Monthly Archives: August 2016

Gulfstream G-V CAD Update (Or: “Who Wants to be a CAD Monkey?”)

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To see previous post click here. This time I will cover how I created all the parts of the G-V.

It pays to read all the way through. Last week, I thought that I had found technical drawings showing all the dimensions of the G-V. What I had actually found was a drawing describing taxi clearance.

GV_Top_TaxiClearance

Drawing courtesy of NSF/NCAR and Lockheed Martin

So… back to the drawing board. Excuse the pun.

I divided the G-V into 4 parts: wing, fuselage, empennage, and engine. The more I separate the easier it makes it on me to get the details right.

Wing:

Going back to our Investigator Handbook from the NSF/NCAR we use a different technical drawing. In 5.1.5 of the handbook the pylon mounts along the wing for scientific investigation are shown. Using WebPlotDigitizer we create a series of points approximating the top of the wing. You have the option to save the points as a .CSV. Since I use Autodesk Inventor I can import Excel files with a series of data points. There are similar features with SolidWorks but I’m more comfortable with Inventor.

GV_Plotting_Points.png

Once in Inventor I can begin making the wing. It’s almost connect-the-dots: except you need to check dimensions. You won’t have gotten all your points in the plot digitizer just right either so you should focus on getting the majority of the points as opposed to every single one. With more experience you’ll find that the more points you have on a curved surface the closer you can approximate the curve. The c⁄4 angle is 27° which is verified through the use of construction lines.

GV_Inventor_Drawing_Through Points.PNG

2D Sketch in Inventor of G-V planform wing area

Now we have a sketch how do we create our 3D model?

Using the excellent resource The Incomplete Guide to Airfoil Usage we can determine the airfoils used for the root and tip of the wing. This provides us with the G-IV root airfoil, NACA 0012 modified, and the tip airfoil, NACA 64A008.5 modified.We don’t need to worry about the modifications or that it is G-IV because we’re developing a base model for concept development. The G-IV airfoils are essentially the same as the G-V anyways. If you were trying to get the airflow characteristics of a G-500 to the 99th percentile then you are either working for Gulfstream and can pull the model yourself or you should contact Gulfstream.

Using the 2D sketch we just created we can place the airfoils at their respective locations and loft the wing between them. That should give you something like this:

GV_Isometric_Wing Loft.PNG

Lofted Wing

Then, using the sketch, which I hid in the previous image, create a work plane and extend your pylons in the appropriate locations.

GV_Isometric_Wing_Pylon.PNG

Extend your pylons through the wing

I have a concept structure that I’m developing below. Currently, Dr. O’Neill is trying to provide Dr. Yan with some feedback on design of radio antenna integration for a Gulfstream G-V and I’m creating the CAD concept models. I cannot picture these currently because it’s ongoing research. Instead here are some example tank concepts.

GV_Example_Concepts

Example Concept

Fuselage:

The fuselage is created in a similar process to the wing. We plot a series of points and rotate the fuselage around the centerline. We will create the saddle with straight sides and extend it through the fuselage. The trick here is that I created 2 different sketches on the same plane to avoid weird things that happen if I make the pieces sequentially.

GV_Isometric_Fuselage.PNG

Sketches for the Saddle and Fuselage Body

GV_Fuselage_Complete.PNG

Fuselage Rotated and Extended

Rolls-Royce BR710A1-10 Turbofan Engine:

The Rolls-Royce engine is built in the exact same way as the fuselage. Two sketches on top of each other and then a rotation and an extension. I then cut into the engine to make it look like an actual engine but if you know how to extend by know this should be an easy process.

GV_Engine.PNG

Engine Section

Empennage:

The tail is created by taking the points from the top view. The points are extended and then cut from the side view. The wings are lofted from the vertical stabilizer using the NACA 64A008.5 airfoil for the root and tip.

GV_Empennage.PNG

Empennage Section

Complete Gulfstream G-V:

The current configuration of the Gulfstream is shown below. The illustrations shown are from the presentation I created for Dr. Yan. The antenna configuration is removed. Inventor has some nice illustration tools that are exceptionally useful when presenting.

