Changes

The Mirage III has approximate dimensions (length,wingspan,height) of 15m x 8m x 4.5m. Or, measured in terms of freespace wavelength at 850 MHz, 42.5 lambda λ x 22.66 lambda λ x 12.75 lambdaλ. Thus, for the purposes of [[EM.Tempo]], we need to solve a region of about 12,279 cubic wavelengths. For problems of this size, a great deal of CPU memory is needed, and a high-performance, multi-core CPU is desirable to reduce simulation time.

[https://aws.amazon.com/ Amazon Web Services ] allows one to acquire high-performance compute instances on demand, and pay on a per-use basis. To be able to log into an Amazon instance via Remote Desktop Protocol, the [[EM.Cube]] license must allow terminal services (for more information, see [[http://www.emagtech.com/content/emcube-2016-licensing-purchasing-options EM.Cube]] Pricing]). For this project, we used a c4.4xlarge instance running Windows Server 2012. This instance has 30 GiB of memory, and 16 virtual CPU cores. The CPU for this instance is an Intel Xeon E5-2666 v3 (Haswell) processor.

The CAD model used for this simulation was found on [https://grabcad.com/ GrabCAD], an online repository of user-contributed CAD files and models. [[EM.Cube]]'s IGES import was then used to import the model. Once we import the model, we move the Mirage to a new PEC material group in [[EM.Tempo]].

<div><ul> <li style="display: inline-block;"> [[Image:glass.png ‎‎|thumb|left|200px|Selecting glass as cockpit material for the Mirage model.]]</li><li style="display: inline-block;"> [[Image:Mirage image.png ‎‎|thumb|left|200px|Complete model of Mirage aircraft.]]</li></ul></div>

First, we create [[Image:ff settings.png|thumb|left|150px|Adding an RCS observable with 1 degree increments in both phi and theta directions. Although increasing for the angular resolution of our farfield can increase simulation time, The RCS of electrically large structures tend to have very narrow peaks and nulls, so the resolution is required.Mirage project]]

We also ===Observables===First, we create two field sensors -- one an RCS observable with a z-normal underneath the aircraft, one degree increments in both phi and another with an x-normal along theta directions. Although increasing the length angular resolution of our farfield will significantly increase simulation time, The RCS of electrically large structures tend to have very narrow peaks and nulls, so the aircraftresolution is required.

[[Image:ff settings.png|thumb|left|150px|Figure 1: Geometry of We also create two field sensors -- one with a z-normal underneath the periodic unit cell aircraft, and another with an x-normal along the length of the dispersive water slab in EMaircraft.Tempo.]][[Image:ff settings.png|thumb|left|150px|Figure 1: Geometry of The nearfields are not the periodic unit cell of prime observable for this project, but they may add insight into the dispersive water slab in EM.Temposimulation, and do not add much overhead to the simulation.]]

For the mesh, we use the "Fast Run:<math> \hat{k} = \frac{\sqrt{2}}{2} \hat{x} - \frac{\sqrt{2}}{2} \hat{z} </Low Memory Settings" preset. This will set the minimum mesh rate at 15 cells per lambda, and permits grid adaptation only where necessary. This preset provides slightly less accuracy than the "High Precision Mesh Settings" preset, but results in smaller meshes, and therefore shorter run times.math>

[[Image:ff settings.png|thumb|left|200px|Figure 1: Geometry of ===Mesh Settings===For the periodic unit cell of mesh, we use the dispersive water slab in EM"Fast Run/Low Memory Settings" preset.Tempo This will set the minimum mesh rate at 15 cells per &#955;, and permits grid adaptation only where necessary.]][[Image:ff settings.png|thumb|left|200px|Figure 1: Geometry of This preset provides slightly less accuracy than the periodic unit cell of the dispersive water slab "High Precision Mesh Settings" preset, but results in EM.Temposmaller meshes, and therefore shorter run times.]]

<div><ul> <li style="display: inline-block;"> [[Image:Large struct article mesh settings.png ‎‎|thumb|left|300px|Mesh settings used for the Mirage project.]]</li><li style= Results =="display: inline-block;"> [[Image:Large struct article mesh detail.png‎|thumb|left|300px|Mesh detail near the cockpit region of the aircraft.]] </li></ul></div>

After For the simulation is completeengine settings, we use the nearfield visualization are available as seen below:default settings, except for "Thread Factor". The "Thread Factor" setting essentially tells the FDTD engine how many CPU threads to use during the time-marching loop.

[[Image:Large struct article ScreenCapture3.png|thumb|left|500px|Figure 1: Geometry of the periodic unit cell of the dispersive water slab in EM.Tempo.Cube]]  [[Image:Large struct article ScreenCapture2.png|thumb|left|500px|Figure 1: Geometry will attempt use a version of the periodic unit cell of the dispersive water slab in EMFDTD engine optimized for use with Intel's AVX instruction set, which provides a significant performance boost.Tempo.]]  [[Image:Large struct article ScreenCapture1.png|thumb|left|500px|Figure 1: Geometry If AVX is unavailable, a less optimal version of the periodic unit cell of the dispersive water slab in EMengine will be used.Tempo.]]   270 million    

[[ImageThe nearfield visualizations are also available as seen below:Large struct article RCS YZ.png‎|thumb|left|500px|Figure 1: Geometry of the periodic unit cell of the dispersive water slab in EM.Tempo.]]

<div><ul> <li style="display: inline-block;"> [[Image:Large struct article mesh detailScreenCapture1.png‎png|thumb|left|500px|Figure 1300px]]</li><li style="display: Geometry of the periodic unit cell of the dispersive water slab in EM.Tempoinline-block;"> [[Image:Large struct article ScreenCapture2.png|thumb|left|300px]]</li></ul></div>

<div><ul> <li style="display: inline-block;"> [[Image:Large struct article mesh settingsRCS XY Polar.png ‎‎||thumb|left|500px300px|Figure 1XY Cut of RCS is dBsm]]</li><li style="display: Geometry of the periodic unit cell inline-block;"> [[Image:RCS ZX Polar.png||thumb|left|300px| ZX Cut of the dispersive water slab in EM.TempoRCS is dBsm]] </li><li style="display: inline-block;"> [[Image:RCS YZ Polar.png||thumb|left|300px| YZ Cut of RCS is dBsm]]</li></ul></div>