vk.com/club152685050In-F ight Icing Tutorial Using| vk.Fluentcom/id446425943Icing

29.Go to the Data tab and change the color range to Spectrum 2 –16.

30.Align the view angle with the Z-symmetry plane and zoom in to capture the following image:

Figure 27.16: Lwc Distribution and Shadow Zones for 44.4 Micron Droplets (Left) and 6.2 Micron Droplets (Right)

Observe the difference in the shadow zones. The smallest droplets follow the airfoil very closely but avoiding it while the largest droplets barely change their path and hit almost straight on, leaving a larger shadow zone.

27.4. Fluent Icing Ice Accretion on the NACA0012

The objective of this tutorial is to compute ice accretion and water runback on the NACA0012 airfoil at different icing temperatures. Icing temperature refers to the free stream of air temperature at which the icing is to be computed. Inside Ice, this temperature can be different than what was used for the airflow free stream temperature. Indeed, the formulation of the heat fluxes in Ice allows to use an air solution obtained at a temperature different than the intended icing temperature. In this manner, several icing temperatures can be investigated using the same airflow solution.

Note

The option to change icing air temperature in icing parameters is provided as a quick method to obtain different ice shapes with different ambient temperatures. It should be understood that this method is not identical in terms of accuracy to running air and droplet flows independently for each of those temperatures. Change in ambient air temperature

	Release 2019 R1 - © ANSYS,Inc.All rights reserved.- Contains proprietary and confidential information
912	of ANSYS, Inc. and its subsidiaries and affiliates.

vk.com/club152685050 | vk.com/id446425943

Fluent Icing Ice Accretion on the NACA0012

would result in a proportional change in air density which would change the momentum transfer between air and particles. This would ultimately affect particle flow paths and collection efficiency. For internal flows, where particle thermal equation and/or vapor transport is enabled, icing air temperature should be kept the same as the reference air temperature.

You are invited to read Set-up → Ice and Set-up User's Guide for more information on how to set

→ Boundary Conditions → Wall within the Fluent up the input parameters of the Ice module.

1.Launch Fluent Icing from your working directory, FLUENT_ICING_NACA0012.

2.Go to File → Preferences…. Select Icing on the left hand-side of the Preferences window. Assign a number of CPUs, 2 to 4 CPUs, next to Default Fluent CPU and set Default work folder to the location of your working directory.

3.Go to File → Open case…. Browse to and select the file naca0012_rough_mvd.cas, created in Monodispersed Calculation (p. 896).

4.A message window will ask you to launch Fluent, click Yes. A new simulation tree appears under naca0012_rough_mvd.cas(loaded) in the Outline View window. All airflow and droplet conditions and solutions previously configured and computed in the previous simulation are automatically imported under that .CAS.

5.Select Set-up under naca0012_rough_mvd.cas(loaded). In its Properties window, make sure that Airflow,

Particles and Ice are checked.

6.Under Set-up → Ice,

•In Ice accretion conditions,

–Set the Recovery factor to 0.9.

–Check Specify Icing air temperature to simulate an icing temperature that is different than the ref- erence/far-field air temperature.

–Set the Icing air temperature to 248.15 K (-25 °C).

•In Model,

–Make sure that Icing model is set to Glaze.

•Leave the other settings as default.

7.In general, there is nothing to set in the Boundary Conditions of Ice unless icing is to be turned off on certain surfaces to reduce computational effort or sink boundaries are to be declared. Examine the options available at each wall without performing any changes.

8.Go to Solve and inside the Properties window, change Log verbosity to Complete to output extra execution and post-processed data in the Console Window.

9.Right-click Particles under Solve, and select Load. A window appears to specify a *.droplet file to load. Select naca0012_rough_mvd.droplet since we will use the monodispersed cloud solution computed in Monodispersed Calculation (p. 896) to accrete ice over the NACA0012.