 

The slideshow shows the stages of development of the Gulfstream G-V. The first model is all one piece. The second model is a lofted fuselage that experienced connectivity issues. The third is the most promising and will probably stay until I need to create updates for higher fidelity. The higher fidelity will be required when we run the antenna configuration through CFD to test the drag force produced by the array. As you can see I abandoned the wingtips until I have the antenna array configuration fixed.

Gulfstream G-V CAD Update (Or: "Who Wants to be a CAD Monkey?")

Leave a reply

To see previous post click here. This time I will cover how I created all the parts of the G-V.

It pays to read all the way through. Last week, I thought that I had found technical drawings showing all the dimensions of the G-V. What I had actually found was a drawing describing taxi clearance.

GV_Top_TaxiClearance

Drawing courtesy of NSF/NCAR and Lockheed Martin

So… back to the drawing board. Excuse the pun.

I divided the G-V into 4 parts: wing, fuselage, empennage, and engine. The more I separate the easier it makes it on me to get the details right.

Wing:

Going back to our Investigator Handbook from the NSF/NCAR we use a different technical drawing. In 5.1.5 of the handbook the pylon mounts along the wing for scientific investigation are shown. Using WebPlotDigitizer we create a series of points approximating the top of the wing. You have the option to save the points as a .CSV. Since I use Autodesk Inventor I can import Excel files with a series of data points. There are similar features with SolidWorks but I’m more comfortable with Inventor.

GV_Plotting_Points.png

Once in Inventor I can begin making the wing. It’s almost connect-the-dots: except you need to check dimensions. You won’t have gotten all your points in the plot digitizer just right either so you should focus on getting the majority of the points as opposed to every single one. With more experience you’ll find that the more points you have on a curved surface the closer you can approximate the curve. The c⁄4 angle is 27° which is verified through the use of construction lines.

GV_Inventor_Drawing_Through Points.PNG

2D Sketch in Inventor of G-V planform wing area

Now we have a sketch how do we create our 3D model?

Using the excellent resource The Incomplete Guide to Airfoil Usage we can determine the airfoils used for the root and tip of the wing. This provides us with the G-IV root airfoil, NACA 0012 modified, and the tip airfoil, NACA 64A008.5 modified.We don’t need to worry about the modifications or that it is G-IV because we’re developing a base model for concept development. The G-IV airfoils are essentially the same as the G-V anyways. If you were trying to get the airflow characteristics of a G-500 to the 99th percentile then you are either working for Gulfstream and can pull the model yourself or you should contact Gulfstream.

Using the 2D sketch we just created we can place the airfoils at their respective locations and loft the wing between them. That should give you something like this:

GV_Isometric_Wing Loft.PNG

Lofted Wing

Then, using the sketch, which I hid in the previous image, create a work plane and extend your pylons in the appropriate locations.

GV_Isometric_Wing_Pylon.PNG

Extend your pylons through the wing

I have a concept structure that I’m developing below. Currently, Dr. O’Neill is trying to provide Dr. Yan with some feedback on design of radio antenna integration for a Gulfstream G-V and I’m creating the CAD concept models. I cannot picture these currently because it’s ongoing research. Instead here are some example tank concepts.

GV_Example_Concepts

Example Concept

Fuselage:

The fuselage is created in a similar process to the wing. We plot a series of points and rotate the fuselage around the centerline. We will create the saddle with straight sides and extend it through the fuselage. The trick here is that I created 2 different sketches on the same plane to avoid weird things that happen if I make the pieces sequentially.

GV_Isometric_Fuselage.PNG

Sketches for the Saddle and Fuselage Body

GV_Fuselage_Complete.PNG

Fuselage Rotated and Extended

Rolls-Royce BR710A1-10 Turbofan Engine:

The Rolls-Royce engine is built in the exact same way as the fuselage. Two sketches on top of each other and then a rotation and an extension. I then cut into the engine to make it look like an actual engine but if you know how to extend by know this should be an easy process.

GV_Engine.PNG

Engine Section

Empennage:

The tail is created by taking the points from the top view. The points are extended and then cut from the side view. The wings are lofted from the vertical stabilizer using the NACA 64A008.5 airfoil for the root and tip.

GV_Empennage.PNG

Empennage Section

Complete Gulfstream G-V:

The current configuration of the Gulfstream is shown below. The illustrations shown are from the presentation I created for Dr. Yan. The antenna configuration is removed. Inventor has some nice illustration tools that are exceptionally useful when presenting.

