Potential use of reduced-scale models in CFD simulations to save numerical resources: Theoretical analysis and case study of flow around an isolated building

This study hypothesizes that reduced-scale models for computational fluid dynamics (CFD) simulations of wind flow and related processes can save numerical resources. To test this hypothesis, both theoretical analysis and a numerical case study are conducted. The CFD simulations are validated against a set of wind tunnel experimental data. Both theoretical and numerical results support the hypothesis. It is found that a reduced-scale model requires fewer cells than a full-scale model to achieve a target near-wall z+z+ value and prediction accuracy and therefore has the potential to save numerical resources. Quantitative analysis shows that this potential is very large, depending on many factors, such as the scaling factor, the target z+z+ value, and the flow problem. The findings of this study should be useful for CFD simulations of wind flow and related processes, particularly over large areas. However, special attention should be paid to the disadvantages of using reduced-scale models, such as the difficulty to fulfill the similarity requirements.