Ansys 2023 R1 delivers platform-powered performance, workflow-enabled collaboration and insight-driven innovations for every stage of the product development process. Discussion. 8. ), you can find the Drag Coefficient. 2. Not only did Ansys Fluent Adjoint Solver perform all these analyses within the window of time allocated for input but the tool enabled engineers to identify opportunities for measurable drag reductions in all areas. Extremely high lift and drag coefficients in ANSYS Fluent, Scan this QR code to download the app now. Components were resolved to set AoA and force report definitions, FREE STUDENT 2023 Copyright ANSYS, Inc. All rights reserved. Its good for everyone. Industry-leading computational fluid dynamics provides advanced physics modeling and accuracy. The mesh morphing results and the simulated flow field. Simulating Battery Pack Cooling System Using Ansys Fluent. . What are the differences between CFX and Fluent? Browse our catalog of applications from fluent, mechanical, and meshing to systems and workflow. The air at high velocity is blowing over it. But so is the human ingenuity to fight it. The result of the drag coefficient using the new Boundary conditions are still too high. Why is my drag and lift coefficient higher than it is supposed to be? Reddit, Inc. 2023. Air (Ideal gas, Sutherland's law of viscosity), 5. The GEKO (GEneralized K-Omega) turbulence model offers a flexible, robust, general-purpose approach to RANS turbulence modeling. These elemental stiffness are used to calculate the global stiffness matrix. Contact Definitions in ANSYS Workbench Mechanical. Fluent over-predicts drag coefficient and moment coefficient!! I have kept more than 400 points on the airfoil surface but no luck! How to display the color of each body based on the material in Mechanical? Draft. I have used the following relations as attached in the image. In this case, the experimental Drag coefficient (Cd) is 1.55.Download File: https://cfd.ninja/ansys-fluent/ansys-fluent-drag-coefficient-reference-values-2d/Computational Fluid Dynamicshttp://cfd.ninja/https://cfdninja.com/https://naviers.xyz/https://3dn.ninja/ANSYSRunning Free by INOSSI https://soundcloud.com/inossiCreative Commons Attribution 3.0 Unported CC BY 3.0Free Download / Stream: https://bit.ly/_running-freeMusic promoted by Audio Library https://youtu.be/QHGlv0K8_fE Ansys prints out (in the solve.out file) the minimum matrix coefficient and the maximum matrix coefficient. Viewing 1 reply thread You must be logged in to reply to this topic. In contrast, had this same simulation been attempted on a similar cluster using the DOE approach, it would likely have taken two to three days to complete the simulation. If 'x' is the AoA, drag component is i*cos(x)+j*sin(x) and lift component is i*-sin(x)+j*cos(x). http://www.cfd-online.com/Forums/flutml#post583347, Calculate Lift and Drag Coefficients CL and CD. I am running an electrochemistry simulation in Fluent. The case is very sensitive to Boundary conditions. 3. Please explain the warning message coefficient ratio exceeds 10e8 ? May 16, 2022 at 9:04 am Rob Ansys Employee Do the post processing in Fluent, other than handling transient data it's better than CFD Post. How did you calculate the farfield static pressure and static temperature? A rectangular plate has been taken as a specimen and placed . Reference area = 1* chord8. SOFTWARE, Suppress Fluent to open with GUI while performing in journal file. Can fluent get the lift and drag coefficients of the two walls (in different directio, Calculation of lift and drag coefficients. I tried everything at my disposal. The ability to run optimization simulations in hours rather than days has important ramifications. By accepting all cookies, you agree to our use of cookies to deliver and maintain our services and site, improve the quality of Reddit, personalize Reddit content and advertising, and measure the effectiveness of advertising. Introducing the GEKO Turbulence Model in Ansys Fluent. I then proceed with standard initialization with X velocity 28m/s. Body refinements designed to reduce drag can also help. Re the Cd, did you alter the reference value? They then ran simulations using Ansys Fluent Adjoint Solver to optimize the body of the mirror so as to achieve the lowest drag coefficient (Cd). Yes, I was taking the dimensionless Cd from Fluent and multiplying it by the dynamic pressure to give it units of N/m^2. Drag or Lift Coeffcient Calculation in ANSYS FLUENT? Scan this QR code to download the app now. - Creating the flow domain in ANSYS Design modeler - Structured Mesh Creation - Solver setup - Drag and Lift calculations - CFD post Processing This is Part 1 of the Tutorial. This lead to increased drag coefficients! I haven't used fluent to calculate drag coefficient, but from my experience