# Step-by-Step Tutorial Session 3 - Yaw Angle Study (Part 1) **URL:** \ **Category:** Formula Student/SAE Workshop - 2017\ **Created:** [September 12, 2017, 6:46am UTC](https://www.simscale.com/forum/t/step-by-step-tutorial-session-3-yaw-angle-study-part-1/79719 "2017-09-12T06:46:50Z")\ **Posts on this page:** 1\ **Showing post:** 1
**Author:** ![drodriguez32](https://www.simscale.com/forum/user_avatar/www.simscale.com/drodriguez32/32/14276_2.png) [@drodriguez32](https://www.simscale.com/forum/u/drodriguez32)\ **Post date:** [September 12, 2017, 6:46am UTC](https://www.simscale.com/forum/t/step-by-step-tutorial-session-3-yaw-angle-study-part-1/79719/1 "2017-09-12T06:46:51Z")
## Recording [![](https://www.simscale.com/forum/uploads/default/original/3X/a/f/af3c81c8fe88fe4e9a295ffee0122e6f128ea9d2.jpeg "CFD in Formula Student and Formula SAE - Session 3: Aerodynamics Development Strategies") ](https://www.youtube.com/watch?v=cy31_MVQlxw) * * * ## Homework Submission For your homework, your task is to investigate the full car running in a straight line at 20 m/s with side wind. You will have the same model we used for the last session, so you will setup _porous media_, _MRF (rotating) zones_, _rotating walls_, and the flap angle will be _0_ degrees. Think about how this setup differs from the previous one and think about the impact of the side wind on the performance of the car and the flow behavior around it. The step-by-step tutorial below contains all of the steps for setting up the simulation in SimScale and visualizing the results. > We’ve made an update to the platform and the sharing procedure has changed. Please go to the following link to see how to get a sharing link for your project: > [New Sharing on SimScale](https://www.simscale.com/forum/t/sharing-a-project/242) **Homework Deadline** : October 17th, 11:59 pm CEST #### [Click Here to Submit your Homework](https://marketing.simscale.com/acton/form/14483/00d3:d-0001/1/-/-/-/-/index.htm) * * * ## Outline ### Part 1: 1. Introduction 2. Project Import 3. Mesh Generation a. Geometry Primitives b. Mesh Refinements c. Start Operation 4. Simulation Setup (Part 1) a. Analysis Type b. Domain c. Material d. Initial Conditions e. Boundary Conditions ### Part 2: 1. Simulation Setup (Part 2) a. Numerics b. Simulation Control c. Result Control d. Simulation Runs 2. Post Processing on SimScale 3. Result Analysis a. Highlights b. Yaw Angle Comparison * * * ## Introduction In this exercise we will investigate the effects of side wind on the performance of the car. Your task is to investigate the full car model **Model-Conf-Yaw.** The velocity of the car will be considered constant at 20 m/s with side wind. * * * ## Project Import To start this exercise, please import the project into your workspace by clicking on the link below: > **[SimScale Login](https://www.simscale.com/workbench?publiclink=67395465-f391-4d60-8e40-653b0f9a8a0e)** > > Log in to your SimScale account. SimScale makes high-fidelity engineering simulation technically and economically accessible. At any scale. In the cloud. If the project appears to be private, please make a copy of it to work on it. * * * ## Mesh Generation ![Mesh operation 0 (alternative)](https://www.simscale.com/forum/uploads/default/original/2X/4/4d9ef1b9175b7556b3a08266316dd649e9cc6283.png) In the **Mesh Creator** tab, click on the geometry **Model-Conf-Yaw** Click on the **New Mesh** button A new mesh operation will be generated automatically. Next change (_ **some** of the settings have been set as default by SimScale. Please double check all your settings_): 1. Type to **Hex-dominant parametric (only CFD)** 2. **Bounding Box geometry primitive** to the following: Number of cells in x direction to **105** Number of cells in y direction to **60** Number of cells in z direction to **30** 3. **Number of parallel computing cores** to **32** [_Scroll down to