TAGGED: ansys-fluent, compressible-flow, nozzle, scarfed-nozzle, supersonic-flow
January 22, 2022 at 4:50 amKSDSubscriber
This is the picture of simulation I want to do, where external flow (supersonic : Mach = 2) is interacting with scarfed nozzle jet. For now I am trying to do steady flow simulation. In below image red arrow represents external flow and blue arrow represents nozzle jet.January 24, 2022 at 9:21 amSPielmeierSubscriberIf you know the ambient pressure you could calculate the total pressure at your desired Ma No. using the isentropic relations. You can then used this calculated pressure as your BC at Inlet 2.
Keep in mind that these relations assume isentropy, so they can┬┤t be used over shocks.
January 24, 2022 at 9:25 amDrAmineAnsys EmployeeYou might use Far Field BC at your Inflow or pressure inlet with appropriate Total and Gauge/Supersonic Static Pressure. You have all input you require given the isentropic relationships.
January 25, 2022 at 2:33 pmKSDSubscriberThanks a lot for responding.
When I tried to give Pressure Inlet at Inlet 2 with stagnation condition corresponding to the Mach No. and Ambient Pressure using isentropic relations, it is working fine
But If I want to use pressure far field with M = 2 and Static pressure/temp = Ambient Pressure/temp (In Ansys Fluent Pressure Far field BC, I think we have to specify static pressure/temp). But it shows stabilizing error.
Could you tell me where I am going wrong.
January 26, 2022 at 7:14 amDrAmineAnsys EmployeeWith your pressure Inlet inputs are you getting good results? Are you getting the expected Mach number? If yes then you should focus on your next steps.
With Far Field yes you provide static pressure which you can get from stagnation pressure and isentropic relationships. I won't use the whole boundary as Pressure Farfield and leave the other two edges or at least one of them as pressure outlet
January 27, 2022 at 6:23 amKSDSubscriberSir, I think using pressure inlet BCs is giving me correct results because when I used isentropic relation corresponding to M = 3.75 and ambient pressure = 101325 Pa at pressure Inlet (Not Nozzle Pressure Inlet but Outer domain one). I am getting these results
As far as ambient pressure is concerned it is matching.
But the Contour of Mach no. is showing 3.65 at the entry of flow which is not same as M = 3.75, What would be the reason for it ?
I have considered gamma = 1.2 for air, and in Ansys fluent I am defining Cp corresponding to the gamma = 1.2 using the relation gamma*R/(gamma-1).
But for far field even after defining only one or two boundary as far field like these as shown in below images
I am getting error like floating point, AMG, stabilizing etc...
January 31, 2022 at 12:45 pmKSDSubscriberSir, Could you please confirm whether I did anything wrong?
January 31, 2022 at 2:59 pmDrAmineAnsys Employeefar field might be sensitive to initialization. However your input is wrong: Stagnation pressure is the ambient pressure. You need to provide the static pressure corresponding to that ambient pressure and Mach number. But again if you have good results with pressure inlet then keep using it and post your input for the BC here: Again the same input will lead to same results. Upstream pressure / farfield pressure is in your case the 1 atm.
February 1, 2022 at 1:56 pmKSDSubscriberSir, I had given stagnation pressure corresponding to desire external flow Mach No. and ambient pressure using isentropic relations.
Means I am treating ambient pressure as static pressure and then finding stagnation pressure according to the desired Mach number I want , when I am using Pressure Inlet as BC, for e.g.
If ambient conditions are as follows Pressure (Pa) = 101325 Pa , (Ta) = 300 K and if I want an external flow of M = 3.75, so by using isentropic relation I am getting (Po) = 19668073.9555 Pa, (To) = 721.875009 K
So this is how I am specifying in BCs section of Fluent:
(1) Pressure Inlet BC = Po, To , (2) At Pressure Outlet BC = Pa, Ta
For this set of BCs inputs I am getting these as results, which I think is correct.
But Sir, as in above answer you are mentioning to treat ambient as stagnation pressure and calculate static pressure corresponding to that Mach No. using isentropic relations, then my simulation is showing floating point error for both cases for e.g.
Po = 101325 Pa, To = 300 K, corresponding to M = 3.75 the static pressure I am getting (P) = 522.0011 Pa
If I give above inputs then for Pressure Inlet or Far field BCs floating point error is occurring.
February 2, 2022 at 1:18 pmKSDSubscriberSir, can you tell me what is going wrong now?
February 3, 2022 at 2:14 pmKSDSubscriberPlease Help.
Viewing 10 reply threads
Ansys Innovation Space
- You must be logged in to reply to this topic.
Boost Ansys Fluent Simulations with AWS
Computational Fluid Dynamics (CFD) helps engineers design products in which the flow of fluid components is a significant challenge. These different use cases often require large complex models to solve on a traditional workstation. Click here to join this event to learn how to leverage Ansys Fluids on the cloud, thanks to Ansys Gateway powered by AWS.
Earth Rescue – An Ansys Online Series
The climate crisis is here. But so is the human ingenuity to fight it. Earth Rescue reveals what visionary companies are doing today to engineer radical new ideas in the fight against climate change. Click here to watch the first episode.
Subscribe to the Ansys Blog to get great new content about the power of simulation delivered right to your email on a weekly basis. With content from Ansys experts, partners and customers you will learn about product development advances, thought leadership and trends and tips to better use Ansys tools. Sign up here.Trending discussions
- Suppress Fluent to open with GUI while performing in journal file
- Floating point exception in Fluent
- What are the differences between CFX and Fluent?
- Heat transfer coefficient
- Getting graph and tabular data from result in workbench mechanical
- The solver failed with a non-zero exit code of : 2
- Difference between K-epsilon and K-omega Turbulence Model
- Time Step Size and Courant Number
- Mesh Interfaces in ANSYS FLUENT
- error in cfd post
Top Rated Tags
© 2023 Copyright ANSYS, Inc. All rights reserved.Ansys does not support the usage of unauthorized Ansys software. Please visit www.ansys.com to obtain an official distribution.