For non-chaotic systems, you can use work-precision diagrams. But with chaotic systems, trajectories diverge exponentially so this approach doesn't work.

I know you can measure statistical quantities instead (mean energy, etc.) but looking for a practical reference/book that walks through the details - how to compute reference values, what quantities to measure, how long to run simulations, etc. More interested in numerical implementation than theoretical analysis.

Anyone have good recommendations that cover this well?

Hello,

I am simulating a Rushton turbine in an MRF condition. As seen by the image, I am getting some weird velocities at the interface between my refined 'rotating' region (I assign the MRF conditions to this area) and the stationary zone. I am unsure as to what is causing this.

I have changed multiple settings with the mesh (using snappyHexMesh) including number of refinement levels on the surfaces of the zone, the level of the refinement in the zone itself and also the size of the mesh overall. I cannot see what is causing this and I am getting confused and frustrated by this.

Any help would be greatly appreciated!

https://preview.redd.it/8awwj7lkf30e1.jpg?width=524&format=pjpg&auto=webp&s=66fc1c176d72e4b5c7e7f5810feac5211d02dec1

Can someone explain how do I make fluid Region in Star CCM+. I'm just currently starting to learn in Star CCM+ as they say that it is more accurate and more flexible that SOLIDWORKS Flow Simulation. The problem is, unlike SOLIDWORKS (which generates fluid Region as long as you create's lid for inlet and outlet boundary condition), in star ccm+ I don't know how to work on this region.

I'm trying to simulate a 2D axisymmetric supersonic nozzle and am running into this error:

https://preview.redd.it/z7j7onwstwzd1.png?width=563&format=png&auto=webp&s=55136ba40046f9212696caf35207401739ae67fc

Any idea what this is?
I'm using the academic version of ansys
Thanks!

Was thinking about making a 3d printed aerospike nozzle that could be attached to a pressurized source.Currently we have the facility to visualise the flow using shadow graph method of the jet plume formed.
Other equipments that are availaible are standard pitot tubes and commericial hand held anemometers but how effective would they be in data gathering? Do i need any specialised equipments? I thought i would simulate the entire thing and use the experimental data to validate the simulations done.
Any sources on experiments/papers involving accelerating cold air through nozzles in general and gathering data for the same?

I am relatively new to cfd and using it for my final year project. Could anybody who has experience with cfd please answer a couple of quick questions I have , I will be incredibly grateful for any help?

I have simulated the ice accumulation on the aircraft wing using FLUENT, and the details are as follows.

=========================================================

1. Basic Setup and Solver Selection

**Model**: After reviewing various models, we selected the **Discrete Phase Model (DPM)** instead of Eulerian and Mixture models, as it was necessary to track individual water droplets.

**Solver**: The Pressure-Based Solver was chosen, and Transient Time was activated to track changes over time.

**Energy Equation**: Enabled to account for temperature changes and heat transfer.

2. Boundary Condition Setup

**Inlet**:

**Velocity**: Set the inflow velocity to determine the speed at which droplets approach the wing.

**Temperature**: Set inlet temperature to 263.15K to increase the potential for ice formation.

**Discrete Phase BC Type**: Set to “escape” to allow particles to reach the wing surface.

**Outlet**:

**Pressure**: Gauge Pressure was set to 0 for a natural outflow.

**Backflow Temperature**: Set to 263.15K to maintain the same temperature at the outlet.

**Wall (Wing Surface)**:

**Wall Motion**: Set as a Stationary Wall, assuming the wing is fixed.

**Thermal Conditions**: Selected “Temperature” and set surface temperature to 263.15K.

**Roughness**: Used the High Roughness (Icing) model to facilitate ice formation.

3. Discrete Phase Model (DPM) Setup

**DPM Model Activation**: Enabled to track individual droplet particles.

**Injection Settings**:

**Injection Type**: Set to “Surface” to ensure droplets are continuously introduced across the entire surface.

**Particle Type**: Set as “Inert” in place of Droplet, as Droplet was not selected.

**Material**: Used “water-liquid” for the particle simulation.

**Temperature**: Set injection temperature to 263.15K to enhance cooling and promote ice formation.

**Velocity**: Aligned with the Inlet Boundary Condition to match particle and fluid flow speeds.

**Injection Start and Stop Time**: Set droplets to enter continuously from 0 to 300 seconds.

4. Time Setup (Time Step Configuration)

Set time intervals appropriately to track the ice formation process over time.

