Speed Optimization - need to calculate the optimum speed for a given voyage

Discussion in 'Boat Design' started by Chris Pap, Jun 10, 2015.

  1. rwatson
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    rwatson Senior Member

    Database management has little to do with hardware. It is software power that is critical. If extra performance is required, an application developed on say a laptop can be moved to a bigger computer in minutes.
    You have abviously never taught students programming if you think C is as easy as VB. The B in Basic the language stands for 'beginners' for a start
     
  2. philSweet
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    philSweet Senior Member

    Chris Pap - Okay, I understand you want to concentrate on fuel prediction or some sort of optimization calculation, but I don't quite understand who the customer is for the info. The info you are going to produce would be of interest to a higher level model that uses fuel consumption characteristics of ships as an input. Understanding what some of these models do would help your cause both for this program and educationally, I think.

    As a specific example, in Game Theory, for example Cournot_competition, The quantity to be produced by a particular competitor is a function of the market's price vs total quantity function (an external variable) and the rate of change of this competitor's cost vs quantity. Not the cost itself (everyone is assumed to have the same base cost in this model), just the rate of change of the cost. If you think of velocity as a proxy for quantity, and fuel cost as a big part of a shipper's cost, then in order to feed one of these models, you need to supply the rate of change in fuel costs, not just find a minimum cost point. In many operations, the cost goes down wrt quantity, but in this case it goes up (for a particular boat). That makes shipping a bit different than chipping. There are many different models of economic decision making that look at expectations and deal with time delays in responses, but changing costs are a very strong factor in this situation because they will change so dramatically with speed. Basically, a rational person will not operate at the lowest cost except under some peculiar conditions. He will choose a bit less than that in this instance using Cournot (Nash equilibrium). If you can produce a more versatile ship with a flatter rate of fuel increase near the expected operating point than the other guy has, that changes the actual speed one would choose to operate at. You can put a "$" on versatility that is paying for itself daily, not just when perturbations occur.
    Another way to look at this is that you have a credible threat of operating faster if you want to, and your competitors will take this into consideration and be a bit more conservative. And there is a formula for it all (or at least a whole bunch of them to choose from;))

    (I'm not suggesting the Cournot model is a good model, it is just a very simple one that does account for quantity/cost decisions)
     
  3. TANSL
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    TANSL Senior Member

    The data storage capacity depends, among other things, on the amount of memory available on your machine. The speed processing information depends on hardware. Machines with 64-bit architecture allows handle more memory and more efficiently than the 32-bit form. This everybody knows (or should know who dares to review these issues).
    Programming languages ​​are just that, programming languages. According to your point of view you could say that, for example, English is better than the Mandarin Chinese, or worse, for the treatment of large amounts of data. Obviously that would be a very difficult information to demonstrate.
    First I want to say is I do not see why one language (of which we are speaking) can be considered more difficult than another. Secondly, they are not comparable C and VB. If you like, please, compare the Visual C with Visual Basic. Another thing, as I said before, is mixing apples and oranges.
    I've never taught anyone programming, you're right, but I had to program in several languages and, therefore, I know of what I speak. I guess you can find some stuff without having given lessons on it.
    The "B" in "VB" does not mean, at all, for "beginners". according to you, "C" could mean something as suitable for "complex" calculations ?:). No, that's not so.
    I think you're not well oriented. But that, precisely, is the exchange of views.
     
  4. rwatson
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    rwatson Senior Member

    This completely irrelevant point, and has nothing to do with Database Management Systems. Your lack of understanding is obvious to anyone with DBMS experience.

    Sigh :rolleyes:

    VB = Visual BASIC
    BASIC = BASIC (Beginners All purpose Symbolic Instruction Code)

    http://encyclopedia2.thefreedictionary.com/Basic computer language)



    You are the guy that delights in saying "dont speak of what you dont know"

    Maybe you can take your own advice ?
     
  5. TANSL
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    TANSL Senior Member

    OK rwatson, I also appreciate and respect you.
    My offer to assist Chris Pap, if he needs it, is there.
     
  6. BertKu
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    BertKu Senior Member

    OK Folks, I see it simple this way. Here is a fellow who is studying and like to involve himself in finding out what makes sense in total trip cost for a large ship from A to B. We members have given him some excellent idea's what to consider for his approach. 25% of the Greek youths don't have a job. When he is finished, he may have to leave his country to find a job somewhere else. However , I feel that if he, while learning, can get the knowledge on costing, he has a better chance to get a position in any large shipping company. Visual Basic is a configuration language and not really a professional software like assembler for hardware interfacing, or C for developing kernels for OS systems and millions of other programs. It does not matter what he is going to use. The fact that he learns and need our help is important. He will figure out quickly what he is able to manipulate for his task. Lets help him and see what is going to happen in a few days time with Greece.
    Bert
     
  7. BertKu
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    BertKu Senior Member

    Hi Chris, here is another field you have to add to your configuration list. .....
    has the ship rotors yes/no This will influence the fuel consumption.
    I suggest you have a field with the question: >>> How many rotors has the ship<<<<< (maximum 1 digit) .
    Go for it.
    Bert
     
  8. BertKu
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    BertKu Senior Member

  9. FAST FRED
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    FAST FRED Senior Member

    Ocean passages for the world has low speed routes and projected winds by the month.

