Towards simple implicit preconditioning Riemann solvers for the simulation of the low mach number flows

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Title:	Towards simple implicit preconditioning Riemann solvers for the simulation of the low mach number flows
Other Titles:	可調式黎曼解模擬低馬赫速流體
Authors:	楊銘榮;Yang, Ming-Jung
Contributors:	淡江大學航空太空工程學系碩士班牛仰堯
Keywords:	預處理;多相流;黎曼解;空蝕;隱式法;無矩陣;Preconditioning;multiphase flow;Riemann Solver;cavitation;Implicit method;Matrix-free
Date:	2016
Issue Date:	2017-08-24 23:52:18 (UTC+8)
Abstract:	我們採用預處理純量無矩陣隱式法和AUSMD(R)來解多相流的問題，因為多尺度的聲速所造成的數值穩定性問題，我們是透過加入預處理的尤拉系統所得到的特徵值，來改善收斂性的問題。本文所介紹的預處理隱式法所模擬出來的結果與完整的隱式法和Runge-Kutta 是非常接近的。由模擬解果得知純量無矩陣隱式法式能夠提高計算效率，並且在許多例子中都得到很好的驗證。 Here, a scalar matrix-free implicit type preconditioning hybrid AUSMD(R) solver for multi-phase flows is developed. The numerical stability problem caused by the multi-scale speed of sound due to uncertain dissipation terms in the current schemes which can be resolved by rescaling the eigenvalues of the Euler type system equations to enhance computational convergence. This paper presents implicit pre-conditioning approaches which indicate similarly accurate results obtained with the fully implicit and Runge-Kutta explicit schemes. The current used homogeneous two-phase mixture model with the assumption of kinematics and thermodynamics equilibriums. The thermodynamics behaviors of liquid phase, vapor phase and their phase transitional process are described by a temperature dependent hybrid equation of state which includes a mass-fraction averaged formula of water-vapor saturation process. The current work shows that the scalar matrix free implicit schemes are capable of improving the computational efficiency over its explicit counterpart. Several benchmark tests are used for numerical validations.
Appears in Collections:	[Graduate Institute & Department of Aerospace Engineering] Thesis

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