Numerical simulation of unsteady Compressible multiphase flows using Unstructured finite volume method

Ramesh Babu, K (2014) Numerical simulation of unsteady Compressible multiphase flows using Unstructured finite volume method. Masters thesis, Manipal Institute of Technology, Manipal.

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Compressible multi-phase flows are very common in engineering applications and they are one of the most challenging areas in computational fluid dynamics. Even for the simple two-phase flows, there is no universally accepted formulation for governing equations and solution techniques. One of the popular formulation is to treat each phase as a separate fluid and write the balance equations for mass, momentum and energy of each phase, together with exchange terms between the phases as source terms A numerical method is developed for the analysis of multi-phase flows. The two-fluid approach is used in which the transport equations are written for the gas phase and the liquid phase. The governing equations include the mass, momentum and energy conservation equations of the gas phase and liquid phase. The governing equations are discretized using unstructured finite volume scheme, with central differencing being used for the convection terms. The artificial dissipation method based on the Jameson Schmidt Turkel scheme is used to overcome the oscillations associated with the central differencing. The solution is advanced in time using four stage explicit Runge-Kutta scheme. To predict these effects accurately, the wave travel in the medium is to be accurately simulated. The two fluids with high pressure ratio are separated by diaphragm. When diaphragm opens then, expansion wave and compression wave travel through the medium at much faster rate than the interface. The popular seven equation model can be reduced to that of six equation model (for 1D system) with the required property of conservation and hyperbolicity by assuming equal pressure for gas phase and particle phase. The computer code is validated for the water-air shock tube problem and is then applied to simulate the unsteady wave travel during a reported water hammer experimental study. It is observed that the marching pressure occur at 4 seconds reaches a peak pressure of 80 bar, which is 20 times the magnitude of initial pressure(4 bar). Sensitivity study of pressure ratio is also accounted. 2D computer code has been developed for simulation of two fluid model and gambit is used for pre-processing.

Item Type: Thesis (Masters)
Subjects: Engineering > MIT Manipal > Instrumentation and Control
Depositing User: MIT Library
Date Deposited: 13 Nov 2014 10:50
Last Modified: 13 Nov 2014 10:50

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