if you use fluent to directly calculate some dimensionless number the results are off. Reddit, Inc. 2023. Save i have the same problem as mentionned. Sign up for the Ansys Academic Webinar Series and take your knowledge to the next level with simulation. Automobile companies around the world know this and design accordingly. The warning message is: The maximum contact stiffness is too big. What should be the range of y+ for the above turbulence model? That is more or less all I touch when setting up a simulation. Can you please show the values? Do you have any specification of the wind tunnel used ? How the fluent ansys find the drag/lift coefficient for 2D analysis for a car ? Please explain the warning message coefficient ratio exceeds 10^8 . If the ratio exceeds 10^8, [] In this case,. Model has a large number of contacts how to reduce them? Why is my drag coefficient way higher than it should be? Sign up here. The value of y+ considered is 1 and that is ensured by calculating the wall spacing and putting that on First Wall thickness and I have even gone through Report in Ansys FLUENT to check the maximum facet value is below 1. I get a value around 1.634. The warning message is: The maximum contact stiffness is too big. Subscribe to the Ansys Blog to get great new content about the power of simulation delivered right to your email on a weekly basis. Ultimately, the result is a better automobile, more efficient use of resources, lower emissions and longer range. aleix.de.toro: FLUENT: 2: August 24, 2015 18:00: Can fluent get the lift and drag coefficients of the two walls (in different directio: yuyuxuan: FLUENT: 8: January 10, 2014 20:13: Calculation of lift and drag . It looks like their Cd is actually drag force per area. Not only y+~1 is important but also the number of grid point sin the boundary layer (10-15). Whether you are driving a car with a traditional internal combustion engine or one with a completely electric power source, the further you can go on a tank of gas or a full battery charge, the better on your wallet as well as on the environment. As you said lift is fine I think that you might made a mistake with the vectors. The problem arises when you look at the numbers, for example, the drag coefficient in one of them is 29826.45, while the lift coefficient is 750630.8, which I think are extremely high, as I have seen more thorough projects that get something close to 10 or 11 for the lift and 3 or 4 for the drag. Thank you very much! Morphing boxes selected for analysis in Ansys Fluent Adjoint Solver. That opens up a wide range of possibilities. For more information, please see our 7. Topics relate to Fluent, CFX, Turbogrid and more. Not entirely. Fluent over-predicts drag coefficient and moment coefficient!! - Ansys But the following problems are prevalent: For Spalart Allmaras Turbulence model,my lift coefficient is within the range i.e less than 5% difference in between but drag coefficient is way too much high in value sometimes even 200% more. I have tried it again for both Turbulence model with a bit more refined mesh but the value of lift coefficient increases in both the cases but the difference for drag coefficient decreases for K-omega SST Turbulence model, The following links indicate the graph acquired for lift coefficient and drag coefficient. Draft. Still, the accuracy of these findings had to be validated, and that called for outfitting a full-sized vehicle with optimized versions of the components and then taking it for a spin in the Shanghai Automotive Wind Tunnel Center (SAWTC) in Tongji University. The GEKO (GEneralized K-Omega) turbulence model offers a flexible, robust, general-purpose approach to RANS turbulence modeling. In this tutorial, it has been shown how you can calculate drag and lift forces and coefficients. Engineers used Fluent to gain insight into areas of particular drag sensitivity, then focused on finding ways to reduce drag in several specific areas. I am doing a school project and I have created some wings out of different NACA profiles that I then attach some winglets to. How can we export high quality image from cfd-post. Please visit, I am trying predict the cd, cl and cm of 2D airfoil (NACA0012) with sharp trailing edge and to compare with. These elemental stiffness are used to calculate the global stiffness matrix. Coefficient of Drag is a dimensionless number, but after looking more at the paper you are referring to. ANSYS DesignXplorer: Using Response Surfaces Part 2. Very High Drag Coefficients? -- CFD Online Discussion Forums 2. Check if you have set the reference values as coming from farfield boundary zone. On calculating I get static pressure as 25629.5 Pa. As for setup, I use 28m/s air speed from an inlet (with turbulent intensity 0%) and I have an outflow. You must be logged in to reply to this