured.

Aerodynamics Questions
  • Complex Vibrations? OK
  • What if you put something in front of it to
    induce vortex shedding before the flow gets to
    the belt?
  • As we explained in class, if we make the flow
    turbulent prior to reaching the belt, we would be
    taking energy out of the flow in order to
    generate the wake an vortices. This creates a
    problem because the mechanical concept of the AED
    is that it draws energy from the viscous wake it
    creates- not a wake that it sits in. Therefore,
    placing an object in front of the windbelt to
    expose it to a vortex street would not produce as
    much power as if it were placed in the

Aerodynamics Questions
  • Nozzle?
  • Converging Nozzle?
  • This is a valid point and suggestion. It is
    entirely possible that a converging duct could be
    used to decrease required wind speed, and thus be
    beneficial to the AED. However, the AED already
    operates at such low wind speeds that it may not
    be needed.

Aerodynamics Questions
  • Any losses from torsion?
  • There will be some losses due to torsion, but the
    torsion is also key for vortex shedding, which
    causes the belt to oscillate. Without it, there
    would not be a large amplitude displacement of
    the belt. It is possible the torsional forces
    will allow the belt to deform too much in a
    rotational sense, causing over-rotation which
    would then create an inefficient mode of
    vibration. Thus, a balance of torsional forces on
    the belt with its vibration must be balanced and
    will be accounted for by determining the belts
    elasticity and ensuring that it can endue the
    torsional forces.

Aerodynamics Questions
  • Is it only vortex shedding which causes the
    vibration? Can the string/beam be designed to
    give more vibration ? more energy?
  • Vortex shedding is required to start the
    vibration. It is the vortex shedding that starts
    the oscillating until the belt becomes
    self-excited. That is, when the aerodynamic
    loading due to torsional displacement becomes 90
    degrees out of phase with the belt displacement,
    this creates a self-exciting behavior. This is
    the way to generate the most energy from the
    device. With careful consideration of belt
    material, it can be manufactured (such as a
    composite that allows for equal twisting in each
    direction) so as to maximize the vibration

Aerodynamics Questions
  • What vibrational frequencies can you expect?
  • Variables that determine the frequency of
    vibration include belt length, cross section,
    moment of inertia, mass/length of the belt,
    tension, and wind velocities (for torsional
    vibration). That being said, for the scale of
    our project, we can expect vibrational
    frequencies in the range of 20-70 Hz (estimated).

Aerodynamics Questions
  • Tunable? What does this mean?
  • By tunable, we mean that we want to be able to
    adjust parameters of the AED such as belt length,
    tension and direction that it approaches the wind
    in order to maximize the energy we can extract
    the wind. The main method for tuning the
    windbelt after the belt has been manufactured is
    to change the tension. By doing this, the
    natural frequency can be changed. It can be
    important to change the natural frequency of
    vibration to tune it to the local wind speed.
    For example, higher wind velocities can permit a
    belt with a higher natural frequency, hence the
    tension in the belt can be increased. This will
    lead to a higher frequency of power generation,
    and more power. On the other hand, lower wind
    velocities require a natural frequency to be
    lower, so tension must decrease in order for belt
    resonance to occur.

Aerodynamics Questions
  • What have you actually done (no plots, charts,
  • Our current work is mostly mathematical analysis
    of equations to determine the correct
    mathematical interpretation of the behavior of
    our belt. Non-dimensional analysis is also
    underway to develop non-dimensional
    specifications for the windbelt. Since this
    involves a lot of time spent deciphering the
    equations, our progress is not easily
    identifiable except for in our ability to
    continuously better explain the vibration of the
    belt. The non-dimensional analysis is near
    completion and the mathematical model is well
    underway. Our goal is to have a mathematical
    model complete and validated (by experimental
    results) at the end of this semester

Aerodynamics Questions
  • Where did you get your numbers for the Alpha
  • By watching video of the Humdinger windbelt and
    estimating dimensions. We were not trying to
    match any dimensions exactly, only prove the
    concept and take a hands-on approach to
    experimenting with different tension setups.

Aerodynamics Questions
  • What exactly are they doing with Windbelts? Are
    they re-producing Humdingers design? Trying to
    improve it? This is something the company cant
  • When Humdinger designed this device, they were
    focusing on cost-effectiveness rather than
    aerodynamics/electromechanical effectiveness.
    Were seeking to improve upon the capabilities of
    this device by researching its characteristics
    and identifying the areas where we can optimize
    the design to improve efficiency of the belt. We
    are creating mathematical models for predicting
    the power generation and aeroelastic behavior of
    this device. Once that has been completed, it
    will be possible to optimize the device for
    maximum power generation.

Aerodynamics Questions
  • Where is vibrational fatigue analysis?
  • That will be completed after the mathematical
    model. Once we have determined frequency and
    displacement data for the AED, it will be much
    easier to use a life-cycle analysis to predict
    the belts life

Aerodynamics Questions
  • Watch calling it string theory as that is a
    physics field doubt you are getting into or
    maybe it is and I misunderstood
  • Well be sure to make a clear distinction for our
    next presentations and in our final report that
    by string theory we mean that we are modeling
    the membrane as a string, rather then as the
    quantum physics topic of string theory.

  • How can a model be built with so little
    information and such large uncertainties?
  • The model we have constructed is simply a proof
    of concept demonstrating the idea that wind
    flowing over a tensioned belt will create
    flutter/vibration. We have a lot of information
    from the Humdinger Design to give us an idea of
    suitable specification ranges for our future
    models. We also have gathered a lot of research
    supporting the concept. Our uncertainties lie in
    specific materials and dimensions of the model
    that should be used, which is where our equations
    will be applied. The equations being derived make
    up a large part of this project that will
    parallel the physical models and explain the
    behavior of the models tested.
  • Speak Up
  • Good Organization
  • Good Explanations

  • Great Update. I like the numerous calculations
    applied with an actual built beta model
  • Current/future work slide would have been
  • Should probably be more general in terms of wind
    speed and direction
  • The specifications given for wind speed are based
    on Melbourne weather conditions. It is important
    to stay within this range so the final design
    could be utilized in Melbourne. A range of 4ft/s
    to 16ft/s is broad enough to allow for design
    variations. It is also important to design in
    consideration of wind gusts so that the model
    does not break.

  • I liked the presentation but it was really thick
    with equations and calculations. I realize you
    had to include them though.
  • Too much detail
  • Pic/movies, how its gonna look visually
  • We provided an image of the Humdinger Design, our
    current CAD model, and a video of our proof of
    concept. These images are appropriate for our
    project at this time. Since our project is also
    largely based on formulating equations, pictures
    do not apply here. The graphs presented are the
    appropriate type of image to use for our
    equations and are given and explained in the

  • Label Equations ? where do they come from?
  • The equations used in our presentation were
    described based on what they applied to (string
    theory, beam theory, strouhal equations, etc.).
    Many are equations we have learned in our
    classes, while others are derivations presented
    by different authors.
  • For our next presentation, we will be more
    specific in labeling each equation so that
    someone viewing the PowerPoint can read what each
    equation is rather then having to be present for
    the presentation to understand what each equation