Location: Watershed Physical Processes ResearchTitle: Velocity correction coefficients in pressure-correction type model
|ZHANG, YAOXIN - University Of Mississippi|
|JIA, YAFEI - University Of Mississippi|
Submitted to: American Society of Civil Engineers Journal of Hydraulic Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/29/2018
Publication Date: 3/20/2019
Citation: Zhang, Y., Jia, Y. 2019. Velocity correction coefficients in pressure-correction type model. American Society of Civil Engineers Journal of Hydraulic Engineering. 145(6). https://doi.org/10.1061/(ASCE)HY.1943-7900.0001604.
Interpretive Summary: In flow simulation of Computational Fluids Dynamics, the governing equations include the continuity equation and the momentum equation. These two equations are not directly coupled, and to solve them, an assumption that the velocity variations are mainly due to the variations of the water surface (pressure gradient) are proposed. This assumption leads to a relationship that the velocity correction is proportional to the corrections of the water surface gradient with a correction coefficient. This study for the first time derived an equation for the velocity correction coefficient, which was evaluated by using a semi-empirical method. According to the examples and application of a laboratory experiment and a field experiment, the proposed method significantly improved the numerical stabilities of the model when using a larger time step, while also improving computational efficiency.
Technical Abstract: Velocity correction methods are often used in numerical models simulating fluid flows. This paper presents a new method to evaluate the velocity correction coefficient: an equation constructed by the coefficient matrix of the linearized momentum equations is simultaneously solved for the velocity correction coefficient. In addition, the implicit ECC (Equation of Correction Coefficients) method includes a smoothing mechanism, which makes it numerically more stable than the commonly used SIMPLEC method because larger relaxation factors and time steps can be used. The ECC method was integrated into a 2D depth-integrated unstructured FVM model based on a hybrid mesh system (triangle + quadrilateral). It was demonstrated using one experimental case and a field case. According to the numerical tests, the proposed ECC method can not only enhance the numerical stability but also improve the computing efficiency due to the capability of using large relaxation factors and large time steps for the pressure-correction type models