topic. I get relatively close to the student version's element limit (311435 elements) and I don't really touch anything else in meshing. The results comparing them to one-another are more or less what I expected, the sharklet outperforming the wingtip fence and the "no wingtip", which is a very simplified winglet so it doesnt leave a rough edge. Tried FMG initialization. Cookie Notice In this tutorial, you will learn how to use the Reference Values window for a 2D simulation- With Reference Values (Lenght, Depth, Area, etc. Setting up adjoint simulations does not require you to define parameters in the way you would using the DOE method, for example. Thats not just good for SAIC Volkswagen. ANSYS Fluent Tutorial : Drag and Lift Calculations in ANSYS Fluent If the ratio exceeds 10^8, it means that the stiffness matrix is ill-conditioned, so the results should be checked carefully. I've just performed simulations alike the ones presented in this post, where the domain extenden for only 10 diameters downstream. Did you manage to get the proper results? One path leading to better mileage with lower greenhouse gas emission targets mechanical solutions more efficient engines and subcomponents, for example. Due to blow of air, the drag and lift forces got developed on this specimen. How can I access the electrochemistry reaction rates with UDF? Alternately, the time might be used to look for other areas where drag could be reduced for greater efficiency. The coefficient ratio is the ratio between these min and max values. This video demonstrates exporting data from Fluent in EnSight Case Gold format, and it reviews the basic postprocessing capabilities of EnSight. Which keywords can be used to introduce(activate)/delete(deactivate) elements in the middle of a calculation (at user-specific time/load steps). I will check those values again. As the global shift toward automated driving (AD) continues, the future of adaptive headlights, or adaptive driving beam headlights (ADB), is quickly becoming focused. Approaches such as parametric simulation, design of experiments (DOE) and others are valuable, but they are highly compute-intensive and can take a long time to produce results. my study is a laminar flow around a circular cylinder the diametre of the cylinder =15 mm the box is 750x400mm2. The coefficient ratio is the ratio between these min and max values. I think sinceRe and M are maintained as same as that of experiment (in the technical report), cd, cl and cm should be same. The outlines at the top of the figure show mirror shape from the side and top, respectively. Static pressure is adjusted to meet Re = 5.97E6 and Ma = 0.156. Air (Ideal gas, Sutherland's law of viscosity)5. Asked 21st Dec, 2020; . SA or k-omega SST turbulence model4. Far field boundary at 100 times chord distance away. SAIC Volkswagen engineers generated surface mesh from ANSA (their preprocess software) then imported that into Fluent meshing to generate volume mesh. During the solving of the model, each elemental stiffness is evaluated. Click here to watch the first episode. Reducing Drag for a Better World | Ansys Does nobody have an idea? To be sure, I calculated the Re once more from reference values and was equal to the value desired (Re = 5.97E6). While cl gives excellent agreement (less than 1%), cd and cm shows large deviation (my best was 25%). Steady, coupled solver, pseudo transient3. Kindly make your reply. Privacy Policy. Better battery designs for electric cars may be able to deliver much greater efficiencies in that space, but, again, improvements there may depend on mechanical and chemical breakthroughs that are harder to achieve. Exporting the . Reliability Engineering Services (RES) delivers valuable insights to the electronics industry. 2023 Copyright ANSYS, Inc. All rights reserved. Will good compliance between Ansys Fluent Adjoint Solver and the real-world results obtained in the SAWTC eliminate the need to put cars through costly wind tunnel tests? It turns out to be a far more efficient way to solve challenges involving shapes and drag reduction. If youre working with more than a few variables, the number of calculations can become huge, and it can take days to complete all the simulations and determine which combination achieves the desired outcome. After Workbench crashes, how can I recover the project from a .mechdb file? The Reynolds Number chosen for this CFD simulation is 3,000,000 and the free stream velocity is 45 m/s. Answer (1 of 2): Assuming you have selected the proper boundary conditions based on your physical model, and you have implemented them correctly in your numerical setup (i.e. For K-omega SST Turbulence model, my lift coefficient is significantly higher in value and as Angle of attack increases this difference gets higher but the highest it gets is below 30% however drag coefficient is also over predicted but in this case the difference is around 50% higher. The wings I enclose has a 6 angle of attack, for mesh, I use tetrahedrons with patch independent, as it is the only thing that seems to produce a mesh and not just fail. The climate crisis is here. The reference temperature might be the stagnation one. Using a multi-node compute cluster with 512 cores and 64 GB of memory, the Fluent simulation took between three and four hours and provided clear insights into the design alterations that could yield . Comparing wind tunnel (test) results to Fluent simulated results. 