[cloudysky]

I am trying to put across a user defined function(parabolic velocity profile) to a rectangular cross section as input velocity(no Z-directional changes, just x and y parabolic velocity). My function doesn't show up at all in the velocity field function tree. How do i apply parabolic velocity using user defined function to the geometry?

[f-w]

Your field function doesn't show up in the tree because it is a scalar type. When creating the field function, select a vector type. Also, make sure to specify dimensions that are appropriate for velocity, and define it in the form of [Vx,Vy,0], where Vx and Vy are equations for x and y components of your custom velocity profile.

[cloudysky]

Originally Posted by f-w

Your field function doesn't show up in the tree because it is a scalar type. When creating the field function, select a vector type. Also, make sure to specify dimensions that are appropriate for velocity, and define it in the form of [Vx,Vy,0], where Vx and Vy are equations for x and y components of your custom velocity profile.

Thank you for your reply. However, I am having difficulties making a parabolic velocity profile function and then implementing as the code i use always has an error. Can you please guide me on how to make a parabolic velocity profile for a rectangular cross section(can be scalar or vector). The velocity need not have vector definition as all flow is normal to surface just varying across the height in a parabolic function. The function i use in scalar type is '(${Vm} * (1 - pow(${Position}[1], 2) / pow(${thickness}, 2)))'

[f-w]

Position is a vector, so ${Position} should be corrected to $${Position}; this should get you going, assuming "Vm" and "thickness" variables are defined.

[Voluped]

Hi,

Ensure Variable Definitions:

${Vm}: Maximum velocity
${Position}[1]: y-coordinate (height direction)
${thickness}: Half the height of the rectangle (if the profile is centered at y = 0)

Correct the Function:
The function should correctly represent the parabolic profile. Your function seems almost correct but ensure that ${Position}[1] ranges correctly within the domain.

Here's an example of a scalar field function for a parabolic velocity profile:
${Vm} * (1 - pow(${Position}[1] / ${thickness}, 2))

Create the User-Defined Field Function:
Go to Tools > Field Functions.
Right-click and select New > Field Function.
Name the field function (e.g., ParabolicVelocity).
Set the function type to Scalar.
Define the function using the above expression.

Assign the Field Function to the Inlet Boundary:
Go to Regions > Boundaries and select the boundary where you want to apply the velocity.
Under the Physics Conditions tab, set the Velocity Specification to Field Function.
For the Velocity property, select the user-defined field function (ParabolicVelocity) you created.

Example Implementation:
If ${Vm} is 1 m/s and ${thickness} is 0.05 m (assuming the height of the rectangular cross-section is 0.1 m), your function would look like:
1 * (1 - pow(${Position}[1] / 0.05, 2))