10.Go to Solve → Ice,

Release 2019 R1 - © ANSYS,Inc.All rights reserved.- Contains proprietary and confidential information
of ANSYS, Inc. and its subsidiaries and affiliates.	913

vk.com/club152685050In-F ight Icing Tutorial Using| vk.Fluentcom/id446425943Icing

•Under Time, keep the Total time of ice accretion [s] at 420 seconds and the Automatic time step option checked. The Ice feature in Fluent Icing is an explicit time-accurate code where the stability of

the solution strongly depends on the value of the time step. The automatic time stepping option calculates the optimal stable time step at every iteration, which can change greatly depending on the size of the geometry and the mesh density.

•Under Output, keep the option for grid displacement unchecked to skip the morphing of the volume mesh due to ice displacement.

11.Right-click Ice under Solve and choose Calculate to run the calculation.

12.After the simulation is complete, save the solution by selecting File → Save Case as… and name it naca0012_rough_mvd_m25C.

Look through the Console window of Fluent Icing. The accumulated time, value of the time step, total impingement, film, and mass of ice are printed at selected iterations. Heat flux and ice mass per wall boundary condition are listed in the following two tables. Finally, energy and mass conservation tables are printed. Most of the items in these tables are self-explanatory except perhaps mass of clipped film and runback flux. Clipped film refers to any film that is removed by sink boundaries and on certain nodes which collect and shed water (trailing edges, wing and blade tips, etc.) that are detected automatically. Runback flux is the sum of all edge fluxes in the domain which will be equal to the film removed by sink boundaries, or close to zero (mass conservation).

Figure 27.17: Mass Conservation Table Printed in the Log File of Fluent Icing

13.Cycle through the Graphs window. You will observe the progress of the total mass of ice in a sub-window and the change in instantaneous ice growth, water film thickness, and ice surface temperature with time in the next sub-window. Since the input flow and droplet solutions are steady-state solutions, the icing solutions will eventually reach a steady-state where instantaneous ice growth, water film thickness, and ice surface temperature do not change after a while.

14.Go to Ribbon menu and select View. In Quick-view, click Ice cover → Ice over - Viewmerical to see the ice shape and the original surface in Viewmerical. You can change the Metallic + Smooth option to other choices in the Object box to see the wireframe profiles and the surface meshes. In the Data panel, you can adjust the Ice thickness threshold based on ice growth to reduce display interlacing due to the overlapping of iced and clean surfaces.

	Release 2019 R1 - © ANSYS,Inc.All rights reserved.- Contains proprietary and confidential information
914	of ANSYS, Inc. and its subsidiaries and affiliates.

vk.com/club152685050 | vk.com/id446425943 Fluent Icing Ice Accretion on the NACA0012

Figure 27.18: Ice View in Viewmerical Showing Shaded + Wireframe, -25 °C

At -25 °C (248.15 K), the result is a pure rime ice shape.

15.Do not close the Fluent Icing session and run two more calculations at warmer temperatures.

16.Right-click Ice under Solve and select Reset to delete the previous ice solution.

17.Select Set-up → Ice and set the Icing air temperature value to 263.15 K (-10 °C) in Ice accretion conditions.

18.Right-click Ice under Solve and click Calculate to run the calculation.

19.After the simulation is complete, save the ice solution by selecting File → Save Case as… and name it naca0012_rough_mvd_m10C.

20.Repeat steps 16 to 19. This time with an Icing air temperature value of 265.67 K (-7.48 °C), same as the airflow Temperature [K] in Set-up → Airflow → Conditions. After the simulation is complete, save the ice solution and name it naca0012_rough_mvd_m7p5C.

21.Now that there are 3 different ice shapes computed, we will analyze them using Quick-View.

22.Go to Ribbon menu and select View. In Quick-view, click Ice cover → Ice cover – Viewmerical. This opens the ice solution calculated in the previous simulation.

