Aerodynamic Analysis of a Sports Car with Ansys Discovery

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Hello, this is Mohsen Seraj. I'm a senior ANSYS application engineer working in OSEAN Engineering. Today I want to talk about the aerodynamic analysis of a sports car using ANSYS Discovery. Please watch this video. Let's open the CAD file in ANSYS Discovery.

In the browser, you can see that all supported files, such as Space Claim, various ANSYS extensions, AutoCAD, CATIA, CREO, and others like Fusion and IGES, are readily available. Different CAD modelers' extension files are also available, including SolidWorks for step files.

We can read many CAD models here in ANSYS Discovery. Let's start with this model. This is the model of a car with a driver, and we want to perform an external aerodynamics analysis using ANSYS Discovery. You can see the different parts, different bodies in this model. Let's learn about these.

Let's choose all of them and move all of them to a new component that we call "car" in the modeling part mode, the main section. It is designed here, and we can start from scratch or a sketch using these tools, which are similar to those in SolidWorks or other CAD modeling software.

Let's start the simulation and see what happens. You can see that the model is now in the modeling mode, and we can see that the model is ready. Let's create the enclosure first. We select the body, which can be a box, cylinder, spherical, or a custom shape.

We go with the box, which is similar to what we have for example for wind tunnels. We can check that these blocks are outdoor for these piles, which we are going to hice, and we can see that it is made of polyethylene in this case.

Now, let's show you the tool we are going to use for the stock material. We would use a EnerGo whisher and noodles that we will start from in the module. We will set the road temperature to, for example, 50 degrees, and if we look at the view from the left and right sides, each should be 50 degrees.

This is the box enclosing the car. We can move it a little if we want. Now, we consider that the core is like a stationary object, and the wall is moving around the car. We're done setting up the model in modeling mode. Now, we can move to the simulation part.

We have two modes for the simulation: Explorer mode and Refined mode. We will work with Explorer mode. In the physics section, we have things like material and a section for the simulation.

If we start here, we can see that it is material, and if we click that, we can see the locked-in, which means basically that we will not have actual bone storage by now. The enclosure is made of steel like the cars that we have.

If we click on the enclosure and instead of structural steel, say that it is air, we can see that now we have air added to the tree under the physics.

One way to define the boundary condition and setup for this material for this problem is to start from here, and another one is that if we click on this hot, this is the material for the setup for the structural analysis, the fluid flow analysis, and the thermal analysis.

We click here, and we have flow, fan walls, porosity, and also rotating flows. We start with the flow boundary condition. For the inlet, we define this as an inlet, and we have options for velocity, mass flow rate, pressure, or swelling flow.

Let's say that it is 30 meters per second for the velocity and click enter. You can see that now we see it here. For the outlet, we choose the top, left, or right side, and it can go to the pressure outlet, which is set to zero Pascal, a gauge pressure.

If we want to add the temperature here, we can have it there. Click OK. Now, you can see that the outlet is also added here. This is for the outlets on the sides and back. This is for the inlet. One more thing is that we need to define this as a stationary wall.

We can come here and say that walls have different options for the walls, free slip, meaning that there is no sleep, there is a sleep condition, or if you have a moving wall option. We just say that stationary and say yes. Now, you can see this symbol for the fluid flow analysis is active.

For the for the analysis for the simulation, you can see this here. This is the car, and this is for the enclosure. We see this green circle symbol that shows that it is included into the domain. For the next step, we have meshing. We have different ways to set up mesh size.

We call it mesh fidelity. We'll go one way, which is this sliding bar, and another way is that if I come here to this fidelity section for global, I can change the approach for the mesh. That it could be standard, aggressive, extreme, or constant.

We usually start with standard and then move to aggressive and extreme for smaller and smaller sizes for the mesh. Now, you can see that everything is already set up, and I can start the simulation. The solution starts first with meshing. You see this moving part.

The meshing is done, and we started the simulation. The simulation is underway, and by default, the GPU native solvers are used here, which really accelerate the solution.

The solution is done, and if you look at here for this dot and rotate this plane for the directional analysis, you can see this for the velocity and these are the magnitudes. You can easily change the units if you want, for example, miles per hour. If you look at that, you can see the magnitude.

I can change the numbers and as I move the cursor over there, I can see that what is the magnitude on each part. You can see that here, for example, I have very, very small amounts, showing that we have a kind of recirculation here for the air.

You can see that the fellow coming here from this side is in the negative Z direction, so that's why you can see that most of the parts for the contours are negative. When it is positive, it means that we have fellow in the opposite direction of this.

Positive velocity in the Z direction means that the fellow is from right to left. You can see that here. I have it. I can also change this to pressure, static pressure, or total pressure for the pressure.

If you look at that, I have high pressure at the front, high pressure at the head of the car, and we can see that where I have high pressure in the kind of cabin behind the driver seat and here. You can see very, very low pressure also here. This is interesting.

So, this part is a low-pressure area between the car and the road. This wall that we have between the car and the road. This wall, this wall, this wall. This is not the only option that I can see for the results here.

