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Skin effect not appearing with union of two cylinders in COMSOL

Posted 11.12.2025, 06:09 GMT-5 Low-Frequency Electromagnetics, RF & Microwave Engineering, Modeling Tools & Definitions 0 Replies

Imke Van den Corput

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I am modeling a conductive disk in COMSOL under AC conditions (14 GHz and 80 GHz) with the following setup.

Geometry and Physical Setup

Geometry: The conductor consists of two thin cylinders stacked on top of each other and merged using the Form Union geometry operation. Radius (per cylinder): 0.015 m Height (per cylinder): 0.0005 m Total Geometry: A disk with R=0.015 m and total height 1×10^−3 m.

Current direction: The current flows radially across the disk (from one side of the diameter to the opposite side, i.e., perpendicular to the stacking direction).

Physics: Coupled interfaces: Magnetic Fields (mf) and Electrical Circuit (cir). Coupling: The mf interface uses Lumped Ports for input and output, coupled to the cir interface via the External I vs. U node. The components in the cir circuit are connected in series.

Problem / Observation

When analyzing the current density ? in a cross section: - With the Union of the two cylinders: The expected skin effect (concentration of current at the outer edges of the disk, parallel to the current direction) is not visible. The current density is uniform across the cross section.

As a control, using only one cylinder (R=0.015 m and total height 0.001 m): The skin effect is observed correctly.

Question I don’t understand why, even though I apply a union to the two cylinders, I don’t get the expected skin effect, just like with a single cylinder?

Reply

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