The Influence of Y-Axis Variables on Tunnel Piston Effect Measurements in 3D Models Simplified to 2D
Dito Afandi1*, Taqia Rahman1 , Latif Budi Suparma1
1Department of Civil and Enviromental Engineering, Universitas Gadjah Mada, Yogyakarta, INDONESIA
*Corresponding author: ditoafandi@mail.ugm.ac.id
INTISARI
The 3D CFD simulation requires a lot of resources, making expensive predictions. This research uses a 2D model to simplify 3D model simulation that previous researchers have studied while keeping x-axis airspeed variation forecasting accuracy. This study aims to analysis the 2D positioning effect of monitoring points in y-axis variables as representation of velocity transducer in 3D model. The 3D model was scaled 1/20 and simplified by using hydraulic diameter and blockage ratio to calculate train and tunnel widths. The modelling is using the SIMPLE, k-𝜀 standard model, 0.04 m mesh size, and CFL number 0.75. Four variables are placed in the middle position of the tunnel, a distance of 50 mm from the middle of the tunnel up and down, and on the tunnel wall. The results show that placing the measurement point in the middle of the tunnel better represents the x-axis airspeed measured at the centre point of the cross section of the inlet and outlet tunnel. This model is validated, which achieves MBE values of 3.9% and 4.5% for the inlet and outlet velocity ratios, respectively.
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