If instead of this directional field, I come and look at the velocity vector, for example, here. And set that, go for animation. You can see that I have a 30 m per second velocity. If I come here, you can see this negative. I change the setup for that. You can see the negative velocity here.

Or if I check it, set it on the Z direction, you can see that. Positive value means the fellow is in the opposite direction that I have. Instead of vectors, I can set the contours for the velocity. I have options, for example, inner. You can see that. And if I add the fellow.

You can see whether there was going on for the velocity vectors. If this is in the Z direction, it could be in terms of the magnitude. This is velocity only for the contours. And for example, here, I can see very, very small amounts for the magnitudes of the velocity.

In the Z direction, you can see positive value. So, it is in the opposite direction. This is in line with the recirculation that I already saw here. It could be inner. It could be outer. Just see the external. The velocity at the external. External size almost zero.

Even for the magnitude, you can see zero value. At the external sides. Highest value. And lowest value. Where I have this. I can also check the amount for the isosurface. Okay. The very low velocity, you can see that at the back. Low velocity amount. And go for the Z direction.

Very, very low velocity. You can see. And right after the car. If I go for higher velocity. Okay. You can see that now I'm seeing higher velocity. Okay. So, in this way, I can check that. Where I have. Same velocity. In the domain. Okay. This is also an emitter that I can set out here if I want.

The location of the emitter. And I can see the streamlines of that. So, if I come here. And I can change the place for that. Okay. And. Go for that. Okay. Or. Go for the control of that. Even I can. Change the size of that. Rotate that. Okay. For example, I want to see. What's going on. Okay.

Again, I take it rear. And also take care of steering. So, what I need to do. Just, I want it's all all not to push. So, it's a changeable shape. Okay. So, I mean it's an electric bike. I actually that's what it means. It. I can see that here. You can see it. Five. Okay.

If you go to, forget that three. One and I. Let's see too. Let's see. 하면서 change combination. And we can choose. Here. Looking at here is see it has green, theta in red the green color. So, it should pass through the plates. But and byending.

The size of the emitter so this is another way to seeing that. Look at the particles. This is for the whole range. I can change it for the smaller range. You can see a smaller range here that I have it. Larger size if I want to have it there. Animation speed more range for the velocity.

You can see even below the car I'm seeing the small amount of the velocity and again back to the this directional field that I have it so if I want if I want to check the mesh, you can see here the size for the elements, the damage size.

Okay, it is almost 38 millimeters or I can come here and say that size preview this is in inches, okay, everywhere it is the same.

If I want to set a monitor to see that when I'm changing some things, for example, suppose I change the velocity from 30 to 40 meters per second and see that was going on, I can choose a variable from this part.

You see that most common parameters are here, velocity, pressures, what is city map, force, this is something that I needed it for example for the calculation of drag force and also other things. If I want, mass value rate is somewhere or whatever.

The good thing is that I have some information ready for the pressure drop, one for the max velocity. So, if I add, for example, if I want to see what's going on, I can change the values to the velocity.

So, this is the speed and this is the for the force, okay, and choose for example one of that, okay, and say that Z or if I come here, choose the car and Z in Z direction, you can see that I have the amount of the force in the direction of motion on the car in this problem, and I have it ready here.

So, this is for the max velocity and this is for the pressure drop. If I now change, for example, the velocity at the inlet from 30 to say that 40 mps, first of all, you can see that the solution automatically restarts to perform the to solve the problem for new conditions.

This is a good thing about ANSYS Discovery. I didn't need to hit this button. No, okay, and if I see that also, I can see the results in during the solution, although you have to be careful that it is not really the final answer.

So, this is the velocity, you can see that the force drops, okay, from actually it is increased for higher velocity; we have higher force on the car but in the negative direction, remember that the Z is in from right to left, but the inlet is from left to right, so you can see that the pressure that the the force on the car increased and at the same time the velocity max the velocity also increased in the domain.

So, this is one way that I can monitor the parameters that I want and see that what is the effect of changing the design or changing parameters of my interest on the problem, and for specifically monitoring the changes in the in the something that I'm interested to know about it, and it is easy to say that for example if I wanna have the recording of the and showing the results and preparing the report, it is very easy, just click on that.

So, you can see that I already have this here, and if I change it to Z velocity and another click, so I have two scenes recorded. So, very easy to save the results here that we can do this. Okay, okay, let's also change the global global fidelity.

If you remember that the size is here, everywhere it is 1.48 or from here in millimeters, it is 38 millimeters. This is 1.48 inches. Now, let's change it to from a standard to say that aggressive. The solution is not at first; we have machine.

You can see after the fellow developed into the domain, this is velocity in Z direction. The solution, the answer, Discovery is solving the model from this moving dot.

You can see that, and if I change if I see that now, I can see that this is the first one, and this is the now the size it is waiting the results broke %ically project in a single now.

So, nanook trust d fast on there on there Rcat 50, 50, and on top, it is 50. The solution is done in less than one minute, as you can see, which is very good.

