El Porsche 911, un ícono en el ámbito del automovilismo, ha sido venerado durante mucho tiempo por su diseño atemporal y su emocionante desempeño. Sin embargo, a medida que la ingeniería automotriz avanza a un ritmo implacable, incluso los clásicos más venerados deben evolucionar para cumplir con los estándares modernos de rendimiento y eficiencia aerodinámica. El Porsche 911 (tipo 964), aunque sigue encarnando la esencia del placer de conducir, tiene ciertas limitaciones aerodinámicas en comparación con sus homólogos contemporáneos. En este proyecto nuestro objetivo era mitigar algunas de estas deficiencias aerodinámicas mejorando la estabilidad a alta velocidad y mejorando la eficiencia general del automóvil.
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Para lograr este objetivo, se llevó a cabo un meticuloso proceso de desarrollo, comenzando con el escaneo preciso del vehículo y su transformación en una superficie adecuada para el análisis de dinámica de fluidos computacional (CFD). Una vez preparado el modelo CAD, se realizaron una serie de mejoras iterativas en la aerodinámica del automóvil, guiadas por circuitos de retroalimentación continua, hasta lograr una mejora notable en el rendimiento aerodinámico. La culminación de este proceso implicó un rediseño del estilo del automóvil, logrando un equilibrio entre el atractivo estético y la funcionalidad de alto rendimiento.
Escaneo de automóviles y modelado CAD
El coche fue escaneado en colaboración con el Motor Sport Institute y las superficies resultantes se convirtieron en un modelo CAD de alta calidad.
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Capturar cada detalle manteniéndolo limpio y simple es primordial en esta fase, ya que esto sienta las bases para simulaciones CFD precisas y optimizadas.
Resultados de geometría base
Como era de esperar, el coche muestra altos niveles de resistencia con un valor Cd de 0,351 y un valor Cl de 0,161 (generación de sustentación). Es evidente que estas métricas se quedan cortas en comparación con los estándares aerodinámicos modernos.
El equilibrio aerodinámico está fuertemente inclinado hacia la parte delantera. El centro de presión está por delante de las ruedas delanteras. Esto provoca que el coche gire demasiado y se vuelva inestable en las curvas a alta velocidad. Esta inestabilidad resalta el papel fundamental del refinamiento aerodinámico para abordar los desafíos de manejo inherentes al Porsche 911 964.
2. Computational Fluid Dynamics (CFD)
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CFD simulations allow engineers to analyze airflow patterns and forces digitally, providing high-resolution data without the need for physical prototypes. CFD complements wind tunnel testing by offering detailed insights into complex flow phenomena. A similar approach to the wind tunnel can be taken using CFD. A number of simulations are performed while varying the attitude of the car in order to understand the sensitivities of the vehicle (variations of pitch, heave, roll and yaw) as well as overall stability and performance across different types or corners or in straight line.
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There are several advantages to performing aerodynamic mapping in CFD compared to the wind tunnel: the obvious one being that there is no need to design and build a physical model but most importantly, it provides a significant amount of data for a low cost which allows engineers to address any shortcomings in the design by analyzing flow fields and flow structures in different conditions accelerating design and development time frames.
3. On-Track Testing
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For applications like motorsports and aviation, real-world testing is conducted using pressure sensors, flow probes, and telemetry systems to validate aerodynamic models in actual operating conditions. This type of aerodynamic testing is mostly used for validation and great care needs to be taken when analyzing the data. Unlike controlled wind tunnel tests, the operating conditions are subject to external variables such as ambient temperature, track temperature, wind speed and direction, which can impact results. Therefore, careful preparation is required to ensure proper sensor placement and data correction strategies, allowing for accurate interpretation of the aerodynamic performance.