Release 2019 R1 - © ANSYS,Inc.All rights reserved.- Contains proprietary and confidential information
of ANSYS, Inc. and its subsidiaries and affiliates.	915

vk.com/club152685050In-F ight Icing Tutorial Using| vk.Fluentcom/id446425943Icing

Figure 27.19: Ice View in Viewmerical Showing Metallic + Smooth, , -7.5 °C

23.Rename this object by double-clicking on its original name in the Object window and enter Ice -7.5C in the window Rename dataset.

24.To load the -10 °C and -25 °C solutions, click on the button located at the right corner of the Object panel. A window appears to load a pair of files, a grid file and its solution file.

25.Click on the folder icon of Grid file and select the naca0012_rough_mvd_m10C.ice.grid file located inside your working directory.

26.Do not specify a solution file as you will only compare ice shapes.

27.Press the Load button. A new data set is added to the Object panel.

28.Rename this new object by double-clicking on its original name in the Object window and enter Ice - 10C in the window Rename dataset.

29.Repeat steps 23 to 27 for the remaining ice shape, file naca0012_rough_mvd_m25C.ice.grid.

30.Click the lock button at the bottom right of the data set list window located in the Objects panel to enable all the grids in the 2D plot.

31.Go to Query panel and enable the 2D plot. Change the Cutting plane to Z and the horizontal axis to X. All four data sets should be plotted in Geometry mode. Change the color and thickness of the curves by right-clicking on the cube menu on the top right and then by choosing the Curve Settings menu.

	Release 2019 R1 - © ANSYS,Inc.All rights reserved.- Contains proprietary and confidential information
916	of ANSYS, Inc. and its subsidiaries and affiliates.

vk.com/club152685050 | vk.com/id446425943	Fluent Icing Ice Accretion on the NACA0012
Figure 27.20: Ice Shapes at -25, -10, and -7.5 C

At -25 °C (248.15 K), the cooling effects are large and all droplets freeze almost instantly producing a rime ice shape. This shape generally resembles the original airfoil profile and can be considered somewhat aerodynamic. As the icing temperature increases, more water can run back away from the stagnation zone and freeze where cooling effects become more predominant. This mechanism

initiates the growth of ice horns on the upper and lower sides of the airfoil. These geometric features are common in glaze icing conditions and induce flow separation therefore they dramatically change the aerodynamic performance of the airfoil.

To properly capture the shape of the horns, a multishot computation is recommended where the grid, air and droplet solutions are updated at certain time intervals.

32.Finally, we will compare the film height of the three solutions. Uncheck all Ice* objects.

33.Click on button located at the right corner of the Object panel. A window appears to load a pair of files, a grid file and its solution file.

34.Click on the folder icon of Grid file and select the naca0012_rough_mvd_m7p5C.map.grid file located inside your working directory.

35.Click on the folder icon of Solution file (optional) and select the naca0012_rough_mvd_m7p5C.swimsol file located inside your working directory.

36.Press the Load button. A new data set is added to the Object panel. Rename this dataset by double-clicking on its original name and enter -7.5C in the window Rename dataset.

37.Repeat steps 32 to 35 for the remaining pairs of *.map.grid and *.swimsol files of -10 °C and -25 °C cases.

Release 2019 R1 - © ANSYS,Inc.All rights reserved.- Contains proprietary and confidential information
of ANSYS, Inc. and its subsidiaries and affiliates.	917

vk.com/club152685050In-F ight Icing Tutorial Using| vk.Fluentcom/id446425943Icing

38.In the Data panel, inside Files, choose Film Thickness as the Data field. Click Shared inside Color range.

39.Go to the Query panel and activate the 2D plot. Set the Mode to Data and Cutting plane to Z. Set the horizontal axis to Y. The three curves showing the film height for the 3 different temperatures should be visible. Change the curve colors and thickness using the Curve Settings in the cube menu located at the top right.

Figure 27.21: Film Height Variation over the Ice at -25, -10, and -7.5 C

	Release 2019 R1 - © ANSYS,Inc.All rights reserved.- Contains proprietary and confidential information
918	of ANSYS, Inc. and its subsidiaries and affiliates.