**Time Step Size**: Set to 1 second for observing ice accretion in stages.

**Number of Time Steps**: Set to 300 steps to cover a total simulation time of 300 seconds.

5. Wall Setup: Ice Accretion Conditions

**Wall Film Option Activation**: Enabled Wall Film Thickness to track droplet accumulation and ice formation on the wing surface.

**Film Condensation Activation**: Used to model the transformation of droplets into ice upon contact with the wing surface.

**Wall Film Thickness**: Set as Wall Film Height to visualize ice buildup over time.

6. Solidification and Melting Activation

Enabled the Solidification and Melting model to realistically simulate ice formation and melting.

**Thermal Properties Configuration**: Discussed the necessity of setting heat capacity and thermal conductivity to model situations where ice accumulates or melts as surface and fluid temperatures change.

7. Post-Processing Setup

**Autosave**: Configured to save data at each Time Step, allowing the tracking of ice accretion states over time.

**Animation Setup**: Visualized ice buildup on the wing over time using properties like Wall Film Thickness.

**Particle Tracks**: Set to Wall Film Height to observe ice thickness changes over time.

8. Run Calculation

After completing all settings, we executed the simulation.

Faced issues with long DPM iterations, discussing potential solutions to improve simulation efficiency, such as adjusting Time Step or Iteration settings.

===========================================================
How do you think about these setup?

I was working on a simple problem of adding a time derivative term to Nvidia Modulus Lid Driven Cavity example. But I am getting some error about the graph roll out. I am new to this package and now able to resolve it. Anyone here might help out? I posted on their developer forum but no response. Thanks!

https://pastebin.com/vqpV6kip

Does any one know how to solve this problem: ERROR Trim operation failed to produce any surfaces for surface Main_blade_tr_low. ERROR Trim operation failed to produce any surfaces for surface Splitter_blade_tr_low.

Hi!

I'm trying to accurately simulate some spherical plastic particles falling in water and I'm having some trouble, the density of the particles is slightly higher than the water's. The particles are falling way too slowly compared to the experiment that I have to compare with and I've isolated the issue to how the drag is calculated. The drag is massively overestimated by Gidaspow and Di-Felice. Does anyone have experience with similar simulations or with adjusting these models to their needs?

I am modeling a cooling system for a heated solid component. I have water at 298K and 5 bar at the inlet. The mass flow rate is 0.75 Kg/s. My objective is to remove as much heat as possibile within a pressure drop of 2 bar. I attach a picture of the geometry.

Initially I set stagnation inlet (with 5 bar and 298K) and outlet with Mfr of 0.75 Kg/s. However I have the doubt it is the correct setting: for example I get different velocities between inlet and outlet, where they should be the same since the cross section is identical and the mass flow rate is constant. I assume that this is due to the stagnation inlet BC (the fluid is initially still.

Thanks for the help!

https://preview.redd.it/d1p76t8munzd1.png?width=920&format=png&auto=webp&s=3200b0cbc63003826e265dde307eaffd387985b5

Is it possible to properly simulate the fuel sloshing on an aircraft 3d wing using Fluent? Getting meaningful results force or pressure exerted onto the walls of fuel tank.

I know that using UDF we can simulate a sinosoidal force that closely resembles sloshing behavior. My doubt is in terms of getting the output as force or pressure exerted onto the walls of fuel tank and also how complex it is when an actual 3d wing of an aircraft is considered.

Thank you

I feel like an idiot for asking this, but I have searched across Google and for the life of me cannot figure out how to extend the inlet and outlet boundary conditions to add slip walls.