4. SAIC Volkswagen engineers used Fluent along with the latest Generalized K-Omega (GEKO) model for steady state calculation and a high-accuracy transient Stress-Blended Eddy Simulation (SBES) model for verification, so engineering felt confident that the solutions suggested by Fluent were optimal within the conditions created by those models. Thats exactly what SAIC Volkswagen has been doing with the help of Ansys Fluent Adjoint Solver. I am sharing a few snaps and set up info. A member of our Ansys sales team will contact you shortly. We have done the NACA0012 for AoA of 1.55 and Ma=0.7 and the results were fine. What should be the valueof AoA above which transient analysis is inevitable? It also works by morphing the existing mesh, so it is not necessary to recreate mesh for different designs. In this tutorial, you will learn how to use the Reference Values window for a 2D simulation- With Reference Values (Lenght, Depth, Area, etc. 3D Transonic Flow Over a Wing Modeling Objectives & Problem Description - Lesson 1 . Set up info:1. The LS-DYNA equivalent of *MODEL_CHANGE card (in ABAQUS). 2023 Copyright ANSYS, Inc. All rights reserved. How to deal with Problem terminated energy error too large?. Discover how to generate a high quality mesh and workflows in this 30-minute presentation. By rejecting non-essential cookies, Reddit may still use certain cookies to ensure the proper functionality of our platform. The wind tunnel test provides the final word, but knowing that there is good compliance between Fluent and the real world gives engineers confidence that the Fluent Adjoint Solvers results are going to be on target. If subtle refinements in design could optimize airflow around the vehicle, driving range and fuel efficiency could improve without depending entirely on chemical and mechanical breakthroughs. I just ran it using pimpleFoam. and our A case in point: SAIC Volkswagen recently used Ansys Fluent Adjoint Solver to explore ways to reduce drag on an existing production Volkswagen SUV. Using a multi-node compute cluster with 512 cores and 64 GB of memory, the Fluent simulation took between three and four hours and provided clear insights into the design alterations that could yield the lowest Cd. Overall, the optimizations suggested by Fluent Adjoint Solver predicted a 10X reduction in Cd in the steady flow simulation and an 8X reduction in the transient flow simulation. Structured meshing in ICEM CFD, y+ almost close to 1 with 200k~250k cells.2. This may affect the accuracy of the results. Why does large contact stiffness affect results accuracy? 1 reply. Read aerodynamic books and gone through understanding how it is represented on CFD but so far I am not able to find the solution. Drag coefficient too high at flow around a cyclinder I would calculate the static pressure and static temperature based on isentropic relationships to get static values from stagnation values. The problem arises when you look at the numbers, for example, the drag coefficient in one of them is 29826.45, while the lift coefficient is 750630.8, which I think are extremely high, as I have seen more thorough projects that get something close to 10 or 11 for the lift and 3 or 4 for the drag. Engineers at SAIC Volkswagen in Shanghai are using Ansys Fluent Adjoint Solver to refine vehicle designs faster and more efficiently. We offer various partnership opportunities for sales, technical and go-to-market collaboration that reaches global audiences. This video article demonstrates how to create a reflector for a center high-mounted stop lamp. Also, my lift seems to be too high, does anyone have the same problem? During the solving of the model, each elemental stiffness is evaluated. Can someone please check if the function I use to calculate the drag coefficient is correct? In addition to analyzing the mirrors for drag optimization, SAIC Volkswagen engineers used Ansys Fluent Adjoint Solver to analyze the air dam on the SUV, the front windshield pillars and the taillight subassembly. for example in the preprocessor of your choice for creating the mesh, or in FLUENT), it is pretty straightforward; you hav. I have used both Spalart Allmaras and K-omega SST Turbulence