change other values to optimize the meshing parameters_] [_You can also **ctrl+f** to find each setting_] 1. **Cell limit for refinement termination** to **10** 2. **Buffer cell count between refinement levels** and **Minimum angle for feature detection [°]** to **1** and **45** respectively 3. **Mesh-to-geometry conformation iterations** to **6** 4. **Max iterations for meshing algorithm** to **150** 5. **Max iterations for removal of bad cells** to **8** 6. **Max iterations for mesh conformation** to **1** 7. **Detect features between multiple surfaces** to **false** 8. **Max smoothing iterations for surface normals [-]** to **1** 9. **Max face aspect ratio for layers [-]** and **Max ratio of layer thickness to medial length [-]** to **0.55** and **0.35** respectively 10. **Max overall iterations for layer addition** to **3** 11. **Max non-orthogonality angle** to **75** 12. **Min cosine for face twist** , **Min normalized cell determinant** , **Min face weight** and **Min volume ratio between neighbouring cells** to **0.005** , **0.005** , **0.01** and **0.0075** respectively 13. **Relaxed max non-orthogonality angle** to **80** 14. Click **Save** to register changes. ### Geometry Primitives Next we’re going to define geometry primitives like in the past sessions so that we can get refinement regions. #### Background Mesh Box ![Background mesh box](https://www.simscale.com/forum/uploads/default/original/2X/1/1379c23afbab5cf854bb83ae6d56c141cb444e6e.png) Go to the **Background Mesh Box** item and change the mesh box dimensions to the values shown below. - Min. Point (x) [m]: **-9.825** - Min. Point (y) [m]: **-9** - Min. Point (z) [m]: **0** - Max. Point (x) [m]: **18** - Max. Point (y) [m]: **9** - Max. Point (z) [m]: **7.2** Click **Save** to save the changes. #### Material Point ![Material point](https://www.simscale.com/forum/uploads/default/original/2X/1/17b87b0b1f291c29911f7feca6607611b0606d57.png) Go to the **MaterialPoint** item and change the values to: - Center (x) [m]: **0** - Center (y) [m]: **0** - Center (z) [m]: **3** Click **Save** to save the changes. #### Cartesian Box-lower ![New cartesian box](https://www.simscale.com/forum/uploads/default/original/2X/0/0afea3d9c4cd943dcf682d366e987fd115745742.png) Next go back to **Geometry Primitives** and click on **+New** and then **Cartesian Box** to define a new Cartesian box that will be used to define mesh refinement area. ![Cartesian box lower](https://www.simscale.com/forum/uploads/default/original/2X/e/e864ca344dd94590a12dc5b2cc458f8f9c99d4d6.png) After creating a new Cartesian box, you will be directed to the definition of this Cartesian box. Rename it to **Cartesian Box-lower** (optional) and change the dimensions to: - Min. Point (x) [m]: **-2** - Min. Point (y) [m]: **-1** - Min. Point (z) [m]: **0** - Max. Point (x) [m]: **5** - Max. Point (y) [m]: **1** - Max. Point (z) [m]: **0.8** Click **Save** to register your changes. #### Cartesian Box-upper Follow the same procedure to create a second cartesian box geometry primitive. ![Cartesian box upper](https://www.simscale.com/forum/uploads/default/original/2X/7/74f5124a6cbcc36096f2324eb9459936c4617dd6.png) Rename it to **Cartesian Box-upper** (optional). This time change the dimensions to: - Min. Point (x) [m]: **-0.4** - Min. Point (y) [m]: **-0.7** - Min. Point (z) [m]: **0.8** - Max. Point (x) [m]: **5** - Max. Point (y) [m]: **0.7** - Max. Point (z) [m]: **1.6** Click **Save** to register your changes. ### Mesh Refinements Now we will start creating the mesh refinements. For this proceed to **Mesh Refinements** and click **+New** #### _Mesh Refinement 1 - Surface_ ![Mesh refinement 1](https://www.simscale.com/forum/uploads/default/original/2X/e/eca33ebd4efb73218ea2b36f95d6c2017377e087.png) A new mesh refinement will be created. Rename it to **Surf-body-diff-Wsides-Radsup** (optional). Change the **Type** to **Surface