Full Version: Anyone wish to develop a custom script?

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Here is a link to an updated screencast, showing how to import the PROP_DESIGN .XYZ data files into MoI for the purpose of creating an aircraft propeller blade model.

Anthony

Edit; the latest screencast link is in a later post

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Hi Brian,

> On a side note, still trying to figure out how to extract the x, y,
> and z values, from a given point.
> Either vector math, or the "get" method in point?

There are a couple of different kinds of points - there's a "point object" which is one that can be added to the geometry database and will then show up on the screen and can be selected and assigned an object name and so forth, and then there's a plain data point as well that only contains x,y,z values and nothing else.

If you have a "point geometry database object" that you might have got as a result from a geometry factory or something like that, then that object has a "pt" property on it that will return a plain data point that has the x,y,z values in it.

So you would do something like this to get the data structure point from a point object:

var datapt = pt_object.pt;

Then for the data structure type point has x,y,z values that can be accessed like:

var x = datapt.x;
var y = datapt.y;
var z = datapt.z;

Hope this helps!

- Michael

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Here is the NACA 4, 5, and 6 series airfoil generator from the PDAS site. I compiled it and created an input file for the NACA 65A009. This is an update to the code I posted previously from their site. It has about half as much error as the older version. However, it is still a substantial amount of error (max. of 2.28% for the new version compared to 5% for the old version). I wouldn't recommend using this code for the 6 series. I'm providing it here for anyone interested.

The updated code is a lot more convenient to use than the older version. It outputs to gnuplot rather than a postscript file. The output matches the coordinate locations of the original data sheet which is nice. I included all of the example input files that the author included in a different folder. I have a comparison file in there comparing the NACA 65A009 data points from the code to those of the original document.

Anthony

update; have since determined it is best to use the data points from NACA RM L51I12 for the 65A009 definition.

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Attached is another update for PropDesignGeo script, which includes mirror of the curve.

The mirror code is very similar to the arccenter code.

One peculiarity is that the Base pt / End pt line appears on the screen, until Done or Cancel are selected. ?????

// To Mirror curve, using the CoordinateFrame:
// Create a point Object list, of the Curve points.
var CurvePtList = factory.calculate();
// The same Coordinate leFrame with same Base pt, pt_leArccenter, can be used.
var factoryMirror = moi.command.createFactory( 'mirror' );
factoryMirror.setInput( 0, CurvePtList );
factoryMirror.setInput( 1, leFrame );
// Set End pt. (pt on y axis works fine.)
factoryMirror.setInput( 2, pt_teArccenter );
// Save the current curve pt mirror.
AirFoilfactories.push( factoryMirror );

Attachments:
PropDesignGeoOpA1_5_2012.7z

Image Attachments:
MirrorBaseAndEndPt_Visible.PNG 

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Hi Brian,

> One peculiarity is that the Base pt / End pt line appears on
> the screen, until Done or Cancel are selected. ?????

Some geometry factories add additional decorative geometry to the geometry database which for the regular commands help to kind of illustrate what is happening. If you run the regular Transform > Mirror command you'll see that when you go to pick the 2 points for the axis line, there is a line drawn between the points basically marking the mirror axis, but that line goes away when the mirror command is finished - that line is the "UI geometry" that the mirror factory is creating.

You can disable the creation of UI geometry by calling the disableUIGeometry() method on a factory, so try doing something like adding this line:

factoryMirror.disableUIGeometry();

immediately after you create the mirror factory.

