SimCafe

Space shortcuts

Child pages
  • Forced Convection - Numerical Results

Versions Compared

Old Version 154

changes.mady.by.user Rajesh Bhaskaran

Saved on

compared with

New Version 155

changes.mady.by.user Rajesh Bhaskaran

Saved on

Key

  • This line was added.
  • This line was removed.
  • Formatting was changed.

...

Importing Experimental Data and Chart Formatting

We can import experimental data in csv format with from a csv file using the procedure shown below. The csv file should contain two columns, corresponding to the x-axis and y-axis values respectively.  , respectively 

HTML
<iframe width="560" height="315" src="https://www.youtube.com/embed/oy3xJrmWNLo?rel=0" frameborder="0" allowfullscreen></iframe>

...

Wall Shear

We plot the wall shear using the procedure shown in the video below.  

HTML
<iframe width="640" height="360" src="//www.youtube.com/embed/WiK1uBTdK-M?rel=0" frameborder="0" allowfullscreen></iframe>

Summary of the above video:

  1. Click on the Chart Viewer tab
  2. Click chart in the top toolbar
    1. Name it Wall Shear
  3. Click on Data Series Tab
    1. In Location dropdown menu, choose Wall
  4. Click on X Axis tab
    1. under Variable, choose X
  5. Click on Y Axis tab
    1. under Variable, choose Wall Shear X or Wall Shear
  6. Go to Location in the tree
    1. Double click on Wall
    2. Increase Sampling from 50 to 200

We then consider the trends in the wall shear in the heated, mixing and flow development sections and try to justify them through physical reasoning.

HTML
<iframe width="640" height="360" src="//www.youtube.com/embed/NbdGrJTesZg?rel=0" frameborder="0" allowfullscreen></iframe>

Summary of the above video:

  • As you heat flow, velocity increases
    1. Momentum at any any average is going to increase when heat is added
    • The gradient of the velocity normal to the wall is higher, the wall shear is higherWall shear increases in the heated region, as shown in the wall shear plot

    You can spiff up your plot using the tips discussed below. This video also shows you how you could read in experimental results for comparing the wall shear between simulation and experiment.
     HTML
    <iframe width="640" height="360" src="//www.youtube.com/embed/6RNykoM86xA?rel=0" frameborder="0" allowfullscreen></iframe>
    Summary of the above video:
    1. To edit how the Wall shear graph is displayed
      1. Select Wall shear in tree
      2. Click on General, check Title and enter title in Title blank
      3. in Data Series, enter series name in Name blank
      4. in X Axis, enter x axis label in Custom Label blank
      5. same for Y Axis
      6. in Line Display, uncheck "Use series..." and type within Legend Name blank
      7. in Chart Display, under Sizes, toggle with the line sizes and font
    2. To add another data series
      1. go to Data series tab of Wall Shear
      2. click on New button
      3. Scroll down, click File as  Data Source > browse for your file
    3. To export the chart
      1. Click the button next to undo
      2. Select location to save
      3. Rename
    When the simulation was repeated for conditions for which experimental data are available, we got the comparison shown below. The difference in the average wall shear in the heated section between the simulation and experiment is a respectable 4%. Note that the wall shear in turbulent flows is difficult to predict accurately due to the steep velocity gradients at the wall. 
     
    Fanning Friction Factor
    The Fanning friction factor, also called the skin friction coefficient, is obtained by non-dimensionalizing the wall shear. It can be calculated and plotted using the procedure outlined below. 
     HTML
    <iframe width="640" height="360" src="//www.youtube.com/embed/Jcht7CAPzAc?rel=0" frameborder="0" allowfullscreen></iframe>
    Summary of the above video:
    1. Create Location > Point 
      1. (2.67, .0294, 0)
    2. Probe wall shear at point: 
      1. Create Expression > Right Click > New Expression
      2. probe(Wall Shear)@w267 / 1.483 (Pa/K) /Tm267
    3. Can duplicate for different locations for a plot
    Final Plots
     HTML
    <iframe width="560" height="315" src="https://www.youtube.com/embed/x-flaXXU7xg?rel=0" frameborder="0" allowfullscreen></iframe>
    Summary of the above video:
  • Display Wall Temperature vs. Position in pipe and compare with experimental data
  • Display Pressure Variation vs. Position in pipe and compare with experimental data
    • Display Temperature at Centerline vs. Position in pipe and compare with experimental data
    Input Summary
    You can view the input summary (model, material properties, boundary conditions, etc) by clicking on Report in the menu bar of FLUENT. A small window will pop up and you can print the selected input summary directly in FLUENT.
    ...