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Old   June 3, 2013, 07:29
Default Jet Deflection
  #21
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Amod Panthee
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I still have the problem with jet deflection. Earlier the jet was deflected in negative direction due to error in assigning the volume fraction of air and water during initialization. But, now the jet is deflected slightly in positive direction of rotation. Initially the jet is not fully developed, therefore, it deflects much (attached picture). But at 3 timesteps which includes timestep 19 to 21, the jet travels in straight path (attached picture). From timestep 22 to the end of simulation the shows small deflection in its flow direction (attached picture). What might be the reason for this?
Does this happen due to improper mesh quality? I have not worked much on meshing in this simulation. And defined maximum possible finer mesh possible without any manual modifications at specific locations.
Thanks in advance!
Attached Images
File Type: jpg timestep_9.jpg (82.1 KB, 46 views)
File Type: jpg timestep_20.jpg (82.5 KB, 37 views)
File Type: jpg timestep_91.jpg (86.4 KB, 40 views)
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Old   June 3, 2013, 07:34
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Glenn Horrocks
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This effect might be real - have a search for the Coanda effect.

But if you are convinced this is wrong then firstly read the FAQ: http://www.cfd-online.com/Wiki/Ansys..._inaccurate.3F

If you want us to help you more you will need to show some views in the other plane, your CCL and other details so we can understand what you are doing.
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Old   June 5, 2013, 05:19
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Can you show a plot of isosurface of water.volumefraction? I think it will show a reasonable result...
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Old   June 5, 2013, 06:13
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Quote:
Does this happen due to improper mesh quality? I have not worked much on meshing in this simulation. And defined maximum possible finer mesh possible without any manual modifications at specific locations.
what do you mean by improper mesh quality? Would you like to please show us some images?

where you have finer mesh? is there any sudden change in cell volume? You can always make the manual modification in mesh and it is good idea to follow the general (best practices) for meshing of turbomachinery!!! specially at the interface.
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Old   March 28, 2017, 13:40
Default please help me solve this problems
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Hello, all
I try to solve this problems for several times. I have no ideas what happens going on. and this is conditions that set for this problem.

