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      How are boundary conditions set up?

      Set the boundary conditions in the Domain Settings

      A screenshot of a computer screen AI-generated content may be incorrect.

       You can define the boundary conditions for your simulation within the Domain properties. The setup process is straightforward: 

      1. In the EMA3D ribbon, click on Domain. This will open the domain properties panel. 
      2. Select the Boundary tab within the properties panel. 
      3. Here, you will see a list of the six faces of the simulation domain: -X, +X, -Y, +Y, -Z, and +Z. You can assign a specific boundary condition to each face individually from its dropdown menu. 
      4. To apply the same condition to all six faces simultaneously, you can use the "All" entry at the top of the list. 

      Choosing the Right Boundary Condition 

      The available boundary conditions can be grouped into three main categories: exact, quasistatic, and open/radiating. The correct choice is crucial for obtaining physically meaningful results. 

      Boundary Condition Type 

      Physical Representation 

      Ideal Use Case 

      Key Considerations/Limitations 

      		  

      PEC (Perfect Electric Conductor) 

      A perfect metallic wall or ground plane. 

      Simulating objects inside a metallic enclosure (e.g., equipment box, test chamber) or leveraging a ground plane symmetry. 

      This is the default condition. It reflects all incident energy and is not suitable for open-region problems. 

      		  

      Symmetric 

      A plane of physical symmetry in the model. 

      Models with one or more planes of symmetry (e.g., simulating only half of a symmetric aircraft) to reduce memory and runtime by a factor of two. 

      The geometry and all sources must be perfectly symmetric across the boundary plane. 

      		  

      Periodic 

      An infinitely repeating structure. 

      Simulating unit cells of periodic structures like antenna arrays or frequency selective surfaces. 

      Requires the geometry to be identical on opposite boundaries of the domain. 

      		  

      Quasistatic 

      Low-frequency problems where wave propagation is negligible. 

      H-Field type: For quasi-magnetostatic problems like lightning interaction. 

      E-Field type: For quasi-electrostatic problems. 

      Only applicable to very low-frequency or DC analysis. 

      Mur  H-Field 

      An open, radiating boundary for absorbing outgoing waves. 

      Lightning (LEMP) simulations. It is computationally efficient and robustly handles the current attachment/detachment lines that must extend through the boundary. 

      Less accurate than PML. It can cause higher reflections, especially for waves hitting the boundary at a shallow angle. 

       

      PML (Perfectly Matched Layer) 

      A high-fidelity open, radiating boundary. 

      HIRF, antenna radiation, and RCS simulations. Use this when high accuracy and very low boundary reflections are critical. 

      The most computationally expensive option in terms of memory and time. Structures should not physically penetrate the PML layers. 

       

      Understanding the Options and Parameters 

      For most boundary conditions, the selection is all you need. However, the Perfectly Matched Layer (PML) has specific parameters you can adjust for performance tuning : 

      • Layer Count: This defines the number of absorbing material layers that surround your simulation domain. More layers provide better absorption of outgoing waves but also increase memory requirements and computation time. The default is 2 layers. 
      • Order: This parameter controls how the conductivity of the absorbing material increases from the inner layer to the outer layer. The default value is 2.0. 
      • Reflection [%]: This specifies the target amount of electromagnetic energy that is allowed to reflect back into the simulation space from the boundary. A smaller value results in better absorption but can require more layers. The default is a very low 0.001%. 

      In summary, your choice of boundary condition is a trade-off. For simulating an aircraft in flight, you need an open/radiating boundary. Use Mur  H-Field for lightning simulations due to its efficiency and robustness with penetrating conductors. For high-frequency radiation problems like HIRF or antenna analysis where accuracy is paramount, PML is the superior choice, provided you have the computational resources. For any enclosed or symmetric problems, use PEC or Symmetric boundaries, respectively.