November 5, 2023 at 7:30 pmSabrina CorsettiSubscriber
Hello! This seems like a silly problem to be having, but I've been trying numerous methods to solve it, to no avail.
The trouble is, I have an FDTD simulation of a grating. The grating creates scattering in all dimensions - up, down, left, and right, with some transmission and reflection.
To measure the power scattered in each direction, I have 6 monitors (top, bottom, left, right, etc.) enclosing the entire simulation region. So, in theory, the sum of the power through the 6 monitors should be 100% of the source power.
The trouble is that, depending on the method I use to calculate the power through each of the monitors, this sum comes out to well over 100%.
For example, suppose I find the power in the "upwards" monitor using the integral of the electric field intensity, e.g.:
- E2_UP = getelectric("UP",2);
- E2_UP_int = integrate(E2_UP,[1,3],x_UP,z_UP);
Power_UP = c*n*eps0/2*E2_UP_int;
- P_Source = sourcepower(getdata('source_WGmode','f'),2);
If I then take Power_UP/P_Source, that quotient alone turns out to be about 1.56. So just one monitor seems to be recording more than 100% of the source power.
The total power does come out to 100% when I take "transmission" through each of the monitors, from getresult. However, since "transmission" integrates only normal to the surface, it seems like power is lost in the calculation, due to the grating emission propagating at 45 degrees. This is confirmed by integrating power in a spot in the far-field over the grating, using the electric field amplitude method above. The fractional power in that spot comes out to be larger than the "transmission" value for the entire upwards monitor.
In short - is there something conceptual I'm missing here, regarding how to integrate power? Essentially, I don't see how taking c*n*eps0/2*E2_UP_int could ever give a value larger than the source power, unless I'm misunderstanding how the source power is normalized?
Any feedback on this issue would be appreciated. Thank you!
- You must be logged in to reply to this topic.
Boost Ansys Fluent Simulations with AWS
Computational Fluid Dynamics (CFD) helps engineers design products in which the flow of fluid components is a significant challenge. These different use cases often require large complex models to solve on a traditional workstation. Click here to join this event to learn how to leverage Ansys Fluids on the cloud, thanks to Ansys Gateway powered by AWS.
Earth Rescue – An Ansys Online Series
The climate crisis is here. But so is the human ingenuity to fight it. Earth Rescue reveals what visionary companies are doing today to engineer radical new ideas in the fight against climate change. Click here to watch the first episode.
Subscribe to the Ansys Blog to get great new content about the power of simulation delivered right to your email on a weekly basis. With content from Ansys experts, partners and customers you will learn about product development advances, thought leadership and trends and tips to better use Ansys tools. Sign up here.
- Ansys Insight: About override mesh in FDTD: its use and settings
- Ansys Insight: Why my simulation result is different from published paper or experiment?
- Ansys Insight: Transmission results greater than one
- Ganhemt Project mistake can you help me
- How to calculate the cross-polarization efficiency and phase in FDTD
- save data error
- Simulation of a single pillar of a peltier cooler
- EME : field profile and cell periodicity
- Ansys Insight: Single frequency CW source
- What is the meaning of this error ” Bad termination of…” ?
© 2023 Copyright ANSYS, Inc. All rights reserved.