Introductions to CFD

What is CFD?
Computational Fluid Dynamics is the simulation of fluid engineering system which is used to analyses the flow over the entire body then to evaluate the performance of the model with the help of initial boundary value problems and numerical methods.

Historically

1. Analytical Fluid Dynamics(AFD)
2. Experimental Fluid Dynamics(EFD)

What We are using CFD?

1. Simulation-based design instead of  built&test
2. More cost-effective and more rapid than EFD
3. Large scale simulation (Eg:Ships and airplanes)
4. Environmental effects (wind,weather.etc.)
5. Artificial Hazards (radiation,pollution,explosions)
6. Physics testing ( planetary boundary layer and stellar evolutions)

Applications of CFD

1. Aerospace (aircrafts,missiles,launch vehicles and spaceships and spacecrafts)
2. Automotive (lighter passenger and large good carrying vehicles)
3. Bio-medical (temperature and natural convections current in the eye flowing laser heating.
4. Chemical processing ( reactor vessels and ic engines)
5. HVAC (heating ventilation airconditioning system- streamlines for workstation ventilations
6. Hydraullics (actuatingthe oil flow into the hydraullic pump)
7. Marine (small boats and ships)
8. Oil and Gas (flow of  oils and gas)
9. Power generation (flow arround the cooling towers)
10. Sports (helmet,footballs,ruggby).

Types of CFD codes
1.Commercial CFD codes
    a.FLUENT
    b.CFX
    c.STAR-CD
    d.Gambit
    e.CFDRC..etc.

2.Research CFD codes
   a.CFDSHIPS-IOWA
3.Public domain softwares
   a.PHI3D
   b.hydro
   c.winpipeD..etc.
4.Grid generation softwares (GRIDGEN GAMBIT)
5.Flow visulation softwares (Tecplot,Fieldview).

Geometric Modeling
     Modelling is the mathematical  physical  problem formulations interms of a continous Intial Boundary Value Problem(IBVP)

                        IBVP is the form of partial differential equation(PDEs) with appropiate boundary and initial conditions.
Geometric and Domain
Simple geometry: It can be easily created geometries such as circle,plateand pipes.

Complex geometry:It can be created by the PDEs and importing the geometry through the commercial softwares CATIA,Pro-E..etc.  using of industrial standards formatssuch as IGES,IGS,STEP,Parasolid,ACIS..etc.

Domain: It is enclosure of the mathmatical model depends on shape and size.

 Flow Conditions
Based on the physical phenomena of the mathematical models with different requirements.

For example turbulent flow simulation video

Cooling process

Screw compressor simulations

Wind turbine simulation

1. Viscous vs invisid (Re)
2. External or internal flow (wall bounded or not)
3. Compressible vs incompressible (Mach,equation of state0
4. Tubulent vs laminar (Re,turbulent models)
5. Single or multi phase (Ca,cavitation model and two fluid models)
6. Thermal effects/density (Pr,Gr,ec) and conservation of energy
7. Free surface flow (Fr) or surface tension flows (We,level-set and surfacr tracking and bubble)
8. Chemical reaction and combustion (Pe,Da)

etc..

Initial Conditions
Based on flow conditions will be either steady or unstaedy flow independently.

1.It is affect the final results then ony affects the convergence path such as no of iterations(steady) and no of time steps (unsteady)

2.For complicated unsteady flow problems.CFD codes are usually run the steady mode for getting the better initial conditions.

Boundary Conditions
It means wheteher ,
                    slip-free walls or no-slip,periodic,inlet (velocity,constant pressure) and outlet conditions (velocity convective and zero-gradient) and non-reflecting for compressible flows such as acoustics.etc.

Numerical Methods
IBVPs are discretized by the algebraic eguations using numerical methods then assemble the system of algebraic equations and solve the system to get a approximate solutions.

The numerical methods includes
Discretization method
     In this method usullay contain three method
        a.Finite difference method (only for regular grids)
        b.Finite volume method (for irregular meshes)
        c.Finite element method (for unstructured meshes or irregular)

Explicit Method (Euler and Runge-kutta method)
      It can be easily applied but yield conditionally stable Finite difference equations(FDEs) which are restricted by the time-step

Implicit Method (Beam-warming method)
It is usally unconditionally stable but need efforts on efficiency.Usually higer-order temporal discretization methods are used.

