Evaluation of the dynamic core of the PALM model system 6.0 in a neutrally stratified urban environment: comparison between LES and wind-tunnel experiments

We demonstrate the capability of the PALM model system version 6.0 to simulate neutrally stratified urban boundary layers. Our simulation uses the real-world building configuration of the HafenCity area in Hamburg, Germany. Using PALM's virtual measurement module, we compare simulation results to wind-tunnel measurements of a downscaled replica of the study area. Wind-tunnel measurements of mean wind speed agree within 5% on average while the wind direction deviates by approximately 4 degrees. Turbulence statistics similarly agree. However, larger differences between measurements and simulation arise in the vicinity of surfaces where building geometry is insufficiently resolved. We discuss how to minimize these differences by improving the grid layout and give tips for setup preparation. Also, we discuss how existing and upcoming features of PALM like the grid nesting and immersed boundary condition help improve the simulation results.

Automated summary

The study demonstrates the capability of the PALM model system version 6.0 in simulating neutrally stratified urban boundary layers, using real-world building configurations of the HafenCity area in Hamburg, Germany. Comparison with wind-tunnel measurements shows good agreement in mean wind speed and wind direction, with slight deviations near insufficiently resolved building surfaces. Improvements in grid layout and utilization of PALM's features like grid nesting and immersed boundary condition are discussed to enhance simulation results.