8787

8148

كارشناسي ارشد

تبديل انرژي

اصفهان: دانشگاه صنعتي اصفهان، دانشكده مكانيك

1392

يازده،83ص.: مصور،جدول،نمودار

ص.ع.به فارسي و انگليسي

احمدرضا پيشه ور اصفهاني

محمود اشرفي زاده

8/2/93

ابراهيم شيراني، محسن ثقفيان

مهندسي مكانيك

ID8148

1 چكيده در اين پاياننامه اعمال شرط مرزي ورود وخروج به روش ISPH با الگوريتم Fractional Step بررسي ميشود و ايدهاي ارائه ميگردد كه همهي الزامات ورودي و خروجي جريان براي روش مبنا ذرهاي SPH در آن لحاظ ميشود ابتدا سعي مي شود نحوهي اعمال شرايط مرزي ورود خروج براي جريان داخل يك لوله افقي توضيح داده شود و نتايج با حل تحليلي صحتسنجي ميشود در ادامه از آن براي مدل كردن جريان بر روي پله وارون Backward Facing Step Flow و حفرهي باز Open Cavity استفاده شده ونتايج با حل حجم محدود مقايسه ميشود كلمات كليدي Projection Method Fractional Step Method ISPH SPH جريان تراكمناپذير شرايط مرزي ورودي خروجي حفره پله

84Implementation of Inflow Outflow Boundary Condition for 2D Internal Flow Using ISPH Method Arash Tavana arash tavana@me iut ac ir January 20th 2014 Department of Mechanical Engineering Isfahan University of Technology Isfahan 84156 83111 IranDegree M Sc Language FarsiSupervisor Ahmad Reza Pishevar a pishe@cc iut ac irAbstract Smoothed Particle Hydrodynamics SPH is a mesh free lagrangian method It is a particle base method inmacroscopic scale works by dividing the fluid into a set of discrete elements referred to as particles rather thanmesh cell These particles have a spatial distance known as the smoothing length over which their properties are smoothed by a kernel function This means that the physical quantity of any particle can be obtained by summingthe relevant properties of all the particles which lie within the range of the kernel Every particle carries mass velocity pressure and different hydrodynamic variable SPH First applied to astrophysics and proves to be wellsuited for studying complex fluid dynamics This method has been successfully used to model free surface flowsespecially when strong free surface deformations take place The simulation of the incompressible flow is normallycarried out by two methods in SPH first approximately simulating incompressible flow with a smallcompressibility called Weakly Compressible SPH WCSPH second fully incompressible procedure that calledIncompressible SPH ISPH In the first method pressure has been obtained from a state equation and in the nextone from a poisson equation In the WCSPH to satisfy Courant Friedrichs Lewy CFL condition the time step islimited to very small value by the speed of sound Also compressibility cause sound wave reflection at theboundaries which can lead to numerical instability In the ISPH the CFL condition is based on the fluid velocityfield rather than the speed of sound and therefore large time step can be used in the simulation In this thesis attention is focused on the boundary condition specially In flow Out flow boundary condition In Eulerian models the imposition of inflow and outflow boundary conditions is relatively simple because each cellof the mesh describes a part of the domain and ghost cells can be used to impose boundary conditions Conversely the implementation of suitable inflow outflow boundary condition in the SPH model is not straightforward becauseof the Lagrangian nature of this scheme Indeed SPH particle move during the simulation and consequently theyhave to be conveniently inserted and removed from the domain Furthermore the interpolation procedure which isthe basis of the SPH scheme makes the implementation of this kind of boundary condition difficult Moreover thefractional step algorithm which compute intermediate velocity pressure and location for particles increasecomplexities In this thesis we present a new idea to overcome most of these difficulties In this method someparticle are defined at solution domain at each time step At the solid boundary these particles are fixed and neverneed to be detected in each time step But at the inlet outlet boundary particles are moving so we need to markthem in every time step By constructing a simple grid this aim is obtainable These boundary particles can be usedfor implementation of boundary condition First the proposed idea is used for 2D internal flow in channel flow The suitability of the in out flow model isshown by comparing the obtained velocity field with the analytical solution Then capabilities of the algorithm aretested in Backward facing step flow which is a more complicate flow that need in out flow boundary conditions The result are validated with standard solution obtained from a Finite Volume Method FVM in different Reynoldsnumber At the end the flow in an open cavity is simulated Key wordsSPH ISPH Incompressible flow Projection method In Out flow boundary condition

احمدرضا پيشه ور اصفهاني

محمود اشرفي زاده

ابراهيم شيراني، محسن ثقفيان