Stability
If it is said to be stable  if  it does not magnify the errors that apperas in the solution process.

Numerical solvers and parameters
Solvers can be either
  a.Direct method-Gauss elimination,cramers rule
  b.Iterative method- Gauss seidal and Jacobin methods.

Numerical Parameters
 a.convergence limit
 b.under relaxation method
 c.monitor residuals
d.single or multi precision
e.number of iteration

Grid generation and transformation
Grids can be classified into
  a.Structured grids (Hexahedral)
  b.Unstructured grids (tetrahedral)
Transformation which means converting the physical domain into the computational domain.

High performance computer postprocessor
CFD computation (eg:3D unsteady flows) are generally very expensive so which requires  parallel high performance super computers with the use of multiblock techniques.
 Post processing which means visualize the CFD results for example contours,velocity vectors,pathlines,stream lines,strealines and 3D particle flows,iso-surface.
Then CFD UA: To validate and verify by the EFD data.


General Implementation Process of CFD
The follwing step by steps are to execute the entire CFD solution process,

1. Geometry
2. Physics
3. Mesh
4. Solver
5. Report
6. Postprocessing

Geometry

1. Set the proper co-ordinate system
2. Create the appropiate domain which means enclosure  shape and size
3. If u wants to import from the commercial CAD/CAM softwares,you could import via STD formats.

Physics

1. Flow conditions which means folw will be turbulent vs laminar or viscous or inviscous..etc
2. Flow properties it will be  density,viscosity,thermal conductivity..etc.
3. These condition and properties are based on the model dimensional form in industrial norms
4. Wheras Non-dimensional means REASERACH CODE ONY

Mesh

1. It would be important factor on analyses the mathematical models
2. Mesh shoul be well designed to solve the model which depends upon the flow parameter such as Re,We,Ca,Pr,etc..
3. Even meshes are generated by the commercial grid generation tools such as GRidgen and gambit.etc.

Solvers

1. Set-up appropiate numerical parameters
2. Select the relevent solver based on the requirements.
3. Solve the problem by using the selection of proper system of equations

Report

1. Report saved the time history of the residuals of the velocity,pressure,temperature.etc.
2. Reports the integral quantities such as total pressure drop,friction factor (pipe-flow) and lift and drag coefficient (airfoil-flow)
3. Plot the graph between  the different parametres such as velocity and pressure distribution..etc.
4. AFD or EFD can be imported and put it from top of the plots

Post-Processing

1. Analyses and visualization of the parameters are vortices,forces,moments,wall shear stress,2D contours and animations.
2. To checking the simulaton errors,validations and verification of the simulated numerical parameters.
3. To evalute the convergence of the input parameters

SUMMARY OF CAE

What is CAE?

         Computer Aided Engineering is the computer method simulation in engineering which can be perform to evaluating the fatigue life and structural behaviour of the testing components with the help of finite element method(FEM) or finite element analysis(FEA).

   It is very important chapter of an engineering,I  request to all students you should contribute much more to learn finite element method through this you would get more practical exposure of an engineering.

What is FEM or FEA?

          It is nothing but finite element method is based on idea of building the complicated objects into simple pieces or dividing a complex body into small or managable pieces or elements in engineering.

It is closely integrated with CAD/CAM application.

3-D Truss

Threaded bolt and nut

Cover of pressure cylinder

Translational joints

High speed impact

Drop test

Application of FEM  in Engineering

1. Aerosapce,Mechnical,Civil,Automobiles
2. Structural analysis(linear/non-linear and static/dynamics)
3. Thermal/fluid flows
4. Electromagnetics
5. Biomechanics
6. Geomechanics ..etc.                          

 

Procedures to implement FEM analysis

1. Divide structure into pieces(Element with nodes)
2. Describe the behaviour of physical quantities on each elements
3. Assemble the elements at the nodes to form an  approximate equation for the entire structure
4. Solve the system of equation involving unknown quantities at the nodes....(eg: displacements)
5. Calculate the desired quantities  such as stress,strains..etc.. at the elements.

