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      Please click here for a short but important announcement   03/26/17

      Dear Users Our Commercial and Academic users around the world can use these same forums here as before i.e. the Altair Support Forum , Commercial users from India with solver queries can go to the Solver Forum for India Commercial Users , Academic Users from India and AOC India Participants are requested to go to the Forum for India Academic Users and AOC India Participants , We will be tending to all queries in all the forums promptly as before, thank you for your understanding. 

riiily

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About riiily

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  1. I am trying to simulate WiFi signal propagation inside a stitched surface using RL-GO but am receiving the following vague errors: (Error 17179: The mesher encountered a problem. Error 16561: Mesher aborted - General error. Error 17580: The mesher aborted abnormally while meshing PlaneShell.) when I try to mesh the structure. "PlaneShell" is the only component giving the error at this point and is a stitched composite of several surfaces imported from SolidWorks. Interestingly the model will mesh if I scale it down to 0.2 size (the the user-defined variable "scale") but not if it is unscaled (i.e., setting "scale" to 1). Additionally, I recently updated from FEKO 7.0 to FEKO 14.0. In FEKO 7.0, I had no issues meshing scaled or unscaled models. I've attached the model. Would anyone have suggestions for eliminating this error? I must use RL-GO. Also, does Altair keep a listing of FEKO errors with explanations anywhere? Such a list would make the software far more user-friendly and would eliminate a lot of searching through and waiting for answers from forums. FullyFunishedBoeing03rayInc8_18_17.zip
  2. Power Warning with Leaky Coax Model

    I'm currently modeling a segment of leaky coax using MoM. The segment has a waveguide source on one end and is terminated with a 50 Ohm structure on the other. I keep receiving the following warning: "WARNING 3397: The power loss is larger than the active power". The warning makes me question the validity of the results. I've attempted increasing the accuracy of my model by reducing the mesh size near the waveguide source and near the wire section containing the load and by adding a plane of magnetic symmetry to the Y=0 plane. I've also decreased the global mesh size and have applied adaptive meshing. The most accurate model is included. Does the warning invalidate my results? How close do the active and dissipated powers have to be for FEKO to be satisfied (and to not return this error)? The ~0.8% discrepancy between the active power and the total power loss is far greater than the total power radiated. Give I am interested in simulating far field gain of the cable segment, the relative magnitude of this error makes me question the accuracy of the results. According to the error estimation request, the error is essentially zero for all elements except the end segments of the line containing the wire port load where the error values jump to 1. I decreased both the mesh segment length of the wire and the global wire radius which had some effect on the wire error but not much. Are there other methods of decreasing the model errors? CopperLFA280SegmentTermSect.zip
  3. Leaky Coax Simulation Power Loss Error

    Thanks Johan, I've tried your suggestions and still receive the same warning stating the power losses exceed the active power. Does the warning invalidate my results? How close do the active and dissipated powers have to be for FEKO to be satisfied (and to not return this error)? I mainly wonder because the ~0.8% discrepancy between the active power and the total power loss is greater than the total power radiated. I am interested in simulating far field gain of the cable segment. I've included an updated model. The model has your suggestions included. I also included an error estimation request. The error is highest on the end segments of the line containing the wire port load. I decreased the wire segment length and the global wire radius which had some effect on the wire error but not much. Are there other methods of decreasing the model errors? CopperLFA280SegmentTermSect.zip
  4. I'm currently modeling a segment of leaky coax using MoM. The segment has a waveguide source on one end and is terminated with a 50 Ohm structure on the other. I keep receiving the following warning: "WARNING 3397: The power loss is larger than the active power". The warning makes me question the validity of the results (which are not exactly what I expected numerically). In the past I have found this warning has occurred with this model with lossless dielectrics and has been fixed by making the loss tangent of the dielectrics a small nonzero number. In this case however, I am using copper as the only lossy medium (as a friend did in a simulation of the same structure with COMSOL). Why are the losses exceeding the power inputs and does this incorrect result have significant physical meaning? Obviously the model has nonphysical results, but does that invalidate the results entirely? What are the unrealistic features of the model causing this incorrect calculation? Can this situation be resolved without making the dielectrics lossy (to maintain equivalence with my friend's COMSOL model)? Even with lossless dielectrics, how can the solution of the wave equations result in the power loss being noticeably (~1%) greater than the active power? CopperLFA280Segment.zip
  5. Leaky Coax Modeling Issue

    I've attached a new version of the leaky coax segment. The segment has a waveguide source on one end and is terminated with a 50 Ohm structure on the other end. I keep receiving the following warning: "WARNING 3397: The power loss is larger than the active power". The warning makes me question the validity of the results (which are not exactly what I expected numerically). In the past I have found this warning has occurred with this model with lossless dielectrics and has been fixed by making the loss tangent of the dielectrics a small nonzero number. In this case however, I am using copper as the only lossy medium (as a friend did in a simulation of the same structure with COMSOL). Why are the losses exceeding the power inputs and does this incorrect result have significant physical meaning? Obviously the model has nonphysical results, but does that invalidate the results entirely? What are the unrealistic features of the model causing this incorrect calculation? Can this situation be resolved without making the dielectrics lossy (to maintain equivalence with my friend's COMSOL model)? How can the solution of the wave equations even result in the power loss being greater than the active power, even with lossless dielectrics? CopperLFA280Segment.zip
  6. RL-GO in Plane Shell Not Allowed with Copper Shell

