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Quantifying Flow using EnSight

EnSight includes two Calculator functions for quantifying flow:  Flow and FlowRate.

1. User Manual
First, do a Help>User Manual and go to section 4.3 and find the Flow and Flow Rate functions and look at the equations used to create these values.  FlowRate results in an EnSight Scalar, and Flow results in a single value, called an EnSight Constant, both of which can vary over time.

2. Visualize normal flow vector on a 2D surface
If you want to see how velocity normal to a 2D part varies over the surface, select the surface part, click on the calculator, choose the FlowRate function and supply the velocity vector as your vector input.  You can then color your 2D surface by this variable and it will show visually how the velocity normal to your 2D surface varies over the surface.

If you want to see how momentum normal to this 2D part varies over the surface, select the surface part, click on the calculator, create a formula that is momentum = density * velocity.  Note that if your density is constant, you can just multiply the velocity by a constant value (make sure your units are correct). Now substitute momentum in for velocity in the FlowRate equation. You can then color your 2D surface by this momentum variable and it will show visually how the momentum normal to your 2D surface varies over the surface.

3. Quantify the flow vector on a 2D surface
If you want to get a single flow value then use the EnSight calculator Function Flow.

a. Volume Flow
If you want volume flow (cubic feet per time, or cubic meters per second, etc.) then select the surface part, click on the calculator, put velocity in the Flow equation. You will get a single number in the calculator which is the volume flow rate per time (if velocity is m/s and area is square meters then velocity * area = m/s * m^2 = cubic meters per second).  When you change timestep, this value will update.

b. Mass Flow
If you want mass flow (kilograms per second or slugs per second, etc. ) then select the surface part, click on the calculator, create a formula that is momentum = density * velocity.  Note that if your density is constant, you can just multiply the velocity by a constant value (make sure your units are correct). If you have a species concentration (say species mass concentration in percent at each element) then you can include this value in the momentum calculation species_momentum = species concentration * density * velocity.  Now substitute momentum in for velocity in the Flow equation.  You get a single number in the calculator which is the mass flow rate per time.  (if velocity is m/s and area is square meters and density is kg / m^3 then density * velocity * area = kg/m^3 * m/s * m^2 = kg per second).  Make sure your units are correct.  When you change timestep, this value will update.

c. Plotting this value vs. time
Click on the query/plot icon.  Choose to plot the max or min over time. Since it's a single value (mass flow or volume flow) it doesn't matter if you choose max or min.  Pick the mass or volume flow variable that you calculated above and create a query over time.  Now plot it.  As you change time, EnSight will animate the plot and show you how mass flow rate changes over time.

d. Plotting this value vs. distance
- Using a iso/clip part over a specified interval and number of samples.
Select the iso/clip part, and create either volume or mass Flow on this part.  Then select the UserDef icon and under Analyze double click the Part constant query icon.  This opens a dialog that allows you to choose a constant variable  as well as specify the range and sampling rate of the selected part.  With make a Plot togged on, clicking OK will create a corresponding plot.

4. Other issues
Volume Fraction.  If your flow is a mixture and you want to only consider the flow of only one of the species, make sure that you multiply your velocity or momentum vector by the appropriate species volume fraction variable.

5. Advanced
Rather than calculating the NET flow perhaps we want the positive and negative portions of the flow? 

You can use the GT and LT Math functions in EnSight's Calculator to strip off the portions of the scalar FlowRate which are negative and positive.
You can then use the IntegralSurface calculator function to integrate up the negative flow rate and positive flow rates separately.

Now, you not only know the "net" flow rate, but you have also quantified how much "reverse" flow you have there as well.
for Details see the screencast tutorial.

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