Computer Implementations

1.Preprocessor
       To built the FEM model,constraints and loading conditions
2.FEM Solver
       To assemble the whole model and solve the system of equations by using mathematical forms
3.Postprocessor
       To order and displays the results which means...stress,strain,shear,displacement on each elements

We might know how many commercial FEM Softwares

1. ANSYS (General purposes)
2. SDRC/I-DEAS (Complete CAD/CAM/CAE packages)
3. NASTRAN (General purpose FEM on mainframes)
4. ABAQUS (Non-linear and dynamic analysis)
5. COSMOS (General purpose FEM)
6. ALGOR (PC and workstation)
7. PATRAN (Pre and Postprocessor)
8. HYPERMESH (Pre and Postprocessor)
9. DYNA-3D (Crash and Impact analysis)...etc.

A Link to CAE softwares and company

FEA of an unloader trolley(click for more info)

For more examples: FEA actions


Types of Finite Elements
1. 1-D Elements(Line)
      a.Beam
      b.Spring
      c.Truss
      d.Bar
      e.Pipe..etc.

2. 2-D Elements(Plane)
     a.Membarane
     b.Shell
     c.Plate..etc.

3. 3-D Elements(Solids)
           3-D fields- temperature,displacement,stress and flow velocity).

Linear Static Analysis
                Most of the structural problems can be treated as linear static problems based on the following assumptions are,

1. Small deformation( loading patterns are not changed due to the deformed shape)
2. Elastic materials (which means no plasticity or failure)
3. Stati loads ( the load applied to the structure at slow and steady)

1-D problems
    Spring Elements
Do's and Dont's in the spring elements

1. It is only for stiffness analysis,not for stress analysis of spring elements
2. can have the spring element with stiffness in lateral direction and torsion.etc.

    Spring Force-Displacement relationship
                             
                     F = KU                        U = (u2 - u1 )
                             
F-  Element Nodal force (lb,N)   U- Element Nodal displacement (in,m,mm)   K- Element Spring stiffness (lb/in,N/m).

Checking the results

1. Deformed shape of the body
2. Balance of the external forces
3. Order of magnitude of the number

Bar and Beam Elements
It is based on the follwing realation,

1. Strain-Displacement relationship
2. Stress-Strain relationship

Procedure for Theoretical Calculation

1. We consider the parameters of 1-D bar elements are length(L),cross-sectional area(A),Elastic modulus(E),Displacement(u),stress and strain.
2. To calculate the stiffness by using direct method or formal approach.
3. Direct method means assuming the displacement varying linearly along with the axis of bar.
4. Formal approach means by using the galarkein method to calculate stiffness matrix through the principal potential energy.

For example:A simple plane truss is made up of two identical bars with loaded condition
Steps:

1. We need to convert them to global co-ordinate
2. Calculate the stiffness matrix for the element of the co-ordinate system.
3. Assemble the system of finite element equation
4. Apply the load and boundary condition
5. Rearrange the finite element equation
6. Solve the unknown value of the displacements
7. Finally we calculate the stresses in each bars

But in 3D case the element stiffness matrices are calculated in the local cordinate and the transformed into the global co-ordinate system.

Cheking the results

1. Calculated stresses in the elements are exacts within the linear theory of 1-D bar elements.
2. For tapered bars averaged value of the cross-sectional areas should be used for the elements.
3. We need to find the displacement at first inorder to stresses under the displacement based FEM.

Degrees of freedom(DOF)
Number of components of the displacement vector at a node
In 1-D element,each node has a DOF.

Beam element
The Parameters of the  simple plane beam are  given below,

1. Length(L),
2. Moment of inertia of the cross-sectional area,
3. Elastic modulus(E),
4. Deflection (Lateral displacement) of the  neutral axis,Rotation about Z-axis(teta),
5. Moment about Z-axis(M),
6. Shear force(F)

 Generally two methods are used to calculate the element stiffness either direct method or formal approach

In direct method using the result from Element Beam Theory  to cumpute each element of the stiffness matrix 

 

In Formal approach using strain energy equation with derivation of the shape function.

In 3D cases the element stiffness matrix are formed in local co-ordinate system(2D)  then transformed into Global co-ordinate system to be assembled.

 

Procedure to Calculate the simple plane beam element

1. To form the element stiffness matrices by given lenth and displacement values.
2. Assemble the global finite element equation
3. Apply loads and constraints(BCs)
4. Do find rection forces and moments from the global FE equations

But in 3D case element the stiffeness matrix is formed in the local coordinate system first then it is transformed into global coordinate system to be assembled.

