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Outline
• CFD Basics• Application of CFD in Hydro Power Plants• Piping system design challenges• Case studies• More Turbo Machinery solutions by ANSYS• Conclusion• Questions and Discussion
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What is CFD?
• Computational Fluid Dynamics (CFD) is the numerical study of how things flow.
• CFD is used as a tool by many engineers (mechanical, chemical, etc.) across a broad range of industries.
• CFD can provide detailed information about what is happening in a process where fluid is in motion.
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Uses of CFD
• Architectural• Environmental
Process/Food Industry
Automotive/MechanicalAerospace
Safety/HealthPower Generation
Bio-medical
Sports
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The Building Block
• The most basic building block in CFD is the conservation volume
Conservation volume: what goes in + what is made/destroyed = what goes out
what goes in what goes out
what ismade/destroyed
conservation volume
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Assembling the Blocks
• Simple algebraic equations describe how the conservation volumes are connected.
• These simple equations conserve mass, momentum and energy.
The conservation volumes are assembled together to fill space.
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Conservation Volumes Assembled Around A Car
• Once the conservation volumes are assembled, a flow field can be calculated.
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The Final Solution
• The final flow field may look like this.
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CFD Basic Concepts
• The Control Volume• Conservation Laws• Governing Equations of CFD• Linear and Non-Linear Partial Differential
Equations• Boundary Conditions• Discrete Methods
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Steps in a CFD Simulation
• Step I: Pre-processing step - define the problem– Define the geometry– Define the domain(s)– Define boundary and initial conditions– Define the mesh– Define solver parameters
• Step II: Solution step– Solve the governing equations
• Step III: Post-processing step– Analyze results
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Step I: Pre-processing• Define the geometry
– Domain in which the governing equations will be solved and solution obtained
– Create a B-rep Solid• Define the fluid domain.
– Create fluid regions (fluid, solid, conducting solid, porous media)
– Assign fluid properties (viscosity, thermal conductivity, specific heat, etc…)
– Select the physical models (turbulence models, compressibility, buoyancy, two-phase flow, etc…)
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Step I: Pre-processing
• Grid Generation– Process of generating finite volumes or cells– Tetrahedral/Pyramidal/Prismatic/Hexahedral cells created– Surface mesh and volume mesh make up the grid
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Step I: Pre-processing
• Define the boundary conditions– Needed on all external surfaces of geometry
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Step II: Solving• Solve the governing
equations– Set the flow solver options– Iteratively solve the
governing equations– Obtain convergence
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Step III: Post-processing• Qualitative
– Graphical format– Pressure, Temperature distribution– Velocity field
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Step III: Post-processing• Quantitative
– Quantitative post-processing is the reduction of data to produce performance coefficients
– Simplifies comparison of designs– Application dependent– Examples:
• 1. Pressure drop in a duct• 2. Lift, drag coefficients of airfoil• 3. Head, Efficiency etc. in pump• 4. Torque, Efficiency etc. in a torque converter• 5. Average NOx emission at a furnace exit