    Thanks JIF, To clarify, by dynamic range do you mean the ratio between the maximum signal value simulated and the minimum accurate signal value simulated? I have run a simple simulation with RL-GO modeling of an electrically large PEC cube filled with free space and having a dipole antenna at the center of the cube and do obtain some non zero electric fields outside the PEC cube which not obtained using MoM to solve the same model. How inaccurate is RL-GO for (large) closed PEC structures? For what kinds of simulations will RL-GO not converge to the full-wave solution (or adequately approximate it)? Would MLFMM or UTD be a better solver method for these structures? Are these issues inherent to FEKO's implementation of GO or to the GO method generally? I have been told FEKO's implementation involves using ray tracing to compute surface currents generated by the impinging of rays on surfaces and from those surface currents, all other requested outputs. Is this true? I would have thought FEKO's RL-GO implementation would have been based more on computing desired outputs from the ray paths directly (i.e., more rays intersecting a given area of say, a near field request plane, directly translates to greater field strengths). I have tried using the MLFMM method on a scaled down model of our plane (which I've attached) but receive the following error on attempting to solve the model: ERROR 832: Segmentation rules have been violated (two triangles touch without a common edge). The plane has been scaled down by a factor of twenty. I did not receive this error on an unscaled model of the plane but instead ran out of memory. Do Scale transformations often produce incorrectly connected models? I believe I properly scaled down all of the plane geometry components so they are scaled with the user-defined variable "scale" so as to maintain the same relative geometry. How can this error be worked around? We are using an imported SolidWorks file for the plane shell. I have tried using the Simplify transformation on all of the geometry import components of the scaled plane assembly but receive the same errors upon simulation. I also tried uniting the simplified geometry components but doing so caused many of the geometry import components to visually disappear (unless selected in the Model Tree) and to not be meshed. I also tried uniting the plane import geometry components without first simplifying them and received another error: ERROR 17448: Geometry union failed. Boeing121DipoleMOM_Scaled.zip
  7. Is it possible to use the ray-launching geometric optics method with lossy materials? We are trying to model RF propagation in an empty airplane shell (consisting only of faces) but receive the following error when we change the shell material from PEC to copper with a thickness of 1 mm: ERROR 33858: Metallic triangles for ray-launching GO found with unsupported losses. Is there any way to work around this error (in FEKO Suite 7.0)? I cannot post the plane model, but the shell can be thought of as an arbitrary closed surface inside of which there is a dipole antenna source. We would like to make the metallic shell have a thickness so to eliminate fields being generated external to the airplane with PEC as the shell material.
  8. Leaky Coax Modeling Issue

    Thanks JIF, I am able to set my dielectric faces to copper. I meant to say that I was unable to set them to say, ePTFE or TEFZEL, the dielectric media I set the regions to be whereas I am only able to assign metallic media to faces of objects and not to the regions of objects. So the rules are, metallic objects are modeled with free space as the region and the desired metallic substance of the object as the face media and dielectric objects are modeled with the dielectric media assigned to the region and a "dielectric boundary" as the face media if the dielectric shares the face with another dielectric region or free space and as a metallic media if the dielectric shares the face with a metallic object. Will these rules hold true generally?
  9. Leaky Coax Modeling Issue

    I am attempting to model a short section of leaky coax with a single slit in the center of the outer conductor with FEKO Suite 7.0. The model is attached. We are trying to evaluate the S21 value between two waveguide ports on the ends of the cable segment but the resulting S21 value is essentially zero (about -115 dB), which I believe is incorrect. When I replace the lossless user-defined dielectric medium of "ePTFE" with free space in the dielectric of the cable, the S21 value becomes more realistic (about 0.995). I believe there is some mistake in my modeling of the dielectric between the inner and outer conductors. What restrictions are there on modeling dielectric materials, specifically regarding the assignment of dielectric materials to regions and faces? For instance, in modeling metallic objects only the faces are assigned the desired metallic media of the modeled objects while the regions are set to free space; I do not seem to be able to set the faces of the dielectric to the desired dielectric media (while I can set the "Jacket" and "Dielectric" regions to the desired dielectric material) and assume the same rule does not apply to the modeling of dielectrics. What are the "Default", "Dielectric Boundary", and PEC face media specifications used for in modeling dielectrics? CopperLFA280SegmentChaoParameters.zip
  10. Why can I not assign all the media I have added to my Media Library to the regions and faces of the objects in my FEKO models? What are the rules for assigning media to regions and faces of models? I was told in an email from the FEKO support team that a metal solid is modeled in FEKO not by setting the region of the object to a metallic medium (which is not allowed) but by making the region medium of the object free space, by making the medium of the object "surfaces" (by which I assume was meant "faces") the needed metallic medium, and by making the thickness of those "surfaces" greater than skin depth. I have tried this but the metallic medium I am using, copper, does not appear on all of the model faces I need to model as copper. I am using FEKO 7.0.
  11. How can a union in CADFEKO be broken back into its constituent components without duplicating the components and then deleting the old union? This workaround works but is annoying. Also is there a way to selectively hide components of a union without breaking up the union? I am using FEKO 7.0.
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