flow analysis
Dear friend I am doing Blood flow analysis in a stenosed artery. (Steady state simulation)
I created venturi type solid model (Blood domain ) The flow is Z direction I assume flow rate is 50 ml/min from which I calculated the velocity (Q= Av : Continuity equation) I set the inlet velocity as Umax(1r^2/R^2) outlet : Mass and momentum >Average Static pressure= 0 Pa Is this correct? I set Domain models>reference pressure 1 atm But I have seen in many papers the pressure varies between 80mm Hg  120mm Hg.( Diastole Systole Pressure) But I did n't use the above pressure anywhere. In CFX post , Which pressure measurement is suitable ? Is it Total pressure or pressure? when I did the simulation I checked the Total pressure before the stenosis the pressure is Approx 230Pa . In a venturi region pressure drops but after venturi the flow pressure decreases and decreases Why not the pressure is recovered to 230 Pa ?Where can I implement 80mm Hg pressure or 120mm Hg pressure in the simulation. Please help me to set up the boundary condition. If I want to introduce transition analysis How can I introduce it. Please help me to give tips Thank you Regards Govind 
First of all, do you need the pressure to vary between 80120 mmHg? If so, why do you do a steadystate simulation?
To prescribe a varying pressure at the outlet have a look at http://www.edr.no/blogg/ansys_blogge...nsient_profile Velocity profile at inlet and pressure at outlet seems like reasonable BCs. Regarding transition, consider RANS models (gammatheta) or LES. Have a look in a CFD text book for the details. Also, you really should consider a basic course in CFD. 
Transient analysis
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I tried Transient analysis . But I have convergent problem. I increased the length of the artery too. The flow is Z dirction My inlet velocity is U=0 V=0 W= 0.2[m/s]*(1+sin(2*pi*2[Hz]*tpi/2) I set the pressure at the outlet 0 Pa initial condition ; U=0, V=0, W= 0 and pressure =0 Here is the CFX Command Language for Run for your reference. Kindly help me . Because I need a pressure at every point .    ++ LIBRARY: CEL: EXPRESSIONS: vin = 0.1[m s^1]*(1+sin(2*pi*2[Hz]*tpi/2)) vin2 = 0.3[m s^1]*(1r^2/(0.0014[m])^2) END END MATERIAL: Blood Material Group = User Option = Pure Substance Thermodynamic State = Liquid PROPERTIES: Option = General Material EQUATION OF STATE: Density = 1060 [kg m^3] Molar Mass = 1.0 [kg kmol^1] Option = Value END DYNAMIC VISCOSITY: Option = Non Newtonian Model NON NEWTONIAN VISCOSITY MODEL: High Shear Viscosity = 0.00345 [Pa s] Low Shear Viscosity = 0.056 [Pa s] Option = Bird Carreau Power Law Index = 0.3568 Time Constant = 3.313 [s] END END END END END FLOW: Flow Analysis 1 SOLUTION UNITS: Angle Units = [rad] Length Units = [m] Mass Units = [kg] Solid Angle Units = [sr] Temperature Units = [K] Time Units = [s] END ANALYSIS TYPE: Option = Transient EXTERNAL SOLVER COUPLING: Option = None END INITIAL TIME: Option = Value Time = 0 [s] END TIME DURATION: Option = Total Time Total Time = 2 [s] END TIME STEPS: Option = Timesteps Timesteps = 0.1 [s] END END DOMAIN: Default Domain Coord Frame = Coord 0 Domain Type = Fluid Location = B27 BOUNDARY: inlet Boundary Type = INLET Location = in BOUNDARY CONDITIONS: FLOW REGIME: Option = Subsonic END MASS AND MOMENTUM: Option = Cartesian Velocity Components U = 0 [m s^1] V = 0 [m s^1] W = vin END END END BOUNDARY: out Boundary Type = OUTLET Location = out BOUNDARY CONDITIONS: FLOW REGIME: Option = Subsonic END MASS AND MOMENTUM: Option = Average Static Pressure Pressure Profile Blend = 0.05 Relative Pressure = 0 [Pa] END PRESSURE AVERAGING: Option = Average Over Whole Outlet END END END BOUNDARY: wall Boundary Type = WALL Location = wall BOUNDARY CONDITIONS: MASS AND MOMENTUM: Option = No Slip Wall END END END DOMAIN MODELS: BUOYANCY MODEL: Option = Non Buoyant END DOMAIN MOTION: Option = Stationary END MESH DEFORMATION: Option = None END REFERENCE PRESSURE: Reference Pressure = 1 [atm] END END FLUID DEFINITION: Fluid 1 Material = Blood Option = Material Library MORPHOLOGY: Option = Continuous Fluid END END FLUID MODELS: COMBUSTION MODEL: Option = None END HEAT TRANSFER MODEL: Option = None END THERMAL RADIATION MODEL: Option = None END TURBULENCE MODEL: Option = Laminar END END END INITIALISATION: Option = Automatic INITIAL CONDITIONS: Velocity Type = Cartesian CARTESIAN VELOCITY COMPONENTS: Option = Automatic with Value U = 0 [m s^1] V = 0 [m s^1] W = 0 [m s^1] END STATIC PRESSURE: Option = Automatic with Value Relative Pressure = 0 [Pa] END END END OUTPUT CONTROL: RESULTS: File Compression Level = Default Option = Standard END TRANSIENT RESULTS: Transient Results 1 File Compression Level = Default Include Mesh = No Option = Selected Variables Output Variables List = Pressure,Velocity OUTPUT FREQUENCY: Option = Every Timestep END END END SOLVER CONTROL: ADVECTION SCHEME: Option = High Resolution END CONVERGENCE CONTROL: Maximum Number of Coefficient Loops = 10 Minimum Number of Coefficient Loops = 1 Timescale Control = Coefficient Loops END CONVERGENCE CRITERIA: Residual Target = 1.E4 Residual Type = RMS END TRANSIENT SCHEME: Option = Second Order Backward Euler TIMESTEP INITIALISATION: Option = Automatic END END END END COMMAND FILE: Version = 13.0 Results Version = 13.0 END SIMULATION CONTROL: EXECUTION CONTROL: EXECUTABLE SELECTION: Double Precision = Off END INTERPOLATOR STEP CONTROL: Runtime Priority = Standard MEMORY CONTROL: Memory Allocation Factor = 1.0 END END PARALLEL HOST LIBRARY: HOST DEFINITION: govindaraju Host Architecture String = winnt Installation Root = C:\Program Files\ANSYS Inc\v%v\CFX END END PARTITIONER STEP CONTROL: Multidomain Option = Independent Partitioning Runtime Priority = Standard EXECUTABLE SELECTION: Use Large Problem Partitioner = Off END MEMORY CONTROL: Memory Allocation Factor = 1.0 END PARTITIONING TYPE: MeTiS Type = kway Option = MeTiS Partition Size Rule = Automatic END END RUN DEFINITION: Run Mode = Full Solver Input File = Model1.def END SOLVER STEP CONTROL: Runtime Priority = Standard MEMORY CONTROL: Memory Allocation Factor = 1.0 END PARALLEL ENVIRONMENT: Number of Processes = 1 Start Method = Serial END END END END 
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