The drag forces exerted by lahar flows on a cylindrical pier: case study of post Mount Merapi eruptions

Quality in Research: International Symposium on Materials, Metallurgy, and Chemical Engineering

材料科学;冶金学;化学工业

Haza, Zainul Faizien^1

Fakultas Teknik Universitas Sarjanawiyata Tamansiswa, Jl.Kusumanegara 157, Yogyakarta, Indonesia^1

关键词: Commercial software;    Drag force coefficients;    Momentum conservations;    Multiphase model;    Non-dimensional parameters;    Problem formulation;    Rheological data;    Two dimensions (2D);   

Others  :  https://iopscience.iop.org/article/10.1088/1757-899X/316/1/012041/pdf
DOI  :  10.1088/1757-899X/316/1/012041

学科分类：材料科学（综合）

来源: IOP

【 摘 要 】

Debris flows of lahar flows occurred in post mount eruption is a phenomenon in which large quantities of water, mud, and gravel flow down a stream at a high velocity. It is a second stage of danger after the first danger of lava flows, pyroclastic, and toxic gases. The debris flow of lahar flows has a high density and also high velocity; therefore it has potential detrimental consequences against homes, bridges, and infrastructures, as well as loss of life along its pathway. The collision event between lahar flows and pier of a bridge is observed. The condition is numerically simulated using commercial software of computational fluid dynamic (CFD). The work is also conducted in order to investigate drag force generated during collision. Rheological data of lahar is observed through laboratory test of lahar model as density and viscosity. These data were used as the input data of the CFD simulation. The numerical model is involving two types of fluid: mud and water, therefore multiphase model is adopted in the current CFD simulation. The problem formulation is referring to the constitutive equations of mass and momentum conservation for incompressible and viscous fluid, which in perspective of two dimension (2D). The simulation models describe the situation of the collision event between lahar flows and pier of a bridge. It provides sequential view images of lahar flow impaction and the propagation trend line of the drag force coefficient values. Lahar flow analysis used non-dimensional parameter of Reynolds number. According to the results of numerical simulations, the drag force coefficients are in range 1.23 to 1.48 those are generated by value of flow velocity in range 11.11 m/s to 16.67 m/s.