4. Data Analysis and Correlation
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Once data is collected from wind tunnel tests, CFD simulations, and real-world experiments, engineers analyze and correlate the results. This step ensures accuracy and consistency, enabling data-driven design improvements. Obtaining data from different sources is the only way to ensure the continuous improvement of the tools. All tools have strengths and weaknesses, wind tunnel tests can be the best representation of reality, however it is important that all boundary conditions are considered and represented correctly which can be challenging for example when dealing with tyres. Furthermore, the preparation of a wind tunnel test can be time consuming and expensive, especially if the level of accuracy required is high, but also the amount of data obtained from the test can be limited to force values unless further investment is made to include several pressure taps and other visualization tools such as PIV. On the other hand, CFD simulations provide a significant amount of data for a much lower cost, however CFD simulations rely on simplifications of the physics being modeled and validation is advisable if not required. Finally, real-world testing can also be expensive as it requires a working prototype, therefore it is reserved for an advanced period of the project. It also involves the inclusion of several sensors to be able to correct for uncontrolled variables (wind, temperature) and in some cases unavoidable deltas which cannot be corrected.
Resultados finales
Resumamos ahora los resultados de nuestro proceso de diseño:
La marea cambia a nuestro favor: ahora, el Porsche 911 964 genera carga aerodinámica general a máxima humedad relativa (Cl = -0,070), con un ligero aumento en la resistencia (Cd = 0,361).
El panorama de la distribución de elevación sufre una transformación notable: aunque aún no es perfecta, esta distribución marca un paso significativo hacia el logro del equilibrio aerodinámico, abordando el notorio desafÃo del sobreviraje a alta velocidad inherente al Porsche 911 964.
Resultados finales
Resumamos ahora los resultados de nuestro proceso de diseño:
La marea cambia a nuestro favor: ahora, el Porsche 911 964 genera carga aerodinámica general a máxima humedad relativa (Cl = -0,070), con un ligero aumento en la resistencia (Cd = 0,361).
El panorama de la distribución de elevación sufre una transformación notable: aunque aún no es perfecta, esta distribución marca un paso significativo hacia el logro del equilibrio aerodinámico, abordando el notorio desafÃo del sobreviraje a alta velocidad inherente al Porsche 911 964.
1. Wind Tunnel Testing
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For a wind tunnel test it is necessary to design and build a prototype, although a released car can also be used for full scale tests. The approach for a model scale test and a full scale test are very different. In the case of a scale model, the prototype needs to have an internal chassis that can accommodate to the wind tunnel facility’s balance, be it internal or external, so that the vehicle RH, roll and yaw angles are modified. The model does not rest on top of the wind tunnel road, it is held by a strut which controls the position with respect to the ground by the use of at least three laser distance sensors which allow the control of pitch and roll angles. It still needs to have a suspension system so that the wheels stay on the ground. The complexity of this system can vary depending on the requirements of each project, for a road car having simple suspension kinematics which allows the wheels to move without major camber variations might be enough given that contact patch shape is not critical. However, when dealing with ground effect race cars, the contact patch shape can have a significant effect on aerodynamic forces. Because of this, the suspension system must represent the real kinematics of the car so that the motion of the wheel is as what will be seen on track. If higher accuracy is required, different actuators can be included to steer the wheels and push the wheels down into the road of the wind tunnel in order to obtain a representative contact patch shape for each attitude.
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When running a full scale model, the setup will depend on the type of car that is being tested and the type of wind tunnel. When testing racing cars, a wind tunnel with a single or a three belt system must be used so that the flow under the vehicle is well represented in comparison to the real-world application. The prototype will have a representative suspension system, but it must accommodate to a hydraulic system which will control the RH and roll angles of the vehicle. The car is fixed to the wind tunnel using a set of arms on the front wheels and in some cases also at the rear depending on the wind tunnel. The yaw angle is controlled by a rotating platform where the car stands. In both cases the setup of the car prior to the test is key to making sure that the ride height system is working properly and accurately. If we are dealing with a road car, the ground effect is minimal and therefore it is possible to run on a five-belt road system. By using this type of road, the car can be fixed using a clamping system that is controlled by actuators which allows for the pitch and roll to be modified without the need for installing a hydraulic RH system of the car (the use of actuators for the clamping system will vary from one tunnel to the next). Unfortunately, this type of road does not provide a representative flow between the car and the road as it does not have a rotating belt between the front and rear wheels so it cannot be used for motorsport purposes.