refinement** Set **Level min** and **Level max** to **5** and **5** respectively. From the navigator on the right (or directly in the viewer) select **body** , **FWEPin** , **FWEPout** , **RWEP** , **Diffuser** , **Radsupport** and **Driver**. You should see these 7 faces in the blue highlighted area under _Refined Surfaces_. Click **Save** to register your changes. #### _Mesh Refinement 2 - Surface_ ![Mesh refinement 2](https://www.simscale.com/forum/uploads/default/original/2X/4/48c695c0b48989c093343d2ad24982483842252d.png) Follow the same procedure and create a new mesh refinement named **Surf-wings-wheels-susp-bars** (optional). Change the **Type** to **Surface refinement** Set **Level min** and **Level max** to **6** and **6** respectively. From the navigator on the right (or directly in the viewer) select **FWmainwing** , **FWflap** , **RWflapa** , **RWflapb** , **RWflapc** , **RWflapd** , **Frontsusp** , **Rearsusp** , **Barre** , **Reartire** and **Fronttire**. You should see these 11 faces in the blue highlighted area under _Refined Surfaces_. Click **Save** to register your changes. #### _Mesh Refinement 3 - Surface_ ![Mesh refinement 3](https://www.simscale.com/forum/uploads/default/original/2X/4/48d3d8d4563348236e3f6892c2d2f00eb0604c69.png) Create a new mesh refinement named **WheelHub-cp** (optional). Change the **Type** to **Surface refinement** Set **Level min** and **Level max** to **7** and **7** respectively. From the navigator on the right (or directly in the viewer) select **Frontur** , **Rearur** , **ReartireCP** and **Fronttirecp**. You should see these 4 faces in the blue highlighted area under _Refined Surfaces_. Click **Save** to register your changes. #### _Mesh Refinement 4 - Surface_ ![Mesh refinement 4](https://www.simscale.com/forum/uploads/default/original/2X/6/608d8360336f2cc545d3e19030373ba5b0241672.png) Create a new mesh refinement named **Sidepod** (optional). Change the **Type** to **Surface refinement** Set **Level min** and **Level max** to **5** and **5** respectively. From the navigator on the right (or directly in the viewer) select **Sidepod**. Click **Save** to register your changes. #### _Mesh Refinement 5 - Porous Zone_ ![Mesh refinement 5](https://www.simscale.com/forum/uploads/default/original/2X/0/0c9fb8024e191e1f876f9196ad0d24119c83a57c.png) Create a new mesh refinement named **Radiator-PorousZone** (optional). Change the **Type** to **Surface refinement** Set **Level min** and **Level max** to **6** and **6** respectively. Set **Create cellZone** to **true** and rename **cellZone name** to **RadiatorZone**. From the navigator on the right (or directly in the viewer) select **Radiator**. Click **Save** to register your changes. #### _Mesh Refinement 6 - Feature_ ![Mesh refinement 6](https://www.simscale.com/forum/uploads/default/original/2X/b/b2d481a50411e8f87f8cfcb488dbaec849ed0891.png) In order to create a separate feature refinement for small features, create a new mesh refinement named **Feat** (optional). Change the **Type** to **Feature refinement** Then click the **+** button to add an extra value. In the first row, change **Distance** and **Level** value to **0.001** and **8** respectively. Similarly, change the value to **0.004** and **6** in second row. Click **Save** to register your changes. #### _Mesh Refinement 7 - Region_ ![Mesh refinement 7](https://www.simscale.com/forum/uploads/default/original/2X/c/c24169fc5cfe8ed6c744ad7c41a9938cfd69d2b8.png) To define the refinement level for the created Cartesian box geometry primitives, create a new refinement and rename it to **Region** (optional). Change the **Type** to **Region refinement** and set the level to **2** Select **Cartesian Box-inner** and **Cartesian Box-outer** under **Assigned Geometry Primitives** Click **Save** to register the refinements for the specific cartesian boxes. #### _Mesh Refinement 8 - Boundary Layer_ ![Mesh refinement 8](https://www.simscale.com/forum/uploads/default/original/2X/7/70004d161f153d6f373398059bb68a5d295e7e36.png) Next we will define the boundary layers over car surfaces in order to have a uniform layer refinements. Layers will allow us to accurately capture and observe the flow behavior close to the surface of the car. Create a new refinement and rename it to **Layer-Car** (optional). Change the **Type** to **Inflate boundary layer** Then change **Number of layers [-]**, **expansionRatio [-]**, **finalLayerThickness [-]** and **minThickness [-]** to **3** , **1.05** , **0.45** and **0.001** respectively. Select all the faces except **Radiator** ; **Radsupport** , **MRF\_F** and **MRF\_R**. You can do this by clicking on the box selector option in the toolbar, drawing a box over the whole car (which will select all the faces) and then unselect the faces mentioned before using the navigator on the right. Click **Save** to register your changes. #### _Mesh Refinement 9 - Boundary Layer_ ![Mesh refinement 9](https://www.simscale.com/forum/uploads/default/original/2X/d/d1198fa78dd9741967403b6a4627c8ec971274e1.png) For the floor layers, create a new refinement named **Floor-layer** (optional). Change the **Type** to **Boundary box layer addition**. Change **Bounding box face** to **Zmin** and then the **Number of layers** and **Minimum overall layer thickness [-] or [m]** to **2** and **0.001** respectively. #### _Mesh Refinement 10 - Rotating Zone_ ![Mesh refinement 10](https://www.simscale.com/forum/uploads/default/original/2X/2/2ae1eb9c9afa03cfe76e127bdc4d5b3161aa6f24.png) Create a new refinement for the front MRF zone named **MRF-Wheel-front** (optional). Change **Type** to **Surface refinement** Set **Level min** and **Level max** to **6** and **7** respectively. Change **Create cellZone** to **true** and rename **cellZone name** to **FrontWheelZone**. From the navigator on the right (or directly in the viewer) select **MRF\_F** Click **Save** to register your changes. #### _Mesh Refinement 11 - Rotating Zone_ ![Mesh refinement 11](https://www.simscale.com/forum/uploads/default/original/2X/7/7f8bf70b356e29f8b08843c0312b18629dde7b66.png) Similarly, for rear MRF zone create a new refinement named **MRF-Wheel-Rear** (optional). Change the **Type** to **Surface refinement** Set both **Level min** and **Level max** to **6** and **7** respectively. Change **Create cellZone** to **true** and rename **cellZone name** to **RearWheelZone**. From the navigator on the right (or directly in the viewer) select **MRF\_R**. Click **Save** to register your changes. ### Start Mesh Operation ![Start mesh operation](https://www.simscale.com/forum/uploads/default/original/2X/4/4fd467cb18ab017e1308436e54bcb7b9d302c75c.png) Once you have defined all 11 of the mesh refinements, go back to the **Operation 1** and click **Start.** Due to the fineness of the mesh, the meshing operation can take 100 to 140 minutes to finish. * * * ## Simulation Once the meshing operation is complete, go to the **Simulation Designer** ![Create simulation](https://www.simscale.com/forum/uploads/default/original/2X/9/9d39936edf174e861471abf471866cf3ce7d5d82.png) Click **New Simulation** and name it _Conf-Yaw_ (optional; you can choose any name you want). Then click **Create.** ### Analysis type ![Analysis type](https://www.simscale.com/forum/uploads/default/original/2X/d/dfae857b6d0592eb69a5d639defe5d3b4e7c941b.png) Under **Analysis Type** , switch to **Fluid dynamics** and then select **Incompressible**. You don’t have to change any other properties here. Click **Save** Once you save the analysis type, the items in the Navigator will expand. All of the red entities must be set up in order to perform a successful simulation run. ### Domain ![Domain](https://www.simscale.com/forum/uploads/default/original/2X/5/5b6a5815c664a29a06197c44ee78be74fe52a885.png) Proceed to the **Domain** item in the Navigator and select the mesh you just created. Then click **Save**. You will see the loaded mesh of the selected domain in the viewer. For the easier mesh handling, it is recommended to switch to the **surfaces** render mode in the top viewer bar. ### Material Next we have to define the fluid material. ![Material 1](https://www.simscale.com/forum/uploads/default/original/2X/f/f47ddd5bf22747e5b427638ad0ebd52cf3faf23e.png) Go to **Materials** and click on **+New** ![Material 2](https://www.simscale.com/forum/uploads/default/original/2X/a/ad24ae309f6fde7597c863952fa109bb1cca8e92.png) Click on **Import from material library** to import the desired material from the material database. ![Material 3](https://www.simscale.com/forum/uploads/default/original/2X/f/f3af79177bea5c3c4f2ea2d87e45daec223ed703.png) Select **Air** and click **Save** to import this material directly from the library. ![Material 4](https://www.simscale.com/forum/uploads/default/original/2X/8/891731f1fbe229d99bbc59445d416b0bf49dd819.png) Select **region0,**** RadiatorZone, ****RearWheelZone,** and **FrontWheelZone** from the navigator in the right. Then click **Save** ### Initial Conditions We will now proceed to change the initial conditions. ![Initial conditions - k](https://www.simscale.com/forum/uploads/default/original/2X/8/8d49ca998697c86a75926f343ead1a4e4fe0ba26.png) Go to **k** and change the **Turbulent kinetic energy value [m²/s²]** value to **0.06** and click **Save**. ![Initial conditions - omgea](https://www.simscale.com/forum/uploads/default/original/2X/3/30040dd10d315a96f3def6b646844a0bbfb91c0c.png) Next go to **Omega** and change **Specific turbulence dissipation rate [1/s]** to **44.7** and click **Save**. _**For a more detailed description on turbulence modelling please refer to the SimScale Documentation ([Turbulence Models](https://www.simscale.com/docs/content/simulation/model/turbulenceModel.html)) or Part 1 of the Step-by-Step Tutorial Session 2 under Initial Conditions ([Step-by-Step Tutorial Session 2 - Full Car Aerodynamics (Part 1)](https://www.simscale.com/forum/t/step-by-step-tutorial-session-2-full-car-aerodynamics-part-1/78878))**_ ### Boundary Conditions Now we will proceed to the most crucial and important section of the simulation setup: setting up the boundary conditions. This is simply telling the platform how we want the simulation to behave. But this time there will be a difference because we want to investigate the side wind effect, so we will customize the inlet boundary condition to control the angle of the free stream according to the car. We will then define the boundary condition for the floor, the roof, and the car (you may have noticed that we don’t have symmetry plane like in the previous session because we are working with the full car). ![New boundary condition](https://www.simscale.com/forum/uploads/default/original/2X/1/1e195e23880a6c0efeb8fb88113ed8ecb5137cbd.png) Go to **Boundary Conditions** and click **New** in order to create a new boundary condition. #### Inlet _Formula for calculating velocity components:_ ![Inlet explanation](https://www.simscale.com/forum/uploads/default/original/2X/5/5bedd54609a40c196251bbd482212eaf6bba3b93.jpg) _Setup:_ ![Inlet](https://www.simscale.com/forum/uploads/default/original/2X/2/21bd82fe65457f7025fc8a59e19393f9405ba1d2.png) Name the newly created boundary condition to **Inlet** (optional). Set the **Type** to **Custom** Under **Details** select **Inlet-Outlet** for **velocity** Then under **Details** \> **Inlet valve** \> **properties** we will specify the **X** and **Y** components of the velocity vector depending on the freestream angle of 20°. We know that the car is travelling forwards at 20 m/s, so we have the _X_ component of the vector. We also know that the yaw angle is 20°, so we can calculate the _Y_ component of the freestream vector with trigonometric