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Fundamentals of Computational Fluid Dynamics
- 1. SEMINAR PRESENTATION ON FUNDAMENTALS OFCOMPUTATIONAL FLUID DYNAMICS(CFD) Presented By:- Pankaj Darbar Koli B.Tech (Mechanical) Roll No:-42 Seminar Guide:- Prof. R.D.Sandhanshiv R.C.PATEL INSTITUTE OF TECHNOLOGY (An ISO 9001:2011 Certified Institution & Accredited by NAAC-UGC) DEPARTMENT OF MECHANICAL ENGINEERING.
- 2. What isComputational Fluid Dynamics(CFD)? Why and where use CFD? Physics of Fluid Grids Boundary Conditions Applications Advantage Limitation References CONTENTS
- 3. What is CFD? Computational fluid dynamics (CFD) is the science of predicting fluid flow, heat transfer, mass transfer, chemical reactions, and related phenomena by solving the mathematical equations which govern these processes using a numerical process We are interested in the forces (pressure , viscous stress etc.) acting on surfaces (Example: In an airplane, we are interested in the lift, drag, power, pressure distribution etc) We would like to determine the velocity field (Example: In a race car, we are interested in the local flow streamlines, so that we can design for less drag) We are interested in knowing the temperature distribution (Example: Heat transfer in the vicinity of a computer chip)
- 4. WHAT IS CFD? Mathematics Navier-Stokes Equations FluidMechanics Physics of Fluid Fluid Problem Computer Program Programming Language Simulation Results Computer Grids Geometry Numerical Methods Discretized Form Comparison& Analysis C F D
- 5. WHY USE CFD? Simulation(CFD)Experiment Cost Cheap Expensive Time Short Long Scale Any Small/Middle Information All Measured Points Repeatable All Some Security Safe Some Dangerous
- 6. WHERE USE CFD? •Aerospace • Automotive • Biomedical • Chemical Processing • HVAC • Hydraulics • Power Generation • Sports • Marine Temperature and natural convection currents in the eye following laser heating. Aerospa ce Automotive Biomedicine
- 7. WHERE USE CFD? reactorvessel - prediction of flow separation and residence time effects. Streamlines for workstation ventilation HVAC Chemical Processing Hydraulics • Aerospace • Automotive • Biomedical • Chemical Processing • HVAC(Heat Ventilation Air Condition) • Hydraulics • Power Generation • Sports • Marine
- 8. WHERE USE CFD? Flowaround cooling towers Marine Sports Power Generation • Aerospace • Automotive • Biomedical • Chemical Processing • HVAC • Hydraulics • Power Generation • Sports • Marine
- 9. PHYSICS OF FLUID Density ρ Fluid = Liquid or Gas le compressib variable ible incompress const Substance Air(18ºC) Water(20ºC) Honey(20ºC) Density(kg/m3) 1.275 1000 1446 Viscosity(P) 1.82e-4 1.002e-2 190 Viscosity μ: resistance to flow of a fluid ) ( 3 Poise m Ns
- 10. CONSERVATION LAW in out M in m out m out in m m dt dM out in m m 0 dt dM Mass Momentum Energy
- 11. DISCRETIZATION Discretization Methods Finite Difference Straightforward to apply, simple, sturctured grids Finite Element Any geometries Finite Volume Conservation, any geometries Analytical Equations Discretized Equations Discretization
- 12. FINITE VOLUME METHOD GeneralForm of Navier-Stokes Equation q x U x t i i i T U j , , 1 S i V i dS n dV x Integrate over the Control Volume(CV) Local change with time Flux Source V S i i i V dV q dS n x U dV t Integral Form of Navier-Stokes Equation Local change with time in CV Flux Over the CV Surface Source in CV
- 13. GRIDS Structured Grid +all nodes have the same number of elements around it – only for simple domains Unstructured Grid + for all geometries – irregular data structure Block Structured Grid
- 14. BOUNDARY CONDITIONS TypicalBoundary Conditions No-slip(Wall), Axisymmetric, Inlet, Outlet, Periodic Inlet ,u=c,v=0 o No-slip walls: u=0,v=0 v=0, dp/dr=0,du/dr=0 Outlet, du/dx=0 dv/dy=0,dp/dx=0 r x Axisymmetric Periodic boundary condition in spanwise direction of an airfoil
- 15. APPLICATIONS Car safetythermal imaging using CFD Heat exchanger imaging Imaging of missile prototypes
- 16. ADVANTAGES Relatively lowcost. CFD simulations are relatively inexpensive, and costs are likely to decrease as computers become more powerful. Speed. CFD simulations can be executed in a short period of time. Ability to simulate real conditions. CFD provides the ability to theoretically simulate any physical condition. Comprehensive information. CFD allows the analyst to examine a large number of locations in the region of interest, and yields a comprehensive set of flow parameters for examination.
- 17. LIMITATIONS • The CFDsolutions can only be as accurate as the physical models on which they are based. • Solving equations on a computer invariably introduces numerical errors. Round-off error: due to finite word size available on the computer. Round-off errors will always exist (though they can be small in most cases). Truncation error: due to approximations in the numerical models. Truncation errors will go to zero as the grid is refined. Mesh refinement is one way to deal with truncation error. Boundary conditions. As with physical models, the accuracy of the CFD solution is only as good as the initial/boundary conditions provided to the numerical model.
- 18. REFERENCES www.google.com www.wikipedia.com www.slideshare.com
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