FE Analysis of frame structures
                 Members in a frames are consider to be a rigid connected and forces and moments can be transmitted to their joints so we need
                 Frames= bar+simple beam elements

 

                                                             

SUMMARY OF DESIGN

What is design?
  
           Design is the process of conceiving or  inventing ideas and communicating those ideas with others in a form that is easily understood.

General Types of Design
        1.Perosonal expression(Artistics)
                 a.Concrete(Realism)
                 b.Abstract

        2.Product development(Technical)
                 a.Aesthetic(industrial design)
                 b.Functional (engineering design)


These are the most following design progress before to perform manufacturing,

1. Planning
2. Concept Development
3. System-Level Design
4. Detail Design
5. Testing and Refinement
6. Production ramp-up

Architecture of CAD system

The following outlines of the CAD systems are,

1.Geometric Modeling
Models exists as a wirframe and surface or solid in either 2D or 3D environment.

2.Engineering Testing
It is the analyse method to estimating the behaviour of physical quantities of the product,clearance,interferences,dimensioning tolerances and kinematics which means range of motion.

3.Design Asessment
It is the optimization of automated dimensioning and tolerances and  testing of virtual prototyping and manufacturing process.

4.Product Documentation
In this process can be perform to get automated drafting by their product specifications and manufacturing database.

STATE OF AN ENGINEERING AND ENGINEERS

What is "ENGINEERING"?
            Engineering is the soul of science which is used to make the complete fabulous ambient through the engineers.It would be converting from traditional designs into modern engineering which means to reducing the workload of the inhabitants at the same time it is used to made for destructive purposes.

Who they should be an "ENGINEER"?
           One who is understand the  basic things about the engineering concepts precisely,one who is not mug-up the entire theory before a day of  an exam and vomiting the answers on the paper at that time of an exam.

              Eventually  my statement is those who having  interest to study about the engineering theory as well as practical theory from start to finish without any intentions such as wants to get place in MNC and wants to enjoy the college life which means involves in miscellaneous activities,otherwise you never become an "engineer".

"YOU ARE THE INVENTOR OF THE HYGENIC AND PEACE WORLD"

"ENGINEER WANTS TO BECOME AN WELL RENOWNED ENGINEER"

(It is the indian engineer's state of mind,but here.......?)

SUMMARY OF CAM

What is CAM?

         Computer Aided Manufacturing which means any software tools allows the users to test the entire manufacturing process of the product from start to fnish.

What we will perform?

• Manufacturing planning process
• Assembly planning
• Robust testing
• test-programming
• Analyse-programming
• Simulation tools

 Major functions of CAM

• Simulate the manufacturing process
• Optimize the process cycles by order of operation of equipments,choice of tools
• cost of production,surface finishing and quality
• To develop an quality inspections control  and product database

Major Functions of CAD

1. To elevate the productivity of the designer
2. To enhance the standard of the designs
3. To enhance quality of the design documentation
4. To develop manufacturing database

Basic techniques of CAD modelling

Three basic modelling techniques are,

Wireframe modelling
     It is the initial stage is  to complete the entire model,which is one of the easiest way of improving the model through some singular and double curves.for example engine oil cover

Surface modelling
It is the second stage is to fill the surfaces (which means it has no thicknesses) through the wire-frames ,eventually the entire product is formed.for example cpu mouse

Solid modelling
This is the final stage of the model techniques which it has to be performing to apply the required thickness of the product depends on their product specificatiion

 

SUMMARY OF CAD

What is CAD?

    Computer Aided Design  which means  any kind of mechanical domain software tools to create,innovate,improve and analysing the engineering product document either 2D or 3D modelling.


The following Commercial CAD software packages are

1. Auto CAD  (Auto desk corporation)
2. Auto Desk
3. Pro-E          (Parametric corporation)
4. Creo-Parametric(Parametric corporation)
5. Unigraphics        (SIEMEN PLM)
6. CATIA               (Daussalts system)
7. Solid works        (Daussalts system)
8. Solid edge..etc.. (Altair corporation

Conceptual Design- 2 seater and coupe