And if I monitor the results, we can see that for example, now, for higher resolution of the mesh, the force calculation changed from 261 to more value, which is 343 newtons. So, it shows the effect of the mesh resolution or mesh fidelity here. Also, the maximum velocity about 60 meters per second.

And for the higher resolution, it is about 51 meters per second. So, this is something that we have to be careful about. We can go further, for example, for extreme, further refinement here. The solution starts, okay, in Z direction or here.

You see that how the fellow developed in the domain, passing through over the car and the driver head, and going to after the car, passing the car. And this is Z velocity. And the size is now 23 millimeters. So, I refined the model meshing from 38 millimeters to 30 millimeters. So, it is very good.

And I will show you the results. So, the result is very good. So, the result is quite good 3 and 2. So, you can re Hermit size and thickness. So, you can go further and zoom to the third finger side of the body clamp. This is missing something. You can see something is missing.

When the video has been was dying for a couple of minutes. You can check the effect of that on the effect of meshing on the force calculation from 343 N it drops to 315. So, we are still seeing the effect of the mesh on other results for the force analysis.

And for the also for the velocity, you can see also so this is 60 m per second for 38 mm mesh size, drops to 51 m per second for 30 mm of the element size. And now goes up to 55 m per second for 23 mm per second.

Okay, so far, I talked about how to set up the model and run the simulation in the explorer mode. Let's move on to another mode of that available in ANSYS Discovery for analysis that we call it the refined mode.

This refined mode basically enjoys the solvers that are native to ANSYS Fluent for CFD applications and ANSYS Mechanical for structural analysis. So, basically, it is like using ANSYS Solver to solve this problem. This is one thing that is different between explorer mode and refined mode.

Another difference is that now I can see the mesh even before starting the solution. This is one other thing that we can have. Also, you can see that this local fidelity is also available. So, I can assign a specific dimension or a specific size to just a part of the domain, not the whole domain.

So, we can use this local size to change the size in a particular area, like for example, a critical area if I want. Also, simulation options are active here. If I work on this part, you can see that now I have some options to have better hands-on how to control the simulation and the solution.

For example, how to stop the solution, what is the criteria for the convergence. You can set it up, even monitor the values for the convergence, similar to what we have in ANSYS Fluent, the solver. By default, it is a GPU solver, but it could be in CPU as well if I want to use CPU.

Method for the turbulence, as you can see, we have more and more turbulent modeling here included in the refined mode, K-epsilons and K-omegas model that we have, even laminar that we have. For specifying convergence settings, these are the items that I can work on.

And also important, another important item in this list is that the element shape and the element type or mesh type of that is available in ANSYS Discovery refined mode. Previously, when I was working in refined mode, I didn't see the mesh. Okay. So, mesh is something that is in the background.

But for the refined mode, not only can I see the mesh, but I can also see tetrahedral mesh and polyhedral mesh. So, this is something that is also good to work on.

And for the fidelity areas, low fidelity areas, unit setting is also something that I can set here, similar to what we have unit settings in fluent. So, we try to get close to the setup in ANSYS Fluent in this ANSYS Discovery.

And for sure, the level of accuracy that we have here from the refined mode in ANSYS Discovery is usually generally better than what we have from the explorer mode. So, far, I showed you how to model and set up a model in ANSYS Discovery. Okay. So, I set up the enclosure.

When I can have access to the model, okay. So, I can access to that from here. Then set up the distance between the sides of the enclosure respect to the object, which is here, a car and the driver.

Then I move to Explorer mode and showed you how to solve the model specifically before that, set up the boundary conditions for fluid flow and also the material, which is air here, for the fluid that is flowing around the object, the car here.

So, I have and also the setup for the walls, stationary walls for the road. Inlet outlet, and easily I can change the values here, whatever I want. Even for example, I can set it to kilometers per hour for the units. I don't need to do anything, okay.

And also change the pressure outlet pressure, it could be velocity pressure, could be mass flow, per outlet, and pressure outlet, with a velocity outlet. And even here for the inlet, velocity inlet, pressure inlet, mass flow inlet. So, this is and gravity automatic. And the gravity automatic added.

So, these are the setups for the physics. And then by hitting the this button, I can start the simulation and see that what's going on here for the simulation. I, for the fidelity of the mesh, are usually a start with the standard fidelity, which gives me quickly an answer.

It is like a low part answer that I can have it. I can control and how to control the mesh.

So, I can have it and different options for the post-processing from vectors, contours, isosurfaces, streamlines, particles, and here for the directional field and this is for the velocity I can easily change it to the magnitudes, change it here to kilometers per hour for the units, and the results are ready, not only for the velocity, for static pressure, total pressure, and vorticity number here.

So, the solution is very quick because it's using GPU native solver in ANSYS Discovery, and the good thing in ANSYS Discovery is that we can easily change the parameters for the index of the value of the value of the value of the value of the value of the value of the value of the value of the value of the value of the value of the value of the value and also if I want to change some things into the geometry, also I can change it here.

I don't need to go back to the CAD modeler. I can also have these changes in the geometry here, and the solution will be restarted and give me the updated answers. Thank you very much for watching this video. I hope you enjoyed it. Thank you.