Why Do Fan Vibration Modes Cluster? | ANSYS Modal Analysis Explained

In this video, we perform a modal analysis of a fan assembly in ANSYS Mechanical to investigate its natural frequencies and vibration mode shapes. Starting with a Static Structural analysis, we use the resulting structural state as the basis for a prestressed modal analysis and extract the first 25 mode shapes of the fan. The most interesting result is the appearance of groups of closely spaced natural frequencies. We’ll look at why this happens and how the periodic geometry and repeated fan blades influence the modal behavior of the structure. The fan is modeled using PA6 (Polyamide 6), with the appropriate material properties, boundary conditions, and finite element mesh. 🔍 What you'll learn How to set up a Static Structural Analysis in ANSYS How structural results can be transferred to a Modal Analysis What a prestressed modal analysis means How to extract and interpret natural frequencies How to visualize and understand mode shapes Why fan blades can produce closely spaced vibration frequencies How geometric symmetry and periodicity influence modal behavior How to interpret the first 25 modes of a fan assembly Important considerations when performing FEA / finite element analysis of rotating components 📐 Analysis Overview Software: ANSYS Mechanical Analysis: Static Structural + Prestressed Modal Analysis Material: PA6 / Polyamide 6 Number of modes: 25 Component: Fan assembly / impeller Method: Finite Element Analysis (FEA) The results shown in this video are specific to the geometry, material properties, mesh, boundary conditions, and modeling assumptions used in the simulation. ⏱️ Video Chapters 00:00 — Introduction 00:50 — Fan Assembly & Geometry 01:30 — Setting Up the Structural Analysis 05:00 — Static Structural Results 06:20 — Setting Up the Modal Analysis 06:50 — Looking at the Mode Shapes 17:30 — Conclusion 📁 Fan CAD Geometry: https://grabcad.com/library/fan-ansys... If you want to reproduce the simulation yourself, you can download the fan geometry and follow along with the analysis. 📚 More ANSYS & FEA Tutorials If you're interested in ANSYS Mechanical, modal analysis, structural analysis, finite element analysis (FEA), vibration analysis, natural frequencies, and engineering simulation, check out the other videos on the channel. More modal analysis examples and engineering simulations are coming soon. 👍 If you found this analysis useful, like the video and consider subscribing for more ANSYS, FEA, CAD, and engineering simulation content. 💬 Question: Have you ever encountered closely spaced or repeated natural frequencies in a structure with periodic geometry? Let me know in the comments. #ANSYS #ModalAnalysis #FEA #FiniteElementAnalysis #ANSYSMechanical #StructuralAnalysis #VibrationAnalysis #NaturalFrequency #ModeShapes #EngineeringSimulation #MechanicalEngineering #CAD #CAE #FanAnalysis #Polyamide6 #PA6