A comprehensive approach for understanding debris flow interaction with pipelines through dynamic impact pressure modeling

•Integration of inertia and viscous forces with attack angle in dynamic impact pressure modelling is presented.•The significance of Hershel-Bulkley rheological model in CFD simulation is highlighted.•Effect of debris flow regime in impact mechanism is revealed.•The findings provide valuable insights of pipeline design and mitigation strategies in mountainous regions. The interaction of debris flows, and impacted structures is still not well understood due to the complex mechanisms of the flows. Although several methodologies from experimental to numerical have developed so far, a thorough assessment of impact mechanism necessitates multiphase modelling approaches. Therefore, this paper presents a dynamic impact pressure modelling approach of debris flows using experimental and numerical techniques. The experimental investigations involved seven type of debris flows based on solid volume fraction (αs), that being released on an inclined flume, impacting a 2″(52 mm) pipe model. The numerical investigations were performed in Computational Fluid Dynamics (CFD) environment by utilising the Spalart-Allmaras turbulence and Hershel- Bulkley rheological models by considering different inclined angle (β) impact scenarios. The findings revealed that all debris flows produced were in supercritical flows regime and characterized as dilute, medium viscous, and highly viscous flows, based on Froude (Fr) and Reynold (Re) numbers. Drag coefficients (CD-90/CD-0) were behaved non-linearly with respect to Fr and Re. The proposed refined dynamic normal (pd-90) and axial (pd-0) impact models using different set of Fr, Re and β will offer valuable insight for pipeline operators seeking to comprehend the complex interaction between debris flows and pipelines.