model. Why is damped frequency is lower than undamped frequency with viscous damping but larger with structural damping? Join us at the 54thInternational Paris Air Show to explore the latest technological innovations in aerospace and defense. While cl gives excellent agreement (less than 1%), cd and cm shows large deviation (my best was 25%). Extremely high lift and drag coefficients in ANSYS Fluent : r/CFD - Reddit This video demonstrates exporting data from Fluent in EnSight Case Gold format, and it reviews the basic postprocessing capabilities of EnSight. What should I do to get drag and lift coefficients on a rocket - Quora Discover how our customers and partners achieve success with simulation. Reddit and its partners use cookies and similar technologies to provide you with a better experience. Autonomous vehicle technology promises a solution. 1. Were here to answer your questions and look forward to speaking with you. i have the same problem as mentionned. A different path to better mileage performance one gaining traction as a result of the adoption of the Worldwide Harmonized Light Vehicle Test Procedure (WLPT) lies in reducing the drag of the vehicle. Also, I am using that formula using the total force output from fluent in the X direction. Drag Coefficient is too large 2000 - Ansys Learning Forum A rectangular plate has been taken as a specimen and placed perpendicular to flow direction. Please correct if I am wrong. - Reference area to be used in drag coefficient calculation . You define specific goals, and the adjoint method modifies the mesh itself to achieve the stated goal within specified manufacturing constraints. For whoever it might concern in the future, a solution to this problem can be the domain size. August 16, 2018 at 2:10 am HHK1992 Subscriber Hi all, I am trying predict the cd, cl and cm of 2D airfoil (NACA0012) with sharp trailing edge and to compare with this technical report . Perhaps this is your mistake, you must know that Fluent considers "Absolute Pressure" = "Operating Pressure" + "Gauge Pressure" If you are setting "Gauge Pressure" equal to atmospheric pressure,. Creating an Animation (optional) . With opportunities around the world, your work can reach further than you ever imagined, join our global community. In contrast to the DOE approach, the adjoint approach involves free-form shape optimization that requires very few simulations to achieve an optimized design. If a designer doesnt like the aesthetics that the changes would involve, they might incorporate other design changes with aesthetics they do like and, in the time gained by using the adjoint simulation methods, another set of drag optimization simulations could be run on the new design to see how that performs. Efficiencies here are possible, but harder to achieve. I am performing CFD simulation over a NACA 4418 airfoil on Ansys FLUENT and I have collected a data chart of NACA (from 1945) for the purpose of validation. Whole vehicle drag sensitivity and regions selected for optimization (1. side mirror, 2. Ansys prints out (in the solve.out file) the minimum matrix coefficient and the maximum matrix coefficient. They then ran simulations using Ansys Fluent Adjoint Solver to optimize the body of the mirror so as to achieve the lowest drag coefficient (Cd). Getting graph and tabular data from result in workbench mechanical, Difference between K-epsilon and K-omega Turbulence Model, The solver failed with a non-zero exit code of : 2. Should be, as you say approx 1.22 but i got 1.4. http://www.cfd-online.com/Tools/turbulence.php, http://www.computationalfluiddynamict-cell-height/, http://www.cfd-online.com/Forums/operesiduals.html, http://www.cfd-online.com/Forums/opetml#post445016, http://www.cfd-online.com/Forums/opence-model.html, Drag Coefficient for flow past a Cylinder, How to calculate the drag coefficient for flow past cylinder, Causes for Drag over prediction in 2D flow, Drag Coefficient of Flow across a Circular Cylinde. This video article demonstrates how to create a reflector for a center high-mounted stop lamp. 6. The force vectors were resolved. #ANSYS FLUENT - Drag Coefficient Tutorial (REFERENCE VALUES) - YouTube Why is my drag and lift coefficient higher than it is supposed - Reddit America's Cup: Simulation Provides Freedom of Speed, Simulation Changes the Climate Change Equation, Fast Tracking Next-Gen Electric Traction Motors, Lightning Response: Faster Assessment of Aircraft Lightning Vulnerability, Composites Expand the Industrial 3D Printing Palette, Additive Manufacturing Hinges on Optimization, Supashock Smoothly Expands Business with Simulation, Use CFD to Improve Efficiency and Reduce Emissions, Corning Engineers Good Vibrations with Simulation, Collaborate on Seamless Optics Design for ADAS.
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