 

The slideshow shows the stages of development of the Gulfstream G-V. The first model is all one piece. The second model is a lofted fuselage that experienced connectivity issues. The third is the most promising and will probably stay until I need to create updates for higher fidelity. The higher fidelity will be required when we run the antenna configuration through CFD to test the drag force produced by the array. As you can see I abandoned the wingtips until I have the antenna array configuration fixed.

Maxwellian Distribution

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This is a brief dip into velocity distribution. It is not intended to be cited nor be academically through. Rather it will hopefully provide some insight and give you links to use other than Wikipedia.

Velocity Space

Imagine a container of particles. Gas particles. As these particles are whizzing about we notice this cloud of molecules seems to be equally spread out in all directions.

Maxwell-Boltzmann Distribution Drawings_0

This is for several reasons:

  • Brownian motion (random movement)
  • Molecules prefer to be at equilibrium for the whole system
    • They don’t want to be moving in the same direction

If we were to examine the velocities of the particles using velocity space, a 3D system

Maxwell-Boltzmann Distribution Drawings_0(1)

Velocity Space System

describing a particle’s velocity, we would find that they are evenly distributed as well.

 

 

 

 

 

We can imagine this as a shell. The velocities of all the particles will be distributed in a common range in order to achieve equilibrium.

Maxwell-Boltzmann Distribution Drawings_1(1)

2D View of Velocity Distribution Shell

 

Velocity Distribution Function

This is where the Maxwellian distribution will come into play. In a real system we know that a molecule will not maintain constant velocity over time. There’s van der Waal’s forces, ionic, covalent, and metallic interactions, collisions, and a whole host of other things that can interact with the molecule. Since the main focus is rarified gas or a dilute gas we can assume intermolecular forces are negligible, (equilibrium kinetic theory).

The velocity distribution function for gas molecules in thermal equilibrium is based on symmetry. One molecule loses 5 m/s, another gains 5 m/s.

Maxwell-Boltzmann Distribution Drawings_2

Maxwellian Distribution of Velocity

Average Quantity, Q

With N, the total number of molecules, and f(Ci), the velocity distribution we can find the average quantity. We find N from integrating the number of molecules with Ci velocity.

This average quantity can be use for anything that uses velocity: start thinking about momentum.

Some things to remember from our assumptions with equilibrium kinetic theory:

  • Intermolecular forces negligible
  • Collisions occur in a unit area
  • All momentum is transferred through the collision process

So we could find normal stress, σ, pressure, P, or etc…

Maxwellian Distribution

Neglecting the derivation we are led to the Maxwellian distribution so that we don’t have to plot every single molecule. The Maxwellian distribution will give the probability that a molecule has speed a certain range of speed.

The information gained from using a Maxwellian distribution:

  1. The most probable speed of the molecules present
  2. The average speed of the molecules present
  3. The root mean square speed, Vrms
  4. Equation of state for perfect gas

Acknowledgements

Thanks to Dr. Wang for teaching Physical Gas Dynamics, where my notes from that class have served as the outline for this article.

I have provided links throughout this article specifically avoiding Wikipedia to help give you more references. Please credit your sources if you use them in your writing. (MLA) (AIAA)

 

 

Gulfstream G-V CAD

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It’s hard finding or making CAD models of aircraft. Companies are fiercely protective of their models that they spent millions of dollars developing. If you’re a researcher sometimes this means using a Plot Digitizer and drawing over images from the internet.

Pylon_Front_View

https://wordpress.com/post/simpsonaerospace.wordpress.com/6 NSF/NCAR Gulfstream G-V

The NSF/NCAR Gulfstream G-V was of particular interest for this project for two reasons. The CAD model was being developed to support proof-of-concept for equipment mounted on the wings. The NSF plane already has pylons to support research equipment. Secondly, Dr. O’Neill had located a Gulfstream G-V that could be used for the research.

After creating a (very rough) CAD model for the aircraft in a day I started work on a high fidelity model.

Sometimes it pays to do a little more research. NSF/NCAR provide an investigator handbook that gives exact dimensions in CAD drawings of the G-V courtesy of Lockheed Martin. Jackpot!

The finished model using the updated dimensions and exact locations of the pods will be provided later this week.