Friday, September 6, 2013

If You Like Jets and Aerodynamics ...

If you like jets, aerodynamics and have a CFD program, you might find yourself doing this:

Yesterday, I visited the NASA OpenVSP Hangar website and saw a model of the Lockheed L-1011.  Because I like the L-1011, I decided to analyze it in Stallion 3D in ground effect  .... (Why not?)

This is how the model loaded in my copy of OpenVSP:

This is the window that I used  to import the .STL file of the model into Stallion 3D using the Design menu and the Import/Edit .STL file option:

This is a wireframe of the model after it loaded into Stallion 3D.  I set the ground plane option because I wanted to simulate takeoff:

 I used the following window to set the resolution of the Cartesian grid in Stallion 3D.  The initial grid in (x,y,z) sub-divisions is (6X2X6):

I opted to use the compressible Euler code for the analysis:

I used the following window to set the ground effect option in the analysis:

After choosing a speed of 100 m/s and a rotation angle of 5 degrees, I clicked the CFD Solver menu and choose Generate Grid/Solve Flow to automatically generate the grid and solve the flow.  I then walked away from my laptop.

I generated this picture (the colors show surface pressure) of the airplane and the ground plane after I returned to the laptop (about 8 hours later):

I rotated the view, changed the display to surface velocity and generated this picture of the aircraft and the ground plane (the colors show velocity):

I thought this picture of the tip airfoil might be interesting.  I also generated the pressure coefficient (Cp) at various stations along the  wing using the Graphs menu and the Pressure Coefficient (Cp) option in Stallion 3D (the colors show pressure).

Granted the OpenVSP model of the L-1011 is not the one sold by Lockheed (airfoils?, plain flaps during takeoff? exposed duct?, etc...), it is still fun to look at the numbers.   The model that I ran measured about 180 feet in length and had a width (wing span) of about 150 feet.

Rotated at 5 degrees during takeoff, here are a few calculations of the lift:
@ 100 mph  --- Lift = 110,000 pounds
@ 150 mph  --- Lift = 245,000 pounds
@ 200 mph  --- Lift = 435,000 pounds
@ 250 mph  --- Lift = 680,000 pounds

Note (mph) is miles per hour.  It will be a good exercise for the reader (I did it myself) to google the performance of the various models of the L-1011 for comparison.

More information about Stallion 3D can be found at

Thanks for reading.