&replace FLOW: Flow Analysis 1
ANALYSIS TYPE:
Option = Steady State
EXTERNAL SOLVER COUPLING:
Option = None
END
END
DOMAIN INTERFACE: s1 to r1
Boundary List1 = s1 to r1 Side 1
Boundary List2 = s1 to r1 Side 2
Filter Domain List1 = s1
Filter Domain List2 = r1
Interface Region List1 = s1 interface part 2,s1 interface part1
Interface Region List2 = r1 interface
Interface Type = Fluid Fluid
INTERFACE MODELS:
Option = General Connection
FRAME CHANGE:
Option = Frozen Rotor
END
MASS AND MOMENTUM:
Option = Conservative Interface Flux
MOMENTUM INTERFACE MODEL:
Option = None
END
END
PITCH CHANGE:
Option = Value
Pitch Ratio = 1
END
END
MESH CONNECTION:
Option = GGI
END
END
DOMAIN: r1
Coord Frame = Coord 0
Domain Type = Fluid
Location = B6299
BOUNDARY: r1 opening
Boundary Type = OPENING
Frame Type = Rotating
Interface Boundary = Off
Location = r1 opening
BOUNDARY CONDITIONS:
FLOW DIRECTION:
Option = Normal to Boundary Condition
END
FLOW REGIME:
Option = Subsonic
END
MASS AND MOMENTUM:
Option = Opening Pressure and Direction
Relative Pressure = 0 [Pa]
END
TURBULENCE:
Option = Medium Intensity and Eddy Viscosity Ratio
END
END
FLUID: air
BOUNDARY CONDITIONS:
VOLUME FRACTION:
Option = Value
Volume Fraction = 0.4
END
END
END
FLUID: water
BOUNDARY CONDITIONS:
VOLUME FRACTION:
Option = Value
Volume Fraction = 0.6
END
END
END
END
BOUNDARY: r1 symmetry
Boundary Type = SYMMETRY
Interface Boundary = Off
Location = r1 symmetry
END
BOUNDARY: r1 wall
Boundary Type = WALL
Create Other Side = Off
Frame Type = Rotating
Interface Boundary = Off
Location = r1 wall
BOUNDARY CONDITIONS:
MASS AND MOMENTUM:
Option = No Slip Wall
END
WALL ROUGHNESS:
Option = Smooth Wall
END
END
FLUID PAIR: air | water
BOUNDARY CONDITIONS:
WALL ADHESION:
Option = None
END
END
END
END
BOUNDARY: s1 to r1 Side 2
Boundary Type = INTERFACE
Interface Boundary = On
Location = r1 interface
BOUNDARY CONDITIONS:
MASS AND MOMENTUM:
Option = Conservative Interface Flux
END
TURBULENCE:
Option = Conservative Interface Flux
END
END
END
DOMAIN MODELS:
BUOYANCY MODEL:
Option = Non Buoyant
END
DOMAIN MOTION:
Angular Velocity = 912 [rev min^-1]
Option = Rotating
AXIS DEFINITION:
Option = Coordinate Axis
Rotation Axis = Coord 0.1
END
END
MESH DEFORMATION:
Option = None
END
REFERENCE PRESSURE:
Reference Pressure = 1 [atm]
END
END
FLUID DEFINITION: air
Material = Air at 25 C
Option = Material Library
MORPHOLOGY:
Option = Continuous Fluid
END
END
FLUID DEFINITION: water
Material = Water
Option = Material Library
MORPHOLOGY:
Option = Continuous Fluid
END
END
FLUID MODELS:
COMBUSTION MODEL:
Option = None
END
HEAT TRANSFER MODEL:
Homogeneous Model = True
Option = None
END
THERMAL RADIATION MODEL:
Option = None
END
TURBULENCE MODEL:
Option = SST
END
TURBULENT WALL FUNCTIONS:
Option = Automatic
END
END
FLUID PAIR: air | water
Surface Tension Coefficient = 72 [N m^-1]
INTERPHASE TRANSFER MODEL:
Interface Length Scale = 1.2 [mm]
Option = Mixture Model
END
MASS TRANSFER:
Option = None
END
SURFACE TENSION MODEL:
Option = Continuum Surface Force
Primary Fluid = water
END
END
MULTIPHASE MODELS:
Homogeneous Model = On
FREE SURFACE MODEL:
Option = Standard
END
END
END
DOMAIN: s1
Coord Frame = Coord 0
Domain Type = Fluid
Location = B6493,B6542
BOUNDARY: s1 free surface
Boundary Type = WALL
Create Other Side = Off
Interface Boundary = Off
Location = s1 free surface part1,s1 free surface part2
BOUNDARY CONDITIONS:
MASS AND MOMENTUM:
Option = Free Slip Wall
END
END
FLUID PAIR: air | water
BOUNDARY CONDITIONS:
WALL ADHESION:
Option = None
END
END
END
END
BOUNDARY: s1 nozzle
Boundary Type = WALL
Create Other Side = Off
Interface Boundary = Off
Location = s1 nozzle
BOUNDARY CONDITIONS:
MASS AND MOMENTUM:
Option = No Slip Wall
END
WALL ROUGHNESS:
Option = Smooth Wall
END
END
FLUID PAIR: air | water
BOUNDARY CONDITIONS:
WALL ADHESION:
Option = None
END
END
END
END
BOUNDARY: s1 opening
Boundary Type = OPENING
Interface Boundary = Off
Location = s1 opening
BOUNDARY CONDITIONS:
FLOW DIRECTION:
Option = Normal to Boundary Condition
END
FLOW REGIME:
Option = Subsonic
END
MASS AND MOMENTUM:
Option = Opening Pressure and Direction
Relative Pressure = 0 [atm]
END
TURBULENCE:
Option = Medium Intensity and Eddy Viscosity Ratio
END
END
FLUID: air
BOUNDARY CONDITIONS:
VOLUME FRACTION:
Option = Value
Volume Fraction = 0.4
END
END
END
FLUID: water
BOUNDARY CONDITIONS:
VOLUME FRACTION:
Option = Value
Volume Fraction = 0.6
END
END
END
END
BOUNDARY: s1 symmetry
Boundary Type = SYMMETRY
Location = s1 symmetry part1,s1 symmetry part 2
END
BOUNDARY: s1 to r1 Side 1
Boundary Type = INTERFACE
Interface Boundary = On
Location = s1 interface part 2,s1 interface part1
BOUNDARY CONDITIONS:
MASS AND MOMENTUM:
Option = Conservative Interface Flux
END
TURBULENCE:
Option = Conservative Interface Flux
END
END
END
BOUNDARY: s1 water in
Boundary Type = INLET
Location = s1 water in
BOUNDARY CONDITIONS:
FLOW DIRECTION:
Option = Normal to Boundary Condition
END
FLOW REGIME:
Option = Subsonic
END
MASS AND MOMENTUM:
Mass Flow Rate = mass flow rate
Option = Bulk Mass Flow Rate
END
TURBULENCE:
Option = Medium Intensity and Eddy Viscosity Ratio
END
END
FLUID: air
BOUNDARY CONDITIONS:
VOLUME FRACTION:
Option = Value
Volume Fraction = 0
END
END
END
FLUID: water
BOUNDARY CONDITIONS:
VOLUME FRACTION:
Option = Value
Volume Fraction = 1
END
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: air
Material = Air at 25 C
Option = Material Library
MORPHOLOGY:
Option = Continuous Fluid
END
END
FLUID DEFINITION: water
Material = Water
Option = Material Library
MORPHOLOGY:
Option = Continuous Fluid
END
END
FLUID MODELS:
COMBUSTION MODEL:
Option = None
END
HEAT TRANSFER MODEL:
Homogeneous Model = True
Option = None
END
THERMAL RADIATION MODEL:
Option = None
END
TURBULENCE MODEL:
Option = SST
END
TURBULENT WALL FUNCTIONS:
Option = Automatic
END
END
FLUID PAIR: air | water
Surface Tension Coefficient = 72 [N m^-1]
INTERPHASE TRANSFER MODEL:
Interface Length Scale = 1.2 [mm]
Option = Mixture Model
END
MASS TRANSFER:
Option = None
END
SURFACE TENSION MODEL:
Option = Continuum Surface Force
Primary Fluid = water
END
END
MULTIPHASE MODELS:
Homogeneous Model = On
FREE SURFACE MODEL:
Option = Standard
END
END
END
EXPERT PARAMETERS:
topology estimate factor zif = 2
END
OUTPUT CONTROL:
RESULTS:
File Compression Level = Default
Option = Standard
END
END
SOLUTION UNITS:
Angle Units = [rad]
Length Units = [m]
Mass Units = [kg]
Solid Angle Units = [sr]
Temperature Units = [K]
Time Units = [s]
END
SOLVER CONTROL:
Turbulence Numerics = First Order
ADVECTION SCHEME:
Option = Upwind
END
CONVERGENCE CONTROL:
Length Scale Option = Conservative
Maximum Number of Iterations = 1000
Minimum Number of Iterations = 1
Timescale Control = Auto Timescale
Timescale Factor = 1.0
END
CONVERGENCE CRITERIA:
Residual Target = 0.0001
Residual Type = RMS
END
DYNAMIC MODEL CONTROL:
Global Dynamic Model Control = On
END
END
END