In Fluent, I would insert a plane where the inlet and outlet are, then use the pull command to drag them out. Then use Split and select the plane to split the wall up. I figured out how to extend the faces and add a place with a specific offset in Star, but haven't been able to find the "Split" command where I can select that plane to add an extra edge on the wall. I am very new to Star-CCM+ and there's probably a feature that does exactly that, I just don't know where it is.

Thank you!

Hello r/CFD,

I'm very new to Computational Fluid Dynamics and have been studying it as I look to integrate it into my business. My work focuses on CNC porting of cylinder heads, where we optimize airflow to improve engine performance. Currently, we rely on a flow bench for testing, but I'm interested in using CFD for digital airflow simulations.

At this stage, my main goal is to get a clear view of how air flows through the cylinder ports and reacts to various shapes. I’m not considering complex variables like fuel-air mixtures right now, aiming to keep things straightforward but still beneficial for practical insights.

I’d appreciate any constructive advice, resources, or tips for beginners, especially those focused on integrating CFD into hands-on applications like this.

I've noticed that in many beginner posts here, experts sometimes seem to discourage newcomers, suggesting that CFD is too complex and implying they’d get better results with simpler, physical methods like taping a ribbon inside the port and blowing on it. While I understand CFD’s challenges, I'm not necessarily looking for those kinds of answers.

I’m open to software recommendations and willing to invest in the right tools. I've experimented a bit with Autodesk CFD and OpenFOAM and recently have spent limited time with ANSYS software. (All just free trials or opens source)

Is this something I can realistically do?

Thanks in advance for any guidance you can share!

I'd like to do some CFD simulation of my solar panels/roof rack on my camper van in hopes of making a somewhat effective front fairing or other methods of reducing drag? I have a model of the van and roof rack/solar panels in Maya I can try exporting.

I'm reasonably tech savvy and have decades of experience in 3D apps for the entertainment business, but have very little experience with CAD or engineering apps, but I really do want to learn more CAD/CAM.

I have Fusion360 installed and a Solidworks 3DExperience license, but can't seem to use that anymore as it seems they have new hardware requirements and my computer that ran it perfectly fine previously won't now?

I have OpenFoam installed via MinGW, but seems that's going to take some time to figure out and I'm wondering if there's something more user friendly?

Hello,

I am currently working on modeling the spray of liquid nitrogen into a cylindrical chamber for cooling purposes. I am using discrete phase model (cone injection), species transport (for evaporation). I am not otherwise modeling heat transfer.

My solutions either diverge, or produce somewhat realistic results with some caveats. The chamber is initialized at 288 Kelvin. The liquid nitrogen comes in at 75K. Pressure is atmospheric. After a few time steps, certain "hot spots" develop that are 400K+, and in general the chamber becomes less than 50K. My only boundary conditions are walls that reflect the DPM sources.

I have tried k-epsilon RNG, k-omega SST. I've tried changing my scheme from simple to PISO. I've tried lowering my time step size (.1 - .05s), more iterations per timestep (30)

Any guidance, whether specific or general is appreciated.

You may be interested, second part of a general introduction to CFD: CFDLecture 2

https://preview.redd.it/0vnxzmo5hfzd1.png?width=927&format=png&auto=webp&s=0102edbd438c47d6ef3da54fa324f8860a8b48d0

Hi, I'm new to CFD and I'm trying to create a 2D mesh in ICEM. Can someone please guide me on how to create this type of mesh? (The one on the right) Thank you!

This is my first time to develop a mesh for the airfoil (NACA 4412)

And the results is as follow. Could you guys evaluate the quality?

Inlet velocity : 12m/s

https://preview.redd.it/hvp825yizdzd1.jpg?width=1500&format=pjpg&auto=webp&s=cf5db44b3ac36100533fc92f8566a3ffc17fd218

link to the paper

The most time-consuming part of combustion simulation is the chemical reaction source term, this paper use AI to tackle this source term and use full GPU to run these codes, it can accelerate the simulation by two order of magnitude,the simulation time achieves a maximum speedup of approximately 310 at the largest mesh size.

comment: maybe in the future, we can see the explosion visual effect in the film will be done with realistic combustion model, and there are also a lot of research about using lattice boltzmann method to simulate the combustion, which will also speed up the simulation by 3 times.