- Michael

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hey brian,

i wanted to give you a heads up that there will be one last change to the prop_design_geo file (and prop_design). i scoured the ntrs site and found several definitions for the naca 65a009. i evaluated them all. i also evaluated the pdas codes. i found one particular set of data from naca that meets all the criteria. moreover:

- the geomtery data document is that which is referenced by the performance data document
- you can fit a through point curve through all the points
- the leading edge can be defined the way burrman and steve desired. however, it is also defined as a circle by naca. both definitions for
the leading edge are now in complete agreement.
- the joined curves can be swept to make a blade without any lumps

the definition that seems to be the right one can be found in naca document:

1951, NACA RM L51I12; Milton D Humphreys, Pressure pulsations on rigid airfoils at transonic speeds

the performance data is in naca document:

1957, NACA RM L57F05; Charles L Ladson, Two-dimensional airfoil characteristics of four NACA 6A series airfoils...

the best historical references as to how the ordinates were obtained is in the following two documents:

1931, NACA Report 411; Theodore Theodorsen, Theory of wing sections of arbitrary shape

1945, NACA Report 824; Ira H Abbott, Summary of airfoil data

however, no one actually shows how they calculated the points specifically. this was done in a time before computers and calculators. so we are talking slide rules and charts. the math is intense. it would take a huge effort to duplicate the work. thus i am using the ordinates as they are shown.

please give me a day or two at the most, to get you a complete update. this will include an updated screencast.

thanks,

anthony

Edit; what was PROP_DESIGN_GEO is now PROP_DESIGN_XYZ. PROP_DESIGN_XYZ is a part of the PROP_DESIGN.zip download available on my website. The latest MoI example screencast can be found on my YouTube page. Here are the links:

http://propdesign.weebly.com/

http://www.youtube.com/user/propdesignsupport/feed

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hey brian,

i tried out your latest script and its looking great. the best one yet.

anthony

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Thank you very much Michael for the information in your last two replies.

Adding (factoryMirror.disableUIGeometry();) to the script, just after the setInputs, was successful.

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I'm trying to script a non-interactive arccontinue. Also trying to script a non-interactive conic, which seems to invole similar problems.

The documentation of Dave Morrill does not mention conic, and for arccontinue, just mentions start and end points, without the curves.

The points need Bind or Snap to the associated curves, which I have no idea how to do non-interactively.

Somehow pointpicker gets bound to 4 conic factory getInputs?

Conic getInput(0) ........Start point.
Conic getInput(1) ........End point.
Conic getInput(2) ........Apex point.
Conic getInput(3) ........Through point.
Conic getInput(4) ........rho value.

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Hi Brian - I don't think it will work to make a non-interactive arc continue, since the arc continue factory is set up to work with an osnapped point as its first input.

That's another variety of point (IMoiPickedPoint) that is generated by the point picker, in addition to containing an x,y,z point in it it also contains a list of snaps that were active for the point, and the arc continue factory finds the curve to be tangent from by going through those object snaps.

There is not currently any way to set up a "picked point" other than having it generated from a pointpicker pick, so I don't think that is one that you will be able to automate currently.


Conic should be possible to script though - the inputs what you wrote, you need the first 3 inputs set to points (these can be regular x,y,z data points), then set either the 4th input (with index = 3 since they start at 0) to a point for the "through point" or instead of that you can set the 5th input (with index = 4) to a rho value which is a floating point number.

If you want to specify a "through point", then leave the rho value completely unset, and if you want to specify a rho value instead then you can leave the "through point" input completely unset. Let me know if you still have problems with it.

- Michael

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also, if worst comes to worst brian I can add back in the tangent points and you can do the le arc as you were. i would have to add in a bunch of other points though to fill out the conic part of the curve. but its not that big of a deal, if you hit a road block with the current method.

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Thank you very much Michael.

The arccontinue did work nicely on the trailing edge, interactively. Instead I'll measure the distance with MoI later, and
do 3pt arc instead.

The conic is a pretty neat curve for the leading edge. I'll try later to see if I can locate the tantan point.
Or just interactively find out the rho value, and then use that in the script... "simple"...

Edit, the le rho value is stated by MoI interactively, as 0.42609.

I was working on a new version for PropDesignGeo, January 5 2012, dropping a lot of "unnecessary" points, with conic le, and arc te, and
fixing up a join factory which I hope will work...

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Got a trailing edge rho value of 0.0952.

The trailing edge arccontinue, and a trailing edge conic,
EDIT: are ALMOST the same. Need to zoom WAY in to see slight difference.

Leading edge arccontinue is different curve from le conic.