************ And this is expresion
LIBRARY:
CEL:
&replace EXPRESSIONS:
mass flow rate = 997 [kg m^-3]*volume flow rate
theta component = 0.192066883 [m]
volume flow rate = 2 [m^3 s^-1]
END
END
END


Can you guys tell me what happens and how to solve this problems. Thanks you all


https://www.dropbox.com/s/64nrjhdpdvo4bxs/1.PNG?dl=0

https://www.dropbox.com/s/46c3e19y6y68sp8/2.PNG?dl=0
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Old   March 28, 2017, 19:35
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What is the problem?
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Old   March 29, 2017, 02:44
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Quote:
Originally Posted by ghorrocks View Post
What is the problem?
The problem is water cant run into rotating domain or cant touch the bucket because in rotating domain has high angular velocity so this water was blown up following this picture


https://www.dropbox.com/s/64nrjhdpdvo4bxs/1.PNG?dl=0

An angular velocity was calculated by equation n=(1-1.15*nq)(C_0/(Pi*Dm))
nq is specific speed = 0.116
C_0 is root(2gH) = 121 m/s
Dm = 2.2 m

so the angular velocity is about 912 rpm. but from simulation C_0 is less than 121 m/s then angular velocity not 912 rpm. I understand this is the cause of water was blown up, isn't it?

what should I do for this problems. (for make water crash into bucket)
thanks you
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Old   March 29, 2017, 05:27
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First of all - how were we possibly meant to answer your first question? You did not even ask a question in it! Please have a think about your post in future before you submit it.

As for your actual question - Are you sure you have the rotation in the correct direction? Also, I have no idea where that equation of speed came from, so if your results are weird then than is the first thing to check.
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Old   March 30, 2017, 13:09
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Quote:
Originally Posted by ghorrocks View Post
First of all - how were we possibly meant to answer your first question? You did not even ask a question in it! Please have a think about your post in future before you submit it.

As for your actual question - Are you sure you have the rotation in the correct direction? Also, I have no idea where that equation of speed came from, so if your results are weird then than is the first thing to check.
First of all, I apologize for my mistake and thank you for your suggestion.
For the direction I try to change direction in CCW so this is the result.

the water was blown down like this. (maybe because of high angular velocity)
https://www.dropbox.com/s/2h2wzug7mq84nbo/4.PNG?dl=0

and look at the waterline,The velocity was increased from green-line to red-line so I think it gonna be weird.

https://www.dropbox.com/s/xnxb34ncn81spte/3.PNG?dl=0

I take velocity equations from Pelton turbines Book by Zhengji Zhang.I'm quite sure it's can be use.

let's me explain you what I'm doing.
I design the pelton turbines with head 750m. and flow rate 8 m3.
with the dimensions by Zhengji Zhang's book. To study the waterline and find Torque by using CFD method.

but in simulation period the result is not correct so I think something wrong with my calculation and designing.

Thanks for your suggestion
and apologize for my mistake in the past and my grammar.
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Old   March 30, 2017, 18:31
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You should not guess what the rotation direction is. You should know what the rotation direction is an make sure it is correctly set.

But your problem looks more fundamental than just rotation direction.

Can you post an image of the water volume fraction?
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