Hi everyone!
I am doing an erosion analysis on the blades of the centrifugal compressor. I am trying to predict the erosion map but facing an issue. During the sand particle injection, the Leading edge of the blade is the most affected area but in my case, it shows the trailing edge as the most affected one. Can anyone tell me please why is it happening? I am using ANSYS CFX for my simulations.

Meridional View of Blade

https://preview.redd.it/sx2nju8rmdzd1.png?width=910&format=png&auto=webp&s=d49c77694d89006d9fbf5a67c254052b731f4cae

Hi guys I'm new to cfd I got an error while meshing in turbogrid that I have negative volume I don't know how to resolve it Any help is appreciated

Thanks to guys in here, they recommended to start a CFD project(undergrad) to simulate a electrical heating of aircraft wing for anti-icing.

Since I am a newbie to this CFD (of course, I have taken thermofluid lectures, heat transfer, etc, enough to understand the simulation theoretically), I need some advice about what are steps when you guys simulate the thermofluid situations via ANSYS FLUENT.

Moreover, if you have tips about boundary conditions and some other solving tools for this project, I ask you guys to help me some.

So , basically imagine a microfluidic system with a fluid reservoir and an attached channel. If we exert pressure on the reservoir , the structure would be deformed and the fluid in it would get displaced to the attached channel, right? I've been trying to do this and it gives me the deformation of the structure when you exert pressure, but I don't know how to get the data of the effects of the pressure on the fluid contained within.

Hi!

I was stunned by the class of these three CFD animations:

https://youtu.be/lSrk2pnlx2I?si=OqFejZdQk9S0MKAU

https://youtu.be/kqX17yytnaY?si=mv1yk3IkyyoPC4a8

https://youtu.be/uxT-VmY3OWc?si=KZfSfPPmdBWV8Qok

In my opinion, the coolest thing is that the camera pans around the model

How is that done? Which software can you use to get that result?

P.S: I already tried to contact the author of the first two animations, but got no response😢 So, that's why I am contacting you beautiful orange people🤗

Thanks to everyone who will dedicate a bit of their time to answer this!!

I was a bit sad that I had no job opportunity in cfd in my country a while ago, since then I had an interview but the company didn't even call back, so here I am earning my wage in BIM as a HVAC engineer, but I love cfd, I saw online that there're some companies that use cfd in hvac applications, my firm is a good one with really nice environment but they don't do this, i want to bring this to my boss and see if he might be interested to add cfd to our services, is there anyone who use cfd in hvac applications or anyone's that might help me to present this idea to my boss, note I want to make a cfd analysis on our office in the next couple of weeks and show that to him as an example, this might be my last attempt at trying to use it as a part of my job.

Hi everyone, I am new to SW flow simulation.
I have task to perform Flow simulation, basically it is mixing of fluid in a tank.
At the moment I want to simulate it for 1 hour of mixing.

There are 2 opening from top, one is inlet to tank, other is outlet (pump is installed).

How can I measure the mixing? I mean I can show many graphical views with velocity patterns using cut plots, but I want to present some numeric values.
As per google, there should be some Reynolds number, what else it could be?

Just for info, it should be just basic simulation, not too much detailed version.

Hi all,

I'm currently running a steady state simulation which comprehends both energy equation and radiation model. To check simulation progress during run-time, I usually create some report definitions, checking for values of interest (i.e. velocity at pressure outlet) and a mass balance expression defined as (mass_flow_outlet-mass_flow_inlet)/mass_flow_inlet. I usually deem a simulation as converged when values of interest are kind of constant and mass balance < 0.01. Being my first thermal simulation, I'm having an hard time defining a balance expression to check for energy during run-time and I'm here seeking for help. The domain is box-shaped with circular shaped holes as hot air inlet at fixed temperature, an hot wall at fixed temperature, pressure outlet, convection at the box walls and shell conduction on faces which exit the box.

Thanks in advance to anybody who can help me.