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Once the vehicle is installed in the wind tunnel, the model is tested on each one of the attitudes depicted in the aero map and the forces are averaged for a specific period of time. Based on the averaged values, the forces are then multiplied by the drag and downforce weightings and a final weighted value is obtained for drag and downforce.
2. CFD Simulation
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When dealing with CFD simulations, the requirements narrow down to a closed surface CAD model, wheel kinematics data and the different boundary conditions such as wind speed, radiator and fan coefficients.
With this information it is possible to generate a template of the CFD model which uses the kinematics of the vehicle to accurately simulate the motion of the wheels for every attitude. The shape of the wheels can also be modified depending on the availability of a tyre model from the manufacturer, this would allow for a more accurate representation of the contact patch.
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With the CFD model finished it is a matter of introducing the different attitudes that need to be tested and submitted to the cluster. VFluid has developed a system that allows for any attitude to be tested automatically without further manual work saving time and costs while ensuring repeatability of the process. A few hours later the results can be analyzed.
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An example of this is provided based on an F1 2026 spec car (prior to the latest regulation update). The drag and downforce coefficients are obtained based on an aero map shown below. This aero map is an educated guess and a simplification of what a real aero map would be based on track data.
The results show that the weighted average performance of this F1 car spec is roughly CdA 1.11 and CzA of -2.47.
As mentioned before, the aero map can be used to understand how the car would behave around a track and if there are any sensitivities that need to be corrected. Some of the information this areo map shows:
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A reduction in SCz at low RHs is accompanied by a reduction in SCx, this is a positive feature for straight line performance.
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Overall, the SCz range across the map is roughly 0.35 SCz which accounts for roughly 14% of the total SCz, the range variation can be improved.
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The SCz performance improves at higher rake angles.
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The aero balance varies mostly with pitch while it remains consistent with heave.
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The yaw sensitivity graph shows a low sensitivity from the front end of the car with a higher sensitivity at the back of the car as the yaw increases. Nearly double the amount of rear downforce is lost compared to front downforce when the car is yawed by 4deg. This also highlights another area of potential improvement.
The analysis of an aero map will serve as a guideline for further development as well as the basis for on-track setup.
Resultados finales
Resumamos ahora los resultados de nuestro proceso de diseño:
La marea cambia a nuestro favor: ahora, el Porsche 911 964 genera carga aerodinámica general a máxima humedad relativa (Cl = -0,070), con un ligero aumento en la resistencia (Cd = 0,361).
El panorama de la distribución de elevación sufre una transformación notable: aunque aún no es perfecta, esta distribución marca un paso significativo hacia el logro del equilibrio aerodinámico, abordando el notorio desafÃo del sobreviraje a alta velocidad inherente al Porsche 911 964.
Escaneo de automóviles y modelado CAD
El coche fue escaneado en colaboración con el Motor Sport Institute y las superficies resultantes se convirtieron en un modelo CAD de alta calidad.
​
Capturar cada detalle manteniéndolo limpio y simple es primordial en esta fase, ya que esto sienta las bases para simulaciones CFD precisas y optimizadas.
En este proyecto, estamos trabajando al unÃsono con Deflect LLC, una pequeña startup estadounidense que está desarrollando nuevos dispositivos para reducir la resistencia aerodinámica para trenes de pasajeros y carga. (Para obtener más información, visite RoofRider .
La resistencia aerodinámica puede representar más de la mitad de la energÃa necesaria para mover trenes de pasajeros. Algunas de las mayores fuentes de arrastre para los trenes de pasajeros y de carga son los espacios entre vagones donde el aire puede entrar en el espacio y golpear la cara delantera de los vagones que se arrastran, aumentando la cantidad de energÃa que se requiere para mover el tren. Los resultados anteriores han demostrado que un deflector aerodinámico pendiente de patente llamado "RoofRider" puede reducir esta resistencia al dirigir el aire sobre el espacio y reducir la fuerza que golpea al siguiente automóvil. Este deflector tiene menos de una pulgada de altura y se coloca en el techo adyacente al espacio entre automóviles con un adhesivo.