ratios (in this case we would use TAN like the above image). The **X** value = **20 [m/s]** and for 20° the **Y** value = **7.28 [m/s]**. > _Take into account that you can also know the velocity of your car, the velocity of the side wind and then calculate the vector/yaw angle. In this particular case we simply decided to approach the problem from a fixed yaw angle scenario and thus we calculated the necessary side wind for that yaw angle to happen._ For **Pressure** select **Fixed value** and under **Details** \> keep the value of **0 [Pa]** For **Turbulent kinetic energy value [m²/s²]** value and **Specific turbulence dissipation rate [1/s]** respectively under **details** enter **0.06** and **44.7**. _These values are the same we assigned in the initial conditions_ Select all the sides of the bounding box. You should see **boundingBox1,** **boundingBox2,** **boundingBox3,** and **boundingBox4** under _Assignment_. Click **Save** #### Roof ![Roof](https://www.simscale.com/forum/uploads/default/original/2X/3/3038bcf1249c8c87a10ab389df240019061f02f6.png) Create a new boundary condition named **Roof** (optional). Change the **Type** to **Wall** and under details select **Slip** Select the top wall of the bounding box ( **boundingBox6** ). Click **Save** #### Floor We will now define a moving floor boundary condition. ![Floor](https://www.simscale.com/forum/uploads/default/original/2X/b/b84ba41ea32b3e28cf54a28a9ac83b79952bffcd.png) Create a new boundary condition named _Floor_ (optional). Change the **Type** to **Wall** and under details set **Velocity** to **Moving wall velocity.** The car is travelling in a straight line at 20 m/s, so this relative motion is what will be specified now. Change the _Type_ to **Wall** , under _Details_ \> _Velocity_ select **Moving wall velocity** , and for the **x value [m/s]** input **20**. Select the bottom face of the bounding box ( **boundingBox5** ) - you should see it under _Assingment_. Click **Save** to define the floor boundary condition. _ **Note** _ Note that in the previous session where we had no yaw angle the settings for the _Floor_ matched the ones for the _Inlet_, but for this session they don’t. Applying the same vector to the floor as we did for the inlet would imply that the car is moving diagonally as if sliding - which is not the case. We have to maintain the condition that there is side wind, and thus in this case there **is** relative motion between the air and the floor in the **Y direction**. #### Car ![Car](https://www.simscale.com/forum/uploads/default/original/2X/0/038e49ee84d392557cf7af7051b66969aa0a2392.png) Create a new boundary condition named **Car** (optional). Select all the entities starting with **solid\_0** except for **solid\_0\_Reartire,** **solid\_0\_Fronttire** Click **Save** to define the boundary condition for the car. #### Front Wheels Next we will add a rotating boundary condition for the wheels. ![Front Tire](https://www.simscale.com/forum/uploads/default/original/2X/0/0bc9161edd4ce590c5b857fe399aa9dfc88a2f4d.png) Create a new boundary condition named **Front wheel** (optional). Change **Type** to **Wall** and **Velocity** to **Rotating wall velocity**. Then change: 1. **Origin** x value [m], y value [m] and z value [m] value to **-0.41566, 0.670378 and 0.219731** respectively. 2. **Axis of rotation** x value [m] and y value [m] to **0** and **1** respectively. 3. **Angular velocity [rad/s]** to **-90.91** 4. Then select **solid\_0\_Fronttire** 5. Click **Save** to register your changes. #### Rear Wheels ![Rear Tire](https://www.simscale.com/forum/uploads/default/original/2X/8/8d41ca9b37d34681e0c9243e03677216d9bcab48.png) Duplicate the previous boundary condition by right clicking on it and selecting **Duplicate**. Rename it to **Rear wheel** (optional). Change the **Type** to **Wall** and **Velocity** to **Rotating wall velocity**. Then change: 1. **Origin** **x value [m]**, **y value [m]** and **z value [m]** value to **1.13634** , **0.670378** and **0.219731** respectively. a. Notice that the origin values for the **y axis** and **z axis** are the same as the previous boundary condition. That’s why it was better to duplicate it. 2. **Axis of rotation** **x value [m]** and **y value [m]** to **0** and **1** respectively. 