    AS it varies your optimum speed would vary , tho most routes are as downwind as can be done.
     
  10. BertKu
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    BertKu Senior Member

    Thank you Fast Fred for trying to help this youngster.

    Am I wrong in the following assumption.

    A 100.000 ton ship does a distance of 1000 knots. i.e. 1820 km
    He does normally 20 knots, with no wind and no high waves.
    It takes this ship normally 50 hours to reach its destination.
    Now he has a 4 knot current against him. The captain decide not to increase power. Thus it means that it will now take him 62.5 hours, therefore the ship has used 12,5 hours more fuel, equals 25% more. Can Chris put in his system a linear calculation. It would mean that if the captain decide to increase power and use more fuel, he need to put 25% more into his diesels, to get the same time.

    But now the influence of waves. What could Chris put into his system to come up with a formula for 0 to 10 meters waves ? Will only Wageningen be able to answer such question?
    Bert
     
  11. FAST FRED
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    FAST FRED Senior Member

    In aircraft the rule of thumb (reciprocating engines) was to add 10% more power as a good trade off between fuel burn and arrival time.

    On many ships such as bulk oil carriers the ship is chartered , so the extra days of charter (perhaps at $50,000 per day) has to be figured into the total cost with the fuel burn.

    Ships are optimized for their speed , the new lower transit speeds require a different bulbous bow , and many changes to the engine , from turbo to oiling system to operate efficiently slower.

    The hull is optimized basically for ONE speed.
     
  12. BertKu
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    BertKu Senior Member

    Thank you Fred, that is valuable information for him. Bert
     
  13. Chris Pap
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    Chris Pap Junior Member

    Trying to put all these information together and searching from google I found the attached table.

    Is that reflecting the reality?
    And if yes this added resistance is only due to winds? Or it contains the waves too? Because if not , and due to the fact(from what I read) that added resistance by wind is approximately 1/2 of the added resistance from waves, it seems to me a very large number.

    As for the current that Bert mentioned, I read somewhere that it's longitudinal component is used rectify the speed over ground that is then used to calculate the time and then the consumption. Is that correct?

    Thank you all again.
    ChrisPap.
     

    Attached Files:

  14. daiquiri
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    daiquiri Engineering and Design

    I would suggest you to use this paper for the evaluation of the aerodynamic drag:
    http://www.dtic.mil/dtic/tr/fulltext/u2/a119984.pdf

    As a rough guideline, it advises to use the following longitudinal drag coefficients for different types of ships (page 3):

    For hull-dominated vessels (like aircraft carriers, tankers):
    Head wind: Cx = 0.4
    Tail wind: Cx = 0.4​

    For ships with high superstructures:
    Head wind: Cx = 0.8
    Tail wind: Cx = 0.8​

    For other ships:
    Head wind: Cx = 0.7
    Tail wind: Cx = 0.6​

    If the ship has a cluttered deck (masts, derricks, piping etc.), then the following correction has to be added to the above values:
    Cx,add = 0.08.​

    Whether you will use the head wind or tail wind value, depends on the ship speed relative to the wind speed:
    • If the wind comes from ahead, then the head-wind Cx should be used.
    • If the wind comes from behind the ship, then:
      1) if the ship speed is higher than the wind speed, the head-wind Cx should be used.
      2) if the ship speed is lower than the wind speed, the tail-wind Cx should be used; the wind actually helps push the boat.​

    The aerodynamic drag is then calculated with the formula
    F = 0.5 rho V^2 A Cx f(Theta)​
    where:
    rho = air density (1.225 kg/m^3)
    V = ship speed (m/s)
    A = cross-section area of the above-the-water structures(m^2)
    Theta = wind angle
    f(Theta) = wind shape function, visible in the Fig.5, page 27
    ( you can assume f(Theta) = 1 for wind angles +/-30° off the bow ).​

    Hope it helps.

    Cheers
     

  15. BertKu
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    BertKu Senior Member

    Thank you Daiquiri, that is the sort of information Chris really needs. You know, we all have studied, most of us had a study loan or bursary. Nothing more disappointing then to study and then not finding a job easy after having obtained our qualifications, but still have to pay back the loans. Nobody knows what will happen to Greece. Although EU would be crazy to let Greece go, but who knows. Come on guys, lets help this youngster. Thank you Daiquiri
    Bert
     
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