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hey brian,

in case you run into a wall with the last version of prop_design_geo, I went ahead and added a bunch of points to the data set so that you don't
have to use the conic section.

edit; a later post replaces this one.

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brian,

i see you said you got a trailing edge rho value. you should only use the conic section for the leading edge. the trailing edge is still done with a circle. in fact the leading edge is also done with a circle. however the conic section defines the transition from the circle to the naca points and it also overlays the circle at the leading edge.

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Oops, the trailing edge conic IS slightly different from a trailing edge arc.
Had to zoom way way in...

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hmm,

i'm having issues with the radius using three point arcs. when i go to fillet it blows up. i'm going to have to work on this a bit more. maybe adjust the points so a two point arc works. i think if you use a three point arc for the le and a two point for the te it will work but haven't tried it yet. otherwise i will adjust the points so you can use a two point arc for both and make it simpler.

edit; after trying a bunch of options including modelling it with the last update of prop_design_geo, i'm thinking the problem might be a smaller te radius. the updated naca file had a slightly smaller radius. when i Boolean union the hub to the blade the te blend is messed up (missing a curve that should be there).

i'm going to try putting the te radius back to the other definition i had and see if that fixes the problem. i will leave the rest of the updated definition in tact, as that fixed a lot of other issues. i want to look at the le points i added too because i'm getting that same error brian found before where the chord is a little bigger than it should be unless you use a three point arc.

update; it wasn't the ter either. i'm stuck right now. the Boolean doesn't work right now. i'm not sure what is causing it. i'll have to get back to you once i figure out what is going on.

update; ok its working. not sure what the issue was. must have been how i was joining the curves or the sweep options. it works with the updated geo. the only thing i want to look at is why the le arc is a little off with the two point option. there is a small error somewhere. i'll have to re-measure and calculate all the points and see if a few are off a little.

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hi brian,

so i updated the points again. the thing is i'm not sure this is going to make it easier for you or not. it made it harder for me. but here it is for your consumption. it seems like you have to use three point arcs, being very careful to get the end of the rails as the third point. it has a tendency to pick perpendicular and i think that was messing things up. also it may have been the sweep options, not sure. but i went with exact and it worked out. i don't know if refit had anything to do with it. basically when you go to boolean the hub to the blade the trailing edge curve would get messed up sometimes. but this doesn't seem to have anything to do with the points.

as far as the added points go, i kind of like it the other way. but if you have problems going with the conical curve, this extracts enough points that you can just make arcs as the le and te. but for whatever reason the two point arc doesn't work like it use to and i'm having to do a three point arc (for the le at least). for consistence i just did a three point at the te too, but a two point should be fine (as was the case before).

the solid resulting from the sweep seems smoother when you just use the conical tool rather than adding in all the points. you can kind of see where the points are in the solid at some angles. not sure if its real or just an optical thing because the edges of the solid look smooth. in any event, this should be a good fall back option for you if you need it.

updates; once i tried to fillet the blade and hub connection I saw the le was indeed unusual with the added points. they seem to be mucking things up somehow. should definitely stick with the conic section for the le for this data set.

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Hi Anthony,
""not sure if its real or just an optical thing because the edges of the solid look smooth. """"""""""

A trick i learned from Michael, to rule out "display artifacts" is to do a quick export to obj, then in the meshing dialogue, select "shaded" only, with no edges, then you can cranck up the dicing of the polys, and see what the surface actually is, without some type af display angle artifact... Then just cancel the command to return. FYI

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Attached is another script, with a conic le, and a 3pt te. (According to MoI docs, the conic is a portion of an ellipse.)
The apex of the conic was hard-coded, based upon MoI previous distance measure of it's z coordinate.

The attempt to join the 4 curves, non-interactively, was not successful. Join factory created duplicates of the 3 non-mirrored curves.
Seemed like the mirrored curve factory did not .calculate the Object list. (?)

Without the non-interactive join, it is just as well to let the user interactively add the conic.

I think that is about it, for this project...

Attachments:
PropDesignGeoA1_6_2012.7z

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