3. **Angular velocity [rad/s]** to **-90.91** 4. Then select **solid\_0\_Reartire**. 5. Click **Save** to register your changes. #### MRF zones _**For a more detailed explanation on MRF zones and the difference between MRF and Rotating Walls please refer to Part 2 of the Step-by-Step Tutorial Session 2 ([Step-by-Step Tutorial Session 2 - Full Car Aerodynamics (Part 2)](https://www.simscale.com/forum/t/step-by-step-tutorial-session-2-full-car-aerodynamics-part-2/79350)) or the SimScale Documentation ([Rotating Zones](https://www.simscale.com/docs/content/simulation/model/advancedConcepts/rotatingZones/rotatingZones.html))**_ _ **MRF Front** _ ![MRF Front](https://www.simscale.com/forum/uploads/default/original/2X/4/49dd422fedf1254facd175cbe1aec007a76fc495.png) Add a **Rotating Zones** under **Advanced Concepts** named **Front wheel MRF**. Then change: 1. **Origin** x value [m], y value [m] and z value [m] value to **-0.41566** , **0.670378** and **0.219731** respectively. 2. **Axis of rotation** x value [m] and y value [m] to **0** and **1** respectively. 3. **Angular velocity [rad/s]** to **-90.91** 4. Then select **FrontWheelZone** 5. Click **Save** to register your changes. _ **MRF Rear** _ ![MRF Rear](https://www.simscale.com/forum/uploads/default/original/2X/2/20af1e5580c7f131647cd516ca076d04d9236176.png) Similarly, perform the same procedure and create a new **Rotating Zone**. Rename it to **Rear wheel MRF**. Then change: 1. **Rotation center** x value [m], y value [m] and z value [m] value to **1.13634** , **0.670378** and **0.219731** respectively. 2. **Rotation axis** y value [m] to **1** 3. **Angular velocity [rad/s]** to **-90.91** 4. Then select **RearWheelZone** 5. Click **Save** to register your changes. #### Porous Media _**For a more detailed explanation on porous media please refer to Part 2 of the Step-by-Step Tutorial Session 2 ([Step-by-Step Tutorial Session 2 - Full Car Aerodynamics (Part 2)](https://www.simscale.com/forum/t/step-by-step-tutorial-session-2-full-car-aerodynamics-part-2/79350)) or the SimScale Documentation ([Porous Media](https://www.simscale.com/docs/content/simulation/model/advancedConcepts/porousMedia/porousMedia.html?highlight=porous%20media))**_ In this section we will define the radiator volume source via porous media. Expand the **Advanced Concepts** tree item and proceed to **Porous Media**. Click **+New** to create a new porous media definition. ![Radiator 1](https://www.simscale.com/forum/uploads/default/original/2X/7/7a2ab502fd641ed3c4d36e2fc1ced9ce32da1098.png) After creating a new porous media definition, you will be automatically directed to the properties panel. We will use the same simplification we used for the previous session, so input the following settings: 1. Name to **Radiator-PorousMedium** (optional). 2. **Coefficient d** x, y and z values to **20,000,000, 0 and 0** respectively. 3. **Coefficient f** x, y and z values to **2000, 0 and 0** respectively. 4. **Coordinate system e1** x, y and z values to **0.93, 0.15 and 0.34** respectively. 5. **Coordinate system e3** x, y and z values to **-0.34, -0.054 and 0.94** respectively. 6. Select **RadiatorZone** 7. Click **Save** to register your changes. * * * ## Link to part 2 of the tutorial [Step-by-Step Tutorial Session 3 - Yaw Angle Study (Part 2)](https://www.simscale.com/forum/t/step-by-step-tutorial-session-3-yaw-angle-study-part-2/79720/1) --- _[View the full topic](https://www.simscale.com/forum/t/step-by-step-tutorial-session-3-yaw-angle-study-part-1/79719)._